Mailing terrorist threats with ricin in the letters while complaining about gun control. Yeah, this could be a gun control advocate trying to make our side look bad. But there are tens of millions of people who passionately oppose gun control; it isn't much of a stretch to imagine that one of those tens of millions have the strategic planning capacity of a bagel.
I am actually pretty pleased with how seldom anyone on our side gets arrested for doing something this stupid. Here's a hint: making threats to overthrow the government if you actually plan to do that isn't exactly keeping the advantage of surprise, is it?
Thursday, May 30, 2013
Remember Trayvon Martin?
The case is getting more and more crooked. From the May 29, 2013 Miami Herald:
ORLANDO, Fla. -- A court employee who retrieved photos and deleted text messages from Trayvon Martin's cellphone has been placed on administrative leave after an attorney testified that prosecutors didn't properly turn over the evidence to the defense, an attorney said Wednesday.
Former prosecutor Wesley White said he was ethically obligated to reveal that Fourth Judicial Circuit Information Technology Director Ben Kruidbos retrieved the data that weren't turned over.And what were some of the pictures that came off the cell phone of the angelic Trayvon Martin?
The defense released photos of a gun, marijuana plant and Martin's text messages publicly, saying that if prosecutors planned to paint Zimmerman as the aggressor and Martin as the innocent bystander, they wanted the information to defend him. Attorneys won't be able to mention the teen's drug use, suspension from school and past fighting during opening statements at the trial, Nelson ruled Tuesday.I think I see why the defense wants that information -- and having that information hidden? Wow.
Sonoma County, California: The Newest Financial Disaster
I'm sure that Sonoma County boosters are overjoyed to see this beautiful place getting media attention -- although perhaps not this May 29, 2013 Financial Post story:
‘A disaster in slow motion’: Wine country latest California region to face fiscal crisisWow. A county of far left millionaires is now in serious financial trouble because of overly generous pensions for public employees. Who would have guessed?
Tuesday, May 28, 2013
Dead Battery
I can't remember the last time that I replaced the battery on the Corvette, which, perhaps because I have not driven it since Thursday, is dead as a doornail this morning. The Chevrolet dealer tells me that they last replaced a battery on the Corvette in 2004, which is a pretty respectable lifespan for a car battery.
Imagine If A Republican Said This...
There's a bill before Congress to prohibited convicted murderers, rapists, and pedophiles from receiving Food Stamps. Mother Jones (well known left-wing publication) explains why this is a problem:
On Wednesday the Senate agriculture committee approved a GOP proposal that would amend the farm bill the Senate is considering to ban "convicted murderers, rapists, and pedophiles" from getting food stamps. On its surface, the idea sounds unobjectionable, but the measure would have "strongly racially discriminatory effects," according to the non-partisan Center on Budget and Policy Priorities (CBPP).So Mother Jones is saying that blacks are disproportionately convicted murderers, rapists, and pedophiles, and so such a law is unfair? Perhaps they meant that it was unfair to black murderers, rapists, and pedophiles? Well, no, it treats all murderers, rapists, and pedophiles badly, regardless of race. How can you parody the progressive mentality effectively when they do it to themselves so well?
Monday, May 27, 2013
Since The Weather Is Bad Anyway...
I mean, it snowed here on Wednesday! And the weekend has been nothing but clouds and rain. Once I successfully adjusted the spider legs to get the diagonal mirror centered in the telescope tube, I was able to collimate the telescope quite quickly. But when I changed the angle of the telescope so that it was no longer horizontal, the collimation was off again. I am pretty sure that the reason is that there are two parts of the diagonal holder that are too flexible:
1. The legs are made of .0325" aluminum -- and that is probably too flexible. I can replace them with 20 gauge steel, which would be the same thickness (and optical path interference) but three times as stiff. I may also go from 2" front to back to 3" front to back, which would improve stiffness even more. The steel will weigh more, but only an ounce or two.
2. The central body of the diagonal holder is made of acetal, which is easy to machine, but has about 1/20th the Young's modulus (flexural deflection) of aluminum. I think I will pick up 3" of .25" ID aluminum tubing, perhaps 1/8" wall, and use that as the new central body. That should improve stiffness substantially with no real difference in weight. (The existing acetal part is fairly thick, so probably about the same net weight.)
1. The legs are made of .0325" aluminum -- and that is probably too flexible. I can replace them with 20 gauge steel, which would be the same thickness (and optical path interference) but three times as stiff. I may also go from 2" front to back to 3" front to back, which would improve stiffness even more. The steel will weigh more, but only an ounce or two.
2. The central body of the diagonal holder is made of acetal, which is easy to machine, but has about 1/20th the Young's modulus (flexural deflection) of aluminum. I think I will pick up 3" of .25" ID aluminum tubing, perhaps 1/8" wall, and use that as the new central body. That should improve stiffness substantially with no real difference in weight. (The existing acetal part is fairly thick, so probably about the same net weight.)
What A Weekend
Most of Saturday and Sunday was spent providing close combat support to my son while he was out car shopping. Once this experience is complete, I am sorely tempted to write an article with the title, "How Car Sales Gives Free Market Capitalism a Black Eye."
Saturday, May 25, 2013
Spiders
The structure that holds the diagonal mirror in a Newtonian telescope is called a spider, because it typically has several legs.
Last night, I was finally ready to do collimation of the optical path, and I discovered that no matter what, I could not get the diagonal mirror centered in the tube! Why? Was it this far off in the old tube?
No. I had to cut down the mirror cell bottom plate because the inner diameter of the tube is 19.875" instead of 20.25"; I forgot that the spider required similar surgery. It was easy to forget, because the legs of the spider are made of .030" aluminum (in the interests of minimizing weight and diffraction of light), and they are flexible enough that they just bent to fit. But they did not bend symmetrically.
My first concern was that I was going to have to start from scratch on this, but it turns out that there was enough spare room where the legs attached to the center point that I was able to redrill the holes in the legs 3/16" over and solve the problem. The picture below was taken with my little HP PhotoSmart camera, and it isn't terribly sharp, but you can see where I moved the holes:
I may buy a ring roller at Harbor Freight today to make tube rings. One of the reviews indicated that one of the plastic parts broke almost immediately, which doesn't surprise me. I will be rolling 1/8" or 3/16" thick aluminum, so I doubt that I will be stressing it much, and it sounds like other than that one part (which I can probably machine a replacement for out of aluminum), it is an adequate tool.
UPDATE: After spending a bit of time, I discovered that because the spider legs are held in tension (rather than compression, as it more typical of spiders), it is very dependent on the order of tightening to keep the body centered. After a little experimentation, it seems to be well-centered, and collimation went very well. But I am a bit concerned that it might not hold collimation as it moves across the sky. Perhaps a more conventional (that is to say, commercial) spider would be a better choice for this.
Frustration: I bought the ring roller at Harbor Freight -- but it appears that some previous purchaser had tapped the taper pin that holds the handle to the roller before putting the handle in place. There seems to be no way to remove the taper pin now without drilling it out. So tomorrow I will go back and ask for one that has the taper pin not yet inserted.
Last night, I was finally ready to do collimation of the optical path, and I discovered that no matter what, I could not get the diagonal mirror centered in the tube! Why? Was it this far off in the old tube?
No. I had to cut down the mirror cell bottom plate because the inner diameter of the tube is 19.875" instead of 20.25"; I forgot that the spider required similar surgery. It was easy to forget, because the legs of the spider are made of .030" aluminum (in the interests of minimizing weight and diffraction of light), and they are flexible enough that they just bent to fit. But they did not bend symmetrically.
My first concern was that I was going to have to start from scratch on this, but it turns out that there was enough spare room where the legs attached to the center point that I was able to redrill the holes in the legs 3/16" over and solve the problem. The picture below was taken with my little HP PhotoSmart camera, and it isn't terribly sharp, but you can see where I moved the holes:
I may buy a ring roller at Harbor Freight today to make tube rings. One of the reviews indicated that one of the plastic parts broke almost immediately, which doesn't surprise me. I will be rolling 1/8" or 3/16" thick aluminum, so I doubt that I will be stressing it much, and it sounds like other than that one part (which I can probably machine a replacement for out of aluminum), it is an adequate tool.
UPDATE: After spending a bit of time, I discovered that because the spider legs are held in tension (rather than compression, as it more typical of spiders), it is very dependent on the order of tightening to keep the body centered. After a little experimentation, it seems to be well-centered, and collimation went very well. But I am a bit concerned that it might not hold collimation as it moves across the sky. Perhaps a more conventional (that is to say, commercial) spider would be a better choice for this.
Frustration: I bought the ring roller at Harbor Freight -- but it appears that some previous purchaser had tapped the taper pin that holds the handle to the roller before putting the handle in place. There seems to be no way to remove the taper pin now without drilling it out. So tomorrow I will go back and ask for one that has the taper pin not yet inserted.
Friday, May 24, 2013
Advantages of Fiberglassing the Sonotube
I had mentioned that I was going to put the polyester resin on the edges of all the holes, big and small, that I made in the Sonotube, to reinforce the edges and prevent fraying. This worked like a charm. I discovered that it also made the holes just a little small -- which meant redrilling the holes for the small ones. I actually found the bolts that hold the mirror cell in place were threading into the holes! I would not count on threads in this stuff holding any real load, but at least the bolts weren't flopping about in there!
The eyepiece focuser hole, however, required some filing -- and unlike Sonotube, which doesn't file well, the composite material I produced actually filed very nicely indeed -- better than the paint, which chipped a bit. A very nice result.
The eyepiece focuser hole, however, required some filing -- and unlike Sonotube, which doesn't file well, the composite material I produced actually filed very nicely indeed -- better than the paint, which chipped a bit. A very nice result.
Thursday, May 23, 2013
Big Bertha, 3.0
I still need to do a bit of adjusting and collimation, and some touch-up paint, especially on the straps. I was hoping to get to that tonight, because we have a clear sky, but I had orders to fill, so....
But everything is back in the tube -- and it appears that it is slightly heavier than it was before. Oh well. At least it should be rigid.
The following two pictures show what happens when you use a flash, and don't use a flash. From the first picture, you would never know the inside of the tube is black.
But everything is back in the tube -- and it appears that it is slightly heavier than it was before. Oh well. At least it should be rigid.
The following two pictures show what happens when you use a flash, and don't use a flash. From the first picture, you would never know the inside of the tube is black.
Individual End Mill Prices...
I was looking online to order up a replacement for the 1/8" end mill that I broke yesterday, and I am startled to see how expensive individual end mills are. Just the 1/8" end mill at Grainger costs almost as much as this entire collection that I bought several years ago from Little Machine Shop. Admittedly, the end mill from Grainger is U.S. made, and might well last forever with the amount of milling I do.
Wednesday, May 22, 2013
Lack of Blogging...
My wife had a shoulder repair operation yesterday at St. Luke's, and pretty much the whole day was spent with getting her checked in, surgery, post-op. I probably should have brought my laptop, but I wasn't expecting the entire day to get consumed. I will say that I am always very impressed with the medical and support staff at St. Luke's (and every other hospital here in the Boise area). Friendly; courteous; concerned.
She is doing okay, but considering that they went in and removed bone spurs inside her shoulder, she is in a bit of pain. I stayed home yesterday and today to take care of her; I just can't imagine what single people do in these situations.
The evenings have been lost in the great telescope rebuild. I discovered that all the work I put into trimming the C-channel pieces down was a mistake; there was not enough clearance for attaching the steel straps without a lot more precision in cutting than I could easily do with a bandsaw, so I started over, and it was much faster. When drilling the attachment holes in the steel straps, the straps are thin enough that they briefly went red-hot as I drilled them! (More oil next time.)
The new versions were faster to make, in spite of breaking the 1/8" end mill that I was using to cut the slot. I finished with a 1/4" end mill, which looks less elegant for an .030" thick piece of steel strap, but it isn't like you can find a 1/8" end mill in Horseshoe Bend.
The upper picture shows the static end of the strap; the lower picture shows the screw that tightens it down. Unfortunately, the thumb screws I bought at Grainger just weren't long enough. A 1" long screw thread sounds good enough, but once the captive nuts were on it, that was not enough travel to be useful, so it now has a conventional hex head bolt. I may replace those when I can order a thumb screw with a longer thread. They work well -- although it takes a while to crank them down enough. Of course, that also makes it less likely that I will overcompress the tube with the straps, so I guess that's a positive.
The mirror cell has turned out to be a "I was too clever for my good" moment (as have several in the project). It turns out that having the mounting brackets separate from the bottom plate was a great idea -- except that the bolts holding the brackets to the bottom plate can't get past the mirror once the brackets are mounted inside the tube. So I guess I will do what I was trying to avoid -- tap the mounting brackets so that I can screw the threads in from the outside of the tube. This is a blind operation, but at least I can see the brackets from the rear. Some other mirror cells have you trying to find the threaded holes in a circular casting where there are no real clues as to location. The slots in the mounting brackets were for 1/4"-20 bolts, so it is easy enough to tap these for 5/16"-18 bolts -- which, fortunately, I have some in black oxide finish that I can use for this.
But that will be tomorrow night, or maybe the night after. I actually have ScopeRoller orders rolling in, and I need to get some of these filled.
She is doing okay, but considering that they went in and removed bone spurs inside her shoulder, she is in a bit of pain. I stayed home yesterday and today to take care of her; I just can't imagine what single people do in these situations.
The evenings have been lost in the great telescope rebuild. I discovered that all the work I put into trimming the C-channel pieces down was a mistake; there was not enough clearance for attaching the steel straps without a lot more precision in cutting than I could easily do with a bandsaw, so I started over, and it was much faster. When drilling the attachment holes in the steel straps, the straps are thin enough that they briefly went red-hot as I drilled them! (More oil next time.)
The new versions were faster to make, in spite of breaking the 1/8" end mill that I was using to cut the slot. I finished with a 1/4" end mill, which looks less elegant for an .030" thick piece of steel strap, but it isn't like you can find a 1/8" end mill in Horseshoe Bend.
The upper picture shows the static end of the strap; the lower picture shows the screw that tightens it down. Unfortunately, the thumb screws I bought at Grainger just weren't long enough. A 1" long screw thread sounds good enough, but once the captive nuts were on it, that was not enough travel to be useful, so it now has a conventional hex head bolt. I may replace those when I can order a thumb screw with a longer thread. They work well -- although it takes a while to crank them down enough. Of course, that also makes it less likely that I will overcompress the tube with the straps, so I guess that's a positive.
The mirror cell has turned out to be a "I was too clever for my good" moment (as have several in the project). It turns out that having the mounting brackets separate from the bottom plate was a great idea -- except that the bolts holding the brackets to the bottom plate can't get past the mirror once the brackets are mounted inside the tube. So I guess I will do what I was trying to avoid -- tap the mounting brackets so that I can screw the threads in from the outside of the tube. This is a blind operation, but at least I can see the brackets from the rear. Some other mirror cells have you trying to find the threaded holes in a circular casting where there are no real clues as to location. The slots in the mounting brackets were for 1/4"-20 bolts, so it is easy enough to tap these for 5/16"-18 bolts -- which, fortunately, I have some in black oxide finish that I can use for this.
But that will be tomorrow night, or maybe the night after. I actually have ScopeRoller orders rolling in, and I need to get some of these filled.
Tuesday, May 21, 2013
I Have A Philosophical Problem With Seat Belt Laws
But here's a warning that if you really prefer bouncing around the inside of your car in the event of an accident, be prepared for increased enforcement of the law. From May 20, 2013 KIVI channel 6:
The Caldwell Police Department and other Idaho law enforcement agencies will be stepping up seatbelt enforcement starting May 20th through June 2nd.
Over 70 Idaho law enforcement agencies will begin dedicating extra hours and patrols to educate and enforce the state’s safety restraint law during a 14-day period including Memorial Day.
Monday, May 20, 2013
No Wonder Ken Dauzat's Rings Didn't Respond...
Ken's Rings is now closed as of April 15, 2012 and is no longer taking orders.Unfortunate. He made a nice product.
Sunday, May 19, 2013
How To Attach The Tube (Cont.)
Here's a diagram of a simple to build tensioner for nylon webbing, stainless steel strap, or even belts.
The fixed side attachment doesn't move; I tap this side of the C-channel for a 1/4"-20 bolt. Depending on the strapping material, I may need a large washer to distribute load across more surface area. For nylon webbing, I would triple the layers for this attachment point.
The adjustment side attachment consists of a 1/4"-20 tapped hole and a bolt (probably a thumbscrew) with two nuts locked in position at the end of the bolt. The way that I have found works most easily for this is to drill through a hex head nut into the bolt, tap the hole for 6-32 threads, and use a 6-32 set screw to lock bolt and nut together. The strap goes through the slot in the side of the C-channel, and is held by two washers inside the captive nuts. The strap can rotate between the washers, so it isn't a tight fit there. You have to the get the length of the strapping pretty precisely correct for a snug fit, and then you turn the thumbscrew to clamp everything down. This also gives some room for strap stretch over time. If you reach the limits of the bolt, you can redrill the holes on the fixed side attachment, but I am considering this a short-term solution to the problem.
Limiting yourself to a thumbscrew not only simplifies tool-free adjustment, but also reduces the change of putting so much force on the tube that it damages it.
UPDATE: Good news: I asked my pastor this morning where I would steel strapping material on a weekend. He just happened to have a 50 foot roll of .030" thick, 1 inch wide steel strapping material. I started work on the device above to use some of this. I discovered that the vertical mill definitely works better with the longer screw holding everything together; I also discovered that once again, the single most important factor in milling is getting the workpiece really well clamped in position. Anything that lets it jostle in the vise is a problem. I also discovered that the 1/4"-20 thumbscrews I had...were something metric, not 1/4"-20. I guess I will buy two of those tomorrow.
The adjustment side attachment consists of a 1/4"-20 tapped hole and a bolt (probably a thumbscrew) with two nuts locked in position at the end of the bolt. The way that I have found works most easily for this is to drill through a hex head nut into the bolt, tap the hole for 6-32 threads, and use a 6-32 set screw to lock bolt and nut together. The strap goes through the slot in the side of the C-channel, and is held by two washers inside the captive nuts. The strap can rotate between the washers, so it isn't a tight fit there. You have to the get the length of the strapping pretty precisely correct for a snug fit, and then you turn the thumbscrew to clamp everything down. This also gives some room for strap stretch over time. If you reach the limits of the bolt, you can redrill the holes on the fixed side attachment, but I am considering this a short-term solution to the problem.
Limiting yourself to a thumbscrew not only simplifies tool-free adjustment, but also reduces the change of putting so much force on the tube that it damages it.
UPDATE: Good news: I asked my pastor this morning where I would steel strapping material on a weekend. He just happened to have a 50 foot roll of .030" thick, 1 inch wide steel strapping material. I started work on the device above to use some of this. I discovered that the vertical mill definitely works better with the longer screw holding everything together; I also discovered that once again, the single most important factor in milling is getting the workpiece really well clamped in position. Anything that lets it jostle in the vise is a problem. I also discovered that the 1/4"-20 thumbscrews I had...were something metric, not 1/4"-20. I guess I will buy two of those tomorrow.
Saturday, May 18, 2013
Telescope Project Marches On
There was some pooling of paint at the bottom of the tube when I painted the first coat with the tube on end, so for the second coat, I went back to the suspension approach that I used when applying the fiberglass resin.
The method of holding the tube in the air at that stage wasn't very good, because sometimes the tube started rocking, and then the aluminum tube holding it would go flying off the chairs. So I came up with a way to prevent the aluminum tube from getting too far afield:
Unlike the first coat, which did not stick spectacularly well to the fiberglassed Sonotube, the second coat stuck quite well. It still wasn't very even, so I sanded it after the second coat as well, which again evened out the surfaces a bit (although taking off a bit of paint in the process). There were still some pretty big depressions caused by air pockets in the area where I had used fiberglass cloth, so I mixed a bit more resin, and tried to fill in the holes.
I still won't call the result, after the third coat, "beautiful," but I think it will do, at least until I can talk myself into believing that the big money for a carbon fiber composite tube that weighs 13 pounds less makes sense:
I mentioned a few days back that I was going to epoxy some steel rod on either side of the center line of the tube where it attaches to the dovetail plate to prevent rocking, which would eventually damage the tube. Then, yesterday, I mentioned that it would be better to have tube rings that lock onto the outside of the tube and screw directly to the dovetail plate.
I am still waiting on a price quote on those rings, and I started thinking. I noticed that at the edges of the dovetail plate there are a bunch of 1/4" holes. Hmmm. Could I mount supports in those holes to prevent rocking? My first thought was to machine some 1/4" (or perhaps slightly longer) plugs that would provide the support? I could even just use 1/4" hex head bolts; the heads would provide just the right elevation to prevent rocking (although at the risk of marring the surface of the tube).
But the more I thought about it (and was glad that enamel dries so slowly), it occurred to me there was an even better solution that gives me the flexibility to rotate the tube, not drill permanent mounting holes, solve the rocking problem, and involves minimal use of materials.
1. I take the C-channel which was used to mount the old scope to the dovetail plate, and cut off two 2" sections (preferably the ones that have 1/4" through holes already).
2. Shorten the legs of the C-channel down to 1/16" inch (since I no longer need long legs for stiffness of the section). Now I have a round tube to flat base adapter.
3. Drill and tap 1/4"-20 holes in each side of the two sections.
4. Buy four leather belts at the thrift store. (I need about 60 inches total length, and preferably 1 3/4" wide belts.)
5. Use a 1/4"-20 bolt and a washer to hold one end of each belt to each side of the C-channel.
6. Use the belt buckles to secure the tube to the C-channel sections. (This means that I will need to get roughly similar belt buckles when picking out belts.)
7. Perhaps drill some holes in these belts to get them in a position where I can tighten down the tube without crushing it marring the surface much.
Now I have the 60 pound or so telescope load held by two belts, which is, I think, sufficient to prevent anything from moving or working loose.
An alternative would be to look for some flexible 2" wide stainless steel straps, and apply felt to the inside to protect the tube. But then I have to figure out a way to secure the steel straps so that they can be loosened without having falling completely off. The Cave Optical mount that I had long ago used this approach, with a screw brazed into one end of the strap, so that you could loosen the straps at one end, rotate the tube, then retighten. If I could find something like this (with roughly 60" long straps) that had some way to tighten and loosen tension, this would be preferable. But the belts might be a quick way to get the telescope operational, and then worry about rings at a later time.
UPDATE: Or Velcro? This claims that the closure shear strength is 11.0 pounds per square inch. I can buy a 15 foot by 2" wide piece of Velcro at Home Depot for $28.97, what they call industrial strength Velcro. If I had ten inches of overlap of hook and loop (and if I understand what they are claiming for the closure shear strength), that would be 220 pounds per strap. That seems more than enough. It would not be as elegant as aluminum rings, but it would be light, I could pick up the Velcro tomorrow, and put the telescope together tomorrow afternoon.
UPDATE 2: Or perhaps use nylon webbing with buckles. The webbing has a tensile strength of 5500 pounds (probably more than the buckles that come with it or where I would attach it).
UPDATE 3: The more I think about it, nylon webbing and Velcro are likely to stretch under load, and that sounds a bit dangerous. If I can find some steel straps at Home Depot, I could put a bolt through the adjustment end, and use a wing nut to tension it.
The method of holding the tube in the air at that stage wasn't very good, because sometimes the tube started rocking, and then the aluminum tube holding it would go flying off the chairs. So I came up with a way to prevent the aluminum tube from getting too far afield:
Unlike the first coat, which did not stick spectacularly well to the fiberglassed Sonotube, the second coat stuck quite well. It still wasn't very even, so I sanded it after the second coat as well, which again evened out the surfaces a bit (although taking off a bit of paint in the process). There were still some pretty big depressions caused by air pockets in the area where I had used fiberglass cloth, so I mixed a bit more resin, and tried to fill in the holes.
I still won't call the result, after the third coat, "beautiful," but I think it will do, at least until I can talk myself into believing that the big money for a carbon fiber composite tube that weighs 13 pounds less makes sense:
I mentioned a few days back that I was going to epoxy some steel rod on either side of the center line of the tube where it attaches to the dovetail plate to prevent rocking, which would eventually damage the tube. Then, yesterday, I mentioned that it would be better to have tube rings that lock onto the outside of the tube and screw directly to the dovetail plate.
I am still waiting on a price quote on those rings, and I started thinking. I noticed that at the edges of the dovetail plate there are a bunch of 1/4" holes. Hmmm. Could I mount supports in those holes to prevent rocking? My first thought was to machine some 1/4" (or perhaps slightly longer) plugs that would provide the support? I could even just use 1/4" hex head bolts; the heads would provide just the right elevation to prevent rocking (although at the risk of marring the surface of the tube).
But the more I thought about it (and was glad that enamel dries so slowly), it occurred to me there was an even better solution that gives me the flexibility to rotate the tube, not drill permanent mounting holes, solve the rocking problem, and involves minimal use of materials.
1. I take the C-channel which was used to mount the old scope to the dovetail plate, and cut off two 2" sections (preferably the ones that have 1/4" through holes already).
2. Shorten the legs of the C-channel down to 1/16" inch (since I no longer need long legs for stiffness of the section). Now I have a round tube to flat base adapter.
3. Drill and tap 1/4"-20 holes in each side of the two sections.
4. Buy four leather belts at the thrift store. (I need about 60 inches total length, and preferably 1 3/4" wide belts.)
5. Use a 1/4"-20 bolt and a washer to hold one end of each belt to each side of the C-channel.
6. Use the belt buckles to secure the tube to the C-channel sections. (This means that I will need to get roughly similar belt buckles when picking out belts.)
7. Perhaps drill some holes in these belts to get them in a position where I can tighten down the tube without crushing it marring the surface much.
Now I have the 60 pound or so telescope load held by two belts, which is, I think, sufficient to prevent anything from moving or working loose.
An alternative would be to look for some flexible 2" wide stainless steel straps, and apply felt to the inside to protect the tube. But then I have to figure out a way to secure the steel straps so that they can be loosened without having falling completely off. The Cave Optical mount that I had long ago used this approach, with a screw brazed into one end of the strap, so that you could loosen the straps at one end, rotate the tube, then retighten. If I could find something like this (with roughly 60" long straps) that had some way to tighten and loosen tension, this would be preferable. But the belts might be a quick way to get the telescope operational, and then worry about rings at a later time.
UPDATE: Or Velcro? This claims that the closure shear strength is 11.0 pounds per square inch. I can buy a 15 foot by 2" wide piece of Velcro at Home Depot for $28.97, what they call industrial strength Velcro. If I had ten inches of overlap of hook and loop (and if I understand what they are claiming for the closure shear strength), that would be 220 pounds per strap. That seems more than enough. It would not be as elegant as aluminum rings, but it would be light, I could pick up the Velcro tomorrow, and put the telescope together tomorrow afternoon.
UPDATE 2: Or perhaps use nylon webbing with buckles. The webbing has a tensile strength of 5500 pounds (probably more than the buckles that come with it or where I would attach it).
UPDATE 3: The more I think about it, nylon webbing and Velcro are likely to stretch under load, and that sounds a bit dangerous. If I can find some steel straps at Home Depot, I could put a bolt through the adjustment end, and use a wing nut to tension it.
Friday, May 17, 2013
Roll Your Own (Rings, That Is)
The quick but inflexible solution for attaching a telescope to the dovetail plate is to drill holes in the tube and turn bolts through the tube into the threaded holes on the dovetail plate. The more elegant solution (because it lets you rotate the tube into more useful viewing positions, with a little bit of effort) is to use rings like these. I have bought Ken Dauzat's rings before for another telescope, and I was very pleased with them. I have asked for a quote for the monster tube, and I am shuddering a little at the likely price.
But I saw this device for rolling your own rings from either tubing or flat. It's $169, but that doesn't seem like a particularly high price if it comes out the same price as buying one pair of rings. Does anyone have experience using such a tool?
But I saw this device for rolling your own rings from either tubing or flat. It's $169, but that doesn't seem like a particularly high price if it comes out the same price as buying one pair of rings. Does anyone have experience using such a tool?
Thursday, May 16, 2013
To Parody The Dojo Owner in Napoleon Dynamite
"I developed this while spending two hours in the hexagon!"
It actually came out rather well. I started with the 20.125" diameter aluminum ring, used a protractor to measure 60o angles, drew lines, then cut them using both the table saw and the bandsaw. The first try with the bandsaw was disappointing -- it produced a very ragged edge, until the blade broke. Then I switched to the table saw, which produced a straighter but very rough edge -- and then I went back to the bandsaw, using a wider blade, which produced a much straighter line. Then I used the belt sander to even out the roughness and get straighter edges. The points were still out at the old diameter, but I trimmed those to the right diameter with the bandsaw and sanded them smooth and straight.
The holes where the brackets attached were in the wrong place, so I just moved the brackets from positions 1, 3, and 5 to 2, 4, 6 (for those who immediately see benzene molecules when you see a hexagon). I also used my stamping dies to mark 1 on the corresponding bracket and hexagon locations.
I rolled the interior with flat black paint Wednesday night, and the exterior with the first coat of white gloss paint this evening.
It doesn't look good yet. After it dries tomorrow, I will sand it with some 400# paper, and apply a second coat. Depending on how it comes out, I may sand again and apply a third coat, but at that point, if it isn't beautiful, it doesn't matter. It will be dark most of the time.
All the holes (except for mounting) are drilled; once the final coat dries, it is ready for assembly. Once assembled, I will determine the balance point, drill four holes for attaching it to the dovetail plate, epoxy in place two pieces of steel rod to prevent rocking on the saddle, and be ready to put it on the mount.
I may even be able to reuse the black flocked material from the existing upper cage for this. I have gone out of my way to buy as many black oxide bolts and screws where something will be exposed on the inside of the tube. Even then, I flat black them; the black oxide just means that if paint does scrape off, it is still pretty much black.
It actually came out rather well. I started with the 20.125" diameter aluminum ring, used a protractor to measure 60o angles, drew lines, then cut them using both the table saw and the bandsaw. The first try with the bandsaw was disappointing -- it produced a very ragged edge, until the blade broke. Then I switched to the table saw, which produced a straighter but very rough edge -- and then I went back to the bandsaw, using a wider blade, which produced a much straighter line. Then I used the belt sander to even out the roughness and get straighter edges. The points were still out at the old diameter, but I trimmed those to the right diameter with the bandsaw and sanded them smooth and straight.
The holes where the brackets attached were in the wrong place, so I just moved the brackets from positions 1, 3, and 5 to 2, 4, 6 (for those who immediately see benzene molecules when you see a hexagon). I also used my stamping dies to mark 1 on the corresponding bracket and hexagon locations.
I rolled the interior with flat black paint Wednesday night, and the exterior with the first coat of white gloss paint this evening.
It doesn't look good yet. After it dries tomorrow, I will sand it with some 400# paper, and apply a second coat. Depending on how it comes out, I may sand again and apply a third coat, but at that point, if it isn't beautiful, it doesn't matter. It will be dark most of the time.
All the holes (except for mounting) are drilled; once the final coat dries, it is ready for assembly. Once assembled, I will determine the balance point, drill four holes for attaching it to the dovetail plate, epoxy in place two pieces of steel rod to prevent rocking on the saddle, and be ready to put it on the mount.
I may even be able to reuse the black flocked material from the existing upper cage for this. I have gone out of my way to buy as many black oxide bolts and screws where something will be exposed on the inside of the tube. Even then, I flat black them; the black oxide just means that if paint does scrape off, it is still pretty much black.
Terrorism Charges Filed in Boise
From May 16, 2013 Boise channel 6:
Fazliddin Kurbanov, 30, was arrested Thursday morning in Boise after a federal terrorism investigation.And in case you notice the byline on the report--yup, that's my son.
Charges were filed Thursday afternoon in Boise and Salt Lake City against Kurbanov who was a United States citizen living in Boise currently.
The charges filed came after a federal grand jury in Boise returned a three-count indictment charging Kurbanov with one count of conspiracy to provide material support to a designated foreign terrorist organization. In addition, one count of conspiracy to provide material support to terrorists and one count of possessing a destructive device.
There Are Descriptions For Which No Comment Is Printable
I know not to trust everything that appears in Wikipedia, but a reader brought this to my attention, and it is rather like a contest to identify the number of despicable, wrong, horrible, evil things that can be done to a person, describing Brenda Spencer, who was one of the first mass murderers at a school in the modern era:
Spencer excelled in photography, winning first prize in a Humane Society competition.[6] After her parents had separated, she lived with her father in virtual poverty; they slept on a single mattress on the living room floor. Police later found half empty alcohol bottles throughout the house. In 2001 she accused her father, Wallace Spencer, of having drunkenly subjected her to beatings and sexual abuse.[7] He said the allegations were not true.[8] Spencer is said to have self-identified herself as "having been gay from birth."[9]
In early 1978, staff at a facility for problem pupils which Spencer had been referred to due to truancy, informed her parents that she was suicidal. In the summer Spencer was arrested for shooting out the windows of the Cleveland Elementary with a BB gun, and burglary. In December a psychiatric evaluation arranged by her probation officer recommended Spencer be admitted to a mental hospital due to her depressed state, but her father refused to give permission. For Christmas 1978 he gave her a Ruger 10/22 semi-automatic .22 caliber rifle with a telescopic sight and 500 rounds of ammunition.[8][10] Spencer later said: "I asked for a radio and he bought me a gun." To the question as to why he might have done that, she answered: "I felt like he wanted me to kill myself."
Not All Cultures Are Equal
Someone mailed me a gruesome picture purportedly of a Syrian pilot's head being grilled by one of the resistance fighters. Fake atrocities are a fundamental part of warfare, but I see this May 14, 2013 Telegraph article refers to a variety of acts of cannibalism by the Syrian resistance, and the leaders of that resistance defending such acts:
A Syrian rebel militia leader filmed cutting the heart and organs out of a regime soldier's corpse and putting it in his mouth has defended his actions as legitimate vengeance.
The actions of Khaled al-Hamad, known by the nom de guerre Abu Sakkar, handed an instant propaganda victory to the Syrian govenrment, which accused the West of ignoring rebel atrocities.
The video purported to show the leader of a breakaway rebel faction cutting the lungs out of a soldier’s corpse before apparently eating a small piece of the organ...As much as I find the Assad government worthy of destruction, I am reminded that in much of the Middle East, this is not a conflict between barbarism and civilization, and between different branches of barbarism. As much as it hurts to see innocent bystanders suffer from such wars, it is rather like what happened when Iraq and Iran went to war against each other in the early 1980s: both were enemies of not only the U.S., but of all civilized notions of proper behavior. You do not want to applaud, but it is hard to justify spilling even one ounce of American blood or spending one penny of tax dollars to "help" either side. The more time that various forms of barbarism kill each other, the less time they have to hurt us.
In Damascus, Ali Haider, the minister for reconciliation, said this was only one of many atrocities carried out by the regime’s enemies. “If the international media has just discovered this now, then they are coming to it very late. These type of atrocities have been happening in Syria since the beginning of the crisis,” he said. “The international community just didn’t want to admit it.”
Mr Haider added: “We have documented hundreds of acts that are equally as horrific as the one documented in this video. We have seen one of our pilot’s heads cut off and cooked on a grill. We have seen rebels toasting their success by drinking the blood of their victims.”
Wednesday, May 15, 2013
Just More Islamophobia, I'm Sure
From May 14, 2013 CBS Boston:
BELCHERTOWN (CBS) – Shortly after midnight Tuesday, seven people were caught trespassing at the Quabbin Reservoir.Note the time: "shortly after midnight." Isn't that when college students usually make unauthorized visits to public water supplies?
State Police say the five men and two women are from Pakistan, Saudi Arabia, and Singapore, and “cited their education and career interests” for being in the area. The men told police they were chemical engineers and recent college graduates.
The Quabbin, in Belchertown, is one of the country’s largest man-made public water supplies. Boston’s drinking water comes from the Quabbin and the Wachusett Reservoirs.
So Busy Being Sick...
I didn't notice this new PJMedia article by me:
Sen. Chris Murphy (D-CT): Credentialed, Not Educated
Robert Sherrill's Saturday Night Special
My friend Nicholas Johnson writes about a book that is now largely forgotten: Robert Sherill's Saturday Night Special (1973);
I just dusted off an entertaining screed from 1973 written by former Washington Post reporter Robert Sherrill. Although you can gather it from his credential as a Posty, the prodigious title of the book better signals his views on the “so-called” right to keep and bear arms. To wit: The Saturday Night Special: And Other Guns With Which Americans Won The West, Protected Bootleg Franchises, Slew Wildlife, Robbed Countless Banks, Shot Husbands Purposely And By Mistake And Killed Presidents – Together With The Debate Over Continuing Same. Absent from Sherrill’s list is any suggestion of the utility of firearms for legitimate self-defense.I agree with Professor Johnson's take on Sherrill's book: it is profoundly hostile to gun ownership and gun culture, but honest enough to recognize that gun control is fundamentally impossible in a free society. Sherrill is also honest enough to admit that the Gun Control Act of 1968 wasn't passed to disarm criminals, but to disarm poor black people -- and as a result, managed to accomplish neither.
The book is a vivid reflection of the times, urging confidently the states’ rights view of the Second Amendment that today not a single member of the United States Supreme Court attempts to prop up. But enough nostalgia.
Concentrated Misery
As bad as Monday night was, at least all the vomiting was concentrated in a very short period of time: from about 8:00 PM to about 5:30 AM Tuesday morning. I have vomited that much before, but over a period of several days. Now I am just sore, partly from strain on muscles causing by the vomiting, and partly because I am still fighting a slight fever. I am not going to work until I am pretty confident that I am not contagious. I wouldn't even meet with President Obama, this stuff is so bad.
Monday, May 13, 2013
Hexagon Time
The machine shop that said that they could turn it down to 19.875" diameter? I showed up, they looked at it, and said, "We can't turn something that big." And then, "We have a five week backlog." Wow. I could have been trimming this down to a hexagon over the weekend instead of waiting for them.
Sunday, May 12, 2013
More Weight Reduction
It turns out that I have a total of six bolts holding the bottom plate of the mirror cell to the attachment brackets -- and the bolt, lock washer, and nut combo weighs 0.4 ounces. Strictly speaking, six bolts are not required. Each one has the tensile strength to easily hold this, and I am not worried about any of them working loose. In addition, I can also remove the extra material on the attachment bracket where the second hole was located, perhaps saving two ounces total.
UPDATE: When I was looking for an alternative to turning down the bottom plate of the mirror cell, I did a little thinking about alternative strategies. One is to cut the circle to a hexagon, which can be done by drawing a circle of the required diameter, measuring 60 degree angles, then drawing lines connecting the points, and running these through a bandsaw. In addition, the area of a hexagon that fills radius r is 3r2, instead of pi * r2, so slightly less weight. A triangle is another possible strategy, where the area of radius r is 2r2, so even more weight reduction.
UPDATE: When I was looking for an alternative to turning down the bottom plate of the mirror cell, I did a little thinking about alternative strategies. One is to cut the circle to a hexagon, which can be done by drawing a circle of the required diameter, measuring 60 degree angles, then drawing lines connecting the points, and running these through a bandsaw. In addition, the area of a hexagon that fills radius r is 3r2, instead of pi * r2, so slightly less weight. A triangle is another possible strategy, where the area of radius r is 2r2, so even more weight reduction.
Saturday, May 11, 2013
Those Tiffen Camera Filters That I Bought...
Last month I bought some Tiffen UV filters to protect the lens on my Pentax K10D; I was pleased to see when I opened the package: "Made in USA." It is possible to make stuff, good stuff, in the U.S.
Why That Vertical Mill Is Troublesome?
I noticed at one point a screw fell into the working area; I found where it had fallen out -- and I don't believe that this is the first time that this has happened. It is a 10-32 x 3/8" Allen head screw that is one of two screws that holds the motor and bracket to the assembly that carries the spindle. It really does not lock down tightly, no matter how hard I try, although it works fine if the bracket that it holds in place is not there. It is the same length as the other screw which does lock down adequately -- but that other screw is in a very slightly narrow part of the bracket. I am beginning to suspect that a 1/2" long screw (perhaps with a washer, if needed) would provide a more rigid connection. Perhaps the reason that milling operations have been problematic is that the increased vibration causes more motion on this bracket. This might also explain why it often starts to slow down -- perhaps because the belt is moving back and forth.
Embarrassing
It turns out that I did not measure the diameter of the base of the mirror cell quite carefully enough. It is actually 20.25"; the inner diameter of the Sonotube is just barely under 20" (probably because of the resin). This is a bit big for me turn myself, so I have to find a machine shop Monday that can turn this down without charging a ridiculous amount of money. It doesn't need to be terribly precise: 19.875" += .05" sufficient.
I did take some more weight off the finderscope base; it is now down from its original 5.2 ozs. to 1.2 ozs. I don't know why milling produces such bad results; oil helps, but not enough. The flycutter does a nice job, but an end mill just makes it catch and stop pretty often. I sometimes wonder if this vertical mill, which I bought used, has some problem.
UPDATE: Good news: a machine shop in Eagle quoted me $20 to turn it down to size. That's a bargain.
I did take some more weight off the finderscope base; it is now down from its original 5.2 ozs. to 1.2 ozs. I don't know why milling produces such bad results; oil helps, but not enough. The flycutter does a nice job, but an end mill just makes it catch and stop pretty often. I sometimes wonder if this vertical mill, which I bought used, has some problem.
UPDATE: Good news: a machine shop in Eagle quoted me $20 to turn it down to size. That's a bargain.
More "What Was I Thinking?" Discoveries
Very typically, telescope mirror cells have little clips on the side that hold the mirror in place. (Yes, there's some felt between the clip and the surface of the mirror.) Here's a fairly gross example:
In my case, I discovered that the clips extended far below the plate on which the mirror sits, and actually were scratching the flat black paint on the first plate. This had several bad effects:
1. Damaging the flat black paint, increasing ambient light (very slightly).
2. Adding unneeded weight to the cell.
3. Increasing the actual distance from the front surface of the mirror to the back of the cell (which is an issue, as I previously have mentioned).
4. Reduced the amount of adjustment that I can actually make to the mirror. This has not been a problem, and in practice, the length of the springs between the two plates is considerably more adjustment room than I should need, unless I put the mirror cell into the tube in a way that wasn't square.
So I took the clips off, trimmed off the excess length with the bandsaw, then milled them precisely to length (even though they don't need to be) on the vertical mill, and repainted them flat black. I doubt that I even saved an ounce, but every reduction in weight is a win, especially at the mirror end of the tube, where any extra weight means more bending of the tube, and the mirror end is where most of the component weight is located.
There are a lot of places where I could probably reduce weight a bit more; the only question is whether it makes sense to do so. When I went to Home Depot earlier to buy 5/16"-18 bolts, nuts, and washers, I looked for aluminum versions -- which they did not have. If I could find them in stock somewhere (especially black), it would make sense. It probably doesn't make sense to pay $20 shipping to have a mail order operation do so, since this can't even a fraction of an ounce that I would save.
In my case, I discovered that the clips extended far below the plate on which the mirror sits, and actually were scratching the flat black paint on the first plate. This had several bad effects:
1. Damaging the flat black paint, increasing ambient light (very slightly).
2. Adding unneeded weight to the cell.
3. Increasing the actual distance from the front surface of the mirror to the back of the cell (which is an issue, as I previously have mentioned).
4. Reduced the amount of adjustment that I can actually make to the mirror. This has not been a problem, and in practice, the length of the springs between the two plates is considerably more adjustment room than I should need, unless I put the mirror cell into the tube in a way that wasn't square.
So I took the clips off, trimmed off the excess length with the bandsaw, then milled them precisely to length (even though they don't need to be) on the vertical mill, and repainted them flat black. I doubt that I even saved an ounce, but every reduction in weight is a win, especially at the mirror end of the tube, where any extra weight means more bending of the tube, and the mirror end is where most of the component weight is located.
There are a lot of places where I could probably reduce weight a bit more; the only question is whether it makes sense to do so. When I went to Home Depot earlier to buy 5/16"-18 bolts, nuts, and washers, I looked for aluminum versions -- which they did not have. If I could find them in stock somewhere (especially black), it would make sense. It probably doesn't make sense to pay $20 shipping to have a mail order operation do so, since this can't even a fraction of an ounce that I would save.
Friday, May 10, 2013
Next Step on the Telescope
I assume that some of you are interested in this project. At least I'm interested in telling you about it. Not to worry, I'll get it done and start being a grumpy political curmudgeon again.
There were a couple of air bubbles that left serious depressions at the lower part of the Sonotube where I did the fiberglass cloth, and since I want this reasonably pretty -- and extra stiffness especially matters in this area where the mirror cell will be mounted -- I dripped some more resin in these holes, which are fortunately all within about 15 degrees of each other -- and left it to dry in the sunlight.
The next step is to reverse the mounting assemblies on the mirror cell so that I can insert the bolts that hold the cell in the tube from the rear of the mirror, not the front. While disassembling these from the big plate that holds the springs and screws for the smaller plate that holds the mirror, I had one of those, "I did this?" moments. I don't think I had the vertical mill yet, which explains why these parts are so crudely made. But I must have obtained my first complete set of taps, because I clearly overapplied the, "I can put threads anywhere I want!" idea.
Threads are good in a deep object where it is impractical to run a through hole (one that bolt just slides through) all the through the object. But threads in a thin plate, with a nut holding the bolt on the other side of that threaded thin plate, not so good, especially if you did not have a way to make absolutely perpendicular threads. Then you just have bolts fighting threads in the object when they hit the threads in the nut on the far side. So I turned all the threads in the mounting hardware into through holes. Much better.
The other mildly surprising moment was that I remembered having bought aluminum 1/4"-20 screws for some project, long ago, but I could not remember for what I used them. Then I discovered them. This mirror cell is almost entirely aluminum, including the screws and nuts that hold the attachment hardware to the big bottom plate. Why? Because I was trying to make this really light. Brilliant. The downside is that aluminum isn't anywhere near as tough as steel, and the threading orgy above meant that some of these screws and nuts were slightly damaged; one had to be Vise-Gripped out of the aluminum to which it was holding on for dear life, and the head of this screw is behind redemption. However, I was able to tap and die four of the six sets by turning a steel bolt through the nuts, and a steel wingnut on the bolts. There are two steel 1/4"-20 hex head screws now part of the process, but I don't expect the weight difference to be serious!
I am painting all these fasteners black (again). I really wish that I had a Boise source for black anodized bolts and screws, but I don't touch these very often, so I don't see it as a big problem to use flat black paint instead. I am considering buying some of this black flocking material for the upper part of the tube interior, in the area near the eyepiece and diagonal. (And read here to see why you don't really need to do the interior tube.)
UPDATE: As I do the arithmetic on placement of various parts, I am discovering that there really isn't room to put the mounting brackets for the mirror cell behind the main plate. When I did this original design, I did not waste a single inch of length. So how to solve this problem? This has been a long gripe of mine about mirror cells -- many of them assume that you will find exactly the right spot on the outside of the tube to drill the hole for a bolt that screws into a blind hole on the mirror cell base. This is not easy to do.
But I have a clever solution. What I am going to do is take the L-brackets that hold the mirror cell in the tube, tap the holes that I just made through holes into 5/16"-18 threads so that the bolts sticking down from these brackets will be captive (actually locked in place once screwed in). Then I will install the L-brackets in the tube and they will be permanently located there; to remove the mirror cell for cleaning is just a matter of unscrewing the nuts and lock washers that will hold the base plate of the mirror cell to the bottom of the L-brackets. That also means very deftly enlarging the holes in the base plate (since it is a big hassle to remove the mirror from the cell) to 5/16" size from their current 1/4"-20 thread.
There were a couple of air bubbles that left serious depressions at the lower part of the Sonotube where I did the fiberglass cloth, and since I want this reasonably pretty -- and extra stiffness especially matters in this area where the mirror cell will be mounted -- I dripped some more resin in these holes, which are fortunately all within about 15 degrees of each other -- and left it to dry in the sunlight.
The next step is to reverse the mounting assemblies on the mirror cell so that I can insert the bolts that hold the cell in the tube from the rear of the mirror, not the front. While disassembling these from the big plate that holds the springs and screws for the smaller plate that holds the mirror, I had one of those, "I did this?" moments. I don't think I had the vertical mill yet, which explains why these parts are so crudely made. But I must have obtained my first complete set of taps, because I clearly overapplied the, "I can put threads anywhere I want!" idea.
Threads are good in a deep object where it is impractical to run a through hole (one that bolt just slides through) all the through the object. But threads in a thin plate, with a nut holding the bolt on the other side of that threaded thin plate, not so good, especially if you did not have a way to make absolutely perpendicular threads. Then you just have bolts fighting threads in the object when they hit the threads in the nut on the far side. So I turned all the threads in the mounting hardware into through holes. Much better.
The other mildly surprising moment was that I remembered having bought aluminum 1/4"-20 screws for some project, long ago, but I could not remember for what I used them. Then I discovered them. This mirror cell is almost entirely aluminum, including the screws and nuts that hold the attachment hardware to the big bottom plate. Why? Because I was trying to make this really light. Brilliant. The downside is that aluminum isn't anywhere near as tough as steel, and the threading orgy above meant that some of these screws and nuts were slightly damaged; one had to be Vise-Gripped out of the aluminum to which it was holding on for dear life, and the head of this screw is behind redemption. However, I was able to tap and die four of the six sets by turning a steel bolt through the nuts, and a steel wingnut on the bolts. There are two steel 1/4"-20 hex head screws now part of the process, but I don't expect the weight difference to be serious!
I am painting all these fasteners black (again). I really wish that I had a Boise source for black anodized bolts and screws, but I don't touch these very often, so I don't see it as a big problem to use flat black paint instead. I am considering buying some of this black flocking material for the upper part of the tube interior, in the area near the eyepiece and diagonal. (And read here to see why you don't really need to do the interior tube.)
UPDATE: As I do the arithmetic on placement of various parts, I am discovering that there really isn't room to put the mounting brackets for the mirror cell behind the main plate. When I did this original design, I did not waste a single inch of length. So how to solve this problem? This has been a long gripe of mine about mirror cells -- many of them assume that you will find exactly the right spot on the outside of the tube to drill the hole for a bolt that screws into a blind hole on the mirror cell base. This is not easy to do.
But I have a clever solution. What I am going to do is take the L-brackets that hold the mirror cell in the tube, tap the holes that I just made through holes into 5/16"-18 threads so that the bolts sticking down from these brackets will be captive (actually locked in place once screwed in). Then I will install the L-brackets in the tube and they will be permanently located there; to remove the mirror cell for cleaning is just a matter of unscrewing the nuts and lock washers that will hold the base plate of the mirror cell to the bottom of the L-brackets. That also means very deftly enlarging the holes in the base plate (since it is a big hassle to remove the mirror from the cell) to 5/16" size from their current 1/4"-20 thread.
Is The Amazon Search Widget Appearing on the Right Side Of My Blog?
I can't see it at the moment, but I am behind a fairly secure firewall.
UPDATE: Most people can see it, but the ones that can't are curious. I think it is firewall related, because I can certainly see it from home.
UPDATE: Most people can see it, but the ones that can't are curious. I think it is firewall related, because I can certainly see it from home.
Thursday, May 9, 2013
Fiberglassing Sonotube
Everything is adequately sanded for the next step -- and my, am I hot and sweaty from doing this, even using a sander. But now I need to do some drawing and some math, and math is a civilized, not sweaty activity.
UPDATE: Weight is 28 lbs., 2 ozs. (Maybe a bit less -- it is hard to keep this tube on the scale without touching it.)
UPDATE: Weight is 28 lbs., 2 ozs. (Maybe a bit less -- it is hard to keep this tube on the scale without touching it.)
That CNN Story About HP Hiring The Modern Dancers To Inspire Their Engineers?
According to this article in the May 8, 2013 Boise Weekly, it wasn't just misleading:
In a story published April 23 by CNNMoney--the online business site by the self-proclaimed "most trusted name in news"--more than a few folks were startled to read, "Why Hewlett-Packard is Hiring Dancers." In the piece, reporter Cheryl Strauss Einhorn described how HP paid the Trey McIntyre Project "around $20,000 for half-day presentations" to dance among HP's cube dwellers.
The story wasn't true.
And while CNN has since apologized and dramatically rewritten the story, the network never disclosed that the reporter's family has direct ties to the Boise-based dance troupe--her mother-in-law, Nancy Einhorn, sits on TMP's board of directors.That's what I get for trusting professional journalists.
Wednesday, May 8, 2013
Fiberglassing Sonotube, Continued
I noticed that the resin was really not setting terribly quickly, even with heaters running under the tube. I am beginning to think that the problem was that I didn't add enough hardener to the polyester resin. Also, this discussion of use of polyester resin for fiberglass makes the point that these resins often include some wax which rises to the surface, cutting off exposure to the air, and thus accelerating the curing process. That's one of the reasons why sanding and painting help the process.
I added a drop of hardener to some of the patches that were staying sticky, and within a couple of hours, they were pretty much hard (although a little more plastic than I would like). Also, because I had not put enough resin on top of the portion of the tube where I put in fiberglass cloth, I applied a second coat of resin, using more hardener this time. This morning, it was much closer to being done than the previous coat had been, and in addition, provides a barrier to the air for the first coat. My hope is that by this evening everything will have hardened enough for me to start sanding.
The inner part of the tube remains a little more sticky than I would like, but this may be an advantage, actually, because it will make it easier to get flat black paint to stick to it. There really isn't a pressing need to sand the inner part of the tube; a rough surface reflects less light than a smooth one, and on the inside of the telescope tube, anything that isn't reflecting is good.
UPDATE: My wife moved it into the sunshine about noon, because it was still not completely dry, and in an hour -- rock solid.
It weighs just over 28 pounds -- so I added a bit less than three pounds of resin. I sanded it down to 320 grit this evening, which probably took it down below 28 pounds again. There were a couple of air bubbles where the fiberglass cloth had been, and a few spots were a little sticky under the top layer; in general, the surface isn't quite as even as I would like, but that's why you sand and add another layer, to smooth these discrepancies out. It does not need to be commercial fiberglass quality, but I would like it relatively pretty before I drill the holes and paint it. So I added one more layer of resin this evening, and I will put it out in the sunlight in the morning to harden up good.
I added a drop of hardener to some of the patches that were staying sticky, and within a couple of hours, they were pretty much hard (although a little more plastic than I would like). Also, because I had not put enough resin on top of the portion of the tube where I put in fiberglass cloth, I applied a second coat of resin, using more hardener this time. This morning, it was much closer to being done than the previous coat had been, and in addition, provides a barrier to the air for the first coat. My hope is that by this evening everything will have hardened enough for me to start sanding.
The inner part of the tube remains a little more sticky than I would like, but this may be an advantage, actually, because it will make it easier to get flat black paint to stick to it. There really isn't a pressing need to sand the inner part of the tube; a rough surface reflects less light than a smooth one, and on the inside of the telescope tube, anything that isn't reflecting is good.
UPDATE: My wife moved it into the sunshine about noon, because it was still not completely dry, and in an hour -- rock solid.
It weighs just over 28 pounds -- so I added a bit less than three pounds of resin. I sanded it down to 320 grit this evening, which probably took it down below 28 pounds again. There were a couple of air bubbles where the fiberglass cloth had been, and a few spots were a little sticky under the top layer; in general, the surface isn't quite as even as I would like, but that's why you sand and add another layer, to smooth these discrepancies out. It does not need to be commercial fiberglass quality, but I would like it relatively pretty before I drill the holes and paint it. So I added one more layer of resin this evening, and I will put it out in the sunlight in the morning to harden up good.
Taxing Online Sales
The Senate has passed a measure that tells states that they can tax online sales, even if the seller is out of state and has no storefront in that state. There are a lot of reflexive, "no new taxes" voices on this, but I really don't have a big problem with this, for several reasons.
The most important is equal protection of the law. Target.com (as well as a lot of single store operations) have to pay sales tax on sales to Idaho residents because they have brick-and-mortar stores here. Why should Amazon be exempt from charging sales tax that most of their competitors have to charge? If sales tax seems pretty minor -- our sales tax in Idaho is 6%. For many businesses, that is more than their profit margin on sales. That's a huge advantage, and not a fair one. (Of course, you as a customer are supposed to pay that sales tax for out of state purchases already; in practice, most states will only catch you on this if you buy a car out of state and then register it.)
Another criticism of the proposed law is that a lot of small online retailers are going to have to keep track of sales taxes for all 50 states (and in some cases, for individual counties and cities). Yes, that's going to be something of an issue. But the law exempts small sellers:
UPDATE: My, what a lot of comments, and many of them quite thoughtful. (I mean, none of them start out, "Clayton, you ignorant fool.")
There are some good points, especially about the complexity of sales tax forms from state to state. I should point out that unless you are making pretty big sales, there is a good chance that nearly all your sales tax returns are going to be from about five to ten states. The bulk of ScopeRoller's sales in almost any year are California, Texas, Florida, Ohio. I know that I have never made a sale in Alaska, Hawaii, Wyoming, Vermont, and at least a dozen other states.
I agree that there is an apparent problem of taxation without representation -- an interesting problem.
One commenter suggested that a million dollars in sales might be $25,000 a year in profit, and complying with the requirements for software updates and filing of returns might well wipe out that profit. I suspect that any online business that is making that little profit is pretty unusual. I would wonder why someone is working that hard for that little profit.
Another commenter suggested that brick-and-mortar stores should pay sales taxes because they are relying on local governmental services, while Amazon relies on USPS and UPS. But the trucks from both are definitely not hovercraft; they use local roads, and if there are thefts or robberies of merchandise from UPS or other private delivery firms in the delivery state, that becomes a matter for local police. There might be a case for a for more service approach to governmental services, but within the current model, it is not clear that Amazon is completely unreliant on distant state governmental services.
The suggestion of taxing goods at point of sales is interesting, and would certainly be simpler. I rather like the idea.
I suspect that many medium sized businesses already use payment processing capabilities (like PayPal) that will handle this quite automatically.
The most important is equal protection of the law. Target.com (as well as a lot of single store operations) have to pay sales tax on sales to Idaho residents because they have brick-and-mortar stores here. Why should Amazon be exempt from charging sales tax that most of their competitors have to charge? If sales tax seems pretty minor -- our sales tax in Idaho is 6%. For many businesses, that is more than their profit margin on sales. That's a huge advantage, and not a fair one. (Of course, you as a customer are supposed to pay that sales tax for out of state purchases already; in practice, most states will only catch you on this if you buy a car out of state and then register it.)
Another criticism of the proposed law is that a lot of small online retailers are going to have to keep track of sales taxes for all 50 states (and in some cases, for individual counties and cities). Yes, that's going to be something of an issue. But the law exempts small sellers:
(c) Small Seller Exception- A State is authorized to require a remote seller to collect sales and use taxes under this Act only if the remote seller has gross annual receipts in total remote sales in the United States in the preceding calendar year exceeding $1,000,000.If you are making a million a year in sales, you can afford whatever software revisions are required to your invoicing software to calculate sales tax based on zipcode. That's a one time investment.
UPDATE: My, what a lot of comments, and many of them quite thoughtful. (I mean, none of them start out, "Clayton, you ignorant fool.")
There are some good points, especially about the complexity of sales tax forms from state to state. I should point out that unless you are making pretty big sales, there is a good chance that nearly all your sales tax returns are going to be from about five to ten states. The bulk of ScopeRoller's sales in almost any year are California, Texas, Florida, Ohio. I know that I have never made a sale in Alaska, Hawaii, Wyoming, Vermont, and at least a dozen other states.
I agree that there is an apparent problem of taxation without representation -- an interesting problem.
One commenter suggested that a million dollars in sales might be $25,000 a year in profit, and complying with the requirements for software updates and filing of returns might well wipe out that profit. I suspect that any online business that is making that little profit is pretty unusual. I would wonder why someone is working that hard for that little profit.
Another commenter suggested that brick-and-mortar stores should pay sales taxes because they are relying on local governmental services, while Amazon relies on USPS and UPS. But the trucks from both are definitely not hovercraft; they use local roads, and if there are thefts or robberies of merchandise from UPS or other private delivery firms in the delivery state, that becomes a matter for local police. There might be a case for a for more service approach to governmental services, but within the current model, it is not clear that Amazon is completely unreliant on distant state governmental services.
The suggestion of taxing goods at point of sales is interesting, and would certainly be simpler. I rather like the idea.
I suspect that many medium sized businesses already use payment processing capabilities (like PayPal) that will handle this quite automatically.
Monday, May 6, 2013
The Benghazi Story Just Gets More Ugly
And this report is from CNN, May 6, 2013:
In an interview with congressional investigators, the former top diplomat in Libya expressed concern that more could have been done by the military on the night of September 11, 2012 and morning of September 12, 2012, to protect those being attacked at the U.S. compound and annex in Benghazi, Libya. Specifically, he wondered why the military did not send a plane as a show of force into Libyan airspace, and why four U.S. Special Operations soldiers were not permitted to travel to Benghazi on a Libyan plane the morning of September 12....
The House Oversight and Government Reform Committee will hear from Hicks and others in a Wednesday hearing on the Benghazi tragedy, which ended in the deaths of four Americans – US Ambassador Chris Stevens, information officer Sean Smith, and former Navy SEALs Tyrone Woods and Glen Doherty.
Rep. Jason Chaffetz, R-Utah, a member of the committee, tells CNN that “military personnel were ready, willing, and able, and within proximity, but the Pentagon told them they had no authority and to stand down.”And CBS, May 6, 2013, is reporting the same:
The deputy of slain U.S. Ambassador Christopher Stevens has told congressional investigators that a team of Special Forces prepared to fly from Tripoli to Benghazi during the Sept. 11, 2012 attacks was forbidden from doing so by U.S. Special Operations Command South Africa.
The account from Gregory Hicks is in stark contrast to assertions from the Obama administration, which insisted that nobody was ever told to stand down and that all available resources were utilized. Hicks gave private testimony to congressional investigators last month in advance of his upcoming appearance at a congressional hearing Wednesday.You might almost get the impression that winning re-election was more important than protecting U.S. diplomats.
Sunday, May 5, 2013
Timelapse Borders of Europe
This is more in the cool category than something that really meaningfully contributes to understanding history, but it is still pretty neat:
I Just Hate It When You Can't Tell Real News From The Onion
The College Fix points to this U.K. Guardian article of May 2, 2013 that is beyond parodying:
Porn Studies needs your contributions. The Routledge academic periodical will debut next spring, and a call for papers appeared this week soliciting submissions for "the first dedicated, international, peer-reviewed journal to critically explore those cultural products and services designated as pornographic". Two dons, Feona Attwood and Clarissa Smith, are the editors.
The timing suggests the EL James phenomenon may have provided the impetus for the launch by making erotica ubiquitous; but literary porn is only one of the interests of the top-shelf journal, which is open to offerings from sociologists, criminologists, technologists and experts in cultural, media and gender studies.
In acknowledging that "pornography studies are still in their infancy", the editors implicitly criticise cultural studies, which clearly should have initiated scholarly investigation of porn long ago. This failure may have reflected the sometimes furious contemporary debate within second-wave feminism, between those viewing pornography as liberating (Angela Carter's The Sadeian Woman) and opponents (Kate Millett, Andrea Dworkin) who saw it as epitomising and reinforcing phallocratic oppression.Don't get me wrong; there is a legitimate need to understand pornography as part of its effect on other fields of study, but an entire periodical devoted to this is right up there with Women's Studies, Gay Studies, Black Studies, and all the other supposedly scholarly programs that are really just identity politics masquerading as scholarship. Unfortunately, this started out as, "We would like to get the Administration Building back without the black militants burning it down, so we'll create a Black Studies program and hire a bunch of people whose only real qualification is their color and the self-righteous rage that they bring to the program." And once that first concession happened, who could seriously dispute the equal validity of the rest of these programs?
Fiberglassing Sonotube
I finished applying resin to the outside of the tube today:
Here are the details of how I supported it between two chairs, with pretty massive amounts of weight on each chair. (If it looks precarious -- it is. At one point when rolling the resin, it started rocking enough to fly off.)
Here you can see the color difference between initially wet and dry:
As the reaction takes place (a peroxide hardening agent) it turns the resin brown. Fortunately, after sanding, I will paint it.
While I decided that it did not truly need to have fiberglass cloth embedded in it, I thought that for the end of the tube where the mirror cell will be mounted (and thus where the load will be most severe), putting in one layer of cloth wasn't a bad idea. This both increases stiffness, and provides an additional layer through which bolts will go. When I drill the holes for the various parts, I will soak the exposed Sonotube material with resin to reinforce support.
It looks awful, but once sanded, it will be an even edge. Unlike some of my previous fiberglass experience, I managed to get all the air bubbles out of it. This time, instead of using a brush, I used a roller. In addition, the last time I made a fiberglass tube, I used too much resin. I applied a thick coat of resin, then the resin-soaked cloth, and not surprisingly, the cloth kept slipping. This time, I waited until the first layer of resin had become sticky, lightly soaked the cloth in the resin in the paint tray, then applied it to the sticky layer. Then I applied a bit more resin to the top of the cloth, squeezing out air bubbles without causing the cloth to slip. I think I am getting the hang of this.
It has been sitting for about six hours now, and the exterior is still tacky in places, but there is absolutely no question that the tube is much stiffer than before. Sonotube by itself would deform slightly if I pressed down on with my hand, enough that I could see it deform if I looked closely. It appears that even though it is not completely cured, there is no obvious deformation.
How much weight have I added? A quart can of this resin weighs a bit less than 2.5 pounds, and I have used the first can. My guess is that the hardening reaction and evaporation causes loss of volatiles; in addition, not all the resin actually ended up on the tube. Some hardened in the reaction vessel; some in the paint tray; some on the brush. (It is much easier to remove the brush from the roller while it is still wet.) I would be surprised if there is actually two pounds added to the tube. For this stiffness, a 28 pound tube is just fine.
I have class tomorrow night, so I won't have a chance to return to this project until Tuesday night, by which point I expect it to be rock solid and dry. At that point, I will drill all the required holes, put some resin on the inside of the holes, and give it another night to harden.
I still need to revise the mounting scheme for the mirror cell. When I designed this mirror cell, I expected to put it in a lower cage, so the bolts go into the tube and you tighten the nuts from the front of the tube. That won't work on 74" long solid tube (unless I can find someone with six feet arms or who stands about 18" tall). Instead, I will remove the clips that point forward and reattach them pointing backward. This will let me access the fasteners from the rear.
I still have not abandoned the idea of fiberglassing the lower cage that was bending under load, but partly because I am curious, and partly because it will make it easier to sell the rest of the truss tube assembly if I have something that is stiff enough to not bend. Unfortunately, fiberglassing the lower cage will make even more of a weight advantage for the solid tube than it had before, and portability just isn't that critical.
I should explain that part of what motivated the concern about portability is that Big Bertha in the form that I first acquired it was too large to move in my wife's Equinox. I actually had to borrow a friend's Ford Expedition to get it to the new house. A solid tube version is still something that can fit into the TrailBlazer that we have now.
Here are the details of how I supported it between two chairs, with pretty massive amounts of weight on each chair. (If it looks precarious -- it is. At one point when rolling the resin, it started rocking enough to fly off.)
Here you can see the color difference between initially wet and dry:
As the reaction takes place (a peroxide hardening agent) it turns the resin brown. Fortunately, after sanding, I will paint it.
While I decided that it did not truly need to have fiberglass cloth embedded in it, I thought that for the end of the tube where the mirror cell will be mounted (and thus where the load will be most severe), putting in one layer of cloth wasn't a bad idea. This both increases stiffness, and provides an additional layer through which bolts will go. When I drill the holes for the various parts, I will soak the exposed Sonotube material with resin to reinforce support.
It looks awful, but once sanded, it will be an even edge. Unlike some of my previous fiberglass experience, I managed to get all the air bubbles out of it. This time, instead of using a brush, I used a roller. In addition, the last time I made a fiberglass tube, I used too much resin. I applied a thick coat of resin, then the resin-soaked cloth, and not surprisingly, the cloth kept slipping. This time, I waited until the first layer of resin had become sticky, lightly soaked the cloth in the resin in the paint tray, then applied it to the sticky layer. Then I applied a bit more resin to the top of the cloth, squeezing out air bubbles without causing the cloth to slip. I think I am getting the hang of this.
It has been sitting for about six hours now, and the exterior is still tacky in places, but there is absolutely no question that the tube is much stiffer than before. Sonotube by itself would deform slightly if I pressed down on with my hand, enough that I could see it deform if I looked closely. It appears that even though it is not completely cured, there is no obvious deformation.
How much weight have I added? A quart can of this resin weighs a bit less than 2.5 pounds, and I have used the first can. My guess is that the hardening reaction and evaporation causes loss of volatiles; in addition, not all the resin actually ended up on the tube. Some hardened in the reaction vessel; some in the paint tray; some on the brush. (It is much easier to remove the brush from the roller while it is still wet.) I would be surprised if there is actually two pounds added to the tube. For this stiffness, a 28 pound tube is just fine.
I have class tomorrow night, so I won't have a chance to return to this project until Tuesday night, by which point I expect it to be rock solid and dry. At that point, I will drill all the required holes, put some resin on the inside of the holes, and give it another night to harden.
I still need to revise the mounting scheme for the mirror cell. When I designed this mirror cell, I expected to put it in a lower cage, so the bolts go into the tube and you tighten the nuts from the front of the tube. That won't work on 74" long solid tube (unless I can find someone with six feet arms or who stands about 18" tall). Instead, I will remove the clips that point forward and reattach them pointing backward. This will let me access the fasteners from the rear.
I still have not abandoned the idea of fiberglassing the lower cage that was bending under load, but partly because I am curious, and partly because it will make it easier to sell the rest of the truss tube assembly if I have something that is stiff enough to not bend. Unfortunately, fiberglassing the lower cage will make even more of a weight advantage for the solid tube than it had before, and portability just isn't that critical.
I should explain that part of what motivated the concern about portability is that Big Bertha in the form that I first acquired it was too large to move in my wife's Equinox. I actually had to borrow a friend's Ford Expedition to get it to the new house. A solid tube version is still something that can fit into the TrailBlazer that we have now.
Saturday, May 4, 2013
A Reminder That Information Is Impossible To Prevent, Even If Manufacturing Is Illegal
Interesting, somewhat paranoid website: this guy builds adapters that screw onto the male threads on gun barrels (like 1/2"-28 for AR-15s) and have male threads that screw into common oil filters (like 3/4"-16 for some STP oil filters). I gather that these create a noise suppressor (although probably not as good as one made for this purpose).
Doubtless, ATF will find some way to classify the adapter as a suppressor, with the all the corresponding paperwork. But making this adapter is dead simple: anyone will a drill press, a piece of aluminum, a drill, and the appropriate taps and dies, can make these adapters. Drill through the aluminum a big enough hole for the female threads, tap it, turn down the other end to a size that you can thread with a die.
Doubtless, ATF will find some way to classify the adapter as a suppressor, with the all the corresponding paperwork. But making this adapter is dead simple: anyone will a drill press, a piece of aluminum, a drill, and the appropriate taps and dies, can make these adapters. Drill through the aluminum a big enough hole for the female threads, tap it, turn down the other end to a size that you can thread with a die.
My Wife Says Nothing Is Scarier Than a Bored Predator
By which, she means our cat. But bored engineers are dangerous, too. I'm waiting, perhaps not sufficiently patiently, for the resin coat on the inside of the Sonotube to harden, before I suspend it by a rod through the interior, and do the exterior. In the meantime, my wife had fallen asleep on the couch, so I couldn't turn on the TV. What to do?
I had realized a couple of days back that there was some room to reduce weight on various accessories on the telescope. For example, the mounting bracket for the finderscope was something that I put together myself, but it was a flat piece of aluminum 3/8" thick. Lots of extra weight, and while it was not under any stress, a flat base against a round tube is less than optimal for stability.
So, I took that base and decided to mill it out to be a channel. The legs on either side would, like the rods in my previous example, provide a very stable base against the tube. (Yes, I should have used lower density acetal, either white to match the tube, or black to match the rest of the hardware on the tube, but I didn't have any pieces that were thin enough and long enough for this purpose.)
I don't use the vertical mill often enough to machine aluminum to remember: use a roughing mill for this. Instead, I somewhat botched the first attempt, and barely saved the piece from becoming scrap. You aren't going to see the bottom side of the channel -- it's functional but the milling marks and irregularities caused by my save are are way too apparent. In addition, because the plate is now much thinner than before, the 8-32 screws that mount this plate to the rings that hold the finderscope were now too long for the holes, so I had to deepen the holes in the rings and re-tap the holes with more threads. But I did knock two ounces off the weight!
I had realized a couple of days back that there was some room to reduce weight on various accessories on the telescope. For example, the mounting bracket for the finderscope was something that I put together myself, but it was a flat piece of aluminum 3/8" thick. Lots of extra weight, and while it was not under any stress, a flat base against a round tube is less than optimal for stability.
So, I took that base and decided to mill it out to be a channel. The legs on either side would, like the rods in my previous example, provide a very stable base against the tube. (Yes, I should have used lower density acetal, either white to match the tube, or black to match the rest of the hardware on the tube, but I didn't have any pieces that were thin enough and long enough for this purpose.)
I don't use the vertical mill often enough to machine aluminum to remember: use a roughing mill for this. Instead, I somewhat botched the first attempt, and barely saved the piece from becoming scrap. You aren't going to see the bottom side of the channel -- it's functional but the milling marks and irregularities caused by my save are are way too apparent. In addition, because the plate is now much thinner than before, the 8-32 screws that mount this plate to the rings that hold the finderscope were now too long for the holes, so I had to deepen the holes in the rings and re-tap the holes with more threads. But I did knock two ounces off the weight!
The Sonotube Fiberglassing Project
I sanded exterior and interior with #80 sandpaper last night; I just finished applying a coat of fiberglass resin to the inside and ends of the tube. The Sonotube absorbed the epoxy in a manner that can only be called greedy, especially on the ends, where there was no wax to discourage it. I decided to just apply epoxy; the fiberglass cloth would make it stronger, but it is actually plenty strong as is; it just needed a bit more stiffness, and the resin should do that just fine.
Now I need to treadmill while I give it a few hours to harden. It is obviously a bit big to pop in the oven.
Now I need to treadmill while I give it a few hours to harden. It is obviously a bit big to pop in the oven.
Friday, May 3, 2013
Mounting Flat Bases to Round Tubes
A fairly common problem for amateur telescope makers is how to mount a flat base to a round tube. Especially as Dobsonian mounts have become more common, which usually have rectangular upper and lower cages, makers of telescope parts have become increasingly focused on flat bottoms. Even before Dobsonians were all the rage, how to mount items such as eyepiece focusers and finder scope rings was sometimes a problem. At best, manufacturers had to offer several different radii of base for each accessory.
I have decided that the Moonlite Telescopes truss connector system isn't going to work for my situation. This is not because there is anything wrong with it; it is well-designed and beautifully made. The problem is that it is really intended for telescopes with much stiffer lower cages than I have. (The truss is very strong and very stiff -- and thus exposed a flaw in using it on a .125" aluminum wall tube.) I could probably make it work, but at this point, it is simpler, cheaper, less frustrating, and to my surprise, less weight, to use a solid tube for the rebuild of Big Bertha, the ill-behaved 17.5" reflector. I'll probably be able to resell at least the truss blocks; I suspect that unless I find someone building a truss 13" or 15" f/4 reflector, the tubes now cut to 55" length will end up being recycled as scrap aluminum.
Along the way, however, I discovered a very useful trick for how to mount flat bases on round tubes.
The trick is to cut round rod of the right diameter to prevent rocking. Here's what I did using 1/8" diameter steel rod:
In this case, I epoxied the rod in place to the round tube, creating a plane upon which the truss block can stably rest. (No matter how you do this: there is one point of contact between a plane and a cylinder.) The epoxy is just to hold the rods in place like enough to bolt the truss block in place; once the bolts are locked down, those rods are not going anywhere.
What diameter of rods do you need? Remember that the formula for calculating the equation of a circle is x2 + y2 = r2. In this case, the outer diameter of the round tube was 20.25"; if you want the supports 1" from the center contact point, solve for y to determine how much elevation (diameter of round rod) you need to clear the space between the tube and the plane (the y axis, assuming that you remember high school geometry).
y = square root of (r2 - x2)
For this example: y = 10.075"; subtract from the radius of the tube, meaning that you need a rod 0.0495" thick. Your local hardware store will have a variety of diameters of steel and aluminum rod available; by cutting it slightly shorter than the base it will be supporting, it will be invisible, and add effectively no weight to your telescope.
I have decided that the Moonlite Telescopes truss connector system isn't going to work for my situation. This is not because there is anything wrong with it; it is well-designed and beautifully made. The problem is that it is really intended for telescopes with much stiffer lower cages than I have. (The truss is very strong and very stiff -- and thus exposed a flaw in using it on a .125" aluminum wall tube.) I could probably make it work, but at this point, it is simpler, cheaper, less frustrating, and to my surprise, less weight, to use a solid tube for the rebuild of Big Bertha, the ill-behaved 17.5" reflector. I'll probably be able to resell at least the truss blocks; I suspect that unless I find someone building a truss 13" or 15" f/4 reflector, the tubes now cut to 55" length will end up being recycled as scrap aluminum.
Along the way, however, I discovered a very useful trick for how to mount flat bases on round tubes.
In this case, I epoxied the rod in place to the round tube, creating a plane upon which the truss block can stably rest. (No matter how you do this: there is one point of contact between a plane and a cylinder.) The epoxy is just to hold the rods in place like enough to bolt the truss block in place; once the bolts are locked down, those rods are not going anywhere.
What diameter of rods do you need? Remember that the formula for calculating the equation of a circle is x2 + y2 = r2. In this case, the outer diameter of the round tube was 20.25"; if you want the supports 1" from the center contact point, solve for y to determine how much elevation (diameter of round rod) you need to clear the space between the tube and the plane (the y axis, assuming that you remember high school geometry).
y = square root of (r2 - x2)
For this example: y = 10.075"; subtract from the radius of the tube, meaning that you need a rod 0.0495" thick. Your local hardware store will have a variety of diameters of steel and aluminum rod available; by cutting it slightly shorter than the base it will be supporting, it will be invisible, and add effectively no weight to your telescope.
Sonotube: Lighter and Stiffer Than I Remembered
I went to American Construction Supply in south Boise today to get a 20" ID Sonotube.
I was a bit concerned if the weight estimates here for Sonotube were correct -- they seemed awfully light for something that you fill with concrete and from which I was going to make a telescope. I picked up a pretty enormous section of it, and had no doubts.
Getting it home was quite an operation. The piece above is 74" tall and 20" ID -- and yes, it just fit in the Corvette's passenger seat, once I removed the top. (But I did get some strange looks on the way back to the office, and even more when I carried into the office because I was concerned about rain.)
I have absolutely no question about the weight or the stiffness. I just weighed this beast, and it was less than 26 pounds -- or a bit more than four pounds per foot. It is also quite stiff (although not quite like fiberglass). I still intend to add a layer of polyester resin (and even a layer of fiberglass cloth) to improve stiffness and water resistance, but I do not expect that to add more than a couple of pounds of weight -- and then I will have a rock-solid tube.
My father and I built an 8" reflector back in the 1970s using a piece of Sonotube. I remember that it cost what seemed like a pretty heavy amount of money -- like $30 or so -- but that was what we could afford at the time, and in retrospect, it worked pretty darn well, and we did not even know to coat it with fiberglass. We just painted it inside and out.
UPDATE: Part of why it is lighter and stiffer than I remembered (aside from the flaws of memory of events and objects now decades away) is that Sonotube, like carbon fiber and fiberglass, is a composite material: paper combined with glue, producing a combination that is stiffer than you expect of paper, and stronger than you expect of glue.
I sanded it inside and out, and now it is hanging, ready to be fiberglassed tomorrow. I was measuring the amount of cloth that I have, so that I know how much more to buy before I get started tomorrow:
The gray thing in the bottom of the picture is the cat skulking away. No, it's not a mouse hunting tool, Tater.
I was a bit concerned if the weight estimates here for Sonotube were correct -- they seemed awfully light for something that you fill with concrete and from which I was going to make a telescope. I picked up a pretty enormous section of it, and had no doubts.
Getting it home was quite an operation. The piece above is 74" tall and 20" ID -- and yes, it just fit in the Corvette's passenger seat, once I removed the top. (But I did get some strange looks on the way back to the office, and even more when I carried into the office because I was concerned about rain.)
I have absolutely no question about the weight or the stiffness. I just weighed this beast, and it was less than 26 pounds -- or a bit more than four pounds per foot. It is also quite stiff (although not quite like fiberglass). I still intend to add a layer of polyester resin (and even a layer of fiberglass cloth) to improve stiffness and water resistance, but I do not expect that to add more than a couple of pounds of weight -- and then I will have a rock-solid tube.
My father and I built an 8" reflector back in the 1970s using a piece of Sonotube. I remember that it cost what seemed like a pretty heavy amount of money -- like $30 or so -- but that was what we could afford at the time, and in retrospect, it worked pretty darn well, and we did not even know to coat it with fiberglass. We just painted it inside and out.
UPDATE: Part of why it is lighter and stiffer than I remembered (aside from the flaws of memory of events and objects now decades away) is that Sonotube, like carbon fiber and fiberglass, is a composite material: paper combined with glue, producing a combination that is stiffer than you expect of paper, and stronger than you expect of glue.
I sanded it inside and out, and now it is hanging, ready to be fiberglassed tomorrow. I was measuring the amount of cloth that I have, so that I know how much more to buy before I get started tomorrow:
The gray thing in the bottom of the picture is the cat skulking away. No, it's not a mouse hunting tool, Tater.
Thursday, May 2, 2013
What Was I Thinking?
Even the reinforcements didn't do the job...and the quotes for stiffer material are pretty horrendous. So I find myself asking, "What if I used a solid tube instead?"
It turns out that Sonotube (the traditional home telescope maker material) weighs 4 pounds per foot in 20" ID size. A 6 foot section would weigh 24 pounds; the lower cage, including the mirror and cell, currently weighs 34 pounds. The tube for the lower cage weighs 6.26 pounds, so the mirror and cell weighs less than 28 pounds. Adding the Sonotube, the mirror and cell, comes to 52 pounds. The finder, the diagonal mirror, the spider, and the focuser, weigh about five pounds. That's 57 pounds. I would bolt the Sonotube directly to the dovetail (perhaps with a couple supports on either side to prevent rocking), which weighs 2 pounds, 6.6 ozs. That's still less weight than what I currently have, and far stiffer. (How stiff is Sonotube? It is used to pour concrete columns that are 20 inches diameter and many feet high.)
If I fiberglass the Sonotube (a common technique to both improve water resistance and appearance), I can't imagine it would add more than a pound or two to it. It won't be terribly portable, but big deal -- I don't need to transport it.
I'll go hunt up a 73" length of this tomorrow. (It ought to fit into the passenger seat of the Corvette with the top off. I shudder to think what others will think of it.) I think I became so enamored of a sophisticated portable design that I completely lost sight of the simplest solution.
UPDATE: $49.48 + tax for 6 feet of it.
It turns out that Sonotube (the traditional home telescope maker material) weighs 4 pounds per foot in 20" ID size. A 6 foot section would weigh 24 pounds; the lower cage, including the mirror and cell, currently weighs 34 pounds. The tube for the lower cage weighs 6.26 pounds, so the mirror and cell weighs less than 28 pounds. Adding the Sonotube, the mirror and cell, comes to 52 pounds. The finder, the diagonal mirror, the spider, and the focuser, weigh about five pounds. That's 57 pounds. I would bolt the Sonotube directly to the dovetail (perhaps with a couple supports on either side to prevent rocking), which weighs 2 pounds, 6.6 ozs. That's still less weight than what I currently have, and far stiffer. (How stiff is Sonotube? It is used to pour concrete columns that are 20 inches diameter and many feet high.)
If I fiberglass the Sonotube (a common technique to both improve water resistance and appearance), I can't imagine it would add more than a pound or two to it. It won't be terribly portable, but big deal -- I don't need to transport it.
I'll go hunt up a 73" length of this tomorrow. (It ought to fit into the passenger seat of the Corvette with the top off. I shudder to think what others will think of it.) I think I became so enamored of a sophisticated portable design that I completely lost sight of the simplest solution.
UPDATE: $49.48 + tax for 6 feet of it.
New Book Out By A Friend
Robert J. Cottrol, The Long, Lingering Shadow: Slavery, Race, and Law in the American Hemisphere (University of Georgia Press, Studies in the Legal History of the South, 2013)
From the press release:
From the press release:
Students of American history know of the law’s critical role in systematizing a racial hierarchy in the United States. Showing that this history is best appreciated in a comparative perspective, The Long, Lingering Shadow (University of Georgia Press, February, 2013) looks at the parallel legal histories of race relations in the United States, Brazil, and Spanish America. Robert J. Cottrol takes the reader on a journey from the origins of New World slavery in colonial Latin America to current debates and litigation over affirmative action in Brazil and the United States, as well as contemporary struggles against racial discrimination and Afro-Latin invisibility in the Spanish-speaking nations of the hemisphere.
Ranging across such topics as slavery, emancipation, scientific racism, immigration policies, racial classifications, and legal processes, Cottrol unravels a complex odyssey. By the eve of the Civil War, the U.S. slave system was rooted in a legal and cultural foundation of racial exclusion unmatched in the Western Hemisphere. That system’s legacy was later echoed in Jim Crow, the practice of legally mandated segregation. Jim Crow in turn caused leading Latin Americans to regard their nations as models of racial equality because their laws did not mandate racial discrimination—a belief that masked very real patterns of racism throughout the Americas. And yet, Cottrol says, if the United States has had a history of more-rigid racial exclusion, since the Second World War it has also had a more thorough civil rights revolution, with significant legal victories over racial discrimination. Cottrol explores this remarkable transformation and shows how it is now inspiring civil rights activists throughout the Americas.Bob teaches at George Washington University School of Law, and sat on my master's thesis committee (which was a stretch, since that was at Sonoma State University). Bob has also been heavily involved in scholarly work about the gun control issue, unsurprisingly, having authored several very important papers about gun control and its racist origins.
You can order a copy from Amazon by clicking here.