Tuesday, December 4, 2018

Lack of Posting

1. It has been a busy day.  I went down to Mustang for snow tire swap on the Jaguar.  Even ice does not scare it with the Michelin X-Ice tires.

2.  I am busy preparing for the Spring semester of American History.  We have switched from a pricey online textbook to a free online textbook, which is requiring some lecture rearrangement and general improvements to my PowerPoints.

3. I am again working on the rebuild of my 3" f/4.5 reflector.  Lots of machining.  Part of why I wrote C programs to do various machining operations instead of using shell scripts to produce gCode, was that I could not gCode subroutines to work.  Problem solved.  I needed to trim half an inch off an aluminum cylinder (which is a bit short to do on the lathe), so I wrote a shell script that copies a subroutine in slicesub.nc to stdout, then uses for to produces calls to remove .01" at a time.  (A Bridgeport this is not.)

g17 g20 g54
o101 sub
     g01 x#1 f1
     g01 y#3 f#2
     g01 y#4 f1
o101 endsub
cat slicesub.nc
for i in `seq 0.01 0.01 .2`;
    echo "o101 call [$i] [.1] [1.5] [0.0]"
echo "m2"
echo "%"
I should make it for elegant, using command line arguments to set feed rates and slice width, but it is cold in the shop.  Tater is on my lap, purring, but even he is not enough heat.


  1. Did you ever solve your "how do I cut large thread sizes" problem from November? We want to know. (Sounds like maybe you did if you are machining stuff for the telescope.)

  2. Your ice is obviously different from our ice, though we have little of it here in MS. Ours tends to be wet on top, and it makes little difference what sort of rubber tire you have. In fact, about the only difference tires will make is that very large ones make better bumpers when you slide and hit something. Even steel-tracked machinery with cleats sometimes has trouble. Studded tires are nonexistent and tire chains are rare here, but chains work. Problem is, we most often have patchy ice so your chains wind up running on bare pavement. Best thing I've seen are the undercarriage-mounted remote-controlled chains. But they're hard to justify for use just a few days a year.

  3. At the temperatures ice is a problem, there is no water on it until your tire goes over it. Humidity is low, so vapor pressure is high. Ice either sublimates or the water evaporates quickly.

  4. Zendo: Several good ideas were suggested in comments. I am so far from that part (a helical focuser) that I am not currently worrying about it. I am busy trying to machine the diagonal mirror holder, a 1.18" diameter rod with a 45 degree cut and a 1/4"-20 through it to hold a screw that goes into the spider that holds to the inside of the tube.

    This is slower than I expected. at least partly because the chuck that attaches to the tilting table has locked itself to the 3/4"-16 adapter that the 10-32 screw uses to bind that adapter to the table. I cannot get the 10-32 screw to hold that part to the table. Threads are okay; just retapped the hole in the table. The 3/4"-16 part may be sliding on the table face.

    Next step is a lock washer to hold the screw tighter. It is a through hole in that adapter; so I see no obvious way to remove it. I tried heating in warm water, but chuck and adapter are both steel, so no net expansion. Perhaps dry ice on the adapter to get a more dramatic and sudden shrinkage. Extreme solution: left hand tap into that through hole, throw it away when it is out.

  5. FYI, in Windows 10 there is a Bash shell, and you can install Ubuntu 18.04. No VM--it's inside the OS. I've used it a lot and it pretty much does everything you would expect--including, if you get a Windows X server, running X programs like Emacs or web browsers.

    Accessing parallel or serial ports might require a bit more work, I don't know.

  6. 10-4 on the ice temps. Ours is commonly right around freezing and while the yankees tend to laugh at us for not being able to drive on it, frankly our ice is different than what they drive on. Wet ice is SLICK. And it's also pretty common that anytime we have ice or snow, it melts some during the day and re-freezes at night, then repeats for a few days until it's gone, so about the time the sun hits it each morning, there's a brand-new slick spot that was not slick yesterday at dusk. We don't have ice/snow that is "dry" or sticks around more than a few days, and we don't have low humidity. We do have ice storms and freezing roads, even when we didn't have any sleet or snow.