Sunday, January 19, 2014

The Baby Carriage

My wife has stopped referring to the big telescope as Big Bertha because it no longer looks like an artillery piece.  She now calls it Clayton's Baby.  So here is the baby carriage that I made:

As I mentioned a couple of days ago, it is a 1/8" thick sheet of steel, 27.5" x 27.5".  I drilled 1/2" holes 1/2" from the corners, and mounted the 3" total locking casters that I use for ScopeRoller there.  The locking casters are necessary, because when you start using the digital setting circles, you do not want any motion relative to the surface; it otherwise would make the sensors on the ground board inaccurate.

I would not want to roll this over gravel or grass, but on pavement and concrete it works just fine.

Friction alone is not enough to keep everything on that sheet of steel.  I took a piece of 1" square aluminum tube that I had lying around, cut it into three pieces, and drilled through the top surface so that I could recess the screws holding the aluminum to the steel sheet.  You can see one of the edges of the ground board here.

There is a bit of flex in the steel sheet, but it isn't very obvious, and I am not particularly worried about the problem getting worse, so I think I will leave it well enough alone for the moment.  I mentioned on the Second Light posting that I had loosened and tightened one of the truss tube connectors, and I thought that explained the collimation problem.  Indeed, when I recollimated, I found that I was significantly off because of that.  I look forward to rolling Baby out in her carriage tonight.

UPDATE: Some more pictures for Dennis Steele at DobSTUFF, who built this telescope.

A bit more detail of the square tubing used to hold the ground board in place:

Because I could not (or at least, did not try) to get high precision on the dimensions of the ground board, here is how I made it a tight fit -- an aluminum spring between tube and ground board!

It took quite literally 30 seconds to roll this from the garage into position, with no lifting.  Awesome!  It has been so long since I had to move a telescope without rolling it (that's my business), I had forgotten what a burden it is when it takes ten minutes and a helper to do this.


  1. Very neat Clayton. Keep the reports coming. Post pictures of the WHOLE scope on her carriage!!

  2. It would be simple to stiffen up that plate, just bolt on a length of angle iron along the edges, leaving enough clearance for the casters (or add wooden blocks to raise the casters clear and run the angle iron to the corners). It's edge-on material that is stiffer, which is why floor joists are vertical instead of horizontal.