October 2001 Newsletter

Stockton Astronomical Society

Valley Skies

Valley Skies - October 2001 Issue

The Telescope Nut
by Jeff Baldwin

Fred Flintstone

The 40" mirror has been polished for a total of about ½ to ¾ hour, and is sporting a shine. The barrel was wobbling dangerously, so we decided it was time to replace it with another support system. Our choice was to make a concrete barrel that was very wide and very heavy.

I placed plastic on the garage floor, then a 24" tall piece of 36" Sonotube. Inside it is an 18" piece of 18" Sonotube suspended 6" off the floor. The next thing is incredible--1300 pounds of concrete! The first 6" is a solid floor layer. The next 18" is a round wall 9" thick to the top of the Sonotubes. It has bolts set into the top surface to connect the tabletop and is otherwise free of internal structural material (rebar). The Sonotube will stay in place during the work. When we're all done with it we will tear off the Sonotube and break it apart (that's why no rebar).

The support is now matched with the floor, no wobble; and heavy, no wobble; and wide, no wobble. (If it wobbles now, I'm strong!)

When we were finished, I had a little sand and gravel left, so I filled the center of the doughnut with it. I guess it now weighs about 1600#. With the mirror on it the weight will go up to about 1800#, and with the tool it'll be about 2100#. Add plywood and workers, and I think the floor will be taking about 3000#. But it won't wobble!

Don't we ATMers get into the weirdest stuff?

Eric Reichenbach is the master of concrete, and it is as beautiful as you can imagine. Eric, if you remember, is the maker of the 36" grinding and polishing tool, which is a 260-pound piece of concrete with tile attached.

Another person I'd like to thank is my wife, Glenda. Imagine allowing your husband to pour 1300 pounds of concrete in your garage only 3 feet from your car!

So...why is this article titled Fred Flintstone? Because this concrete barrel reminds me of the wheels on Fred's foot-powered car.

Yaba-daba-doo!

Clear Skies!...Jeff Baldwin
For more information on Telescope Making jump to the ATM page.