Sunday, April 6, 2008

Thanks For All The Machining Suggestions

Thanks For All The Machining Suggestions

I finished the part, got it installed--and then decided it wasn't worth taking the mount apart to take a picture. It mostly looks terrible (at least the parts that I machined first), but it works, and the segment that was broken on the original is now twice as thick on the replacement. This may limit my ability to use this mount in the tropics, but I can't picture taking it there.

There are two next steps before I can mount Big Bertha 2.0 on the mount:

1. Get another Losmandy counterweight. (I didn't have enough.)

2. Build a lower tripod. Because of the size of Big Bertha 2.0, the eyepiece would be at ladder height if I used the current tripod. Also, the center of gravity is so high that it makes it less stable than I would prefer. Finally, lifting Big Bertha 2.0, all 55 pounds of her, to the height of the saddle is an enormously difficult and slightly risky maneuver, even with two of us doing so.

So, to build a lower tripod, I need to find some pipe 5 1/2" inside diameter (or perhaps slightly larger) and about 12 inches long. Then I will bolt legs made from 1/4" x 1" steel, about 20" long. This will give me a very wide, very low base to lower the center of gravity and make it less likely to tip--even with 55 pounds of scope, 30 pounds of equatorial mount head, and 75 pounds of counterweights.

UPDATE: I found a vendor with short sections of 5 1/2" ID, 1/4" aluminum tubing--exactly what the current tripod uses. I've done the math, and I can cut some of the 6' sections of aluminum square tube left over from the first attempt at Big Bertha 2.0 into 2' legs. These provide enough stiffness to handle the weight of this behemoth with only fraction of an inch of deformation. I'll use 1/4" thick, 3/4" wide L-brackets to bolt the legs to the 5 1/2" ID tube, with the L-brackets held in both places using 3/8"-16 bolts, and the L-bracket inside the square tube.

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