Here's where it all started, with a pile of plywood, a lot of courage, and some plans I modified to suit my needs. Although the plans called for 3/4" plywood, I thought that 1/2" would save weight, and nearly used it. I'm glad we didn't try that, as the stresses would have been too great for 1/2"! Birch was used, as it was supposedly lighter.|
At right is the material we used for the tube: it's good old cheap, round concrete forming tube. (This has come to be almost universally referred to as "Sonotube" ® (a Sonoco product), but is also generically made by other companies, sold under various brand names, and is available at your local builder's supply. Use what is at hand.) It had to be throughly scraped with #00 steel wool before we started painting it. Some advise total de-waxing with solvent, if necessary, but I felt that would have been discarding a valuable property of the tube: water resistance! As it turned out, I was able to get a type of acrylic garage floor paint (Ace hardware) that adheres to darn near anything! (It's been 12 years, now, and it's still adhering.) In order to find a paint that would stick to the waxy surface, I tested out quite a few, hence the various red and black blotches!
This is the tube box. Until I had to try and make one, I really didn't realize how hard it is to make a box that's perfectly squared-off. The two black round thingies on top are actually a PVC coupling sawed in half, (the future tube box bearings) and the steel tube/plumbing assembly is a recycled Coulter focuser. Our main concern with the PVC coupler/bearings were thier small diameter; Some recommend 6", and these are only 4.5"; as it later turned out, the smaller size (greater pressure) led to some scoring of the PVC by the harder Teflon, and we had to encase the PVC with aluminum flashing (not shown).
This is the main bearing (a formica sink-top cut-out from a cabinet shop) being attached to the bottom of the rocker box. (Note: Most cabinet-making shops that do kitchen remodels will give the cut-out away for free, or very little money indeed.) The screws were countersunk so there would be no interference with the three teflon bearing pads on the mating surface, which is, of course, the base (next picture).
Finally, it was "cell time". The one you see here is made entirely of wood and steel fittings. The design you see here is from an obscure source, and there are no drawings. Someday I'll get some done and put them here.
Here's the mirror (Orion Optical-the Pyrex Standard Coating model) in the cell. The mirror sits in the cell retained by six metal brackets, keeping the mirror firmly centered and stable. A detailed shot of the cell can be seen by clicking here. It must be noted that this cell has been fairly easy to collimate, and, once collimated, has stayed there since the original calibration was done. The 'scope has been over hill and dale, across railroad tracks, and overland many hundreds of miles, and the alignment of the mirrors has never changed a whit. I attribute this to the very solid cell design, and the excellent spider by Novak we ended up with.
"The Big Push". Once all the pieces have been fabricated, all the mail-order parts delivered, and the tube balanced and painted, it's time to put the whole thing together! The author, in welding goggles, drill, and hacksaw, is shown here brandishing his tools of trade amid the remains of his living room, clearly indicating that he means business. His Faithful Native Companion (wife) is offscreen calling 911.
Nearly done! The external plywood tube ring ring at the base was discarded in favor of some heavy-duty rubber window channeling (see base in previous photo) gleaned for free from a local glazier. I thought that the tube rings, while they would have improved the structural integrity of the tube, might make getting the thing in and out of my Mazda trunk a real pain. As it worked out, the channeling works super; the tube is quite strong enough without the plywood tube rings. "Free," you say? Yep. I just marched into the place, said, "Hey, guys, I'm an Amateur Astronomer, and I need some channeling for a 'scope I'm building! Got any?" The two guys running the place looked at each other, shrugged and gave me some! I guess it was easier than holding me down until help arrived......
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