Spiders and Cells

Regarding the spider, I’m working on a spider in the style of Patrick Swayze’s, linked here. I’ve milled a 1.5″ cube out of 1.5″ hollow aluminum tubing (diameter blocked/hypotenuse: 2.12; the minor axis of the elliptical secondary is 2.46″). The spider legs will be made out of band saw blade.

2014.11.19. I’ve made considerable progress on the spider and the mirror hub.

2014.11.23. … and yet more.

Regarding the mirror cell, I’m inclined to avoid working with metal. I stumbled across plans for a wooden cell for a mirror as large as 12.5″. I printed the pages out. Later I went to find the website and it seems to have disappeared. Fortunately I could still find my print out, which I have scanned and post here for reference: Papa Joe – Lefevre

Lefevre’s mirror cell calls for oak lumber. I originally simply replaced the oak he called for with maple ply. I began having second thoughts about the plywood support beams for the cell sagging. So I’ve supplemented the design with steel: I got steel angled bar from the local hardware store and cut it into four lengths that the plywood supporting beams could rest in. I then bolted those steel supports into place and bolted the plywood/steel beams into the mirror box.

2015 04 06. In the face of some skepticism at the idea of a 3-point cell made principally of plywood, I went back to the drawing board and came up with a new plan. My quandary inspired a lively conversation on Cloudy Nights. I’ve ended up using a six-point PLOP layout. The three aluminum bars holding the six points are resting on small hinges; the points themselves are raised up from the aluminum bars by pieces of plexiglass on which the felt pads rest. Lock-tight holds the nuts steady.

The sling is held by two 3/8″ carriage bolts. I milled down the threads and drilled a hole 1 1/4″ down from the top of the bolt so that I could bolt down the nylon strap, which I purchased by the foot from the local five and dime.

The push-pull collimation system is made Stellafane-style. I used three 1/4″ carriage bolts for the spring-loaded pull, and 1/4″ threaded stock cut to 3 1/2″ for the push with a nut and a wingnut at the end of each to work as a knob. These lengths may need to be trimmed once I have things in place.

The cell sits on two pieces of 2″-wide plywood with angled steel bar running along the sides and in which the plywood rests (or is reinforced, depending on how you look at it).

 

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