The legs are made of poplar to cut down on weight. The middle section can be positioned up or down the legs to provide for three height settings.
Fig. 8
Voila! The legs are bolted onto the head, a coat of finish applied, and three segments of chain on a key ring provide leg bracing. This should prove to be a stout base for several different instruments. I do some woodworking, so I had all the oak on hand, as well as some of the poplar leaving just the hardware - bolts, PVC drain cap, chain, and Teflon sheet to buy.
After using the setup over several sessions on both turf and concrete pavement, all seemed well. Then I was asked to show the bino chair at a DIY astronomy club meeting, which had me setting it up on a waxed tiled floor. I was a bit embarassed - as I turned the parallelogram, the legs kept sliding and made the top of the tripod get out of level which hadn't happened before. I figured I needed to replace the chain with something to keep the legs more rigid, so I replaced it with a simple spreader shelf.
First, I made three brackets from 1/8 inch strap aluminum, bent at 120 degrees and drilled, shown in the upper right of Figure 9. Then I cut a piece of 1/4 inch plywood to fit and drilled it to match the brackets, holding it place with some 1/4 inch bolts and wingnuts. This means one more step to do during set-up, and one more piece to carry, but the tripod is quite rigid now, regardless of what surface it is on. Plus, there is now a shelf to place things next to the chair, like a nice adult beverage.