Finalized Concept Drawing
Detail: Top of Hanger
The shafts for the sheaves and snap hooks were made from 3/16" steel rod. This was the perfect size for a #10-32 die. The rod was clamped in a vise between two blocks of wood. Eight threads were cut on the end which was 1/4" of thread. The shaft was cut to length off of the rod. Two nuts were locked together on the threads, and clamped in a vice. 3-1/2 or eight threads were cut on the opposite side of the shaft. The shafts at the side of the tent were cut shorter, and threaded into the aluminum u-channel to prevent wear on the tent wall.
The sheaves mounted in the hanger were removed from 3/4" (20mm) pulleys. The shafts were ground down to the block, and punched out. The holes were too small for the 3/16 shafts I used, and needed to be drilled out. I did one with a hand drill to determine how to do it. The easiest way was to wrap the sheave with a piece of rope, and clamp it in a vice. Care must be taken to keep the hole square with the face of the sheave. For the remaining five, I cheated. I chucked them up in my lathe, and drilled them out there. The sheaves were drilled 1/64" oversize so they would turn freely on the shaft.
The sheaves were mounted on the shafts, with washers filling the remaining space. Note the fender washer between sheaves two and three. There is a standard washer, the fender washer, and another standard washer between the sheaves. The standard washers do not extend to the rim of the sheaves, so this arrangement reduces friction. The fender washer prevents the cord from jumping sheaves. I highly recommend using this arrangement where ever the sheaves are spaced away from the u-channel walls as well, for the same reason. I'll upgrade this later.
The turnbuckle / snap hook arrangement connects the two sides of the light fixture to the main pull rope. The core is a scrap piece of the aluminum u-channel. The threaded eye has a washer followed by two nuts locked together. For extra security, I used a center punch to peen over the threads so there's not a chance of this coming apart.
The ratchet hanger was a disappointment. There is a lot of friction in this device, and the fixture will not lower by its weight alone. I need to find one of better quality.
Detail: Bottom of Hanger
Light Fixture as Low as Possible
Light Fixture as High as Possible
The fixture can be lowered to within 6" or 15cm fron the tent floor, and raised to within 10" or 25cm from the top of the tent. The force required to raise the fixture is approximately 1/3 the fixture weight, of 32 lbs, or 14.5 Kg. That fixture is heavy, but well within the capability of the tent frame.
As you read through this part of the thread, you'll realize that I started with several misconceptions. The major one was the functioning of the pulleys. You can tell that I was not a Boatswain's Mate in the Navy.
Over all, I'm happy with the way this turned out.
Next, ventilation needs to be addressed.