Redesigned Mid-span Elevator Hinge by Jay
They were constructed from 1” thick nylon sheet stock. I did not measure exactly but if the strap is ½” with a little slop to fit without binding, then you have a little less than ¼” on either side of the strap. I would think that even 1/8” would be sufficient if the stock is less than 1” thick.
Here’s the key. Make sure you cut the stock in half first to create the axial split in the final bushing, then surface this cut and fit it together again before you use a hole saw to cut the bushing out of the stock (centered on the cut you just made). This makes sure the hole is symmetrical, even across the split and won’t bind the torque tube when assembled.
Then you can clamp the two halves of the bushing together again and cut the center hole to fit the torque tube OD. The outer perimeter profile of the bushing can be done on a lathe with the chuck holding the assembly together. First you do the inboard profile, then flip it around in the chuck and do the identical outboard profile.
If you have a small piece of left over torque tube, or something of the same diameter, put it in the hole between the two halves of the nylon bushing before you load it into the chuck. This will give the necessary support to clamp the chuck down without distorting the roundness of the bushing assembly. If you leave this tube sticking out from the chuck it gives you a reference to make sure it is clamped in the chuck so it is axially aligned with the lathe.
If you don’t have a lathe but have access to a standard milling machine, you can probably do the same job pretty easily with similar precautions.
One other point, the cherry rivets that you use to secure the internal stiffener tube, must be placed so as to not interfere with the assembled bearing surface of the bushing on the torque tube or too close to the bushing to prevent easy assembly/disassembly when you need to remove the elevator for maintenance.
I use grease to lubricate the bushing/torque tube contact surface in order to keep out any moisture or dirt. This can be renewed each annual by removing only the rear half of the bushing, applying the grease to the torque tube top and rotating the elevator upward, then applying some grease to the torque tube bottom and rotating the elevator downward.
They were constructed from 1” thick nylon sheet stock. I did not measure exactly but if the strap is ½” with a little slop to fit without binding, then you have a little less than ¼” on either side of the strap. I would think that even 1/8” would be sufficient if the stock is less than 1” thick.
Here’s the key. Make sure you cut the stock in half first to create the axial split in the final bushing, then surface this cut and fit it together again before you use a hole saw to cut the bushing out of the stock (centered on the cut you just made). This makes sure the hole is symmetrical, even across the split and won’t bind the torque tube when assembled.
Then you can clamp the two halves of the bushing together again and cut the center hole to fit the torque tube OD. The outer perimeter profile of the bushing can be done on a lathe with the chuck holding the assembly together. First you do the inboard profile, then flip it around in the chuck and do the identical outboard profile.
If you have a small piece of left over torque tube, or something of the same diameter, put it in the hole between the two halves of the nylon bushing before you load it into the chuck. This will give the necessary support to clamp the chuck down without distorting the roundness of the bushing assembly. If you leave this tube sticking out from the chuck it gives you a reference to make sure it is clamped in the chuck so it is axially aligned with the lathe.
If you don’t have a lathe but have access to a standard milling machine, you can probably do the same job pretty easily with similar precautions.
One other point, the cherry rivets that you use to secure the internal stiffener tube, must be placed so as to not interfere with the assembled bearing surface of the bushing on the torque tube or too close to the bushing to prevent easy assembly/disassembly when you need to remove the elevator for maintenance.
I use grease to lubricate the bushing/torque tube contact surface in order to keep out any moisture or dirt. This can be renewed each annual by removing only the rear half of the bushing, applying the grease to the torque tube top and rotating the elevator upward, then applying some grease to the torque tube bottom and rotating the elevator downward.
| redesigned_midspan_elevator_hinge_--_scheevel_2012-07-21.pdf |
