Aileron sprocket / chain timing

[TimHicks]

I'm ready to dissemble my aileron cable circuit that runs inside the cabin on my '46 BC-12D.

But before I take it apart, I was trying to figure out how make sure that it goes back the same way.

I can't find any easy way to assure that when I go back together, I get the correct sprocket tooth in the corresponding link of each chain so that I have the same timing (and therefore the same yoke positions).

I searched this forum but couldn't find any process for timing the u-joints to each other. Is this so easy that I'm making too big a deal about it? Or is there some trick to assure the timing?

[N96337]

Re: Aileron sprocket / chain timing

Tim, I center both yokes, using clamps and a piece of aluminum angle on the bottom of them, then check to make sure the stop pins on the back are centered (by measuring), then center the chain. It sounds like a big deal, but it's not bad at all.
John

[Robert Lees]

Re: Aileron sprocket / chain timing

It really helps if you have a turnbuckle between the two yokes in the aileron control circuit.

This turnbuckle runs along the horizontal part of the "H" control column. So close, I used prop leading edge tape to prevent scoring the paint on the control column.

Edit: found the photo (view looking aft from firewall):

[TimHicks]

Re: Aileron sprocket / chain timing

OK, I think that I've got it.
My set-up does have a turnbuckle between the sides.

On the bracket that holds the innermost pulley (between the chain and the turnbuckle) there is a cotter pin that doesn't seem to be doing anything. See the picture attached.

This is at the elbows on the H-Frame, both sides.

Does anybody know why there is a cotter pin there (near the OD of the pulley)?

[3Dreaming]

Re: Aileron sprocket / chain timing

It's to keep the cable from being able to jump out of the pulley.

[Ray]

Re: Aileron sprocket / chain timing

Man I wish I had thought of this before I took mine apart I thought pictures would work but 3 days later I finally got it right. These were not full days but I could only take a few hours of aggrivation at a time. Persistance paid off though.

[TimHicks]

Re: Aileron sprocket / chain timing

The way that I documented my timing before I dissembled the assembly was:
1. rotated the pilot-side control shaft until the two stop-pins on the sprocket were centered at Top-Dead-Center
2. In that position, a single sprocket tooth was at TDC. So I marked the chain link on that tooth by wrapping a piece of safety wire.
3. Then I moved to the co-pilot side and wrapped another piece of safety wire through the chain link at TDC.
4. Then I marked the co-pilot sprocket tooth at TDC with soapstone.

I also measured the distance from the center hole of the center turnbuckle to both pilot-side and the copilot-side adjacent pulleys. But I don't think that I'm going to need that info.

5. Then I dissembled everything. But the wires in the chain and the marks on the pulley will remain until reassembly.

I'm sorry that I don't have any good pictures of this. I just happened to break the screen on my camera. So I took some pictures (without the ability to see what I took). Later when I downloaded them, they were pretty crummy. I've got a new camera now.