Building Tips and technical articles. > Building techniques

Belcrank controls

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Larry Wong:
I think it's been ask before, But I will ask again ..   What is the diffrence of having the belcrank with reverse leads. (  front line up/ and back lead down)?
I see that the builders use both .    n~

RC Storick:
Well I will try to give you my input. I have done it both ways. T-bolt 1 has bell crank with up line on the rear. Tbolt 2 has up line in the front. There is some difference but it is slight. The lead out are also dropped 3/16 from the center line of the wing. This gives the vertical CG above the lead out outlet. (more line tension) Now with the lead out in front it seems to rotate on the line better in a hard corner.

I can't explain it very well but it works for large power plants in the nose.

Larry Wong:
Thanks Robert I'm At the point of installing the belcrank , and I've all ways had the  back line up. but I think I'll try the other , I guess it can't hurt.

Dick Fowler:
The current thought revolves around trying to compensate for yaw caused by gyroscopic precession of the prop during a turn.

Turning inside (up) creates yaw of the nose out and nose in yaw on outside maneuvers. The idea with the up line forward is that when you give up there will be more tension on the forward leadout which if ahead of the CG  will cause the nose to yaw in to compensate.

Keeping the line spacing narrow (close together) and it really doesn't matter a whole lot.

Randy Powell:
Al Rabe is partly responsible for this. I think he may have been the first to do this to compensate for the yaw issues on hard, outside controls. But as Dick notes, it's less of an issue if the leadouts are space close together.

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