Aileron push rod attachment at bellcrank

[Sonex1243]

Fitting the short (SNX-C03-02) aileron push rod and trying to visualize the "rotation that is to occur between the bushing and plate on the push rod" per plans note. When assembled, I get a rotation of the bushing in the push rod end? Is this right?

Per SNX-W02 plans page, detail "F", I worked the flanged bearing length to get .015" clearance between the thrust bearing and push rod assembly when the bolt is tightened just enough to insert a cotter key. Also, "the push rod assembly should be free to rotate with respect to the bell crank without excessive freeplay". I must be missing something here?

[peter anson]

Yes, that's right. The rod turns on the bushing rather than the bushing turning on the bolt. It makes sense because the bushing and bolt together make a stronger part than if it pivoted on the bolt. The rest is just saying that the push-rod must be free to turn but not too sloppy and the bolt must be tight but not over-tightened.

Peter Anson
Sonex 894
221 hours

[Sonex1243]

Thanks for the help pete;
I ended up re-working the flanged bushing some more and got the gap down to .008. Nice fit and everything is rotating right. It seems with the flanged bushing too long, it locked it to the drive plate with the bolt tightened and made the pressed in flanged bushing rotate in the steel rod end with everything else "locked" up.

[Direct C51]

I too am having a bit of trouble visualizing this. Should the flanged bushing be .005 - .015 longer than the thickness of the pushrod and thrust bearing, so that it makes contact with the bellcrank, causing the thrust bearing to 'float' a bit? Or should the flanged bushing be .005 - .015 shorter, causing the thrust bearing to make contact with the bellcrank? So far, the way I have it the bolt is pivoting in the bellcrank, which cannot be correct. If the flanged bushing is supposed to rotate inside of the pushrod, I suspect the fitment is much to tight, as the flanged bushing took a bit of force to press in to the pushrod.

Thanks

[Sonex1243]

I too am having a bit of trouble visualizing this. So far, the way I have it the bolt is pivoting in the bellcrank, which cannot be correct.

I worked the flanged bushing end shorter, giving me .005 - .015 between the thrust bearing, bellcrank and bushed rod end with the bolt tightened just enough to get the cotter pin in. I ultimately ended up with .008. The tightened bolt / nut assembly can be rotated with slight force only, but, the actual rotation now occurs between the bellcrank, thrust bearing and bolt in flanged bushing. No rotation of the actual bushing itself in the rod end.

[Direct C51]

So Peter says the flanged bushing rotates within rod end and Ken says its the bolt that rotates inside the flanged bushing and bellcrank. Anyone want to be the tie breaker?

[Bryan Cotton]

I have not looked at this on the plans yet. I will say that every rod end on a Sikorsky helicopter has the ball rotating inside the rod end.

[sonex892.]

So Peter says the flanged bushing rotates within rod end and Ken says its the bolt that rotates inside the flanged bushing and bellcrank. Anyone want to be the tie breaker?

I am with Peter. Both the bolt and the bush should be considered fixed to the bellcrank and not rotate in relation to the bellcrank. See note on plans SNX W02 detail F. "Rotation to occur between bushing and plate on push rod".

The reason for the .005__.015 end play is the pushrod doesn't just go back and forth. It pivots up and down very slightly at the bush whilst travelling from aileron up to aileron down.


Steve
Sonex 892

[Direct C51]

I am glad to hear that most agree with the way Peter has explained it. I too built mine so that the bushing, bolt, and bellcrank are fixed and rotate about the pushrod. My flanged bushing fit very tight inside the pushrod, so I used some sandpaper and took off the powdercoating on the bearing surface of the pushrod. Everything now rotates pretty freely. Does anyone see anything wrong with me sanding the inside of the pushrod hole so that the flanged bushing can be pushed in with moderate force by hand?

[wlarson861]

Not as long as you lubricate the push-rod plate at annual to prevent corrosion of the pushrod.