Throttle Quadrant "Lock" - Std RV-8 3 level control

[walkman]

I have the more or less standard 3 level throttle quadrant in my RV-8. It looks like the ACS one, but I did not build this airplane.

Recently I replaced the throttle and mixture cables which had become very stiff.

Now I realize the new cables are too smooth! They creep around in flight. The biggest culprit is actually the cable I didn't replace - the prop control. I did disconnect and reconnect this cable, and relocated an Adel clamp during the process.

The throttle quadrant has a black plastic thumbscrew on it which I assume is intended to be an adjustable drag/lock on the controls. It appears to have no effect.

How is this supposed to work? Are there washers or spacers that may have gone missing?

Thanks

 

[clam]

The thumbscrew you describe is a friction adjustment feature. The design is such that turning the thumbscrew clockwise tightens the friction on the three levers and thus holds them in place, or at least prevents them walking. There should be an AN364 or AN365 lock nut concentric with this thumbscrew securing it in place on the AN bolt at the base of the quadrant. That bolt spans the width of the quadrant, and it centers each lever, 4 spacers (roughly 3/16" thick) and 6 brass bushings. Each control lever should have a brass bushing on each side of it (3 levers, 2 bushings each). Tighten the lock nut (inboard side, next to your left leg) sufficient to take the play out of the thumbscrew. The thumbscrew should then tighten within 1/4 to 1/2 turn. I use this friction lock every flight.