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Tailwheel arm play - normal?

Radius

The threaded post on the tailwheel fork often has a fairly large radius where it transitions to the larger diameter steering shaft. This prevents the washer from seating flat against the surface at the top of the steering shaft. If you cut a chamfer on the ID of the bottom side of the washer, you will get rid of most of that play.

Skylor
 
Hard to say what's normal

It's hard to say what's normal here... the amount of play you're seeing will probably never cause any real problems. If you want it to go away, get a feeler gauge and get an idea of how much space there is between the top of the control arm and the washer that's capturing it, then add an appropriate shim washer on top of the control arm or under the mounting socket.

Be careful not to over-do it though... if you shim too much, the top nut will tighten down to the control arm and the assembly will bind up.

For more tailwheel troubleshooting discussion, you can find our troubleshooting document here: http://flyboyblog.com/2020/04/20/tailwheel-troubleshooting/
 
Steering Arm play

Wingnut,

To eliminate the play, and to provide a better bearing surface for the steering arm, I bought a 1/2" ID by 1.5" OD bronze washer from McMaster-Carr. I then counter-bored the washer to a diameter matching the shaft diameter of the tailwheel fork to the depth matching the vertical play (less .005" for clearance) of the steering arm as measured with a feeler gauge. The counter bore allows the washer to drop down over the tailwheel fork shaft taking up the play. I will be heading to the hanger later this morning and I will take the assembly apart to photograph it for you.

Former VA-25 A7 pilot from long, long ago in a galaxy far, far away....

By the way, when is your next deployment?
 
Allow me to add a few thoughts here:

1) Don't make moving assemblies exposed to dirt, so tight that a grain of sand causes a failure. Think AK-47, not M-16

2) Don't let your answer go in search of a problem. Obviously, there is some limit to looseness and wear, but if the system is working, don't cause a maintenance induced failure. Trust us. We've seen all manner of "improvements" and mis-assembly cause problems, usually because the owner simply doesn't take time to understand how these things work.

3) KISS - keep it simple stupid. These things are built to relatively loose tolerances so that various vendor's parts will play nicely together. Clean and grease it once or twice a year, specifically the locking pin, and go fly.

4) There is no way to clean, inspect, re-profile (if necessary), and grease the locking pin than to disassemble it periodically... regardless of who made the tailwheel.

5) The control arm is a wear item that WILL need to be replaced occasionally, regardless of manufacturer. When it doesn't lock properly, inspect the locking pin and related notch in the control arm. If the control arm shows wear on the square edges of the notch, replace it. They're dirt cheap!

6) Go fly.
 
Agree with Vince

The tailwheel parts take a beating but are probably the most overlooked assemblies on our planes. Seems even more neglected by those who buy used RV's than those that build. The tailwheel assembly MUST be serviced several times a year. I always recommend servicing during oil changes. I live my tail onto a small saw horse and completely disassemble the tailwheel, clean, check for burrs in the pin and arm and reassemble while the oil is draining. 20 minutes max.

I'm often asked what grease to use. It really doesn't matter as long as you clean and replace often.

One of the real keys to the tailwheel assembly is finding that sweet spot between too tight and too loose on the top bolt. Once you have it, file a small notch in the top shaft and the nut. Then take a picture of the exposed threads. Now you have the same tension as before.

Finally, post flight your plane and check the tail wheel assembly. I keep a microfiber cloth in my cleaning supplies that has light oil on it. I wipe down the tail wheel assembly and check for any problems. Doing these simple things will give your tailwheel assembly a long and dependable life.

As Vince said, things wear out. Check them and replace as necessary!!!
 
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