[stepdaddy]

I have nosewheel shimmy. I understand that breakout force should be 22 pounds, but I dont know where to measure from. I dont have all of the original manuals so I cant referance it there. do I apply the fish scale at the axle line, fork end, tire tread?
N914C at 44 hours and going strong. Just purchased/ordered a new blue mountain lite for it. Hope that unit is all it is cracked up to be.
Dan

 

[Bob Axsom]

The axle line is correct but

I just reset mine this week. I noticed a little nibble of vibration after leaving LOE. When I got the nose wheel fairing off and the nose jacked up I made up a pull "fixture" out of some excess piano hinge pin wire - think of a double loop or very distorted figure "8" with one larger end flattened to conform with the height of the fork sidewall. The big loop is openable/closeable with a hook. I opened it and stuck the end into the fork opening in front of the axle and closed it again by hooking the wire loop upon itself. I positioned the wire against the axle which obviously provides less breakout leverage than if it were centered on the axle (shorted arm). I pulled sideways and the first movement of the fork around the lower end of the nosegear strut was at 20 pounds. I removed the cotter pin and rotated the castellated nut one cotter pin notch tighter and retested. The breakout force was 24 pounds. I installed a new couterpin (I get them and virtually everything else from Aircraft Spruce) reinstalled the nosewheel fairing and all hints of a shimmy were gone on subsequent flights. In my opinion the 22 pounds breakout force you mention is too low to start with and it will get lower with use. Go for at least 23 and preferrably higher if you don't want to go through the process again right away. As it settles in the retightening requirement becomes less frequent but do not hesitate to do the deed at the first hint of shimmy - damage will occur if you don't do this maintenance when the airplane tells you it is needed (don't try to hold off until the next condition inspection for example).

Bob Axsom