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  #31  
Old 03-25-2018, 12:34 AM
CAVU Mark CAVU Mark is offline
 
Join Date: Dec 2014
Location: San Diego, CA
Posts: 68
Default What happened today

Repair consisted of welding steel bushings on the top of the gear tube after alignment. We welded the bushes on with the gear legs in place.

I installed the repaired gear, this would be the second time I had it welded, the first shot did not meet with my alignment specs. The second was closer but when taxied it shimmied worst than ever. Shook everything inside at a fast taxi. Finished the wood/glass mod today and at fast taxi no shimmy. Yeah! Now for a test flight.

Noteworthy points. I used wood on the front and back of the gear. I did not use "oak" as suggested by my fellow EAA members. I used finger jointed pine trim on the front and solid pine trim on the aft. Didn't think about the finger joints until my contractor friend piped up. Used a mill to bore the groove for the new brake lines.

I did contact Langford and they suggested swapping the gear legs and drilling new holes in the top and the subsequent axle holes. I didn't dig that suggestion and carried on with the weld repair.

My gut said I should not jig in the shop but align it on the plane and tack weld it. I think I will listen to my gut next time since I was expecting it not to shimmy without the wood/glass mod. I am a slightly better fiberglass person now.

New Michelin tires, tubes and balancing took place.

I suppose this gear works well if installed correctly from the start but it is not fun as a repair.
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RV-3 restored - learning to land
Stearman - building - near 1st flight
L3 converting/building ribs
Helio Courier constructing
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  #32  
Old 03-29-2018, 11:38 AM
dacronwall's Avatar
dacronwall dacronwall is offline
 
Join Date: Oct 2013
Location: Palo Alto,CA
Posts: 81
Default Gear shmmy

Mark
I had similar experience with my gear. The mount was broken when I bought it, and we replaced with the new motor mount and gear legs. I checked the alignment and it was spot-on, but still would get the shimmy unless my landing technique was PERFECT.
SO I put the wood stiffeners on, I did front and back with Maple, and I let in the round with a router, and even put a channel down the leading edge for my brake lines.
All was great after that, but I had a couple of hard landings in gusty conditions and ended up finding the wood had cracked. I ground the glass out and wrapped it again, but I think the wood being partially un-bonded is still causing a periodic shimmy, mostly as I slow (using brakes) after putting the tail down and approaching the runway turn out.
I need to pull the wheel pants and leg fairings off again and see if I can figure out what needs to be done, but that means jacking the plane up and all that fun stuff.
Feel your pain brother....The round gear legs are more susceptible to shimmy than other types, I wish I could say I nail my landing every time, but I don't. Just part of the RV game I guess.
Cheers
Dave Cronwall
N66GB
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  #33  
Old 04-06-2018, 08:44 PM
Michael Henning Michael Henning is offline
 
Join Date: Jun 2011
Location: Nashua, NH
Posts: 470
Default

I am not familiar with the landing gear on a -3, but on the -4 the gear is sensitive to tire pressure. Too much or too little, and it will shimmy. I run 32 PSI. Smoky I think mentioned he uses 30 psi. Just a thought. The plans in the -4 manual spell out how to add the wood to the landing gear, but I never needed it.
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