Gear leg shimmy

[WaiexN143NM]

Hi Larry, all,
I thought id start a new thread on this topic, although its been talked about before here.
Things to look for would be a good fit of gear leg onto motor mount. Maybe another bolt like larry did to secure it better might help. How's the condition of your tires? Balanced? We put dyna beads in ours to help the balance. We also put the wood strips sold by flyboyaccessories on, and wrapped with glass. (Fits just fine under the gear fairings). I remember one post from bob mika putting some oak strips on his gear legs. Is the alignment ok? Are you using stock, upgraded machine drums, or hyd. Brakes? How's your wheel pants and mounting structure. Solid? Any cracks? If your going hyd brakes i suggest buying the steel backing plates from tracy obrien. Jim hicke mentioned recently that the single tab broke off on his axle fitting. Index the backing plate withe the tab, take it to your local welding shop. You can then pick up 3 bolts to distribute the load. Hope this helps. Anyone else please advise of your experiece , suggestions, or questions.
WaiexN143NM
Michael

[LarryEWaiex121]

Michael,

In addition to the many factors you pointed out in your comments about gear leg shimmy, I'm curious if you've ever heard about in flight shimmy?
My wheels turn so freely now with the hydraulic brakes (Sonex) that I now have a situation where I get a shimmy on my left gear leg at high speed on descents. I experienced it yesterday on a fun day of 4 takeoffs and landings at 4 different airports.
The air was butter smooth and I was getting a whallowing, shimmy feel at around 165 mph on a 300fpm descent. I was concerned that a wheel pant was coming loose or something?
For whatever reason one might dream up I reached forward and lightly pulled the brake handle and it immediately stopped. A few moments later the shimmy came back. I pulled the brake and it stopped.
Well the airflow is spinning up the left wheel and its out of balance and causing the shimmy. I don't run across it at speeds of 150 or less. I tested my hypothesis several times with the same result. Get a head of speed and the shimmy comes back. Pull the brake and all is smooth.
I felt on a couple of flights, weeks earlier I had felt something? The air was so bumpy, I wasn't sure. Yesterday there was no mistaking it. Go fast shimmy, go slow no shimmy, pull brake handle no shimmy. What to do?
In all seriousness, I believe I'm going to adjust the preload on my wheel bearings since things turn really, really easy. Next I guess I can go to the level of balanceing the wheel and tire. Probably should do the balance beads in the tires?

Larry
Waiex121YX, Camit 3300

[WaiexN143NM]

Hi larry,
Interesting. Yep try the beads. White little ceramic balls. You need to let the air out of tube, take out valve stem, little bottle of beads and clear plastic tube. Go easy, easy to clog up. You can then blow into tube, and of course it wouldnt be any fun unless a few blow back and get in your mouth. ! We have never had any shimmy. (In the air) The fastest we've had our waiex is 180 in a decent, no shimmy. Let us know if this helps.
WaiexN143NM
Michael

[DCASonex]

Those wheel bearings should be tight enough that there is no play, and that is quite snug. Also make sure bearing races are fully seated in the wheels. Seems most are not when received. Have the larger and heavier 5.00 x 5 tires and never encountered the shimmy you observed. Plane has seen VNE more than once.

If you have to seat those bearing races, do not use the bearings to push these in and be sure back up the hub center, not the rim if using a press. Some have used threaded rod through sockets having the right OD to press on the OD of the bearing races.

David A. Sonex TD, CAMit 3300.

[WaiexN143NM]

Hi david, all,
Thanks for the reminder on the bearing races david. A few years ago saw the post about it, took our wheels off , and yes they needed to be seated.

Off topic. Bob Hoover died today. 94. Rancho Palos Verde CA (south of LA) The greatest aviator ever.
Good reading:
Www.eaa.org
Www.aero-news.net
Www.avweb.com

WaiexN143NM
Michael

[LarryEWaiex121]

David and Michael,

You guys got to have some fun with your Waiex's and get them up to speed now and then. :lol:
As part of my phase 1 testing, I took my Waiex to vne 4 times and after tests, I've had it right at or very close at least 2 dozen times.
Highest actual indicated airspeed I've seen is 204 mph, and that was by accident being a bit too aggressive on the nose down.
Before getting up the confidence to push to vne I stepped it up 5 mph each time till I got to 197, or as stated above, slightly over quite by accident.
Prior to my purchase of the Waiex kit, I had an interesting discussion with John Monnett about flutter and design integrity at the workshop I attended.
I asked him to put a number to the "limit" of the design and he was unwilling. My guess is if you tell someone its good to "here" then some fool will go out and see if he was right? LOL
Obviously, the published VNE is well within safety limits for the design and flutter limits. My concern was not wings, tail or elevator, but aileron flutter.
Being unable to coax a number I asked another way. "So if I accidently split S out of a barrel roll and manage to get going 225 is the tail or an aileron going to magically disappear?" Nope. "How about 235?" Nope. So, no actual number was ever disclosed but it seemed a fair bargain that there was good safety margin all the way around.
In the end it became clear that testing was conducted in such a manner to leave a considerable margin for flutter in case someone does something really, really dumb. Don't pull excessive G and if the plane is built solidly according to plan, things should turn out well.
I was all good with everything until the tail fell off the Whooten Waiex and that got my attention. As matters stand, I did the SB on the tail and I'm all good with that. I don't think anyone ever has fully understood all the issues that led up to that one?
Morale of the story: build well, maintain well, keep proficient and if the little devil on your shoulder says, "You'd be wise to not do that", well then, let your devil be your conscience.

Larry
Waiex121YX, Camit 3300

[WaiexN143NM]

Hi larry,
The sonex/waiex is very stout. Im a safety minded guy , im sure there is a large margin for vne. The waiex the the tail came off, im not sure that we will ever know the exact sequence of events/cause. If my aging memory serves me, the pilot had some heart trouble, and a witness was watching and said engine quit. The fuel tank was not breached, but held no fuel. Good that sonex took another look at the design and beefed it up. I think that was a faa update to far part 23.
Fly safe be safe.
WaiexN143NM
Michael

[fastj22]

Hi larry,
The sonex/waiex is very stout. Im a safety minded guy , im sure there is a large margin for vne. The waiex the the tail came off, im not sure that we will ever know the exact sequence of events/cause. If my aging memory serves me, the pilot had some heart trouble, and a witness was watching and said engine quit. The fuel tank was not breached, but held no fuel. Good that sonex took another look at the design and beefed it up.
Fly safe be safe.
WaiexN143NM
Michael

There were several red flags in that accident. The pilot was low time (65 hours). He had documented medical issues, hence flew sport pilot. He ran out of fuel. The build quality was sub-par. The radar track showed erratic flight path after reaching altitude (and really high for a pleasure flight). Did he run out of gas, panic and overstress the sub-par airframe? Did he have a medical episode after running out of gas, putting the plane in an overstress attitude?

[WaiexN143NM]

Hi john, all,
Thanks for the memory refresh. Yes i remember seeing the pics up close of the build. Also i think the plane was bought. Pilot did not build it. And yes john your right on point, the fuel exhaustion , medical problem, tail overstress, all added up in the right sequence, like many accidents, and fatal results occured.
Be safe all,
Regards,
Michael

[daleandee]

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