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  #41  
Old 04-20-2011, 11:28 AM
rbutler rbutler is offline
 
Join Date: Apr 2011
Location: Jackson, CA.
Posts: 3
Default Nose wheel shimmy

We've started to notice nose wheel shimmy on our 6A. Anyone have thoughts on cause?
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  #42  
Old 04-20-2011, 11:50 AM
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Gregmarlow Gregmarlow is offline
 
Join Date: Jan 2007
Location: TN
Posts: 183
Default Just the obvious...

Check your breakout force on your nosewheel at 20 lbs or so?
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  #43  
Old 04-20-2011, 01:22 PM
Phlyan Pan Phlyan Pan is offline
 
Join Date: Aug 2010
Location: Rochester, NY
Posts: 174
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Shouldn't someone throw out the obligatory "you put the single wheel on the wrong end of the plane" ?
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  #44  
Old 04-20-2011, 01:32 PM
rbutler rbutler is offline
 
Join Date: Apr 2011
Location: Jackson, CA.
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Default Nose wheel

Yeah maybe the single wheel is at the wrong end but it's the only one I've got!

Greg can you give me the procedure on checking the "breakout force"? I suspect that we are well shy of 20lbs.
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  #45  
Old 04-20-2011, 01:34 PM
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L.Adamson L.Adamson is offline
 
Join Date: Apr 2005
Location: KSLC
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Default

Quote:
Originally Posted by Phlyan Pan View Post
Shouldn't someone throw out the obligatory "you put the single wheel on the wrong end of the plane" ?
No...............Sixes look like "squatting dogs" when viewed with their short fat wings from certain angles...

Other than that, the 22 lb. or slightly more, side force is important. Air pressure, out of balance or out of round tires also can have an effect. Keep the nose wheel off as much as possible. I have had severe landing shimmy in the past. Once and a while, I'll get a slight shimmy at a certain speed while taxiing after landing. It's very infrequent these days.

L.Adamson --- RV6A
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  #46  
Old 04-20-2011, 01:45 PM
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Ron Lee Ron Lee is offline
 
Join Date: Jun 2005
Posts: 3,275
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I suspect that you do not know if it is shimmy or out of balance/out of round. Have someone knowledgeable observe the tire when it is doing whatever it is doing.
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  #47  
Old 04-20-2011, 06:49 PM
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Flybuddy2 Flybuddy2 is offline
 
Join Date: Oct 2009
Location: Fort Myers
Posts: 370
Default

Trying to get an "A" model that doesn't shimmy is like trying to find a smooth shopping cart at WalMart.
Breakout force, tire pressure, type of tire and weight on front wheel all affect.
I had a lot of experience with a Velocity trying to eliminate shimmy which is a much more difficult issue due to no weight on wheel and lower breakout forces (you can't go too tight as the wheel slides in turns)--Also, there's no stops so when shimmy gets a good wiggle going it can literally destroy the fairing and even the fork assembly. My eventual fix was a locking nosewheel. (Here's a link)
http://www.velocityaircraft.com/news...eel%20Lock.pdf

Breakout force--Grummans, Velo, RVs, etc all call for at least 22lbs of pull before the fork moves. Get the nosewheel off the ground and pull with a luggage or fish scale at (or even with) the axle. On an RV you can go significantly higher--your only concern is to keep it loose enough that the nosewheel swivels in flight otherwise you'll have an uncontrollable rudder out front. We've got a few RVs here with 30+ pounds on the pull with no adverse affect. This is the most common issue as they tend to loosen up over time. Take several readings as it will vary.

Tire pressure--key here is amount of rubber on the runway. On some tires as you increase the pressure, the tire eggs and lower/outer portions of the tire no longer contact the ground. The small amount of wobbling this can cause may initiate a shimmy. (Less side to side movement resistance)

Weight on wheel--larger engines and constant speed props get more tread on the nosewheel contacting the surface as well as providing more movement resistance.
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  #48  
Old 04-20-2011, 08:52 PM
rbutler rbutler is offline
 
Join Date: Apr 2011
Location: Jackson, CA.
Posts: 3
Default thx

Thx all, very helpful info, gonna work on fixes tomorrow!
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  #49  
Old 04-20-2011, 10:47 PM
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Mike D Mike D is offline
 
Join Date: Jul 2008
Location: Houston, TX
Posts: 456
Default nose gear bolt

You might also want to check the bolt that holds the nose gear leg on. Best thing to do is have someone hold the back down to get the front wheel off the ground. Then try to see if you can rotate the leg in the engine mount. If so you may have to one of the two fixes. Taper pin or next size up on the bolt. Search the forums and you will find the instructions on the fix.

Here is a link to the wiki instructions.
http://www.matronics.com/wiki/index.php/Nose_Gear_Strut
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  #50  
Old 02-05-2018, 09:09 AM
PG13 PG13 is offline
 
Join Date: Apr 2017
Location: Fresno
Posts: 18
Default

As a purchaser of my 7A and now also someone who doesn't feel a thing in the cockpit, but has an observer on the ground telling me I have a bad nosewheel shimmy.... Can someone lead me to the procedure for checking the breakout force? I see it referred to on a LOT of different threads but no actual reference to the procedure. Thanks.
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