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  #11  
Old 01-11-2008, 05:46 PM
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AlexPeterson AlexPeterson is offline
 
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Quote:
Originally Posted by JAT View Post
Chuck,

SNIP My tube had gotten pinched between the halves and I suspect that may have happened to yours. SNIP

Jim
I've done this, but the originator of this thread had a different problem. I agree that there is a flaw in the tube's sidewall, and baby powder seems to be the only thing that prevents the spallating (chewing out little bits until it leaks) on the sidewall.
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  #12  
Old 01-11-2008, 08:44 PM
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rvbuilder2002 rvbuilder2002 is offline
 
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Location: Hubbard Oregon
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Quote:
Originally Posted by n468ac View Post
like everyone ...
1. LOTS of baby powder
2. Up the air pressure to 40psi
3. check the inside of the tire for a rough spot that can stick the tube
I agree with #1 and #3 but I strongly disagree with #2.
You can not indiscriminately use 40 PSI in the nose tire of any trigear RV.

A high nose tire pressure is a major cause of nose wheel shimmy.
The higher the pressure, the more round the contact area of the tire becomes and the less actual contact footprint the tire has on the ground/runway.
You need footprint/contact area to produce a friction resistance to the tire twisting...this friction helps reduce any tendency for shimmy.
The actual pressure you should use varies depending on your airplanes empty C.G. (amount of weight on your nose wheel). If you have a smaller engine and a wood prop, 40 PSI would probably be a very bad choice, especially on a 6A. If you have a heavy engine and a constant speed prop. then you can use a higher pressure.

I usually adjust the pressure so that when parked on a smooth level surface, all of the tire area that is between the two outboard most tread grooves is contacting the surface. Some people may get away with running higher pressure than that, but I believe they are pushing the limits and have a very small margin between no shimmy and a small disturbance that can set it off.
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  #13  
Old 01-12-2008, 07:03 AM
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Originally Posted by rvbuilder2002 View Post
You can not indiscriminately use 40 PSI in the nose tire of any trigear RV.
Have you tried higher air pressure? We have less nose wheel shimmy at higher air pressures.

How freely does your nose wheel turn aournd the axel and is your break out force set correctly?
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Allen Checca (father)
Christopher Checca (son)

RV-6A - N468AC
ENGINE: Lycoming 180 HP O-360-A1A
PROPELLER: Senisentch 72FM859-1-85
WEIGHT: Empty Aircraft 1152 lbs
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  #14  
Old 01-12-2008, 11:34 AM
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rvbuilder2002 rvbuilder2002 is offline
 
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Quote:
Originally Posted by n468ac View Post
Have you tried higher air pressure? We have less nose wheel shimmy at higher air pressures.

How freely does your nose wheel turn around the Axel and is your break out force set correctly?
I have worked with RV's for 20 years (probably at least a dozen A models) and this is what I have learned. Yes I have tried high pressures, low pressures, different breakout force adjustments, etc....I have found that the process I mentioned in my other post for setting the tire pressure works for all A models, giving a good resistance to shimmy but still a good margin for tire stiffness (ground clearance).
Once the ideal pressure for your airplane is determined, then you can just use that pressure value when airing the nose wheel tire. As I posted before...I think recommending a one pressure fits all airplanes airpressure is a
bad idea (there is a wide range between what weight is on the nose wheel, and the tire pressure has to be adjusted in accordance with that weight).

If you had better experience with higher pressure. I wonder if it is because your tire is slightly out of round or shape side to side, which is maybe improved by raising the pressure
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  #15  
Old 01-12-2008, 02:13 PM
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Quote:
Originally Posted by rvbuilder2002 View Post
Once the ideal pressure for your airplane is determined, then you can just use that pressure value when airing the nose wheel tire. As I posted before...I think recommending a one pressure fits all airplanes airpressure is a
bad idea (there is a wide range between what weight is on the nose wheel, and the tire pressure has to be adjusted in accordance with that weight).

If you had better experience with higher pressure. I wonder if it is because your tire is slightly out of round or shape side to side, which is maybe improved by raising the pressure

I agree with you that you have to experiment with different pressures with YOUR plane, as we know there are many different configurations that make it hard to use one pressure for all RV?s. I just wanted the forum to know that higher air pressures have helped some of us.

As for our current nose wheel ? we just replaced it this fall with a new tire and tube direct from vans. Still using the higher pressure with good results ? but it could also be our take off and landing technique. We started using a higher pressure under the though that the shimmy was caused by tire dragging from being under pressure.
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(This post by: Christopher Checca EAA Lifetime Member #799388)

Allen Checca (father)
Christopher Checca (son)

RV-6A - N468AC
ENGINE: Lycoming 180 HP O-360-A1A
PROPELLER: Senisentch 72FM859-1-85
WEIGHT: Empty Aircraft 1152 lbs
BASED: KC09 - Morris, IL.
Flying since June 6, 2005
N468AC Web Site
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  #16  
Old 01-12-2008, 04:41 PM
chuckh1197 chuckh1197 is offline
 
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Posts: 43
Default Thanks for all the good info

I have a fairly heavy plane with 200 IO360 and constant speed prop. Put a lot of baby powder in, inflated and deflated , made sure nothing pinched this time. Will let you know how it behaves. Put in about 38 psi now.
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  #17  
Old 01-12-2008, 05:37 PM
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AlexPeterson AlexPeterson is offline
 
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Chuck, I predict your flat tire problems are behind you now...
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  #18  
Old 01-16-2008, 04:18 PM
chuckh1197 chuckh1197 is offline
 
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Default Still having a problem

Flew to Portillo yesterday and landed , no problem
Upon landing back in Puerto Plata, on roll out I turned off runway and bam another flat. I had put 35 lbs in. lots of baby powder. Dont know what to do. I have my last good tube. Just ordered another tire and a couple of tubes from Aircraft Spruce and having them fedexed down. Same failure on side of tube not pinched. I am just wondering if wheel is folding on turning. Breakout force is about 26 lbs. Dont know how to solve this .
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  #19  
Old 01-16-2008, 07:48 PM
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AlexPeterson AlexPeterson is offline
 
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Well, I guess you just proved me wrong...

Have you looked very carefully at the tire to see if there is a little burr or something in it?

No sign of scuffing on the outside of the tire in the location of the innertube's hole?

Hmmm. Changing the tire would seem to make sense.

With regard to your comment on turning - how fast do you taxi while making turns? Turns should be made such that you feel essentially no lateral acceleration (not like in a car). I am not sure how that could do it anyway, but good practice would suggest slow speed turns anyway.

Good luck!
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  #20  
Old 01-16-2008, 09:44 PM
casper casper is offline
 
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Location: Derby Kansas
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Are the tubes that keep going flat the same brand. I had the same problem that you are having and My tubes were the shin fin or what ever tywan tubes. I still think that some of them have a manufactures defect in them. They kept going out in the same spot and you would think it was the tire, but you know what you couldn't put that tire back in the exact same spot. Think about it.
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