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  #1  
Old 09-24-2013, 09:15 AM
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blahphish blahphish is offline
 
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Default nose wheel shimmy [video]

I want to share some findings that Brandi and I had regarding nose wheel shimmy.

Lately we had been having increasing instances of nose wheel shimmy on landing and suspected the tension needed to be tightened again (since we had already tightened it once after annual). Before we tightened it, we shot a video and I was amazed to see just how much the nose wheel will turn due to prop wash!! The nose wheel stayed in this position for the entire duration of the flight and surely had to impact airspeed.

https://www.youtube.com/watch?v=IrnD...I&noredirect=1

I measured the break out force at around 17 or so lbs when I took the fairings off. Tightening it to the next notch in the castle nut put it around 35+ lbs, which is unpleasant to taxi around with due to having to drag the brakes a lot. I decided to drill a new hole through the threaded nose gear so that we could get closer to the vans recommended 26 lbs. Got it around 29 lbs or so and I'm happy with that.
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Old 09-24-2013, 09:30 AM
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Auburntsts Auburntsts is offline
 
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Nice video - thanks for sharing. However, I'm wondering if in lieu of drilling a new hole you could have added another spacer to achieve the target breakout force.
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  #3  
Old 09-24-2013, 09:38 AM
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Mike S Mike S is offline
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It looks like you are letting the nose wheel down a lot earlier than you need to, I know that the few times I have had nose wheel shimmy, speed was a big factor.

Try keeping it on the mains only as long as you can.

Or, did you edit out the sequence a bit and just fool me

Anyway really interesting how the nose wheel weathervanes in the first take off. I would have expected the relative wind to keep it straight.
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  #4  
Old 09-24-2013, 10:00 AM
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flyboy1963 flyboy1963 is offline
 
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Default thanks for sharing!

Brian, just another data point. I had some mild nosewheel shimmy ( that I felt, did not view) with about 15 lbs. breakout on the nosegear...so naturally, at annual, I tightened to 26 lbs.
....made NO difference.( except, perhaps, to hold it straighter in flight.?)

FYI this has been discussed a lot on VAF, another option to achieve the correct crush can be drilling the NUT for a new cotter pin, so it lines up with the existing hole in the gear leg.
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  #5  
Old 09-24-2013, 10:29 AM
ReidVaitor ReidVaitor is offline
 
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Default RV-10 shimmy

Quote:
Originally Posted by Auburntsts View Post
Nice video - thanks for sharing. However, I'm wondering if in lieu of drilling a new hole you could have added another spacer to achieve the target breakout force.
Does not work, it requires very little space on the threads to go from one to the next notch. I used .025 and it was too much. What Brian did was smarter, now he can move in half notch increments. I drilled a hole on the nut and it was a one time use since once I moved it it became a nut with an extra hole and will never serve a benefit when I need to tighten again.
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  #6  
Old 09-24-2013, 10:46 AM
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Auburntsts Auburntsts is offline
 
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Quote:
Originally Posted by ReidVaitor View Post
Does not work, it requires very little space on the threads to go from one to the next notch. I used .025 and it was too much. What Brian did was smarter, now he can move in half notch increments. I drilled a hole on the nut and it was a one time use since once I moved it it became a nut with an extra hole and will never serve a benefit when I need to tighten again.
OK, but is it possible the same thing could happen with the new hole in threaded portion of the gear leg should a subsequent adjustment be needed? IOW the new hole becomes a one time use but it's now in the gear leg vs. the nut? Just trying to figure out the best approach.
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  #7  
Old 09-24-2013, 11:51 AM
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A second hole in the shaft that is a half flat of the nut off-----30* will allow either of the holes to be used each time you tighten the nut.

Good solution as I see it.
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  #8  
Old 09-24-2013, 12:13 PM
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blahphish blahphish is offline
 
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I have no regrets (at least yet ) for drilling new holes. I assumed that two #30 holes in steel in an area that didnt seem to be load bearing would be fine, but I'm sure we could all gain some good insight from one of the many engineers who read these forums who may care to chime in with their knowledge.

Quote:
Originally Posted by Mike S View Post
It looks like you are letting the nose wheel down a lot earlier than you need to, I know that the few times I have had nose wheel shimmy, speed was a big factor.

Try keeping it on the mains only as long as you can.

Or, did you edit out the sequence a bit and just fool me
Its edited - we were actually pretty slow at that point.
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  #9  
Old 09-24-2013, 12:17 PM
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blahphish blahphish is offline
 
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Default

Quote:
Originally Posted by flyboy1963 View Post
Brian, just another data point. I had some mild nosewheel shimmy ( that I felt, did not view) with about 15 lbs. breakout on the nosegear...so naturally, at annual, I tightened to 26 lbs.
....made NO difference.( except, perhaps, to hold it straighter in flight.?)
That is interesting and thanks for the data point. Are you certain you are feeling a nose wheel shimmy and its not the mains? The mains shimmy too at certain conditions and that's a whole separate topic Maybe a video is in order, if you can pull it off.
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  #10  
Old 09-24-2013, 12:39 PM
868RM 868RM is offline
 
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Default Holes

Brian, I drilled (2) holes in the gear leg during initial set-up. Works very well and allows more accurate setting so that taxi way travel is far more friendly. Ron
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