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nose wheel shimmy [video]

blahphish

Well Known Member
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=IrnDztLJbSI&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.
 
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.
 
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:confused:

Anyway really interesting how the nose wheel weathervanes in the first take off. I would have expected the relative wind to keep it straight.
 
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.
 
RV-10 shimmy

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.
 
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.
 
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.
 
I have no regrets (at least yet :eek: ) 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.

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:confused:

Its edited - we were actually pretty slow at that point.
 
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.
 
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
 
that is REALLY fascinating how the wheel is cockeyed inthe prop wash. I just assumed it'd straighten right out in the airstream. Great video. Thanks for posting that.
 
Upon landing a few weeks ago, I had some nosewheel shimmy to the point that my wheel pant was fractured. I checked the breakout force and it was pretty low. Don't know why it wasn't a factor until then, but it took several notches worth of turning to get it right.

I guess it's for the better, because it forced me to do some cleanup on the wheel pant after I fixed it and now I will have to primer and paint it! (I'm having too much fun flying to want the airplane out of service.)

Jim Bower
RV-6A N143DJ
 
alternatives to cup washers alone?

It seems that even at specified crush, the cup washers aren't damping oscillation all that well.
You can easily see with moving it by hand...... Once the breakout force is reached, there is little to no further resistance.
Does anyone have experience with other types of swivel dampers? Not that the tiny oleo style on the nosewheel of a cessna are much better.
....could using a viscous fibre washer of some kind produce a more predictable drag, without affecting steering?
I will speculate that the metal-on-metal washers are going to vary a lot with temperature, oil film, etc.
 
that is REALLY fascinating how the wheel is cockeyed inthe prop wash. I just assumed it'd straighten right out in the airstream. Great video. Thanks for posting that.

Surely it IS straightened out in the airstream. It's just that the flow coming off the prop corkscrews, it's not parallel to the longitudinal axis of the air raft.
 
Weathervane

Nose wheel weathervane is NOT due to propwash. It is due to the wheel pant not centered over the nose wheel. To get the amount of turn in the earlier part of video you only need to be off .100 of an inch. Ask me haw I know! Gene
 
As has been stated and discussed in many previous texts: do NOT lubricate the Bellville washers (per Van). The nose gear is a taxi gear not a landing gear. Hold that nose wheel off of the pavement till it won't stay up anymore and you will alleviate a lot of problems.
 
so did you see a speed increase with the straighter pointing nose wheel?

I wish I would have tested to find out. Going to have to wait until after its painted, and at that point its not really a great test anymore. Unfortunately, I took it right to the painter after the adjustment on a quick 15 minute flight and didnt check.
 
Old thread, new shimmy.

Resurrecting an old thread here.

I've been flying for about 1.5 years and have *never had a nose wheel shimmy problem. This morning I landed in some moderate cross-wind conditions and the landing was a little sloppy, coming down onto the nose-wheel quickly after the main gear. And there was a shimmy during roll out. The shimmy remained until I turned off the runway.

Several months ago I noticed the same thing. As I recall, that time was something like 10 gusting to 20 all crosswind and I had the same issue. I quickly put the nose wheel down after landing an the nose shimmied during roll out until turn off.

I fly about once a week and apart from these two incidents my nose wheel does not shimmy.

Anyone have any idea what might be going on here?
 
Have you checked the break out force on the nose wheel? I believe it?s very common for it to loosen up, especially during the first year of flying.
 
Have you checked the break out force on the nose wheel? I believe it?s very common for it to loosen up, especially during the first year of flying.

It had loosened up but I reset it according to the plans at my annual last August. Both incidence of my shimmy were after this.
 
Anti-Splat Nose Wheel Job

When I acquired my RV-10 almost 3 years ago I also had nose wheel shimmy. As a previous owner of an RV-9A and having done the Anti-Splat nose wheel and main wheel mods, I am a believer in the mod.


I sent my My RV-10 nose wheel off and had the mod performed. Once returned and installed I have NO nose wheel shimmy problems.


Now if there was only enough demand for Allen to be able to tool up to do the mains on an RV-10 I would ecstatic. Until then I still have main gear shimmy issues no matter what I do.
 
In my case, I've only had a shimmy twice and both times after I let the nose down too fast during a cross-wind landing. And then it doesn't seem to stop until I get very slow and turn off the runway. I'm wondering if it gets triggered by a side load or something like that when it hits the ground. ... By the way, I have the Berringer nose wheel.
 
In my case, I've only had a shimmy twice and both times after I let the nose down too fast during a cross-wind landing. And then it doesn't seem to stop until I get very slow and turn off the runway. I'm wondering if it gets triggered by a side load or something like that when it hits the ground. ... By the way, I have the Berringer nose wheel.

This going to be something that isn't uniform across the fleet, but most people should check the nose wheel tension multiple times a year the first few years.

I severely damage my nose wheel pant when the tension had dropped to 13lbs and landed in a cross wind condition. It was the week before my condition inspection for my third year of flying. I had tightened in twice before that and was planning to check again during my condition inspection. The good news is that three years later and it had held it's tension that entire time.
 
This going to be something that isn't uniform across the fleet, but most people should check the nose wheel tension multiple times a year the first few years.

I severely damage my nose wheel pant when the tension had dropped to 13lbs and landed in a cross wind condition. It was the week before my condition inspection for my third year of flying. I had tightened in twice before that and was planning to check again during my condition inspection. The good news is that three years later and it had held it's tension that entire time.

Wow. Thanks for the tip. I'm going to check my breakout force again as soon as possible.
 
I too had the shimmy and breakout force was correct. Upon lifting the nose (holding tail down with tie-down), I found the entire leg was moving side to side. Ordered and installed a close tolerance bolt from ACS and the problem is solved. The old bolt showed signs of wear. The new one fit perfectly. Currently have 225 hrs on the plane with the Anti-Splat nose wheel bearing mod done since day one.
 
What's the verdict?

So I need to increase the break-out force on my Nose Gear spindle but turning the nut one flat to the next hole makes it way too tight. Is the common thinking that it's OK to drill a second hole in the spindle or add a hole (or notch) to the nut?

Also, if you are drilling the leg do you remove it and use a drill press or free-hand it with a drill motor?

-Marc
 
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I made another notch in the nut and used AN3 bolt (or a short cutter pin) to lock the nut only on the handmade notch. No need to lock the nut across the axle. And a lot easier to notch the nut than drilling the axle.

Michel
 
If it’s a new installation you’re okay going on the high side. It will loosen up over the first 50 hours or so. Also be sure you’ve got it well greased and also exercise the pivot while you’re adding grease to ensure it’s well distributed before you take any measurements.

Another tip is to tighten it, then exercise the full range of motion before you take the measurement. Exercising the pivot across the range of motion will loosen the breakout force.

But, if I had it to do again, I’d error on the tight side and let it wear into the proper range rather than going for perfection and having it run away from you.

Phil
 
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I ended up cutting a new slot in the nut and tightening it up to get 32 pounds of breakout force. We will see how well that works today. Also, someone mentioned that no grease should be applied to the Bellville washers. mine were greased so I cleaned them and put it back together dry.

-Marc
 
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