RV-8A nosewheel breakout

srbooher · #1 10-24-2015, 04:31 PM

I have a problem with my nosegear rotating to the limits on touchdown. It has caused damage to the pants where the tire contacts the pants when the wheel hits the limits. I've mounted a camera under the wing and recorded the action and it's a violent side to side oscillation of the wheel and pants where inertia brings the side of the pants opening in contact with the tire. I've checked the breakout and it's 23 lbs. I don't believe I'm landing in a crab, and I hold the nose off on a paved runway until it finally falls through. Andy suggestions on what is happening? Video available if there's a place to post it.

aerhed · #2 10-24-2015, 04:59 PM

Is your T stop facing forward like it should be?

rvbuilder2002 · #3 10-24-2015, 06:10 PM

Quote:

Originally Posted by srbooher

I have a problem with my nosegear rotating to the limits on touchdown. It has caused damage to the pants where the tire contacts the pants when the wheel hits the limits. I've mounted a camera under the wing and recorded the action and it's a violent side to side oscillation of the wheel and pants where inertia brings the side of the pants opening in contact with the tire. I've checked the breakout and it's 23 lbs. I don't believe I'm landing in a crab, and I hold the nose off on a paved runway until it finally falls through. Andy suggestions on what is happening? Video available if there's a place to post it.

I think the specification is for 26 pounds measured by pulling at the axle.

868RM · #4 10-24-2015, 06:23 PM

What bearing setup do you have?

gasman · #5 10-24-2015, 08:44 PM

Quote:

Originally Posted by rvbuilder2002

I think the specification is for 26 pounds measured by pulling at the axle.

With the wheel off of the ground.......

You never know.

greghughespdx · #6 10-24-2015, 10:19 PM

1. Tire pressure: check for 30-35 pounds (which is what the plans specify, const. manual page 10-7). Some will tell you 30 is pretty low in the real world. If it's too low, you can get all sorts of potentially weird behavior. And the further down the low scale you go, the further up the potential weird behavior scale you are.

2. Just looked it up in my plans, and specified break out force for the 8A nose wheel is 22 pounds, measured with a spring scale pulling continuously in-line with the axle, and as mentioned that's measured with the wheel off the ground. Check the breakout force required in both directions. See construction manual page 10-7.

3. Take off the wheel fairing and check to make sure this part is installed correctly and there's no damage. If it's not installed properly, given the behavior you described I'd be concerned, and would make good and sure any damage is addressed before flying it.

rvbuilder2002 · #7 10-24-2015, 11:07 PM

Quote:

Originally Posted by greghughespdx

1. Tire pressure: check for 30-35 pounds (which is what the plans specify, const. manual page 10-7). Some will tell you 30 is pretty low in the real world. If it's too low, you can get all sorts of potentially weird behavior. And the further down the low scale you go, the further up the potential weird behavior scale you are.

2. Just looked it up in my plans, and specified break out force for the 8A nose wheel is 22 pounds, measured with a spring scale pulling continuously in-line with the axle, and as mentioned that's measured with the wheel off the ground. Check the breakout force required in both directions. See construction manual page 10-7.

3. Take off the wheel fairing and check to make sure this part is installed correctly and there's no damage. If it's not installed properly, given the behavior you described I'd be concerned, and would make good and sure any damage is addressed before flying it.

Greg's right about 22 pounds. I shouldn't trust my memory....

Too high of air pressure cause extreme shimmy issues as well. In fact that is much more likely to cause excessive shimmy than too low.

Holding nose off until it "falls through" could also be a problem depending on what you actually mean by that.
Best technique is hold it off until it you are close to loosing elevator effectiveness, and then just before that happens let it down easy, but do not stop at a point where the tire is just barely touching (that is a prime time for shimmy). Once you start the process, smoothly transfer from not touching, to fully down.

David-aviator · #8 10-25-2015, 05:36 AM

Quote:

Originally Posted by srbooher

I have a problem with my nosegear rotating to the limits on touchdown. It has caused damage to the pants where the tire contacts the pants when the wheel hits the limits. I've mounted a camera under the wing and recorded the action and it's a violent side to side oscillation of the wheel and pants where inertia brings the side of the pants opening in contact with the tire. I've checked the breakout and it's 23 lbs. I don't believe I'm landing in a crab, and I hold the nose off on a paved runway until it finally falls through. Andy suggestions on what is happening? Video available if there's a place to post it.

Steve, get an 8 with a tail wheel and your NG troubles are gone forever.

srbooher · #9 10-25-2015, 09:42 AM

So, the nose stop flange is installed correctly, and the breakout force of 23 lbs was measured by the book with nose wheel off the ground and fairings removed. I can see where my "nose falls through" technique might aggravate the problem. I'll try lowering it before I lose elevator authority and see if that helps. It's only done it 2 or 3 times so it sounds like slight differences in technique could cause the problem..