Vibration after lift off

[seagull]

Originally Posted by Piper J3

Question: Has anyone dynamically balanced front wheel to fix this problem?

I dynamic balance all (3) of my wheels with the tires mounted, done properly it absolutely removes ALL wheel vibrations.
I have had instances where the nose wheel will shake on take off to 500’. When I spin it up on the ground it reveals itself. After rebalancing it is smooth.

[Piper J3]

Can you explain procedure / equipment needed to dynamic balance nose wheel?

[seagull]

see post #11 of this thread:
That was my early method, I have streamlined it a bit over the years.

To check balance on the plane, example nose wheel.
1) Add weight to the tail tie down hook to raise nose wheel off the ground.
2) Remove nose wheel pant.
3) Spin the nose wheel to 1500 RPM (there are many ways to accomplish this but this is approximately 60 MPH take off speed. If you can only get 700 RPM it will still probably show you the imbalance.
4) I use a 8" rubber backing disk on a corded drill and rub the edge of the disk to the tire tread.
5) Let the tire spin down to a stop and observe the shaking the airframe goes through. This is what you feel inside.

To adjust the balance, example nose wheel
1) Clean the tread area with rubbing alcohol all the way around
2) Put a mark on the tire as a reference to 12:00
3) Lightly turn the tire and see if it prefers to stop at a particular clock position.
4) I use a stack (2" squares) of duct tape starting with 4 layers onto the tread opposite the heavy side. Add more or less layers until it feels balanced statically.
5) spin the wheel up and let it spin down observing the shake. If it is better or worse. If it is vibration free go to #8
6) At this point it is trial and error for the correct position and amount of tape.
7) If you get completely lost start with a stack of 6 tapes at 12:00. Spin it up and if it is worse move the tape to 2:00, repeat the spin and move process. There will be a point in the "clock" that is noticeably better. At that location you can move the tape a little in either direction to center on the best spot, then start adjusting the number of tape layers until it spins down without any vibration.
8) Mark the location then remove the tape stack and weigh it. The ratio on the RV-12 wheels is about 3x, if the tape weighs 8 grams then the lead applied to the wheel will be 24 grams. Draw a line from the axle center to the center of where the tape was on the tread, where it intersects the wheel is where to put the weight.
9) I use lead tire weights but remove the tape they come with and replace it with 3M VHB tape. It is much better than what comes on the weights, plus I can reuse weights. I put the weight on the outer most lip of the wheel facing in. Centrifugal force works to keep the weight stuck better.

[Piper J3]

That sounds like a lot of trial and error… I was hoping someone had figured out a balancer similar to prop balancing with use of accelerometer and position sensing to calculate amount of weight and radial position on wheel.

[seagull]

Originally Posted by Piper J3

That sounds like a lot of trial and error… I was hoping someone had figured out a balancer similar to prop balancing with use of accelerometer and position sensing to calculate amount of weight and radial position on wheel.

I have the prop balancer and plans to build the fixture.
If I told you that method the response would be "that requires a $4000 balancer and a fixture I don't have", "I wish someone had a method easier to the common folk".:

[docjjrmd]

Thinking out of the box I asked one of my Go-Kart Racing patients what he uses. Very quick answer, 90 to 110 mph on 5 or 6 inch wheels they have to be dynamically balanced. So how do you do it, I ask? He said ask around at a motorcycle shop or bring the mounted tire and wheels to his shop and he would put them on his balancer, a Leo L9067. Appears the balancer cost about $1500. It takes a rim down to 1" and 2" wide. I haven't tried yet but I will take wheels and tires once finish kit shows up mid summer. Worth a try, I reckon. -JJR

[WJaviation]

Originally Posted by Piper J3

That sounds like a lot of trial and error… I was hoping someone had figured out a balancer similar to prop balancing with use of accelerometer and position sensing to calculate amount of weight and radial position on wheel.

Harbor Freight sells a motorcycle wheels balancer for $50. They also sell stick on weights. That's what I used. Took about 45min to complete the process. Wheel hasn't shaken since.

[NLPete]

Maybe you could get some ideas from this video. I have not tried it myself.

https://youtu.be/M0HPJjKXzzE

[FlyingDiver]

Originally Posted by WJaviation

Harbor Freight sells a motorcycle wheels balancer for $50. They also sell stick on weights. That's what I used. Took about 45min to complete the process. Wheel hasn't shaken since.

I don't think they have it anymore. At least, I could not find it on their website.

[OKAV8r]

Originally Posted by Mike S

This is a new "system" and probably has different vibration frequency.

And, it sounds like the system is most susceptible to vibration at a frequency that is near the frequency of full throttle prop pulses.
One way to advance toward a solution would be to use camera tech combined with nose fairing tufting to get definition of the aerodynamics in play.
Vans should have some interest in this phenomenon, as it could lead to something as simple as a small nose fairing modification for the RV-12 fleet.