Vibration after lift off

[Tacco]

I think everyone is overthinking this. It's simple. Buy one of these, ~$50. Spin it by hand and let it settle. Use those sticky auto weights on the inside race of the rim. NEVER place anything inside the tire where it could puncture the tube. I check the nose wheel every annual whether or not I've felt vibration. It's super easy.

There is really no need to balance the mains unless they're really gross. Bearing drag will stop them from rotating shortly after takeoff.

See this video if you don't believe me.

https://youtu.be/P5N8C4_f8eE

[Draker]

Nice thread. I am chasing an intermittent vibration issue on my -7A, and I would not have thought to suspect gear legs or wheels.

[Reilly]

Thought I would share my vibration issue. I have a original 12 with AM15 engine.
Also have experienced a shudder after lift off for a few seconds on every takeoff.
After reading this thread I checked my nose wheel and found it to be out of round and unbalanced. Fitted with a Vans supplied Aero Classic.

Not sure if it's a manufacture fault or from standing prolonged on the same spot during build.

I did not want to try balancing it like that so bought a new Goodyear.
Lined the valve up with the red dot and it was in perfect balance.

Test flight today with no vibration and shudder at all

Also found that the RHS fairing bracket had cracked due to this as well.

[Hotscam]

Bougth a new tyre (Michelin) which is even better quality than Aero Classic.
Balanced it dynamically up to about 3000 rpm. Perfect
Nothing changed. Bad vibration in take off and every time you climb.

The only thing that works is taking the pant off. All gone.

My guess
it seems like the wheel spins very fast with the pant and just the lower half sticking out to excite it.
Without the pant both upper and lower side get the same airflow which stops or reduces the spin.
To prove this I fitted a rubber flap rubbing against the tyre to add drag, which proved this point. The flap is gone after one flight so no permanent solution.
Not so easy to brake this wheel in a safe way

regards

Jack
Netherlanda

[rvbuilder2002]

Originally Posted by Hotscam

Bougth a new tyre (Michelin) which is even better quality than Aero Classic.
Balanced it dynamically up to about 3000 rpm. Perfect
Nothing changed. Bad vibration in take off and every time you climb.

The only thing that works is taking the pant off. All gone.

My guess
it seems like the wheel spins very fast with the pant and just the lower half sticking out to excite it.
Without the pant both upper and lower side get the same airflow which stops or reduces the spin.
To prove this I fitted a rubber flap rubbing against the tyre to add drag, which proved this point. The flap is gone after one flight so no permanent solution.
Not so easy to brake this wheel in a safe way

regards

Jack
Netherlanda

Jack
I think the fact that others have totally resolved a vibration problem by balancing the nose wheel assembly of their RV-12, and since you have proven that your nose wheel rotating is causing your vibration, it proves that even though you say yours has been balanced, that it actually is not (unless your airplane has some amazing mods that allows to fly at Mach .9 or some other crazy fast speed )

[FitzRX7]

Posting this to multiple balance threads so people don't go on the wild goose chase I just did:

Harbor Freight/Amazon cones (1 1/8") no longer fit the either with bearings (not best option) or even close to bearing races. According to another VAF'r if you purchase the "DC42 Parts" from here (http://www.marcparnes.com/Ducati_Mot...ancer.htm#DU42) for $50 shipped you'll be able to use the $50 balancer. $100.

Another option which I wish I had seen before assembling the HF one is from Desser, $100 for a bubble balancer style desktop unit that doesn't have bearings that will rust out. (https://shop.desser.com/desser-ga-05...detail/324692/). Another bonus is you don't have to pull out bearings to get a decent balance like you do with the HF type.

YMMV, hopefully not as many miles as I had.

[rvbuilder2002]

Originally Posted by FitzRX7

Another bonus is you don't have to pull out bearings to get a decent balance like you do with the HF type.

I have always balanced with the bearings still in place. They have enough friction from the rubber seal that they don't rotate. The cones included with the HF balancer fit in the bearings fine.

What is the reason for balancing with the bearings removed?

[Hotscam]

Originally Posted by rvbuilder2002

Jack
I think the fact that others have totally resolved a vibration problem by balancing the nose wheel assembly of their RV-12, and since you have proven that your nose wheel rotating is causing your vibration, it proves that even though you say yours has been balanced, that it actually is not (unless your airplane has some amazing mods that allows to fly at Mach .9 or some other crazy fast speed )

Scot

That might be the case and will try again, but does mot explain to me why the old nose leg and fork did not have this problem at all

[BillL]

Originally Posted by Hotscam

Scot

That might be the case and will try again, but does mot explain to me why the old nose leg and fork did not have this problem at all

Jack, I don't know much about the 12, but I was flying with a friend and noticed his front gear was vibrating and the wheel turning in flight. He was happy to know as he was sorting an inflight vibration. Also, after sitting, my tires will have a flat spot and that affects the balance.

[Piper J3]

I installed a new nose wheel tire and Michelin AirStop ($150) during Annual Condition Inspection back in March. I did the wheel balance with the wheel installed on the nose fork and I’m not happy with outcome. I now balanced on a Harbour Frt balancer and had to add 2 oz more to get good balance.

Tire is 5.00x5 Aero Classic LSA. The tire did not have a painted dot to indicate light portion of tire. Normally the dot is placed to offset the weight of the valve stem and things work out pretty well. I now have 14 pcs of ¼ ounce lead weights placed inside the wheel hub and packed around the valve stem. This is wild... I used some Gorilla Glue to prevent weights from shaking loose when wheel spins up suddenly. I plan a test flight tomorrow.
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