rocketbob
Well Known Member
About 5 years ago a friend of mine installed 380 tires on his RV7. I fly this airplane regularly. With the 380 tires a shake would develop right around 19 KTS GS which required firm braking to slow thru that speed fairly rapidly to get the shake to stop. Lived with it but it was pretty annoying. Things tried to fix the shake: carefully balancing the tires, new tires instead of recaps, new wooden gear leg stiffeners, various tire pressures, tried one gearleg with a stiffener without the other having one thinking a resonance was developing between the two. Nothing really worked but there were varying degrees of effect on dampening the oscillation. That is, until the new idea we came up with and implemented a few weeks ago.
Wrap the gear legs with 3K 5.8oz carbon fiber. No stiffeners.
Using a 48" roll of carbon fiber, squeegee wetted a 4ft or so square, 8" wide strips were cut using a rotary knife which were then rolled up and wrapped around clean gearlegs bottom to top in one pass overlapping 50% which amounts to two layers of carbon.
No peel ply or vacuum bagging was used as this was considered an experiment.
The layup was done with mains on the floor.
After about a dozen or so hours still no shimmy or shake at all and it seems to be holding up fine.
The gear feels absolutely perfect now with no tendency to rebound or skip. Tires are 35psi. In no way does the gear feel stiffer, but feels well dampened. For this reason I don't think any additional stresses are placed on the engine mount.
Wrap the gear legs with 3K 5.8oz carbon fiber. No stiffeners.
Using a 48" roll of carbon fiber, squeegee wetted a 4ft or so square, 8" wide strips were cut using a rotary knife which were then rolled up and wrapped around clean gearlegs bottom to top in one pass overlapping 50% which amounts to two layers of carbon.
No peel ply or vacuum bagging was used as this was considered an experiment.
The layup was done with mains on the floor.
After about a dozen or so hours still no shimmy or shake at all and it seems to be holding up fine.
The gear feels absolutely perfect now with no tendency to rebound or skip. Tires are 35psi. In no way does the gear feel stiffer, but feels well dampened. For this reason I don't think any additional stresses are placed on the engine mount.