wcalvert
Well Known Member
I realize this has been discussed recently in other contexts, and likely known by many, but here's my story.
My -7 had a main wheel shimmy since it was new 200+ hours ago. It would reliably shake as it slowed on landing at 18-21 kts, seemingly dependent on a/c weight and mostly tire pressure. All the talk of the need for gear leg stiffeners had me believing that it was an inherent issue with the aircraft, so I decided to live with it.
Then a few weeks ago I was doing a section takeoff with Ken out to the islands. On return he mentioned that the shake I was feeling was likely my left main, he could see it shudder after liftoff.
So that made me suspect that the issue may not be with the gear leg, but with the tire balance. Given the tiny size of the wheel and the low speed when the issue occurred, I just didn't suspect tire balance as the culprit.
Off to HF and got the static balancer they sell for motorcycle tires, with a horizontal rod on bearings. It did take some searching to find large enough cones to fit the bearings, but with all the tools together I balanced both sides. For sure the left was well out of balance, and as a side note, has no mark on the tire for the stem location, so it's most likely in the wrong place on the rim.
Test flight resulted in super smooth operation during taxi out, and no shimmy or shake on roll out! What a difference. That and the new tailwheel with sealed bearings made the taxi out very nice and smooth.
Long story short, if you're having the shakes, check your balance. Worth a try.
Cheers
My -7 had a main wheel shimmy since it was new 200+ hours ago. It would reliably shake as it slowed on landing at 18-21 kts, seemingly dependent on a/c weight and mostly tire pressure. All the talk of the need for gear leg stiffeners had me believing that it was an inherent issue with the aircraft, so I decided to live with it.
Then a few weeks ago I was doing a section takeoff with Ken out to the islands. On return he mentioned that the shake I was feeling was likely my left main, he could see it shudder after liftoff.
So that made me suspect that the issue may not be with the gear leg, but with the tire balance. Given the tiny size of the wheel and the low speed when the issue occurred, I just didn't suspect tire balance as the culprit.
Off to HF and got the static balancer they sell for motorcycle tires, with a horizontal rod on bearings. It did take some searching to find large enough cones to fit the bearings, but with all the tools together I balanced both sides. For sure the left was well out of balance, and as a side note, has no mark on the tire for the stem location, so it's most likely in the wrong place on the rim.
Test flight resulted in super smooth operation during taxi out, and no shimmy or shake on roll out! What a difference. That and the new tailwheel with sealed bearings made the taxi out very nice and smooth.
Long story short, if you're having the shakes, check your balance. Worth a try.
Cheers