Ouch! Hope you heal up quickly.
Originally Posted by
JohnJ80
The classic advice given is to clamp the top tube between your knees. This works if it’s the top tube (less but still effective if down tube) that’s oscillating. What this does from a frequency perspective is make your top tube shorter so that you push the resonant frequency higher. Once it’s higher, then it will stop oscillating from the current input frequency because it’s no longer the resonant frequency. Of course, this is going to matter what the frequency is, where you clamp your knees on the tube etc.... So that’s why it doesn’t work *all* the time.
Scary problem. Been there.
J.
That was the drill for those flexible flyers of the 1980's. John gave a very good explanation of the forces involved. Basically anything that can create a vibration can cause this, so most of the suggestions may help.
I have a Peugeot CFX-10 from the early 1980s with a 61 cm top tube. It seems to wobble if anything is wrong. One item which has changed the wobble point on that bike is tire balance. Patch a tube, by the side of the road, wobble at 30 MPH. Good wheel balance, wobble at 35, so I would add wheel balance to the list of wobble causes.