Kit-car Cycle Arch Brackets

[starkus]

Hi,

Has anyone looked into the Cycle arch brakets on kit-cars. Which fail due to cyclic load due to being mounted directly on the hub.The cycle arch bracket vibrates or ossilates at the close to the natural frequency of the road.(300HZ)
The problem maybe solved by adding a simple bobbin between the bracket and the hub.

Rick

 

[PTwizz]

The issue with cycle wings is that the mountings are limited to a design with large overhang to the load, and rely on the stiffness of the join to the hub. I would be surprised if the natural frequency is anywhere close to 300Hz. 30Hz might be closer to the mark. Adding a bobbin (I assume you mean a rubber bush) will reduce stiffness, lowering the natural frequency and allowing greater amplitude of motion, potentially allowing the wing to contatct the tyre. The solution would be to increase stiffness of the mounts, particularly toward the joint at the hub. Spreading the joints to the hub as far apart as possible will also help.

Pete.