Fibreglass vs aluminium?

[Mental Trousers]

Yesterday at Hampton Downs I came across a guy who had replaced the broken aluminium footpeg hanger with one he'd made up from fibreglass!!

Is that really a viable (ie safe) alternative?? What are the advantages of this (besides ease of manufacture)??

[Robtharalson]

Yesterday at Hampton Downs I came across a guy who had replaced the broken aluminium footpeg hanger with one he'd made up from fibreglass!!

Is that really a viable (ie safe) alternative?? What are the advantages of this (besides ease of manufacture)??A heavily loaded part such as a footpeg hanger can be made from FRP or CFRP, but the design has to be perfect and the materials, especially the resin used, must be very carefully selected, laid up, and cured to prevent the "shade tree mechanic's lament" -- in other words "I was sure that would be strong enough until my foot hit the ground and then the back of my head."

Unless you know exactly what you're doing it could be a deathtrap, and after a crash of any sort it becomes trash can fodder regardless of the quality of manufacture. Don't ask how I know this.

Rob

[schrodingers cat]

Did you talk to the guy and ask him any questions. It is likely that the layup contained a bit of carbon to improve the strength of the item.

As a point of interest - fishing rods and pole vaulting poles are made from fibreglass. Done properly it has plenty of 'spring'. Carbon (fibre) has the problem that the Ultimate Tensile Strength is also the Yeild Point. That means no warning. Just snap.

[Mental Trousers]

It was just fibreglass, no carbon.

What about polycarbonate?? Wouldn't that be better for this sort of application than fibreglass??

[imdying]

Sure... why not?

The main reason manufacturers don't use more composite objects is the cost of manufacturing them.