Carbon Process

A very interesting read over at BikeRumour.com. They are going through the process Guru uses for their carbon frames.

Factory Tour – Guru Cycles, Part 2: Building a Carbon Bicycle Frame

Factory Tour – Guru Cycles, Part 2: Building a Carbon Bicycle Frame

Nothing too unexpected but a few cool bits. Using glass beads to fill/stiffen the internal bladder for layup is a neat idea. I'm working on something using low melt alloy instead. It looks like they're using an AirTech fairing compound at the joints (pink). I tried that but didn't like the results and didn't want to have the bake the frame too many times in the process.

One thing I noticed is the fillets don't leave much exposed tube at the joints (HT and BB tubes). I've always thought it best the have the joint wrap adhere to both tubes, carbon to carbon, with a smaller fillet. Would their method not leave just a tiny bond line where the carbon wrap meets the tube at a sharp angle?

Glen
back40 bicycleworks

I like the simplicity of their test rig.

I've been talking to Todd about getting him to make me an EN14781 test rig, this should make it cheaper and easier.

in what way is it simpler than exactly what the spec calls out? it has all the elements of most EN14781 test beds i've seen. i'm about 2/3rds through building mine. pneumatics, solenoids and timing are all done. just need to build the frame. if i am missing something I'd like it pointed out. ;-)

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Originally Posted by Mark Kelly

I like the simplicity of their test rig.

I've been talking to Todd about getting him to make me an EN14781 test rig, this should make it cheaper and easier.

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Wow...they gave them a surprising amount of access to their process.

Thanks for posting this.

Dave

It's simpler than the version of which I was thinking but that's probably my natural tendency to overcomplicate everything talking.

The spec is for an applied force of 1100N, I was thinking of doing this with a calibrated air ram or similar. Just hanging a weight and lifting it off like Guru do is much simpler to implement and automatically already calibrated.

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Originally Posted by back40

A very interesting read over at BikeRumour.com. They are going through the process Guru uses for their carbon frames.

Factory Tour – Guru Cycles, Part 2: Building a Carbon Bicycle Frame

Factory Tour – Guru Cycles, Part 2: Building a Carbon Bicycle Frame

Nothing too unexpected but a few cool bits. Using glass beads to fill/stiffen the internal bladder for layup is a neat idea. I'm working on something using low melt alloy instead. It looks like they're using an AirTech fairing compound at the joints (pink). I tried that but didn't like the results and didn't want to have the bake the frame too many times in the process.

One thing I noticed is the fillets don't leave much exposed tube at the joints (HT and BB tubes). I've always thought it best the have the joint wrap adhere to both tubes, carbon to carbon, with a smaller fillet. Would their method not leave just a tiny bond line where the carbon wrap meets the tube at a sharp angle?

Glen
back40 bicycleworks

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We invented a low melt alloy process for aircraft props 15 years ago i mentioned it on the old FF for shorts aircraft it has been obsolete for many years as basically more advanced methods were developed off the back of them though i dont know if there was a patent placed on it there was talk

Test rigs for carbon in and metallics in general just wiggle till something breaks, nearly engineering science but we found you need other bits of info to mske it truly accurate and representative

Hey Mark, i think the hanging weight is more about the un-official over valued STW(Stiffness To Weight) thing so many are into. Watch the video for the EN testbed.

Pneumatic cylinders force calculations are pretty simple. F=P A where P is the air pressure and A is the area of the piston. So if you are looking for a force of 1100N(250lb) with a 3" cylinder, 84psi will get you there. Some dual action cylinders introduce losses but their data sheets would provide insight.

Quote:

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Originally Posted by Mark Kelly

It's simpler than the version of which I was thinking but that's probably my natural tendency to overcomplicate everything talking.

The spec is for an applied force of 1100N, I was thinking of doing this with a calibrated air ram or similar. Just hanging a weight and lifting it off like Guru do is much simpler to implement and automatically already calibrated.

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