Carbon Thru Axle
Moderator: robbosmans
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So wanting to reduce the weight ofthe Thru axles fitted to my Cannondale, I saw some carbon tube on ebay and did a thing 20 grams for the front axle. all done in my garage with DIY tools.
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- gabriiaia7273
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Good job. How much does it weigh now and how soon? Does the carbon tube start from the shaft head and stop before the thread? Glued with which resin?
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I reduced the diameter of the thruaxle to 10mm for 20mm length( It was suggested to do twice the diameter) then bonded the two ends onto the carbon tube with epoxy.
Make sure that there is no direct contact between ALU and carbon (galvanic cosrosion), you can solve that with a thin layer of fibreglass in the inside of the tube (if you produce it by your own)
That sounds good.mikemelbrooks wrote: ↑Wed Jan 26, 2022 12:38 pmI reduced the diameter of the thruaxle to 10mm for 20mm length( It was suggested to do twice the diameter) then bonded the two ends onto the carbon tube with epoxy.
You may well know exactly what you're doing; the only thing I'll suggest is very careful regular inspection once it goes into use.
Even the lightest thru axles seem to be made out of aluminum alloy's and I assume there is a reason for that, perhaps that the carbon wouldn't react well to certain forces. It very well could be a non-issue as after all we are all on carbon wheels, carbon frames, and carbon saddles, but just be careful as a thru axle failure could lead to a serious wreck.
That being said, it's a really cool idea and beutifully made.
For those curious (I was) a Robert Axle Project thru axle made from 7075 (12mmx119mm) is 26g and $42USD.
That being said, it's a really cool idea and beutifully made.
For those curious (I was) a Robert Axle Project thru axle made from 7075 (12mmx119mm) is 26g and $42USD.
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I would say : keep an eye on it !! composite materials do not like shear stress... I would avoid it.
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That's the one.mikemelbrooks wrote: ↑Wed Jan 26, 2022 6:58 pmThis?
https://bikerumor.com/found-aserras-ins ... thru-axle/
Few years ago I made many prototypes of carbon thru-axles.
All attempts at aerospace grade glue interface between the carbon and aluminum head/threads ultimately failed strong stress tests.
Mostly sheer cracking in the carbon.
Better results with actually tapping the carbon and fiberglas bonding the head/thread parts machined from bolts (of all things).
But the end result was abandonment of the project, as nothing really withstood my own standards.
Thus how Aserra manufactures theirs must be wildly good if they have had no issues. Stress or just general wear & tear.
I can see holding up to support wheel weight, but it's the repeated torque and sheer stresses (even microscopic movements) that seem to generate issues.
Metal just seems to be far better at this application, unless their carbon is coated with something unique.
All attempts at aerospace grade glue interface between the carbon and aluminum head/threads ultimately failed strong stress tests.
Mostly sheer cracking in the carbon.
Better results with actually tapping the carbon and fiberglas bonding the head/thread parts machined from bolts (of all things).
But the end result was abandonment of the project, as nothing really withstood my own standards.
Thus how Aserra manufactures theirs must be wildly good if they have had no issues. Stress or just general wear & tear.
I can see holding up to support wheel weight, but it's the repeated torque and sheer stresses (even microscopic movements) that seem to generate issues.
Metal just seems to be far better at this application, unless their carbon is coated with something unique.
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