hehehe, I'm reminded of the old proverb "The person saying it cannot be done should not interupt the person doing it....
Below is one of the frames I fixed. Cracked the top tube right through. Performed a carbon repair in my garage and then stress tested that repair for 4 years as my huck it and hope bike with zero failure. As evidenced by the below sizable huck. That photo is 4 years after the repaired.
Can carbon be repaired? yes it can. If you have the knowledge its quite easy and can be done with basic tools.
Regarding weight. I most definitely can tell the difference in 500 grams. However total weight savings is the sum of all weight savings initiatives.... Carbon frame and wheels, integrated carbon bar/stem, ti bolts, smaller battery options ect. then i'm into 1.5 kgs lighter which is really noticable. To me it seems pretty silly to put all that light stuff onto a heavy frame......
Re my alloy knowledge. I would say i likely have more alloy knowledge than most on this forum having spent several years manufacturing aircraft components in varying grades of alloy in generally 2000, 6000 and 7000 series (and carbon fibre products too). In general terms we form components in 0 condition then heat treaded to T6. Various machined parts 7000 series already heat treated to T6.
Atherton have chosen to use 7075 alloy. Likely T6 heat treatment.
7075-T6 is very hard to weld and not something that is easily undertaken in your garage or at all and it definitely requires heat treatment if you can achieve welding at all. Why would they use 7075-T6 rather than the more traditional 6061-T6?
Because uts of 7075-T6 at 572mpa is 85% stronger than 6061-T6.
Side note. I owned a Pole Voima Made from bonded 7075-T6 and that was the worst bike decision I have made. I will not touch a bonded alloy bike ever again.......
I do enjoy a boutique frame manufacturer. But they do have a tendency to go out of business. Current bike notwithstanding the last two bike brands i have owned have gone out of business. Pole and Deviate. The Pole was not practically repairable at all. It was a freaken desk weight when it cracked. At least i'll be able to fix my Claymore if i break it.,,,,,,
Thus my original reasoning. I dont want to throw down a load of cash on to a boutique builder made from a frame material that isnt easily repairable.
PS Just for you, here's some ai detail on the weldability of 7075-T6 and comparing it to carbon fibre so you can get a bit of a better understanding about what im talking about.
"Weldability of 7075-T6
7075-T6 is notoriously difficult to weld because the very heat treatments that provide its strength also make it vulnerable during the welding process.
- Hot Cracking: The high copper and zinc content leads to a wide solidification temperature range, making the alloy extremely sensitive to solidification cracking as it cools.
- Heat-Affected Zone (HAZ) Softening: The intense heat of welding causes the carefully formed strengthening precipitates (
View attachment 174914
MgZn2cap M g cap Z n sub 2
) in the T6 matrix to coarsen or dissolve. This creates a "softened" zone that is significantly weaker than the base metal.
- Joint Performance: As-welded 7075-T6 typically retains only 50% to 60% of the base metal's original strength.
- Post-Weld Heat Treatment (PWHT): To recover strength, welded 7075-T6 components often require a full Post-Weld T6 Treatment(SHT + Quench + Aging).
- This can restore up to 80%–97% of the original tensile strength.
- Limitation: PWHT can significantly improve strength but offers only marginal improvements in ductility, and the risk of grain coarsening or residual stress remains.
- Preferred Joining Methods: Due to these fusion welding risks, industry standards often prefer mechanical fastening (riveting) or Friction Stir Welding (FSW), a solid-state process that avoids melting the material.
Carbon fiber composite products exhibit a significantly higher strength-to-weight ratio than
7075-T6 aluminum alloy, with a specific tensile strength that is approximately
3.8 times greater.
UTS and Weight Comparison (Specific Strength)
The specific strength is calculated by dividing the Ultimate Tensile Strength (UTS) by the density. This "weight to MPa rating" is a key metric in weight-sensitive engineering, such as in aerospace applications.
| Property | 7075-T6 Aluminum Alloy | Carbon Fibre Composite Product |
|---|
| UTS (MPa) | ~572 MPa | Up to 6,000 MPa (typical range 2,500 - 6,000 MPa) |
| Density (g/cm³) | ~2.81 g/cm³ | ~1.6 g/cm³ (for a carbon-epoxy composite) |
| Specific Strength (MPa·cm³/g) | ~203.5 | Up to ~3,750 |
- 7075-T6 Specific Strength: 572 MPa / 2.81 g/cm³ ≈ 203.5 MPa·cm³/g
- Carbon Fibre Composite Specific Strength: Up to 6,000 MPa / 1.6 g/cm³ ≈ 3,750 MPa·cm³/g
Key Takeaways
- Superior Efficiency: Carbon fiber composite materials offer exceptional performance for their weight, allowing for structures that are significantly lighter yet stronger than those made from 7075-T6 aluminum.
- Strength is Directional: The strength of carbon fiber composites is highly dependent on fiber orientation. The high values listed above typically refer to loads applied in the direction of the fibers. In contrast, 7075-T6 aluminum is an isotropic material, meaning its strength is consistent in all directions.
- Design Complexity: Designing with carbon fiber requires more complex engineering due to its anisotropic nature, failure characteristics (brittle failure vs. yielding in metal), and higher cost."
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