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And hey @Ryan Burney I looked back and noticed you were working with 6061, 7075 should give a different result.

It's not that you won't, just that the stresses should be below the fatigue limit at the weldment. A well designed joint is important, a quick transition from thick to thin in an area that sees high forces might be bad if it relies on the weld joint.

I've learned a ton about welding, rivets, and metalurgy from these answers, but I'm still wondering: aren't you gonna increase the failure rate at welds by inducing additional flex in a welded aluminum structure?

I'll only speak to "boats" but riveted construction is usually limited to small jon boats (12-14' length) using thin gauge sheetmetal (1.5mm or so) construction. Welding requires higher skill and a slower manufacturing speed. Rivets are quick and low skill in comparison. That said, most small boats for rougher water use are welded these days. The type of aluminum used in the design drives the way parts are manufactured. 5052 used in marine applications has a relatively low tensile strength but is less affected by the heat from welding and has good corrosion resistance. These qualities work well for boats...

Absolutely fantastic article, thanks a lot! Such interesting findings and very well written 👌 I'm really surprised how well the cnc chainstay holds up against the tubed version. What's your prediction, would one of the solutions have more potential / have more room for optimization?

+1 for rim width. Spoke no. Could also be a size specific option. I have no problem running ex471 28 spokes over 32 ex511’s at 90kg I had 29” roval 28/20 spoke carbon rims on my enduro and they actually held up really well. I think the narrow rear thing is actually a tyre profile/roll thing as much as a stiffness thing, like there’s 20g in the difference between an ex471 and 511

Brilliant write up again Ryan. One thing I'll add, is that it's interesting that the engineering has become so good, that a lot of pros and frame builders are now looking to make frames more compliant, and that is with fancy high end suspension and light weight bikes. We really are approaching the final frontier of design.

At what point are you going to increase failures at the welds by increasing flex in a welded aluminum structure? I think that's why they use rivets instead of welds on planes and boat hulls.

Also, how much does the shape of the rear triangle make a frame prone to flex or not ? I mean, if you compare for instance a Giant Glory to an Intense M1 (moreover the high pivot one) or a V10, doesn't the shape of those 2 bikes is more prone to flex because the triangle is way more compact tha nthe glory ? To explain better, let's compare a similar set up, that of a Santa Cruz Hightower for instance (or most SC), and that of a Scor. They're quite similar, both are VPP, except the SC has the...

@Ryan Burney thanks for the write up! Excited to get going with the build, will be sure to write an update once I get to test everything over the summer. For context, I weigh 220lbs and generally prefer a stiffer bike. Im curious to see what a 10% vs ~100% difference in compliance feels like on trail. Eventually I’d like to have a set of replaceable stays to adjust frame compliance for particular tracks/conditions which would be a more minor change. Then if I need to make a significant adjustment (if I were to build a frame for someone much...

Replying to @AvgMTBEnjoyer re: Would CNC lugs bonded to drawn tubes be the best compromise between the two? Typically no. Bonded overlap joints require a double thickness of material, so they're heavier than a welded joint. The edges of lap joints can suffer stress risers where the overall thickness transitions abruptly from one layer to two. Being thicker, the lug and lapped areas are typically much stiffer than the tube, that localized stiffening can increase the stress/strain on the tube spans. Also, CNC parts are typically structurally inferior to forged parts (including drawn tubes). Machining is most suitable when production...

A while back I proposed some magazine editors do a test to compare an aluminum-frame-with-carbon-wheels vs a carbon-frame-with-aluminum-wheels. I think they made some progress but changed jobs before concluding/writing/publishing.

great read, thanks. also, 69% (Nice)

Great work Ryan, Keep the good stuff coming! I’m all in for bracing coming on bikes, it would saving me from taking angle grinders and cutting my frames 😇. There’s no way the frame should be the same stiffness for a pro racer, 190lb novice and 140lb kid.