breeze-eng

@Tambo: switch to single lap joint, weld small tube onto big tube, bond small tube into carbon tube. Or even better use tapered end tubes for tapered single lap, and weld tubes into lugs as normal. My previous comment explains why their double lap joint isn’t needed, and why they use it anyway.

@mi-bike: I believe their marketing is technically accurate, but I think they should be marketing it differently, hence the confusion. As with most engineers I’m good at numbers not words.

@vinay: Not a bike expert, but I’ve got enough experience to tell you that double lap joints on tubes are complete overkill for anything other than pullout resistance, which AFAIK is useless on a bike frame. Bonded joints are very often the strongest area of a bonded tube assembly, even if it’s “only” a single lap joint. Single lap joints typically fail by peeling in tension, which is really hard to achieve on a bonded tube. Ideally on a tube you’d use a tapered single lap joint to spread the load evenly between components. I’d be surprised if double lap joints don’t overstiffen the lugs and cause the carbon to fail at the end of the joint. I imagine there’s a lot of additional local lamina in their tubes to counteract this. IMO the only benefit atherton gain from using double lap joints is decreasing the length of the bonding area, making their lugs smaller, which helps from an additive standpoint. But cleaning supports out of the inside of a double lap joint will be a nightmare, so the benefit they get from the size is likely completely lost on some of their lugs. Anything else anybody spouts about double lap joints being better for bikes is marketing BS.

Don't worry Pinkbike commenters, an ACTUAL engineer who ACTUALLY works with additive is here to call out all your (and Mythos') ridiculous bulls***. First off, all you keyboard engineers who think putting holes in something makes it less stiff. WRONG! This looks a lot like a truss style structure to me (diagonal lines everywhere). Truss structures have been around forever, and work great because they can be light, strong and stiff. See: cranes, bridges. Because I'm a total nerd with far too much time on my hands I did my own little FEA experiment, and hey what do you know, cutting some holes out of simple round and square section stems had little effect on stiffness. This plus Ti has a higher elastic modulus than Al, this stupid titanium stem with holes in being stiffer than an average stem feels easily believable. My FEA also showed a strain distribution that pretty much explains exactly where the design for this overpriced chunk of titanium bragging rights probably comes from - the material in the corners doesn't look like it does a whole lot, so they cut it out. Second, those webs on the inside of the stem are not for stiffening IMO. Integrating super thin webs of material into a part to support other bits of the part during the process is really common in design for additive. They're probably no thicker than the spot size of the beam (around 0.4mm) and probably melted using a fast and low energy parameter, giving them roughly the load bearing properties of aluminum foil. They probably weigh less than 5 grams total. To give Mythos credit, keeping these in as a design feature is pretty genius, and far better than the stupid meshes everybody else seems to use when they design for additive. Third, someone at Mythos has definitely given this the full can o' Bri'ish baked beans, because if my very rough measurements are correct its like 5mm thick on the sides which is total overkill (assuming my FEA is anywhere near right). I get they're used to designing roadie stuff, and I guess thought that us off-roadies would just want something burly that weighs a ton, and they're kinda right actually? Nevermind, good job Mythos, but make it lighter for the apparently very prevalent XC crowd in the Pinkbike comments next time. Fourth, comparing this to any composite stem is totally pointless, because this will survive an impact, and your carbon stem will delaminate and snap. At least after your carbon stem brakes, you can run one of these without a weight penalty after all the weight you've saved by not having teeth any more. Downside being I'm not sure you'll be able to say Mythos with a lisp. Comparing it to alloy stems, is it really that much heavier? I've got stems from Hope and Burgtec which both are about 150g for a 40mm. Plus they're advertising weight with bolts which barely anyone seems to do- if they put Ti bolts on it (which for this price they really should) there's an easy 10 grams saved. Fifth, it's nice to see somebody finally make an additive mtb component that uses an obviously additive geometry. Everybody thinks Sturdy and the Athertons are doing such a good job making round tubes with additive, but its a total waste. Athertons could take loads of cost out of their lugs if they just welded them out of Ti tubes and still keep every other feature, including the custom sizes, and they'd look basically identical. Sturdy's bikes look super nice, sure, but do they really look THAT different to any other welded Ti tube bike? I will say though Mythos could definitely have done a better job with this design, could easily be lighter, surface finish needs work, whole thing looks like a rush job to me. Just my 2 cents, but this smells like a marketing exercise to me. Put their name on the front page and in the mouths of the people by making a wacky half-baked stem with very little time, effort or money. Does it do everything a stem needs to do? Yes, it holds a handlebar onto a steerer tube. Does it do anything else functionally? No. Does it "play to the strengths of additive"? Probably, I bet they spend less time making these than the combined lead time and shipping time of your average Taiwanese CNC shop. No tooling needed either, so I bet they'll tweak the design every time they make one. I can't decide if I like this thing or not. I believe their marketing, and I'm interested in them as a company, but this feels like unjustified and overpriced additive bike bling just as much as Atherton bikes and Sturdy. Equally, I'm not sure what other features I actually want to see from an additive stem, I think I'm more pissed off with their marketing than I am the stem itself.