@manzanitacycles I agree that 90 look like a prime failure point to me as well. I’m twoish weeks into my first foray with CAD design, trying to understand the sweep function among a host of other things. That would be awesome to pool some funds for testing, I’d be happy to do the welding as well. Looking at the yoke @adamsklar designed it has a pretty tight radius in the same spot. I wonder if he has had any failures…pretty sure his is printed.
I have probably 30ish of those yokes out in the world and haven’t seen any failures. I do destructive testing on a sample from each batch I get in and every time the failure on that design was at the bend in the middle of the yoke. That design really didn’t take advantage of what you can do with 3D printing so now I am using this design below. Gentler curves with more internal support. Probably have 40 of those out there with no issues as well. So far…
I would take everyone’s 3D-printed suggestions with a grain of salt (including mine ). Printed parts are not like CNC bulk material. Different printers, lattices, heat treating, post-processing, powders, and designs affect the final product.
For the record, I don’t agree with a lot of the ways bike industry people are approaching 3D printing. I question where people are getting their 3D-printed info from.
To give some perspective, I was an engineer at an industrial 3D printing company. One of the most frustrating parts was that the printing fabs were giving out bad advice to customers, which lead to bad designs and bad outcomes. It’s a giant game of telephone.
Is there a 3D printing discussion that has any of this good and bad advice? Seems like that could be useful. The more this gets talked about, the more I want to try to design some parts for 3D printing.
I mean, it’s the thinnest, least supported section right in between two very strong supported sections, so this is right where we would expect it to break.
As Daniel pointed out, the info available on 3D printing stuff is still kind of murky. Based on the material specs my print vendor supplies, these are crazy overbuilt. My current vendor has been really consistent, but I went through another where I had to toss whole batches of parts because I could break them in my hands. There were layers missing or something like that. Anyhow, the destructive testing shows me that the parts break in a way that I expect them to break and that is helpful info. Snapping these off takes a giant cheater bar and a few minutes of back and forth. Doing some measurable fatigue testing would be cool. These overbuilt parts solve a manufacturing issue but with better data we could build lighter parts that didn’t take away from ride quality as much. Not that it’s that much but if you’re going to overthink it why not overthink it?
Agreed, failure from a properly designed 3D printed part will more likely fail from fatigue than exceeding its yield strength. There was not much data I could find on 3D-printed fatigue, and to me, that’s the greatest risk at the moment.
I don’t use 17-4 or 15-5 because the printed data shows they are much less ductile than 316. Typically ductility and fatigue resistance are correlated, but again, who knows how it translates to 3D printing without lab testing. And even lab testing is blind to real-world conditions.
Sorry to revive an old thread…what are the options of pre-made 3" yokes for sale in the US except for Paragon (which is so nice, but umm $250)? I really like Konga yoke design, but he’s out of stock and he’s in Finland. Maybe something similar available that I’m missing? (I will check Strato, but I;m not sure theirs can fit a 3")
Doesn’t Konga sell the design and then you can make your own?
You could get all the parts from SCS including both sides of the press to give it the shape it needs (it’s late and I cannot remember how to properly call those but you get the idea)
fillet brazing. Can I get a raincheck on this? From dozens of yokes I’ve seen I find Konga most aesthetically pleasing, with all my respect to other solutions in this thread. The RTUOTB yoke in your link is a practical solution, less elegant maybe. Let me try to push Konga again, if that fails I will get back to you
Aesthetics aside, which yoke design has the best stiffness? This is an important concern for me since I’m building a frame for singlespeed which naturally involves a lot of out of the saddle pedalling
I cannot find the Konga design anymore. I recall it being downloadable on the website. Where do you get it?
Also, I am building a fixie MTB frame with the $12 chainstay yoke. I’m pretty skeptical if it’s stiffness due to how easy it is to bend with an adjustable wrench… I’ll update once I ride it.
For the Konga you need to shot him a message and buy the design.
I remember something being downloadable but I have a vague memory that something happened and he removed all of those drawings, maybe people were sharing it too much?
). Printed parts are not like CNC bulk material. Different printers, lattices, heat treating, post-processing, powders, and designs affect the final product.
