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Discussion Starter · #1 ·
TL,DR,
Here's a chainstay yoke design I'm putting out into the wild. It's cheap, It's easy, and it works great.
Go put one on your next bike.

This post goes along with a video I just put up on my youtube channel, HERE

I needed to design a new chainstay yoke for modern MTB's. And when I was starting out in the framebuilding world, the chainstay yoke was a big obstacle to figure out, and it led to compromises in my first few bikes. So I'm sharing this design in hopes that somebody like me will be able to benefit from it.
The design as it sits will work nicely as a 'drop-in' without much worry. But of course it is very simple to adjust if you need something different.

Some of the numbers:
Chainstay length Min : 415mm
Wheel / Tire Max : 760x66mm (29"x2.6")
34t Chainring

These numbers can of course be adjusted to suit what you are building.

One of the design goals was to make it as simply as possible, with minimal tooling.
The only material needed is some 0.190" 4130 plate. Something like this : McMaster
The tools required can be as simple as hacksaw, grinder, etc. There's really not much to it.
I designed around TIG welding, but I imagine a few small tweaks would make it suitable for fillet brazing also.

Any thoughts or design critiques are always welcome. Put them here so others can benefit from them also.
 

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Nice! Great work. The accompanying video is very helpful. The doccumentation and the process is really useful.

If I could a few make suggestions:
  1. List/show the chainline
  2. Create an accompanying 1:1 and 8.5x11 sheet size. That way people can print it out 1:1 and line it up. Fusion sucks for this. You will need to export your parts as DXF, then lay it out with inkscape or Autocad
  3. If you use the sheet metal tool, you can flatten the pattern of the NDS plate
  4. This sounds dumb, but works really well... if you have a 1:1 print out, you can just glue stick it onto your sheet stock, and hacksaw/grinder the parts

Bonus: in my yoke adventures, I found that many hobby builders don't have access to a mill, CS fixtures, or TIG. To reduce dependency on a mill, you can cut-extrude the 1.5in miter, then flatten the sheet metal to a 2D pattern. The user can hand file the final miter. To help with fillet brazing, if you could add self locating tabs to help fixture the parts in place

Jank flat pattern example:

1944953
1944951
 

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Discussion Starter · #5 ·
Nice! Great work. The accompanying video is very helpful. The doccumentation and the process is really useful.

If I could a few make suggestions:
  1. List/show the chainline
  2. Create an accompanying 1:1 and 8.5x11 sheet size. That way people can print it out 1:1 and line it up. Fusion sucks for this. You will need to export your parts as DXF, then lay it out with inkscape or Autocad
  3. If you use the sheet metal tool, you can flatten the pattern of the NDS plate
  4. This sounds dumb, but works really well... if you have a 1:1 print out, you can just glue stick it onto your sheet stock, and hacksaw/grinder the parts

Bonus: in my yoke adventures, I found that many hobby builders don't have access to a mill, CS fixtures, or TIG. To reduce dependency on a mill, you can cut-extrude the 1.5in miter, then flatten the sheet metal to a 2D pattern. The user can hand file the final miter. To help with fillet brazing, if you could add self locating tabs to help fixture the parts in place
That is good stuff, thanks.

I actually have been working on adding some stuff to the drawings. You're not the first to suggest adding the chainline. haha.
May take me a day or two, my 'play' time on the computer has been limited lately.
And ya know, I completely forgot about having it be printable 1:1 as templates. Duh. I'll definitely add that.

Couple of thoughts about the 'flat-pack' idea.
That was actually the original idea, to design it so someone could just upload the 3 parts to someone like SendCutSend, bend them, weld them, little bit of filing, etc.

But the biggest problem with that is the bend radius (or bend allowance in this case) of the part. So that's why I settled on showing the bent part, with the critical dimension as a center-to-center.
That way any reasonable bend radius (if the center-to-center distance is followed) will result in the important dimensions being close enough for bicycles. Then the other two are just minimums so it can be finished to length.

Although now that I think of it if I draw it up with some reasonable bend allowance as the 'median', it will likely be fine. There's a decent tolerance on everything anyways. I'm gonna have to brainstorm on that a bit more, I may be overthinking it more than necessary.
 

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I personally feel that including bonus info never hurts. Someone hoping to glue a bike together can figure out how to get a tight bend radius and or change the length of the bar stock.

This is on my list of things to figure out, but many people have had great results with low cost FDM 3D printed sheet metal dies:

This guy does great work:
Simple 3D printed vice break:
There is some potential for tube ovalizing with these rollers:

How cool would it be to 3D print a die to clamp in a vise to get your 35deg bends? You might need to relax the chainring requirement and the bend radius for that to work...
 

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Discussion Starter · #7 ·
I personally feel that including bonus info never hurts. Someone hoping to glue a bike together can figure out how to get a tight bend radius and or change the length of the bar stock.

This is on my list of things to figure out, but many people have had great results with low cost FDM 3D printed sheet metal dies:

This guy does great work:
Simple 3D printed vice break:
There is some potential for tube ovalizing with these rollers:

How cool would it be to 3D print a die to clamp in a vise to get your 35deg bends? You might need to relax the chainring requirement and the bend radius for that to work...
Funny you should say that, I've been looking at a lot at 3DP tooling lately.
My next project I'm going to tackle is a tubing bender for chainstays & seatstays. Just a simple press-bending setup with the curved die (and potentially all the dies) being printed.
I'm basically ready to get started on that soon, Just been too busy with other stuff lately.
 

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Nice! Great work. The accompanying video is very helpful. The doccumentation and the process is really useful.

If I could a few make suggestions:
  1. List/show the chainline
  2. Create an accompanying 1:1 and 8.5x11 sheet size. That way people can print it out 1:1 and line it up. Fusion sucks for this. You will need to export your parts as DXF, then lay it out with inkscape or Autocad
  3. If you use the sheet metal tool, you can flatten the pattern of the NDS plate
  4. This sounds dumb, but works really well... if you have a 1:1 print out, you can just glue stick it onto your sheet stock, and hacksaw/grinder the parts

Bonus: in my yoke adventures, I found that many hobby builders don't have access to a mill, CS fixtures, or TIG. To reduce dependency on a mill, you can cut-extrude the 1.5in miter, then flatten the sheet metal to a 2D pattern. The user can hand file the final miter. To help with fillet brazing, if you could add self locating tabs to help fixture the parts in place

Jank flat pattern example:

View attachment 1944953 View attachment 1944951
I'm working on some modeling of a new frame in Fusion, I'm planning on using the sheet metal commands. I just finished a huge project revolving around bent sheet metal, all modeled in Fusion. You can set the material to be what you want, and it will use its own internal bending rules regarding the bend radius, then you can export flat patterns at 1:1 rather easily. The key is to start drawing it as a sheet metal part, rather than a basic solid body. Although, I don't know if it's that critical to be bang on perfect with some of these dimensions. Just a comment on the Fusion modeling process.

Also, Ben, this is a great design. Your other work posted on Youtube is also very good. Thanks!
 

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Thanks for this great design, and for providing the dimensions. I used sendcutsend to fabricate the pieces for me, and it came together great. They charged $21.30 total, using .190" for the plates and .125" for the web.

I can't upload dwg files here, so I'll try to put them in a dropbox link and see if that works. If anyone wants to use sendcutsend, just upload these files. There's also an image of the bent piece they need to understand the intent.


Thanks again for sharing your design work!
Grey Font Art Tints and shades Pattern
 

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Another kudos to @Ben.land101 for sharing this yoke design. I used it on my first frame build, and it works great.

410mm chain stays
29x2.6 Bontrager XR4 mounted on a 30mm internal rim
Shimano XT M8000 non-boost crank with a 34T chainring

With this setup I have about 3mm of clearance at the center knobs, and plenty of clearance on the sides. I have horizontal dropouts, so I could probably fit a 3" tire if I slide the wheel back a little bit.

Automotive tire Motor vehicle Tire Wheel Asphalt
 
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