Twin Top Tube Bending w/ Meriwether Cycles

Every few months Whit @Meriwether Cycles hits me up for help on a cool project. In this case… A titanium, fat bike, drop bar, twin tube, klunker, with sliding dropouts. This bike wins the custom framebuilding bingo card.

This is the first time I have seen CAD being used to sequence the compound bends to achieve the twin top tube + s bend stays.

Why this was so challenging:

  • all 3 bends must be done in one shot
  • Tire clearance for fat bike tires
  • Cobra bender is limited to 36deg w/ 19mm titanium
  • Bends must have enough overlap at the seat tube miter
  • Left and right stays must be exactly same (done in tandem)
  • titanium means expensive mistakes

Process

Whit sent me bikeCAD which I converted 3D in order map out the bends and tire clearances :

From there, I created the sequences of 2D drawings which show the:

  • bend location
  • bend angle
  • phasing angle




Thanks to the CAD, I knew it was physically possible, but we still had a three-hour call to figure out how to do the bend sequence in real life :rofl:. Whit caught a pretty big issue: due to springback, the Cobra bender maxes out at 36deg w/ 19mm titanium tubing. The first draft had the SS-TT bend at 37degs! We ended up massaging the geometry and bends to bring it to 36deg.

The results

This is all Whit’s work, so make sure to give him some kudos. I am always impressed by his level of fabrication skill.

Bending and Mitering




Final Results:



I’m really happy about how this one came out!

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Thanks @Daniel_Y for the much needed assistance! I’d never had completed the top tube bends on my own, especially in one try. It would have been a lot of trial and error ($$$) and I’d likely have had to use a splitter at the seat tube since that bend is the trickiest to figure out and get right! The Cobra bender is so great for stuff like this. Totally doable on other benders such as a Diacro but being able to bend them in tandem saves time and I think increased accuracy.

I’m psyched how this frame turned out. It’s a low-Q fatbike with clearance for 27.5x4’s using a 187 Q and 62mm chain line with 435-455mm chainstay length thanks to yokes made by @Rollingdale_Cycles

Some more process shots:









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You guys killed it! @Daniel_Y was showing me that and all I could think was “better him than me!”

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Beautiful work, I imagine there were a few moments with a high heart beat.

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Lol :rofl:
You probably made 10 frames in the time I made this one.
Such a headscratcher for me, but it was super fun to see it come together. I don’t know how Blacksheep, Oddity, and others do this every frame…

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You got that right!
And thanks :blush:

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We all have our skills.

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Incredible work!

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Sweet! Reminds me of the old school Redline RL-20 II, but with more tire clearance. :slight_smile:

Capture - RL 20 II

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