Bending a Dana 3-speed crank

[Harold_B]

I have bent steel by heating it but this thing is a beast. I used a propane torch to preheat it then a MAPPS torch with an oxygen tank (using the brazing flame setting) to get it cherry red. It glowed in the daylight. Went to bend it using a pipe and a large wrench an snapped the base of my bench vise. I need to bend it to clear an engine. Suggestions? Notch it first and then weld it after bending?

 

[Onewheelsqueel]

Cheap vise? lol. Probably not the best thing to do to it in the first place. Why use one of those on a gas bike? I have a 7spd Schwinn and only use 1st. Motor takes over after that.

Those Dana 3spd cranks are cool looking. Is that the one that just sold on ebay? I had been watching it and considered the buy it now but decided to pass, ended up getting a Nexus 3spd worksman wheel set from Ind-chuckz that Im waiting to show up.

 

[Walker]

What about cutting it and welding in a chunk to create some offset. that way the arm wouldn't be any shorter.

 

[Uncle Stretch]

Ah the Ol Dana 3 speed...doesn't everybody have one?

 

[user 135]

I would think you need to extend the spindle on the three speed. Or cut and weld an offset like Walker suggested.

Bending might cause the pedal hole to not be square and you would end up with a wobbly pedal. :roll:

 

[Onewheelsqueel]

Ah the Ol Dana 3 speed...doesn't everybody have one?

No, but you can send yours to me. Lol

 

[Walker]

if it's cast or forged it may not want to bend for you.

been a while since I studied material science so someone correct me if I'm wrong

 

[Harold_B]

Yup, cheap vise but a gift. Took the base off and bolted it straight to the table. Feh. I want a higher range of gears to get a little more speed on the flats and a lot more help for the motor on the hills. 50cc and 2hp are the legal max for an assembled moped in Michigan so there's not a lot..., OK there's NO extra oomph to get my girth and this heavy bike going. I also wanted something a little different and the Dana popped up about a month or so ago on eBay. I am considering a jackshaft to run the engine through the Dana as well but that will be a next summer project.

I suppose I could cut and weld in an offset to maintain the length. That would be nice. That way I don't need to mess with the other crank. Not sure how I would match up the profile though. Definitely don't have the tools or the skills to cut and weld the spindle.

 

[Walker]

if you cut and weld it, try for an angled cut instead of straight through, with some artful grinding it may come out looking factory.

 

[Harold_B]

if you cut and weld it, try for an angled cut instead of straight through, with some artful grinding it may come out looking factory.

This is an excellent thought. Thanks. I'll want both cranks the same length so perhaps I'll just cut a hunk form the other crank and use it for the offset.

 

[Harold_B]

Thanks Cee Bee. I appreciate the input. Your experiences with the Dana are very helpful. Any modifications I make to fit the transmission to the bike are being made to the transmission case, not the frame. It is the novelty to a big extent of putting it on but I do want it to be functional. If it doesn't work out for me I can take it off. So far I like the look. Getting the pedal axis and the spindle axis parallel after the crank is modified will be a trick but hopefully whatever small error is there will be tolerable. This is what it's looking like so far. I removed the scratched up black paint and gave it a light buff. I might leave it or I might repaint it when it gets warm again.

 

[Harold_B]

Thanks but looks can be deceiving as far as how much effort it has taken. I feel like I spend a lot more time getting the results I want than it seems like it should take. Grand visions, mediocre skills! I hope no one assumes I know what I am doing and skips over something that might have been important. Even if I do know perhaps someone else just browsing doesn't and will get something useful from my tinkering with stuff!

 

[Walker]

Another idea... make some kind of extension adaptor for the existing spindle so you dont have to mess with the arm.

 

[Euphman06]

That is one ...... bike you're building there. Seriously man, that thing is a sexy beast!

 

[Harold_B]

Sexy Beast! I like it. Might have to paint that discretely someplace on the frame....

I have sent the crank home with an associate that has an acetylene torch and a son that graduated from MI Tech. His son knows metallurgy and is handy with a torch so if the crank can be bent he'll know. If not then it's off to the machine shop to see if they can turn an adaptor for me. Thanks again for the suggestions and the feedback. Very much appreciated!

 

[Harold_B]

Crank is bent, just need to weld, grind and paint:

Length is fine too:

 

[Harold_B]

Yup, thanks again CeeBee. Cut the crank using a nice new hacksaw blade then got it cherry red with a torch. Bent it using a 12" cresent wrench. I'm not sure when I'll get the welding done. Either I'll have to ask a friend or get the garage wired for 220VAC and brush up on my skills. It's been a long while!

 

[Harold_B]

Welding the crank will be a little more of a challenge than I expected but my friend says he's up to it. Apparently the process will require heating the whole crank arm to about 1200F, weld up the cuts, then let it cool in sand.

 

[jlr551CFD]

Hey Harold_B, how has your dog-leg crank arm held up?


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[BARTO]

Ah the Ol Dana 3 speed...doesn't everybody have one?

There's thoes that do and thoes that want one