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Board Trackers and Vintage Motorized Bicycles Vintage enthusiasts share your board trackers and other vintage motorized bicycles ideas, builds and replicas here

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  #21  
Old 11-29-2016, 08:58 AM
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indian22 indian22 is offline
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Default Re: What vintage fork will fit a 3-inch tire?

That's the attitude of a fabricator Wret, just build one! I'm certain you will be successful. If you've not considered some of the measurements required to design a fork such as trail and rake take a look at the thread by Veskt & his v-twin build...lot of info there as he got it wrong & then corrected (hard way lessons) as he learned. It's not rocket science but will get you pretty close for everyday riding. Rick C.
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  #22  
Old 11-29-2016, 10:34 AM
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wret wret is offline
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Default Re: What vintage fork will fit a 3-inch tire?

Yes, I did the math when setting the head angle on my frame. I must of gotten something right because I like the way it tracks and handles now; not twitchy and plenty stable at higher speeds. I did try to err on the side of stability. I'll try to keep the rake and trail the same if I can but the trailing axle might require more of a bend in the fork than would look right. We'll see.
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  #23  
Old 11-29-2016, 11:28 AM
curtisfox curtisfox is offline
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Default Re: What vintage fork will fit a 3-inch tire?

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Originally Posted by wret View Post
This may seem obvious but the shape of the bend in the spring is highly dependent on the form you bend it around. A good blacksmith might be able to do this over an anvil but my practice bend on a trailer spring was not pretty.

I was working on setting up a bending jig using two straight hardwood boards I had laying around when it occurred to me the parallel sides of my harbor freight pipe bender would be nearly ideal to set up my jig. I used a stack of large washers for the "mandrel". The only other fixture in the jig was an anchor where the eye rests. I'll link a simple sketch. Whatever you use for a jig, you need to be able to anchor it so that can resist your 100 or so pounds of bending force. Keep the anchor close to the mandrel to get a nice round shape in the bend. Mine started out a little flat close to the eye.

You might be able to get the spring to bending temperature with a propane torch but I found that the torch used with my bucket forge (see youtube) worked well to heat a six-inch or so section of spring. I'm no expert on heat treatment of steel and after heating and bending it probably should be tempered, but I've seen several accounts of home mechanics that have heated and bent springs with no ill effects.
Thanks for the info, going to give it a try, built the bending jig a long time ago. Just not ready to do it yet, others first............Curt
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  #24  
Old 11-29-2016, 01:41 PM
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Default Re: What vintage fork will fit a 3-inch tire?

Wret, I once asked a friend, who was a NASA metallurgist, about tempering re arched leaf springs for rock crawlers & his reply was try them & see if they work & retain their arch after bending or start to relax. Measure ride height periodically to verify the spring is not collapsing. If you allowed your leaf to air cool after bending, not speeding the process using oil or water to quench, then some temper will be retained in the steel. The light weight of your application shouldn't put tremendous strain on the steel. Of course resulting spring rate will be quite by accident, but could be within the range required for your safe daily riding requirements. To firm the action just add a tempered, stiffer section to the leaf stack. Of course a quality spring shop can temper to spec once you see the direction you need to go to acquire the ride you need. Best of everthing, Rick C.
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  #25  
Old 11-29-2016, 10:32 PM
curtisfox curtisfox is offline
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Default Re: What vintage fork will fit a 3-inch tire?

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Thanks for the information Rick. I took a look at Simplex forks. They do look great! I would feel bad cutting up a vintage fork as much as I would need to to make it look right and I fear there wouldn't be much of it left and the wheels are already turning on how to set up a fork assembly jig.

Curtis, I did find fork blades available pre-flattened. I do have access to a press but that takes a little of the guess work out it.
Got the link? ..................Curt
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  #26  
Old 11-30-2016, 10:21 AM
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wret wret is offline
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Default Re: What vintage fork will fit a 3-inch tire?

Fork blades:

https://framebuildersupply.com/colle...all-length-390

Rick, I let the bent spring slowly cool inside my covered bucket forge. I think it will be fine. If it shows any signs of sagging I can always fill the loop with a rubber support, which was commonly used at the time.

I'd love to go on excursion like you did. I'll have to see what kind of clubs there are around here that would be tolerant of a poser.
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  #27  
Old 11-30-2016, 10:59 AM
curtisfox curtisfox is offline
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Default Re: What vintage fork will fit a 3-inch tire?

Quote:
Originally Posted by wret View Post
Fork blades:

https://framebuildersupply.com/colle...all-length-390

Rick, I let the bent spring slowly cool inside my covered bucket forge. I think it will be fine. If it shows any signs of sagging I can always fill the loop with a rubber support, which was commonly used at the time.

I'd love to go on excursion like you did. I'll have to see what kind of clubs there are around here that would be tolerant of a poser.
Thank you, good to know, as may be building one............Curt
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  #28  
Old 12-12-2016, 07:40 AM
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wret wret is offline
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Default Re: What vintage fork will fit a 3-inch tire?

Getting things laid out. I decided to use the legs from an old Monark fork I had laying around. They are much beefier than those available for framebuilder supply.


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  #29  
Old 12-12-2016, 08:41 AM
curtisfox curtisfox is offline
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Default Re: What vintage fork will fit a 3-inch tire?

LOOKS AWESOME! Just make sure the axle is off the bench the same height, or level. Love it, i use a lot of wood jigging also. .............Curt
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  #30  
Old 12-12-2016, 01:34 PM
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Harold_B Harold_B is offline
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Default Re: What vintage fork will fit a 3-inch tire?

Great looking rockers too. This will make a dandy fork.
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