What vintage fork will fit a 3-inch tire?

[indian22]

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.

 

[wret]

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.

 

[curtisfox]

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

 

[indian22]

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.

 

[curtisfox]

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

 

[wret]

Fork blades:

https://framebuildersupply.com/coll...omor-fork-blades-28x19-oval-9-wall-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.

 

[curtisfox]

Fork blades:

https://framebuildersupply.com/coll...omor-fork-blades-28x19-oval-9-wall-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

 

[wret]

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.

 

[curtisfox]

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

 

[Harold_B]

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

 

[wret]

Thanks guys. The things I thought would be difficult aren't really so bad. Cutting a complex shape in 1/4 or 1/2 inch steel plate with an angle grinder? No problem. The hard thing is an oval hole.

 

[Harold_B]

You'll need to run to Sears for an oval drill bit.

 

[wret]

Making progress

 

[Velodrome]

DANG! Thats looking GOOD!

 

[wret]

Almost done

 

[Harold_B]

Looks terrific! Nice work.

 

[racie35]

Where did you get the levers?

 

[indian22]

Wret you, Harold B. & Truck'd all have great leaf spring forks started. I have however 5 bikes, each with distinctly different forks... not one of which has a leaf spring. I must eventually remedy my terrible neglect. Rick C.

 

[wret]

Where did you get the levers?

Do you mean the spring connecting links? They are steel tubing joined to bar stock at the ends, with bushings welded on at the spring mounting points. One of the hardest parts of this whole deal was getting the clevis ends right. This was the only part of the whole thing where several items went into the scrap bin.

 

[Gbrebes]

Wret,

That is hands down the nicest home-made fork I have seen on this forum!

You should be proud of such a wonderful creation.

I look forward to seeing the forks on your bike.

Great work,

Gilbert