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warren
human power expert

USA
6643 Posts

Posted - 02/19/2021 :  08:40:57  Show Profile  Visit warren's Homepage  Reply with Quote
Seth - these forks have metal inserts on the dropouts. Hopefully that doesn't cause me grief while I'm adding the derailleur hanger.

Cut the forks with the hacksaw, spaced the dropouts to 135mm and centered them. I'm considering whether to remove some length from the fork to bring it back to standard MTB fork length or leave it longer in case I want to use a 29er wheel.



29 days and counting on the wheels from China.
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SpiderMonkey
recumbent guru

USA
785 Posts

Posted - 02/19/2021 :  13:40:24  Show Profile  Reply with Quote
That looks exactly like the ones I've been buying. IIRC on mine, the metal was just a facing on either side of the fork end, so that one might have required a bit of dremel work to straighten on my end. I seem to remember a spot of rust, so likely steel plate.



Wait, I documented my entire process!

https://www.crazyguyonabike.com/doc/page/?o=1mr&page_id=590045&v=DY

Looks like I had to widen the fork slots a bit on mine, which has been fairly standard for me on all these. (I also have always needed to face the crown top and thin the race seat.)

I modded the bottoms of these ones a decent amount, including drilling a hole in the disc side to bond in a T-nut and bonding another one on the other side.

I think you'll have no problem tacking on then wrapping a derailleur mount. If it were my job, I'd just cut the hanger from Alu with a longish lever running up the side to help it stay put, tack, putty, then do the first wraps with my walmart glass, then CF wrap.

Or I might bond on a CF plate with a couple holes drilled for M6 screws and put an alu hanger on that way. (I have seen a couple hangers cracked / broken along the road so I am paranoid about making mine easily replaceable.)

But I'm sure you have a plan for that. Maybe a full CF hanger? I'm too paranoid for that, too, and alu is so easy to drill and tap for that.

--SpiderMonkey

Edited by - SpiderMonkey on 02/19/2021 13:45:12
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warren
human power expert

USA
6643 Posts

Posted - 02/19/2021 :  18:18:25  Show Profile  Visit warren's Homepage  Reply with Quote
Garrie made me an ~1/8" and a ~1/16" CF plate. I'll use the 1/16" for joining the fork back together and the 1/8" to make the derailleur hanger.

Nice write-up, Seth!

Edited by - warren on 02/19/2021 19:07:59
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warren
human power expert

USA
6643 Posts

Posted - 02/20/2021 :  10:39:24  Show Profile  Visit warren's Homepage  Reply with Quote
I did some measuring and took 1.5" out of the length of the fork. This new fork and my existing 700c fork seem to have about the same rake but the MTB fork is longer. After removing the 1.5" the axle to bottom headset race distance is 16" vs 15" on the 700c fork so I will have a bit more trail.

There's no space for a 29er wheel in the rear dropouts so no use leaving space in the front either...
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SpiderMonkey
recumbent guru

USA
785 Posts

Posted - 02/20/2021 :  11:57:41  Show Profile  Reply with Quote
That makes sense. I think the reason these stiffy "26er" forks are so long is to account for replacing a suspension fork and not changing the HTA drastically by dropping all the stanchion slack.

--SpiderMonkey
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warren
human power expert

USA
6643 Posts

Posted - 02/21/2021 :  15:08:44  Show Profile  Visit warren's Homepage  Reply with Quote
I cut two CF extender plates from the ~1/8" CF plate. After measuring every which way to Sunday, I "tack" JB Welded the extender plates into the fork. I had to build a small foam box and use a space heater in the garage to make sure the epoxy cures.



And yes Seth you are right, I will need to ream the fork out a bit to get the hub to fit into the dropouts, while I'm making sure it's all straight. I still need to clean up what I did here and add more reinforcement.


Edited by - warren on 02/21/2021 19:46:11
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SpiderMonkey
recumbent guru

USA
785 Posts

Posted - 02/21/2021 :  17:36:10  Show Profile  Reply with Quote
Winter is my favorite CF build time. I can work in the 55 degree garage and get long pot life, and then my basement heat duct work is accessible, and there's parchment paper on the ducts, so I can put stuff on there and it gets cured super hard by morning.

--SpiderMonkey
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SpiderMonkey
recumbent guru

USA
785 Posts

Posted - 02/22/2021 :  09:32:22  Show Profile  Reply with Quote
That looks exactly like I thought it would. Makes me want to build one like this just to have the fun of desroying and rebuilding another bike part. I still have enough of my 0 / 90 / 45 / -45 fabric to make a buttload of plate.

What's your plan from there? My move would be a strip of uni on the outside / inside of each of those plate interfaces as a preliminary (orange), then a small chop / bubble / epoxy fillet on the inside (blue), and a bigger one on the outside, with 2 more uni layers covering those, also cover front/back sides of legs, and some 3k weave as a final, nicer looking finish (red).



Possibly overkill, but would only be about 50-70g more than just wrapping with a few sheets of CF alone and maybe push those loads further up the legs and over more area?

--SpiderMonkey
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warren
human power expert

USA
6643 Posts

Posted - 02/23/2021 :  17:36:05  Show Profile  Visit warren's Homepage  Reply with Quote
Today I was going to use the 29er wheel that I forgot I had to check the fork for straightness. First I had to file the dropouts to get the hub to fit. Of course that broke one of the JB Welded forks loose.

I filed the dropouts, put the fork back into the jig, re-applied epoxy and waited for the epoxy to cure under the space heater.

A few hours later I was able to test fit the wheel. Looks pretty good, I will have to make a small adjustment to dropout depth on one side.

Edited by - warren on 02/24/2021 09:21:11
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warren
human power expert

USA
6643 Posts

Posted - 02/23/2021 :  17:43:05  Show Profile  Visit warren's Homepage  Reply with Quote
Yes Seth, I'll be reinforcing the jog in the fork with some additional CF plates, some CF/epoxy fillets, and then a few layers of CF over the whole thing. If anything fails on that fork it won't be the jog.
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