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Fred Johnson magnesium clinchers

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Fred Johnson magnesium clinchers

Postby über-goober » Sat Mar 12, 2011 5:01 am

A buddy of mine scored almost all of the remaining supply of the mythical Fred Johnson mag rims, and i'm helping out with the last steps so they can hit the road.

The last steps being the cutting, sleeving, joining and drilling.. Here's what we got (this is about 1/4 of them):
fj-mags-blanks2.jpg

fj-mags-blanks1.jpg


Some of you are familiar w/ these rims from Donald's amazing Ruegamer WW bike. He has tuned them down to around 215g w/ some aggressive drilling on the rim beds. These are about 285g stock, without doing anything crazy to them.

Looking at these, i wonder about all the rim manufacturers and what they had to figure out to cut their rims accurately. I take for granted that they are always going to be the same diameter, w/ a good seam, and that a tire will always fit not too loose/ not too tight..
Last edited by über-goober on Sun Mar 13, 2011 1:51 am, edited 1 time in total.
the problem? could be the nut behind the handlebars.
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Re: Fred Johnson magnesium clinchers

Postby über-goober » Sat Mar 12, 2011 5:13 am

If you're thinking i'm crazy, i have moments where i agreee completely. :D :cry: :lol: More about the rims. They are 19.4mm wide and 21mm deep. They were made in the late 80s (i think) here in the U S and A.

FJ was going to market them under the name 'Cheetah Paws' but came to his senses before any were sold to the public. And so, are they going to be for sale? Probably not.. and for the same reason (the hazards of selling scary light stuff in the Age of Litigation).

The cross section looks suspiciously like the Matrix ISO clinchers from the same era. I had to cut an old rim apart to convince myself they aren't a straight-up duplicate. But the FJ mags are slightly different, and with thicker walls. Here's the Matrix on the left and FJ on the right:
matrix-iso__fj-mag__1.jpg

matrix-iso_fj-mag.jpg
the problem? could be the nut behind the handlebars.
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Re: Fred Johnson magnesium clinchers

Postby über-goober » Sat Mar 12, 2011 5:32 am

More to come.. next is to figure out a jig to cut these to the correct length, and to drill them accurately and straight.

Meanwhile the 866g mags from last year held up nicely on some big rides in the mtns. They are still true and are working out surprisingly well.

Some people's concerns were that the bare finish will corrode, and it did. Not too badly though. A few minutes with some polishing compound and they look bright and shiny again, maybe a couple times a year. But we are looking into a black ceramic paint as another option.
the problem? could be the nut behind the handlebars.
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Re: Fred Johnson magnesium clinchers

Postby pritchet74 » Sat Mar 12, 2011 5:27 pm

Wow. What a project. Keep us posted!
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Re: Fred Johnson magnesium clinchers

Postby Gumgardner » Sat Mar 12, 2011 6:14 pm

Good stuff.
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Re: Fred Johnson magnesium clinchers

Postby über-goober » Sun Mar 13, 2011 2:06 am

My buddy TD helped me make this jig. We started out w/ CAD drawings of complicated fixtures but then became simpler the more we thought about it.

for cutting:
rim-jig1.jpg


for drilling:
rim-jig3.jpg


I think everything you see was under 10 bucks. And the diameter is working out perfectly -- a Michelin folding tire just barely goes on without a tire lever.
the problem? could be the nut behind the handlebars.
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Re: Fred Johnson magnesium clinchers

Postby dunlinii » Sun Mar 13, 2011 5:33 pm

This really is a cool project. Love the simplicity of the fixtures.
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Re: Fred Johnson magnesium clinchers

Postby Donald » Wed Mar 16, 2011 12:25 am

About 20 years ago Fred showed me a way to measure the correct length of rim with a piece of tape, similar to a cloth tape measure. I have put many of these rims together and they all were right on at 700 c , or very close. I have never really had any serious problems with corrosion. I have continued to use these rims during the last 20 years and yes, one rim I modified down to 215 grams. I hope you have continued good luck and fun riding these rims. Also back then Fred made a mag crank. I had a couple of these but one of them broke but at the time is was one of the lightest cranks around. I'm sure some of you guys know of people who experimented and made different very light components years before there was the Internet, etc. and it was not always easy to find out about these small builders.
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Re: Fred Johnson magnesium clinchers

Postby über-goober » Wed Mar 16, 2011 3:26 am

some progress:
fj-mags-blanks4.jpg


Before getting any holes drilled in them, they are right around 288g.

Here's a finished rim.. tuned a bit, but nothing like what Donald has accomplished. :shock: :D
fred-johnson-mag-268g.jpg
the problem? could be the nut behind the handlebars.
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Re: Fred Johnson magnesium clinchers

Postby skimons » Wed Mar 16, 2011 8:18 pm

pretty cool! how do you connect the 2 ends in a normal and light way without ruining the braking capabilities?
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Re: Fred Johnson magnesium clinchers

Postby über-goober » Thu Mar 17, 2011 5:17 am

I've found that the problem spot on most wheels (w/ that last bit of deviation no matter how well it is trued) is the seam.. and these are no different. It takes a lot of patience to sand and file the edges so there is no gap. The joint gets a 40mm sleeve inserted with some epoxy and then they're all ready "for display use only". :wink:

If only I had these machines in my garage..
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Re: Fred Johnson magnesium clinchers

Postby dalai » Thu Mar 17, 2011 5:51 am

Amazing project über-goober!
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Re: Fred Johnson magnesium clinchers

Postby skimons » Thu Mar 17, 2011 10:59 am

über-goober wrote: "for display use only". :wink:


that's what i thought... too bad, nonetheless great work & way to go :toppie:
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Re: Fred Johnson magnesium clinchers

Postby über-goober » Mon Mar 28, 2011 3:08 am

Drilled some rims..

mags-drilling.jpg

mags-drilling1.jpg


5 are heading to my friend Mamba in AZ. (He is the one who got these from Fred.) And then 1 is going to the madcow midschool museum.

I am going to try these out w/ this build at around 1100g:

polished 24/28h rims - 280 + 280g
Sapim CX-Ray silver 2x/3x, silver alloy nipples 5g/ea (x48) - 260g
Alchemy ELF/ORC Shimano polished silver 65+220 - 285g
:D
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Re: Fred Johnson magnesium clinchers

Postby FAQinc » Mon Mar 28, 2011 3:45 am

Dang Uber those pics definetly have a back in time artisan feel about them as long as you replace the cordless power drill with something like this Image

and maybe some sepia colour or instamatic on your Iphone can definetly get something pretty cool going.

A bit of a shame with the display only aspect but hey not many people can say they've drilled magnesium clincher rims 8-)
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