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-   -   braze-ons and JB weld (http://www.bikeforums.net/framebuilders/551189-braze-ons-jb-weld.html)

eleven 06-12-09 01:30 PM

braze-ons and JB weld
 
I recently acquired a Lemond 853 frame with all the braze-ons shaved off in an attempt to make it more streamlined for fixie cult approval (@#$!%&*!!!!). It's a tragic thing I know but I am determined to breathe life into this frame and restore it at least to some semblance of functionality but here's the thing.....I've never brazed before. And cost of local builders repairing it is not an option. So...couple questions. JB-Weld. Strong enough for airplane wings, strong enough for bicycle braze-ons? The tensile strength of an average JB-Weld listed on their website is 3950 PSI. Is this a good number for downtube cable stops etc? I know it sounds extreme but... The other option that is slightly less cost prohibitive than taking it to a local builder would be to buy an eccentric hub (white Industries makes a good one for about $175) and build up a wheel for it but forever condemn the bike to singlespeed/fixiedom.
Suggestions anyone?

eleven 06-12-09 01:39 PM

Also, with heat treated frames such as Reynolds 853, does brazing after the heat treatment brake the temper of the steel?

squirtdad 06-12-09 03:55 PM

You could go old school with the clamp on brake and shifter guides. Bikes were built this way for a long time.

If the derailler hanger is gone...you could consider IGH.

You could also do some research, get some extra fittings, a cheap tube (donor cycle) and practice brazing....if there is no problem with the 753

eleven 06-12-09 05:28 PM

Immunoglobulin heavy locus?
um...intergalactic hamster?
in good health?
I give up...what is IGH?

ItchyZipper 06-12-09 06:51 PM

IGH= Internal geared hub, 3,5,7,8,14 speeds

eleven 06-12-09 09:31 PM

wow. awesome.

unterhausen 06-12-09 11:46 PM

I was also going to suggest going old school clamp on fittings. It might cost you though. Is the derailleur hangar gone?

Where are you located?

eleven 06-13-09 12:34 AM

Yep, no more derailleur hanger. The frame fittings are a good idea but the hanger is going to be a tough one...I wanted to avoid building up a new wheel with an internally geared hub as I have a wheeset with a cassette ready to go. I'm in norcal.

NoReg 06-13-09 12:43 AM

3950 sounds like a lot, but it is a 20th of low end welding. Very strong if there is enough surface area.

The deraileur mount is also a newfangled thing. The first few Peugeots I had had little clamped on hangers.

I thought 853 was hardened tubing but not the whole frame heat treated. I thought that pia was reserved for 953, and last I heard that was mostly being used only in hardened tube format. However I must confess to mostly glazing over when the subject comes up. If the frame was not globaly heat treated, then it should be fine to braze bits and pieces on because that would be how it would have been handled originally.

unterhausen 06-13-09 01:01 AM

You might want to limit the repairs to a new right rear dropout. Too bad you aren't closer to me.

JohnDThompson 06-13-09 01:53 PM

Quote:

Originally Posted by eleven (Post 9093781)
Yep, no more derailleur hanger. The frame fittings are a good idea but the hanger is going to be a tough one...I wanted to avoid building up a new wheel with an internally geared hub as I have a wheeset with a cassette ready to go. I'm in norcal.

Campy used to make this little piece to replace broken tabs:

http://os2.dhs.org/~john/dropout-tab.jpg

I doubt you can find one now, but it would be easy enough to make one from a donor dropout. PM me if you want to try this and need a donor dropout.

KNEEL 06-13-09 10:08 PM

yet another soulution
 
heres a ss tugnut with a hanger on it............
http://www.dmrbikes.com/?Section=pro...&itemid=FPCTMH just an idea...............

rodar y rodar 06-14-09 01:04 AM

Quote:

Originally Posted by Peterpan1 (Post 9093807)
The deraileur mount is also a newfangled thing. The first few Peugeots I had had little clamped on hangers.

You don`t mean claw mounted derailers, do you? It sounds like you`re talking about something else, but I`m not sure. Can these clamp on hangers adapt to most frames? Also, would claw mounts work even with a QR skewer hub (OP doesn`t say, but if his wheel has a cassette and freehub, I assume it uses a skewer).

Kneel, the Tugnut looks cool- I`ve never seen that before.

NoReg 06-14-09 12:52 PM

I don't know what a claw mount is...

It was a metal piece that hung down next to the drop and was sandwiched with the skewer. There was normally a screw that held it from rotating, which I guess raised the issue eventually of why not just screwing the derailleur to the drop. I think a lot of stuff back then was actually harder to manufacture, and was worse, but allowed them to create different value levels. Similar kinds of things, though different also, are used to put derailleur on department store aluminum bikes, so maybe one could get one at a not too snooty shop. Some of the alternatives above are a lot neater, but require fire to do.

squirtdad 06-17-09 10:59 AM

Clawmount derailers were used on low end bikes (like the 78 univega I am rehabbing). You choice in derailler and quality will be a bit limited if you go this way, the tugnut hanger posted by Kneel looks like it has potential, but the real fix is replacing the dropout as unterhausen noted.

NoReg 06-18-09 01:03 AM

OK, what I had was... I thought the mount held a tapped hole for a regular derailluer, since I think I may have upgraded to Campy, but it could be that the simplex deraileur it came with was as you describe. 37ish years ago so a bit lost in time.


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