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Old 09-12-10, 11:58 PM   #1
dnomel
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JB weld a threaded fork steerer extension?

I'm trying to cobble together an old bike, and the fork I've found is about a half inch short. I'm thinking about using JB weld to glue a small section of threaded fork steerer tube to a quill stem for the upper headset to screw onto. This section of steerer could be from some other junked fork, and it would be glued onto the stem well above the wedge with little gap to the fork below. I'm thinking if it is glued neatly, and set up and adjusted before hardening, things may be aligned properly and the hoped for result would be a quill stem with an aligned JB welded on section of threaded steerer for use with the upper headset, and still removable from the fork. Obvioulsy no height adjustment, but I know my size.
Does this sound possible? Has anyone tried it?
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Old 09-13-10, 01:30 AM   #2
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There are many problems, but it's not worth going into. I would buy at least $1-mil in life-insurance before trying that. Replacement chromoly forks can be had for $30. Call around, some shops have leftovers they'll give you for free.
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Old 09-13-10, 01:37 AM   #3
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Not to be blunt, but I wouldn't do this if you want to live.
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Old 09-13-10, 01:49 AM   #4
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JB Weld is not the same as real welding.
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Old 09-13-10, 02:24 AM   #5
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Tell us how it works out.
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Old 09-13-10, 04:48 AM   #6
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Could you please arrange for someone to video your first (and last) ride?
You can console yourself in your last moments of life with the knowledge that you will be a star on Youtube.
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Old 09-13-10, 05:08 AM   #7
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OK, I see. You wouldn't be glueing the steeerer tubes together, but you'd glue one bit to the stem, then use the stem wedge to lock the top part to the rest of the fork. That might actually be doable w/o being too horribly reckless.
If it was me, I'd splurge on some loctite used for mounting bushings instead, it's made for filling gaps like that. And I'd be really careful about surface prep of the concerned areas. If it's a chrome steel stem I'd grind the chrome off.

And at the end of the day it's still in the category of "doable, but not recommended or worthwhile fixes".
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Old 09-13-10, 05:47 AM   #8
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Quote:
Originally Posted by dnomel View Post
Does this sound possible? Has anyone tried it?
Not and lived to tell about it.

Find another fork.
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Old 09-13-10, 07:32 AM   #9
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Old 09-13-10, 07:48 AM   #10
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Old 09-13-10, 09:52 AM   #11
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denomel is off in a non reality if they think glue is welding..

JB Weld is an epoxy + aluminum filler, Adhesive, not welding..

But , Here is a possibility, It involves converting headset type to Threadless.
You need a quill extension. Its a steel tube with a quill wedge at the bottom, to tighten inside the fork, a mechanical reinforcement as half the extension tube doubles the inside if the fork, were it able to take the whole headset , the original Quill stem can go in the top.
That was it's original purpose
If you have enough fork exposed above the top of the frame to thread the upper race in,

But not enough to put the lock ring-Nut on, this is possible ,
But It is not going to be the strongest thing.. [Huge Understatement]

JB can fill in the threads, to bring the surface back to smooth to bring tube OD back to 1" , the tube quill adds 3 inches .. Its just a filler , there is still the weakness of cutting the threads.. buying list,
a threadless headset, + you buy new stem , a compression cap , to adjust a threadless headset and perhaps new bars.

Buying the appropriate fork is best, or hiring a machinist/ framebuilder can properly weld on another section of tube.

Bernie Mikkelsen, Oakland Cal I think can do this .. cost : a couple hundred + is reasonable .

But I suspect its not a Collector's bike you are restoring..

I wouldn't ride that, better to spend the money on a new fork.

I have added height to a threadless steerer tube with a mechanical fix,
using a quill stem raiser , from BBB in NL, it relocates the headset adjustment to the
top as before .. , core is beefed up a foot long and so the spacer stack is quite a bit longer , and the bars have a handlebar bag beneath them on a 2nd stem.

but the original steerer tube was already long enough if I were 25 and flexible , the stem sat on 3 10mm thick spacers, , so there is good support for the scheme..

Its not a Down Hill bike , a JRA bike ridden by a 63 old guy with no speed ambitions..

Last edited by fietsbob; 09-13-10 at 11:32 AM.
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Old 09-13-10, 11:00 AM   #12
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Even if it doesn't actually fail and fall out and make you eat pavement it will still have a couple of problems. Being smaller the quill will flex more easily and this will allow the epoxy at the joint to fail. Since part or all of your upper headset components will be supported by the bit above the joint it's going to allow the bearings to flex out of alignment and wear away at parts of the cup and cone far more quickly than normal. On top of that there's a good chance that the levering action of the flexing will make the glued portions creep and you'll continually be fighting with loosening headset issues.
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Old 09-13-10, 11:05 AM   #13
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WOW this is a really scary post. someone should take this guys wrenches
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Old 09-13-10, 11:24 AM   #14
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Oh c'mon now, why is everybody so down on this?

Not every bad idea ends in death....

Some just end in high dental bills, and/or a great youtube vid....
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Old 09-13-10, 11:41 AM   #15
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Just save up for a proper size fork instead.......it's way cheaper than your health insurance deductables, I'm sure......

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Old 09-13-10, 12:37 PM   #16
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Even if it doesn't actually fail and fall out and make you eat pavement it will still have a couple of problems. Being smaller the quill will flex more easily and this will allow the epoxy at the joint to fail. Since part or all of your upper headset components will be supported by the bit above the joint it's going to allow the bearings to flex out of alignment and wear away at parts of the cup and cone far more quickly than normal. On top of that there's a good chance that the levering action of the flexing will make the glued portions creep and you'll continually be fighting with loosening headset issues.
That's what I was mainly wondering about. Not sure what the forces would be on that part. If it did fail I don't think it would be completely and immediately catastrophic. The stem would still be stuck in the fork and on this bike it would be set low. It was just an idea out of frustration for a tiny bit too short fork. No way I would try to sell it to anyone or just get on it and go down a big hill. Thanks for the feedback.
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Old 09-13-10, 02:04 PM   #17
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The term "welding" is total BS****t in this usage. JB "weld" is epoxy glue. When you use the correct terminology, your answer should be self-evident.

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Old 09-13-10, 02:18 PM   #18
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Aside from the insufficient strength of a JB-welded joint, there is the alignment issue BCRider pointed out. Due to the large amount of clearance between the quill and steerer-tube, you will never be able to get the top section axially parallel to the bottom part. Especially when the stem's wedge is tightened. The top portion will be off at an angle, making the bearing-surfaces of the top and bottom headset cups not parallel. This will put ALL of the weight and road-shock forces carry through a couple of bearings rather than be spread out amongst all of them. You'll end up with an indexed headset in no time, not safe for handling.

There are two safe methods I would employ to extend a steerer:

1. unbraze the steerer tube and braze in a longer one.

2. use a precision-milled sleeve to press-fit inside the steerer to join the original steerer with the extension piece. Ideally, this sleeve would have tapered thickness, thick in the middle, thin at the ends (variable ID, fixed OD). Bevel the mating surfaces of the original steerer and extension piece by 45-degrees so you end up with a 90-degree V-notch. Braze or weld the three pieces together. Then spin the steerer in a lathe and mill down the join so that it's uniform to remove stress-risers (and allow the headfork crown-race to slide down).

Both a lot of work compared to getting another fork.
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Old 09-13-10, 03:35 PM   #19
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Don't listen to the nay-sayers!!!

DO IT! DO IT! DO IT! DO IT! DO IT! DO IT! DO IT! DO IT! DO IT! DO IT! DO IT! DO IT!

VIDEO! VIDEO! VIDEO! VIDEO! VIDEO! VIDEO! VIDEO! VIDEO! VIDEO! VIDEO! VIDEO! VIDEO!

DARWIN AWARDS! DARWIN AWARDS! DARWIN AWARDS! DARWIN AWARDS! DARWIN AWARDS! DARWIN AWARDS!




sorry, that's probably not very neighborly... Scary thing is, it might actually work for a while... not long but a while.
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Old 09-13-10, 03:49 PM   #20
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There's Shear forces between the parts of a threaded headset's 2 nuts.
pulling against each other .
OTOH, with a threadless headset the forces keeping the top race adjusted
is compression .

the top nut is inside the steerer tube and the bolt thru a top cap
is forcing down on the stem and the stack of spacers underneath it.

the adjustment is held by tightening the bolts holding the stem to the steerer tube.

Last edited by fietsbob; 09-13-10 at 03:52 PM.
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Old 09-13-10, 04:20 PM   #21
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If you do this, I'd like to borrow it--there's someone who screwed me over in a business deal who should ride this bike! Even better since I live in the mountains.
CC
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Old 09-13-10, 04:38 PM   #22
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i think JB weld gets way too much credit, and is WAY over-hyped on the package...
i think it looses it effectiveness over time...
and I have never seen anything JB-ed that did not fail or break again the same way as before.

although i do not exactly understand your proposed fix, my poor opinion of JB would lead me to suggest a no-go on anything related to a mechanical function.

but then you cannot really know without trying...

and supposedly billy-bob mcgraw finished out his manly work week by JBing the engine block of a bulldozer back together...in reality he had the cylinder-head of it removed from the abdomen of his charred corpse at the montgomery memorial coroners office.lol
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Old 09-13-10, 04:50 PM   #23
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Quote:
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Just save up for a proper size fork instead.......it's way cheaper than your health insurance deductables, I'm sure......

Chombi
A new fork doesn't cost much more than JB Weld.
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Old 09-13-10, 09:44 PM   #24
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How about a replacement fork for $8.15???


Not worth losing your teeth or life over the cost of a beer and slice of pizza. Heck, in the amount of time spent on this thread, anyone could've earned enough money working at minimum-wage jobs to buy this fork.
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Old 09-13-10, 10:48 PM   #25
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Man that is one ugly fork. The fork I'm considering for this experiment is an old vitus alum blades/steel steerer that I thought was a good match to an old sv980 frame.
The stem is steel, and the small section of threaded steerer from another fork.
I wish I could change the title to this thread because I think it has caused some confusion. Just to be clear, there is no gluing of steerer tube to steerer tube. The stem still fully inserts into the fork. It may be a stupid idea for a variety of known and not yet known reasons, but with the setup I am imagining on this paricular bike with a low stem, if the glue fails I don't think I'll have much nore than a very loos headset. Bad, but probably not disasterous even at some speed.
And to an earlier post about alignment, the idea was to set it up in such a way that the bearings would hopefully keep it aligned while the glue hardened. There is a bit of slop in there and it seems like epoxy might work ok, jb weld is all I've heard of.
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