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TheKid
09-28-2008, 07:52 PM
I finally got to test JB Weld, using two pieces of aluminum. I clamped the pieces together and waited a week to test the strength. I couldn't bang the pieces apart with a 3 lb. hammer. Next I'll be using it to affix cable guides to a frame. It's much neater than welding, and easier than braising.

macka
09-28-2008, 07:59 PM
You can also use a product called Sikaflex. They make adhesives that will hold stronger then welds, as they glue bus bodies together with it. Its not cheap, but if you precut and fit all your bike pieces together, you could "glue" them and not really need to learn how to weld. I plan on doing one bike completely like this. I know some of the custom racing bikes are done like this to save weight. A completely carbon fiber bent bike would be awesome.

TheKid
09-28-2008, 09:05 PM
I read somewhere that Greenspeed trikes are epoxied together to avoid the pre and post heat treatment required for aluminum, but I'm not sure if it's true. I'll google Sikaflex for more info. Thanks.

savarin
09-28-2008, 09:22 PM
I read somewhere that Greenspeed trikes are epoxied together to avoid the pre and post heat treatment required for aluminum, but I'm not sure if it's true. I'll google Sikaflex for more info. Thanks.

the 2 greenspeeds I have access to are definitely tig welded

John Lewis
09-28-2008, 09:44 PM
Years ago a friend built gyrocopters commercially. The rotor blades had an extruded leading section for about 1/3 the blade chord. The remainder top and bottom was thin sheet aluminium. They were glued to the leading extrusion about 1/2" wide and the trailing section the same. There was a single small pop rivit at each end to stop them starting to peel and that was all. they used to run a thin bead of glue lay the ali coated with activator onto it and clamp until set.

When you consider the forces on a rotor blade that glue was pretty damn strong. I wish I could remember what it was called. It was a two pack. a thick component that was the adhesive and a thin component that was the activator.

By the way I think most Greenspeed trikes were 4130 CroMo and TIG welded.

The Anura however is Aluminum. I know somebody locally who has bought one and will get to study it closely soon.

John Lewis

TheKid
09-29-2008, 12:43 AM
I couldn't find the article about Greenspeed and other manufacturers using epoxy to assemble the frames, but apparently, it was in error. The Greenspeed site mentions the frames being welded.
Windcheetahs are glued together using lugs.

http://www.windcheetah.co.uk/manufacturing.htm

trikeman
09-29-2008, 05:18 AM
747s and military fighter jets are also "glued" together in many places. Many carbon fiber frames were also glued at the lugs in the old days. I once priced the glue to do sucn things and it gave me sticker shock, but I haven't looked lately.

http://whyfiles.org/145composite_materials/3.html

TheKid
09-29-2008, 01:27 PM
I checked out adhesives several times. Anything I would trust for gluing a bike together costs a fortune. Sticker shock is an excellent term to describe the feeling when the prices are displayed.

AtomicZombie
09-29-2008, 02:49 PM
And "road rash" would be a good term to describe the effects of a glued together frame failing due to low quality adhesive!

Brad

Sparky
09-29-2008, 02:57 PM
on my old cheapie mtn bike, one of the cable stops snapped off. too small to weld, but kinda important. i used a 2 part epoxy from walley world and a zip tie to anchor it back on there.

it broke not too long after, so i scuffed the metal some, and added more epoxy. that was about 2 years and alot of hard riding ago- its still stuck on there.

i could post pics if yall are interested.

TheKid
09-29-2008, 04:08 PM
Scuffing so the epoxy could bite is important for a good bond. I see no reason why using a good quality epoxy wouldn't work for cable guides and stops.
Is it neater than if you welded it on?

trikeman
09-29-2008, 05:06 PM
Many modern epoxies have tensile strengths on the order of 2,000-3,000 psi. That means that if you put it in a lug to give it enough area it might hold. You won't be doing a simple T-Joint. Of course a conventional weld on steel is about 60,000 psi or more. That means that glued frames require a lot more engineering to get them right. On the other hand, most of Brad's steel designs are ***** proof, which is a good thing in my case.

Sparky
09-29-2008, 07:11 PM
no, mine is pretty globby. but with attention to detail and possibly sanding it down after it dries, i have no doubt you could get good results.

i didnt weld it cause a cable stop is pretty small for an arc welder. come to think of it, i might have done that before i got the welder.

TheKid
09-29-2008, 07:47 PM
I welded some on the Meridian. I didn't use new guides, I cut them off donors and left a bit of the tube on and welded. After some trial and error, I found the best way to get them to look halfway decent was to spot weld the four corners, sand the real high spots, then use glazing putty to smooth it out. I think using epoxy would be easier.