Instructables

How strong is JB weld compared to real welding?

I want to build a recumbent bike, but I can't weld. Any other ways to build one. Mabye make one from hockey sticks.

skunkbait5 years ago
JB weld is great for SMALL repairs. I even patched a hole in the crankcase of an old Harley with it. But it probably would be unsuitable for a bike frame. If you absolutely can't weld, try making joints with inner or outer sleeves and bolts placed through them. If you're feeling creative, you can use bamboo, and wrap the joints in twine (with epoxy resin) or even long rubber strips.
-CCCP-3 months ago

Really strong. But not good for bikes because it may fail. On my hybrid spud gun, the spark plug is insulated with 1/2 inch PVC.The spark plug is JB welded to the inside of the PVC. The PVC is glued to the 3/4 inch by 1 inch steel bushing.

dlbott2 years ago
Remember this folks, you or someone you love is going to be riding this. If you have ever been riding at speed and had a failure of any kind you will know how serious it can be. It is compounded if you are in or near traffic. Don't mess around with welding if you are not really accomplished at it. As stated bike tubing is incredibly thin, made so to be light.

As far as J.B. Weld I think if you asked the company and told them you would be riding a bike at speeds they would tell you not to use the product for these purposes. Very dangerous.

Be safe first, it only takes one fall at speed to alter your life forever!!!!
Andy!!! evrybody can weld mig!! You only say that you cant weld if you must do heavy structural stuff but you can buy a 150 bucks flux mig welder and weld
ANDY! (author)  sthealthraider4 years ago
im too young and lazy and i dont have $150
Your school probably has a way to weld. I'm only 15 and I saved up and bought a Mig gas welder
ANDY! (author)  snowluck23453 years ago
Once I get enough time to build something requring a welder, I'll look into that!
You can weld with a car battery or two, but I can dig being too lazy. :-)
Before you compare the strength of various adhesives, you should study materials science terminology a bit.

Pressures on a joint can be classified as compression (pushing together), tension (pulling apart), and shear (sliding apart). The measure of a material's strength can likewise be classified in various ways.

Cyanoacrylate adhesives are quite strong in general, but their shear strength is not the best. This includes the J-B Weld brand, which is just epoxy with added chalk and powdered iron. (The Wikipedia article reports an advertised 1040 psi shear strength.)
and it uses steel paste not powdered iron
J-B Weld is not a cyanoacrylate. The rest is right, though.
I used JB weld to fasten a weed whacker engine to a round bar to use for a motorized bicycle. It's held for several weeks so far with no sign of slipping or breaking. So far I have to say it works amazingly. As they say, where welding isn't practical or possible, use JB Weld...
co2wms7whcc4 years ago
I would have to disagree, I bought a cheap Flux cored MIG at Harbor Freight and it is fairly difficult to weld something that thin. This is because the cheap welders only have 2 heat settings (Low and High). I don't doubt it would be possible to weld it, but you would risk crystallising the steel around the weld by overheating it. I think the best way to make a metal bike frame is to make fittings and braze them on with Oxy-Acetylene. You could probably get access to a Oxy-Acetylene torch if you took a welding class at a local community collage, then you would have an instructor to help you.
A proper weld is as strong as the base material, sometimes stronger. If you're welding steel, which is what most bikes are made of, then it will be as strong as steel. J-B Weld has a tensile strength of 3900 PSI; which is 65% the strength of filler metal. J-B Weld only adheres to the surface, so the bond strength is actually only 1800 PSI. A joint is only as strong as its weakest spot, which in this case is 1800 PSI on a good day. That is only 30% the strength of a good steel weld. Even less if you don't do the surface prep just right. I'd say the strongest joint you can get get without welding is to bolt or rivet it together and then J-B Weld over that. My advice to you is to learn how to weld. By the time you buy enough rivets and J-B Weld to build a bike, you could've bought a cheap stick welder and some rods. Also, don't build anything to trust your life with (ie, bike) until you know what 100% penetration, pull tests, and surface preparation are and can do them successfully.
ANDY! (author) 5 years ago
Thanks!
frollard5 years ago
a properly welded metal frame is *significantly* stronger than a properly jb-welded frame. Skunk has it on the nose - either tied/bolted wood/bamboo, or use sheathes on the metal tubing you have.

Bike tubing is thin - cheap welders (less than a hundred dollars) can weld them - and a good opportunity to learn. Be advised - anything you intend to ride - overbuild it. A failure at speed/in traffic would be awful.