I'm going to use this method to extend my swingarm. People say "cap" or "build up" or some other phrase (in the japanesse guy's thread.)
Is that body filler or what? Why not just use square tube that matches ID of the original, and another square tube to wrap around it? I also want a smooth finish.
Has anyone bought a long swing arm from Japan? I'm looking at them at the moment and there seems to be a few makes. One make, Beams is about half the price of the others, does anyone know what the quality is like? I can't weld to save myself hence buying a pre made one.
Theoretically, a weld is as strong as the media. Theoretically. Theoretically, epoxy and fiberglass are stronger than plywood. In reality, no, a composite butt joint wrapped in fiberglass will eventually break. When scarfing 2 pieces of ply together taper is always at least 12 times the width. I was taught 45* on the long side of a rectangular swingarm was about right.
It is not possible to extend a swingarm with a tube inside the originals, than a tube the same as the original. How are you going to get the second tube in place?
Instead, cut tubes that fit inside 6-10cm long. Cut slots in the original parts parallel to the cut ends of the original parts for welding. Weld the stubs to both ends of the original parts. Form tubes the length of the desired extension the same height and width as original. Cut slots to weld to the stubs. Weld the tubes to the stubs and original front part of the swingarm, weld the stubs and rear parts of the swingarm to the extensions. Grind and paint. What you end up with is three rows of welds at each joint instead of one, and a smooth, attractive appearance. If you want to get fancy, the inner tubes can be cut at an angle to match the angle of the outer tubes. Saves a bit of weight, but doesn't affect appearance.
It might not be a Forth Road Bridge,but the outcome of a swingarm failing from a faulty unknown weld going down a road with traffic is going to horrific.