So, how do you prove to yourself your TIG welds are good enough for something like a motorcycle frame?

When I used to rebuild salvage motorcycles I had a box built that weighed just over 750 pounds straddling the frame where the seat normally mounted. A fully repaired motorcycle frame was subjected to vigorous and abusive testing before being sold. This was done with the triple tree removed so no front suspension movement and the test table had a hydraulic drive eccentric weight that rotated to set up harmonics never seen during normal operation. Sure, had a couple failures in the early days as testing to failure was the norm. Once your process was figured out and the man behind the machine was proficient, there were no more problems and literally hundreds of bike were repaired.

 

If I was building frames for profit, I would do my best to find tests that covers fillets in all positions for whatever material your using. I would be looking for maybe a xray or UT test. Then practice and certify in that particular process. Come to think of it, I'd probably do the same thing if it was just for me. Whatever you do, do everything you can to cya. IMHO.

 

When I was younger I often questioned this on my motorcycle projects, do some destructive testing on simulated joints/situations. A lot of old frames were brazed together very poorly I might add and still withstood the test of time. I would focus a lot on stress and stress relieving after welding. Most frames never crack in the welds, but somewhere that is under load from tension. I cut a top tube on a frame once and it jumped about 10" apart when I got through it. Think stress relief cuts as you build. When I was in my teens I read all of Ron Covells books that really helped restore confidence in my ability. I'm 45 now and never had one fail with my name attached to it. Never practice on a project, research and experiment bud!

 

3/8 bend test or weld 3/16 t joint and etch it see you penetration and make sure legg heights are good. I'll bend it for you

 

how about etch testing to view the HAZ? I've seen/done that to test penetration depth & profile.

 

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with handrail on the side of a building getting rusty and designed to keep people from falling off building or fire escape the code at one time was able to withstand 250lbs in any direction on any part continuously and handrail was tested every few years for rust damage
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i have also seen chemically attacked welds that were brittle. that is a good fast whack at 200 lbs might break it where 250 lbs gently applied did not break it.
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ideally most structural items should have a 4 x safety factor. so something designed for 250 lbs should hold 1000 lbs without breaking. the safety factor is often needed as shock load and vibration load can often break something close to breaking point.

 

Hard thing about motorcycle frames is the design and material selection, the weld design will be based upon them. The welds themselves should be the easy part.

The most common defect I have found in my own tig welds, has been a lack of fusion at the root of fillet welds, which seems to be caused by poor technique in allowing the puddle to lap over the root and overestimating the penetration of the puddle.