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Posted by David Sherman [216.18.131.236] on Wednesday, December 23, 2009 at 11:51:52 :
In Reply to: Re: how to weld posted by Glen Idaho [64.126.155.200] on Wednesday, December 23, 2009 at 11:05:58 :
Good point about the sleeve causing stress concentrations. In a shaft that was just strong enough to do the job, you might need the flexibility of the shaft to take up shock loads. However, here where the shaft is way over-designed anyway (probably for rigidity and resistance to getting bent from hitting things rather than for torque-carrying ability), and shock loads are minimal because of the worm gearing and springiness of the winch cable, and such shock loads as there are can never exceed the strength of the shear pin, I don't think stress concentrations caused by a sleeve would hurt anything. Put simply, there isn't much "give" to that shaft anyway.
If I was in that situation (and maybe I will be by the time I get my jerry-rigged winch cobbled back together), I would give welding it a try, without a sleeve, based on the calculations I did. I might refine the calculations based on the actual diameters at the weld and at the shear pin, but if a 1/8" weld bead is theoretically over twice as strong as the shear pin, I'd feel pretty good about doing a 1/4" weld all around and calling it good. If I really wanted to be sure, I suppose I could deliberately overload it and see that the shear pin breaks.
Like everything with old machinery, it depends on how much money you have to spend, versus how much time you want to put into it, both of those in the context of how you intend to use it and how perfect everything else is. Since drive shafts are available and not too expensive, there's no point in getting really exotic with the welding, but since even simple welding would appear to be strong enough, it seems like it would be worth a try.
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