Reasonable warranty period for hand-wound pickups?

[SonnyW]

Right. I meant each turn doesn't make the tension on the bobbin higher since you aren't pulling the early wraps tighter.

I have to agree now, after reading some of the posts. I described this problem to a mechanical engineer at my work, and he said that off the bat he wouldn't have any idea how to calculate it and pointed out that the friction between the wires is increased as the compression increases. That prevents them from moving freely against each other. I forgot about and shouldn't have neglected this. The block and tackle model is not correct. There is still a compressive force on the bobbin core, but it doesn't work like a block and tackle because like you say David, it isn't pulling the early wraps tighter. Consequently my calculations were bunk - way too high, no matter how convinced I was when I posted them. By the way I had no intention of introducing controversy here or hijacking the post. I just wanted to explain how the wire shorts to the magnets. I should have thought about it more and posed my theory as a question in another thread. It is a beauty of open forums that bunk often gets debunked in short order. I would still warranty a pickup that failed by shorting to the magnets.

[RedHouse]

I would think that the tension is distributed amongst the windings and not cumulative.

Yep!

Plus the copper tends to "set" or relax to a much lower effect in very little time.

I offer a limited lifetime warranty to the original purchaser, parts and labor but conditionally:

›no sign of tampering or dis-assembly
›no obvious physical abuse

I discuss this with them before the sale, and drive the point home by mentioning that if they are into Townsend windmills or banging them with a bow (ala Jimmy Page) then normal shop rates apply for parts and labor.