Re: [ATM] wire spiders

["Arjan te Marvelde" <arjan.te.marvelde@hetnet.nl>]

Hi Tony, e.a.

> Everyone except engineers know what I mean Arjan......:-)
> Personally I think you've made the situation more complicated then need
be.

Well, sometimes things are not exactly the way they seem to be, so that's
where engineering comes in play. I always like to find some rational backing
for a hypothesis.
For example: one of the things that came out of the analysis is that the
amount of pre-tensioning does not make any difference for the static case.
This means that there is (collimation-wise) no point in pulling the wires
more than just enough to keep them straight. Of course the amount of tension
will have its effect on vibration frequency, but I do not know (yet) how
much.

Also there was an error in the example I calculated: the stretch in one wire
and shrink in the other should not be subtracted but added. This results for
the specific case in a force of 8.6kg for a 1mm axial shift (instead of
62gr). This is more in line with gut feeling!

You can find the spreadsheet at:
http://home.hetnet.nl/~artm/atm/resource/wirespider.xls

Arjan te Marvelde


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