I need suggestions of a locost way to measure spring stiffness. The donor bike I've got has a pair of coilovers that I'd like to use 'cos they're free.

I've tried pushing them against a pair of bathroom scales and I've found out that at the softest adjustment it takes 30 kg before they start to move and 40kg at the hardest. 60kg moves them some way towards the bottom but I don't weigh a lot more than that and its hard to put all your weight on a coilover and balance enough to measure the displacement with a ruler. Help.

BTW, my project is a 3 wheeler is a real lightweight with 150kg on the rear wheel with me in it, so the donor springs may well be fine.

can't you stick the spring under a car and lower it down on it, that will get it compressed

or you could see if anyone at the local weight watchers class could assist



[Edited on 3/2/08 by Mr Whippy]

First remove the spring. Then measure the height. Weight yourself and then stand on the spring. Measure the height again and do the math.

quote:

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Originally posted by Aico
First remove the spring. Then measure the height. Weight yourself and then stand on the spring. Measure the height again and do the math.

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Have a look here,
http://efunda.com/DesignStandards/springs/calc_comp_designer.cfm
All spring rates can de calculated with the spring ID, wire dia and no of coils. The only exceptions are non parallel springs and progressive springs (where the gaps between the coils are not equal).