Measuring spring stiffness..
I put together a simple way to measure spring stiffness today. Very useful, as seemingly identical springs can actually be quite different. In my case the reverse was true.. I found a 3.2 guage spring that was actually no stiffer than a near identical wind in 3.0mm..
Figured I'd share...
Use two spring guies, slightly loose fit. thread into each end of test spring. Get a 9" length of M10 stud, with one end threaded into a small metal plate to support the weight that will be stood on it. Thread rod through the spring / guides. Mount in a vice / clamp, secured vertically by the lower guide flange. Must be very secure. Stick a big weight on top and measure the compression.
I used a convinent spare car battery (I guess around 18 kg), and got useful differences. e.g.
225mm long springs, x3
Spring A 3.2mm wire, 18mm deflection
Spring B 3.0mm wire, 17mm deflection
Sping C (std TX mk3 2.9 wire), 33mm deflection
I found it quite handy, so I will gradually label up my springs so I can compare when looking for the "right" spring.
Another approach BTW would be to use a sash clamp with some bathroom scales between the end of one guide and the clamp., and measure the deflection at a certain weight, e.g. 30kg. Probably safer than my car battery balancing method But we've no bathroom scales in the house...
Always looking for any cheap, interesting, knackered "project" guns. Thanks, JB.