Shock Dyno

[Horace]

Has anybody ever used a materials testing machine to dyno a shock?

The reason I ask this is because I have access to these machines but our school doesn't have a shock dyno.

I can see how this can be dangerous since if the machine stretches or compresses after the shock's limits then I would damage the shock. But with my zero experience in shock dynoing, I do not know if it is necessary to have the shock travel through its entire range or just part of its range.

[Horace]

Has anybody ever used a materials testing machine to dyno a shock?

The reason I ask this is because I have access to these machines but our school doesn't have a shock dyno.

I can see how this can be dangerous since if the machine stretches or compresses after the shock's limits then I would damage the shock. But with my zero experience in shock dynoing, I do not know if it is necessary to have the shock travel through its entire range or just part of its range.

[BrettHutchens]

I used an in house MTS machine, and as long as you keep your test stroke smaller than your damper's stroke than you should be good. Make sure your units are the same from measuring to input into the machine. I believe you have to input the displacement as an amplitude, half of the overall stroke(in a sinusoidal test). You don't necessarily have to test the full stroke of the damper if you are concerned about reaching the limit of the stroke a breaking the test damper.

[murpia]

Good damper dynos are very similar to a good materials test machine, it's the older / cheaper kind that use a crank mechanism to actuate the damper.

Just be sure your tester can handle the velocities of interest. You probably won't be limited to a sine input either, you can do a 'sawtooth' so the velocity is constant through the middle of the damper stroke.

Regards, Ian

[exFSAE]

A standard screw-driven tensile test machine will not be able to source the velocities you need. You'll need a hydraulic tester (like a fatigue tester).

[John Grego]

As far as I know, all you need is a motor, a linear potentiometer, a strain gauge, and software that is able to collect and interpret the data. That's all a shock dyno is anyway.

[rjwoods77]

You need a dyno that dOes cyclical testing at some frequency that your suspension works at. MTS machines don't cycle like that.

http://www.spatechnique.com/dynamometers/index.asp

[B Hise]

Cyclical testing (sine wave) is the most rudimentary of damper testing and is good for establishing basics.

MTS machines (the ones meant for dampers anyway) go far beyond that and can produce position and/or velocity signals at a very broad frequency range. If the machine you have in that picture can get to a 1" total amplitude and operate in frequencies between 0-20Hz with a reasonable signal of your choice I would say that you have a leg up. The only problem I can foresee is the sensitivity of the load cell.

-Bryan