seeking cheap extensometer

[Trix4kids]

Hello,

I am looking for a cheap ($200) extensometer to measure strain of a bike spoke. Are there any extensometers available that will simply attach to the spoke to measure strain? The max load will be 50lb.

Thanks.

 

[randi]

Get it from china. They have the most bikes in the world. They ought to have one. They must be making safe bicycles. Check China manufacturing, extensiometers. If they don't have one I am sure they could make one around that price. How many do you need?

If china can't make one. India surely can make one. Good luck in your search.

 

[skills]

I don't understand why you want a cheap instrument; but, Omega Engineering has LRD linear resistive devices that I use for these type of tests. They costs about $150-$200 and you can get them in 1",2",3" strokes with 5k resistance. I built a lash checker for a gearbox last month with these and it works great.

 

[cpretty]

Why not just bond a strain gauge to the spoke. Assuming you can find Youngs modulus and diameter, you should easily find the strain. Strain gauges cost $5-$10, and a bit of effort to set up the bridge circuit. The advantage will be negligible change in mass, so if the wheel is running at high speeds, centripetal acceleration wont have the effect that an extensometer may have.

What are you trying to measure strain for?