Speed of an elastic/highly flexible object (i.e rubber band)

Projects General Guidance
1

Hello, I was wondering if anyone had any ideas about how to measure the speed of highly elastic or flexible objects.

I've thought of a few ways to measure speed in general (IR lights/receivers, Ultrasonic sensors, etc). These would work great for a solid body like a ball.

However, an rubber band for instance has a lot of "dead space" (such that it is conceivably possible the IR light might not hit it?).

It is also highly flexible (for instance it may be 90° to the ground at one instant but even a few milliseconds later the angle may change, this would possibly highly distort measurements if you hit the leading edge).

A friend makes little rubber band shooting guns and i have always been interested in measuring the speed of the rubber bands coming out of them. Accuracy is not paramount but even a relative sense between different guns would be good.

Any thoughts?

2

A somewhat simple device would use a sensitive target, so that the time between fire and hit can be measured.

3

Use a photodiode with a high pass filter and look for a dip in the received signal as the shadow of the rubber band passes by.