Measuring thrust

a spring?

mounted horizontally, it should not be that difficult to measure how far laterally it will move before the spring holds it steady. the distance travelled is then used against the spring contant...etc ....

you could get a scale and attach the rocket to the top of it, also mabey a camera so you can read it without getting too close

Yeah, build a metal bracket with a known mass, then plunk it down on a simple bathroom scale and fire up the rocket. Record the "weight", subtract the weight of the bracket, and it's just algebra from there.

A batroom scale is a good idea, but most of my rockets are too small to register on those.

I once saw what looked like a circular balance. The rocket was on one end of a stick, a weight on the other, with a pivot in the center. For a backdrop there was some sort of calibrated markings. I am just not sure how to calculate the calibrations.

I'm sure it would be pretty easy to come up with a rig similar to that on your own. If your rockets produce less thrust than is measurable on a standard bathroom scale, then a postal scale should work.

actually with that rig if it dosent register all you have to do is ajust the ratio of the length of the top bar to the lower one to get a 1:X leverage

You could dramatically increase the precision of measuring the compression of a spring by using a very simple optical lever, e.g. rigidly attach a mirror to free end of spring and reflect a laser pointer, with an incidence angle of nearly 90 degrees, then simply measure how far the laser point moves on a wall that is parallel to the mirror. Then the amount of spring compression is simply the distance the point moved on the wall divided by the tangent of the angle of incidence.

Here is an idea. A cylinder floating vertically in a tub of water. The cylindar would displace the volume of water equal to it's weight. So calculating the weight of the change in displaced water volume, I should get a reasonably accurate measure right? If so, I could also attach a pen perendicular to to the cylindar, so I could record thrust over time, perhaps on a scrolling piece of paper.

Although, there would be some extra calculations wouldnt there. Because as the cylindar went deeper, the water would go higher in the tub, so more would be displaced. Or am I wrong about that?

Well, more wouldnt be displaced, but the calculations would need to take into account the water surface height.

[Edited by - Witchcraven on September 30, 2006 5:20:16 PM]