[petek]

I wasn't measuring the rate, I was attempting to calculate the rate. And after thinking about what Dreamer said ("Your spring rate should not change because you cut the spring.") I think I've come up with a reason the spring rate changes when you change the length of the spring; not using any math :-)

The formula I used earlier indicates that the spring rate (K) changes when you change the length of the spring. I believe this to be true as when ever someone cuts the springs on their car, the car rides rougher. The question is why would this happen and I think I've got an example that would explain it...

Unroll the spring into a long, straight rod. The rod will have a certain amount of flex to it, "springy" rod as it were. Heck, think of a fishing pole. (We're going to ignore the mass of the rod in the next part.)

Hold one end of the rod fixed and press on the opposite end with a known amount of force. The rod deflects. Now cut the rod so that the length of the rod is 1/2 of the initial length of the rod. Hold one end fixed and press on the other end. More force will be needed to deflect the rod an equal distance. Two things in play: lever action and strain.

So, changing the length of a spring changes it's K value.

Now, having said all of this it could all still be pie-in-the-sky BS as I haven't the foggiest idea of what I'm talking about (there are times when I wished I had not slept through physics)!