[artdutra04]

Originally Posted by Woody1458

Is the spring constant approximately equal between the real and reproduced? A good test would be resting a heavy book on one, measuring then depression then doing the same to the other.

Originally Posted by Vikesrock

Unfortunately this is also a good way to break them.

Originally Posted by Woody1458

OK maybe a medium weight book Start at Dr Suess, and move up to JK Rowling.

I just did this test by stacking six encyclopedia volumes each upon both the real Orbit ball and the reproduction side by side, and they compressed nearly the exact same amount (they were within 3/8" of each other, which I'd guess is within the tolerance of the balls anyway).

Originally Posted by EricVicenti

I also reccomend dropping the real one and fake one at the same time while videotaping. On the tape you can count the bounces and see the height, comparing the consistancy.

I also did this test by simultaneously dropping both balls next to each other, as well as a second test of throwing the balls at the ground at the same time with same velocity. In both tests, they bounced to the exact same height. Between these results, and the compression results from above, I'd consider these a nearly perfect reproduction of the Orbit Ball. (Except the polycarbonate rings don't break easily!)

Originally Posted by EricVicenti

What are the actual balls made of?

I still don't know, but .062" polycarbonate provides a very good approximation for cheaper than many other plastics (using McMaster prices).

Originally Posted by AdamHeard

Also, did you happen to measure the internal plastic on a stock ball?

I don't want to take apart one of our five actual Orbit balls, as they are all still unbroken. However using calipers I estimate that the interior ring is 1.00" wide with an I or C channel shape. The edges are about .093" thick, and I cannot really tell the thickness of the inside between the two, but I'm estimating it's about .050"

Originally Posted by Mr_I

Perhaps this might plant a seed of thought: We're wondering if we can find a plastic jug (gallon or 1.5 gallon, maybe from a bleach bottle?) that is about the right size, and then slice it on a bandsaw to 1" strips. Finding such a container might make it easier to make, since A) you could use 2 or three rings whole, B) the plastic is already round, and C) the jugs might be readily available and essentially free.

Milk jugs or similar plastic containers are only a few thousandths thick, and lose nearly all of their strength as soon as the container is breached (with holes, cuts, etc). I don't think it would be feasible to make full-scale reproduction with same characteristics, but they may have potential for 1/3-scale Vex prototyping.