On 01/06/10 09:47, Matty F wrote:
I wish to make a large Newton's Cradle. That usually consists of five
suspended steel balls. Ideally the balls will be at least 2" in
diameter or up to 12" or 24" in diameter.
If they were steel they are likely to injure childen. So they can't be
steel. Billiard balls bounce well but are still too heavy.
Golf balls don't seem to bounce properly so they are no good, and are
too small. Soccer balls don't bounce that well either.
Polystyrene foam is too flimsy.

Any brilliant ideas? I have an idea which I will experiment with.

Yes - I believe I have the answer...

(You can thank my messy sproglets for leaving crap everywhere!)

http://megabloks.iparenting.com/graphics/starterpic.jpg

They are made by "Mega Bloks" (spelling correct). Can't find a source,
right now, think we got them at ToysRUs or Argos a few years ago.

They are a giant sized version of "MagNext"

The balls are hollow steel getting on for 3" diameter. Very light, but
one thing I noticed was they bounce extremely well on concrete (and
thus, probably, on each other - which makes sense - they are exhibiting
the restitution of steel without the bulk mass). I think they will work
for you.

You may need to go hunting though - can't find them on google shopping.
Charity shops would be one place, or ebay. The original pachkaging was a
platic tub about 5" deep, 12" tall, 18" wide (all +/- few inches!).

Stop press...

Just found them:

They are called "Magnetix Jr" (or Junior) and there are a few places
selling them, eg:

http://www.pharmacyplace.co.uk/produ...ty-system.html

--
Tim Watts

Hung parliament? Rather have a hanged parliament.