From:    Ben Jackson <>
To:      John L Eaton
Subject: Re: Rolling Ball Scruptures
Date:    Mon, 21 Aug 2000 21:38:07 PDT
[hope you don't mind, I've cc'd the mailing list because I make several
points I've considered mailing out before and this is a good excuse]

> My name is John Eaton and I have just started in my effort to build a
> rolling ball sculpture. I have acquired several different types of
> metal to use for tracks. I like the strength of solid 9 gage copper but

Copper is also easy to work with.  I've been using 10ga copper which is
easily strong enough to make track for 5/8" steel bearings.  The weakness
is in making support structures.  You can't expect to "push" with copper
wire of that size, so you have to hang everything (or use alternate
supports).  I've built a frame out of 1/2" copper tubing (the type L is
very sturdy) and plan to hang stuff from it soon.

Remember that copper work-hardens, so once you take some wire and stretch
it to make it straight it's pretty stiff.

One disadvantage of copper (which I think I mention somewhere on my
website) is that it is such a good conductor of heat that it can be
hard to solder dense/complicated structures because you end up building
an excellent heatsink.  You need a high powered gun or torch to heat
your work area fast enough that you 1) get a joint where you want it and
2) don't accidentally reflow the surrounding joints.

> I like the feel of 1/4 # aluminum tubing. It is easy to work with. The

I don't know that rating.  Is that 1/4" OD?  That'd be some big tubing!

> 9 gage copper will work better with a 3/8" ball while the tubing works
> best with a 1/2# ball. What are the pros and cons of the larger ball?

Wow, those are tiny balls.  One lesson it took me YEARS to learn was that
building an RBS on a small scale does *not* make it easier!  If anything,
it's much harder to make the smaller track and devices because of the
tighter tolerances and reduced clearance for clamping etc.

I've got a lot of 5/8" bearings because it was the largest size I could
find locally.  They're small enough that copper track is feasible.  When
I get the skills (hopefully this fall) I want to try welded steel track
on billiard-ball scale.