On 11/15/2010 1:58 PM, SMS wrote:
My daughter needs to build a marble roller coaster for her physics
class. Most of the class is using pipe foam cut in half, but her team
wants to do rails because you get more points if the design is mostly open.

So she's using stiff steel wire for the rails (my friend had a big
supply of it from old political signs). I was trying to help her figure
out how to support the wire rails at the proper spacing, remembering
that the marble has to be able to roll over any supports. She thought
about using short pieces of PVC pipe as supports, with the rails
attached to the inside. I don't thing cyanocryolate glue would hold well
enough.

I thought maybe drilling small holes in the PVC and using thin steel
wire to tie the rails to the sides.

Any ideas for rail supports welcome. It's okay, parents are allowed to
help!


There is almost nothing like wood for ease of construction. Cut a
hole larger than the marble in a small piece of 1/2" plywood or
similar. File a couple slots toward the bottom of the hole for the
rails. Use you favorite glue and then sand/file it all down so the the
support does not rub the marble.

You could cut a 1/2" slot in the end of some PVC pipe (or a cardboard
tube) and slip the wood into that for pylons.

For creativity, have the marble fly through the air at some point and
catch it in a funnel.

You may have issues keeping the rails at the same separation so be
prepared to make many supports. You can get threaded rod and drill a
hole through the wood and put a nut on each side. Assemble that before
you bend the rod. Don't forget to bank the curves.

Consider also gator board and other foam core "mounting boards" at
your art supply store. For more or less straight runs you could make
this entirely out of such stuff and cut your rails out of strips and
slot it together. Cut it all up with an Exacto.

Or take two pieces of foam core and cut them both at the same time. Glue
some foam core between and create whatever down hill runs you want. Good
for long hilly stretches.

Mix and match. Wander through a craft store.

Jeff

Jeff