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!

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!

What size marbles and how long an overall length, etc.?

The wire tie would work but it'll add resistance; if do go something
like that I'd suggest a small diameter filament fishing line or the like
instead of the wire.

Obviously, the best would be if could solder/braze a pre-bent "Y" or
somesuch to the under-side...are they old enough to teach?

Will have to cogitate some more; that's just otoh...

--

On Mon, 15 Nov 2010 10:58:07 -0800, SMS
wrote:
-snip-

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

Weld the wire supports- or buy copper and solder them.

Jim

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.

Use a hot glue gun, and be careful where the glue gets.

Pre-heating the parts with a hair dryer will improve the bond.

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

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!

HO guage model train track? Balsa wood?

SMS wrote in
:

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!



Nobody's mentioned epoxy yet, so I will.

I think the structure ought to do all the work of keeping the track from
flexing. The wires should depend on the structure for their location and
rigidity.

Fit the support structure and the wires together carefully, so the wires
sit in place without gaps or binding. Remove the wires, put dots of epoxy
on the support structure where the wires will touch, then carefully install
the wires in place on the structure. If the support structure is rigid
enough, you won't need more than a dot of epoxy to hold the wires in place.
Minimal epoxy means less chance of the stuff ending up near the travel
surface and upsetting the ball's path.

Clean the wires and structure contact points with rubbing alcohol to ensure
proper adhesion with the epoxy.

In case it helps... you might want to try securely fastening both wires
together with masking tape before you bend them, then separate after
bending. This way the wires are bent as a set, which will make the track
profile more consistent.


--
Tegger

wrote in
:




I was thinking epoxy myself. Get the putty style


Even the gel stuff is OK, provided you design the receiving points
properly.


so you can work it
easier and be sure your support forks are outboard of the marble
radius. When the putty is hard you can use a Dremel tool to dress the
inside smooth.



I considered a Dremel as well, but I think there's too much risk of
damaging the travel surface of the wires; I'd just be sparing and careful
in application of the epoxy. Given proper structure, it would take
vanishingly little adhesive to do the job.



--
Tegger

On Nov 15, 12:58*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.

On 11/15/2010 7:44 PM, Joe wrote:

Buy some 1/2" electrical conduit (gray) and slice it down the middle
with a table saw or whatever you have in your shop. Bend and twist it
any way you want it using a heat gun or hair dyer and mount it with
glue, hot melt, whatever, on some plywood or other substrate. The
conduit should be sized about right for a marble. If not, try 3/4"
conduit. Be careful with the heat as conduit takes very little to get
rather limp. Too much heat could distort the hemispherical cross
section, so care is needed. Conduit is made to be bent this way.
Regular PVC pipe is not, so don't bother trying it. With nice 10'
lengths, this method will give you a lot of track.

Conduit's easy, but there's extra credit if you have an open design with
rails.

They are using 1/4" rails which are made from hanger wire (not coat
hangers) inside 1/4" black irrigation tubing. This is just the right
stiffness to be able to bend but that still holds its shape, and was all
very cheap. The tubing adds friction, but that's a good thing because
they need it to run for as long as possible.

At first I suggested they use thin wire to tie the rails to the inside
of a piece of PVC at the proper spacing but then I went to the
electronics surplus store and got them some fuse clips and they bolted
them to the outside of a short piece of 3/4" PVC pipe at the proper
spacing using 4-40 nuts and bolts. The PVC goes into a tee, and the tee
can be rotated on the support pipe and the short piece can be rotated,
so it's not hard to position things and experiment. The rails snap in
nicely, but I suggested that they trim the inner part of the fuse clip
down to the level of the track so there's a minimum of a discontinuity.
I also suggested that they raise the outer track a little on curves for
banking, which they can do with a spacer under the fuse clip.

The one on the right is like what they're using:
http://www.ilsco.com/Images/ProductImages/Fuse%20Clips.jpg

They need to fabricate a lot of the spacers/support thingees even when
they are just floating spacers to keep the tracks the proper distance
apart. Welding would be great but this is their project and I'm not
welding anything for them.

The project can be 75 cm square and 100 cm high. There is extra credit
for loops, and for a design that goes for a longer time.

No funnels are allowed unless there are tracks in the funnel. You can't
slow down the marble with intentional bumps on the track. Apparently
this teacher has been assigning the same project for more than a decade,
and knows all the tricks the students use to try to increase the running
time.

It's hard for me to resist going out there to help them! They are
unrealistically optimistic about the time it will take to complete this
project. These things always take far longer than they expect.

I hope we get a Youtube link when it's done. ;-)

Edward

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!

Here ya go, build one this and it ought to get at least honorable
mention,
http://w.videowap.tv/video/0dT8pdv0L...ploration.html