Cool project! I actually did one of these a number of years ago from a
kit. Mine used small metal balls instead of tennnis balls, but the
basic ideas are the same. What I used was a flat base that I could
attach a whole bunch of tall metal rods to. The metal rods stood
straight up and held up the tracks every ten inches or so, which were
made out of two long plastic cords. (Since you're using a bigger ball,
you probably can get away with attaching something to the track only
every 15 or 20 inches.) The cords were separated so that the balls
could roll on them. If you decide to use this basic plan, you'll have
to figure out a way to attach the cords to the metal rods, since you
probably won't be able to find the same type of connectors that I used.
The most important thing to remember when building your roller
coaster is that the ball would always prefer to go in a straight line.
For example, this means that when you build the jump, the part of the
track that the ball lands on has to be lined up straight with the part
of the track that it jumped off of.
This will also make it harder to have the ball turn corners. When
you build a corner into the track, it's important that you have it be
"banked." Banking the corners means that the track tilts inward around
the curve. (If you've ever seen one of the tracks that they use for
racing cars, you should know what this looks like.) This helps to keep
the ball from rolling in a straight line right off the track. This will
probably be important to remember when you're building your corkscrew.
Also, the ball would prefer to be going downwards. In order to have
it do anything where it has to move upwards, you have to make sure that
it's going very fast first. This means that it has to roll down a hill
before it will be able to roll up one. (And because it loses some
energy by rolling, the hill it rolls down should be taller than the one
it has to roll up.) The ball's energy comes from how high up it starts,
and gravity pulling it towards the ground is what keeps it going and
speeds it up. So, unless you can use an electric elevator of some sort,
you will probably have to have your track be pretty tall.
The hardest part of all this will be the Loop-D-Loop. The track
that I built had one, and it took me a /very/ long time to get this to
work. But be patient! It is possible, I promise! Again, remember that
the ball will always try to move in a straight line. Unfortunately,
Loop-D-Loops require that the ball shift over to the side a bit
(because it would be hard for the track to go through itself). The
biggest problem you will probably have is that the ball will fall off
the track and go to one side or the other. Just keep tweaking the track
so that there's always some track in between the ball and where it's
heading.
The other tough thing about Loop-D-Loops is that the ball has to be
moved up, against gravity. This means that the ball has to be going
very fast when it starts it. You can make sure this happens by making a
tall hill in the track right before the Loop-D-Loop. Rolling down this
will give the ball a lot of speed. Once you get the Loop-D-Loop to the
point where the ball doesn't fall off to one side, it will probably
just fall straight down from the top of the loop. If this happens, it
means that the ball isn't going fast enough. So make the hill before it
even taller.
Most importantly, be patient. I would be very surprised if your
track works perfectly the first time. Just keep adjusting it until it
does work. If there's a problem spot, you can run the ball through it
over and over again until you've figured out how to fix it. Good luck!
-Tamara
(published on 10/22/2007)
