Rubberband powered car, with a twist

[canucks13]

Hey there, I was wondering if i could get some help from some of the people here. I have a problem, I have to create a rubber band powered car that first has to go on a half circle (diameter on the outside is 16 feet inside is 10 feet) then make it up a two stage ramp straight away. The ramp its self isn't very steep and has a slope then flat then slope then flat again at the top. There cannot be any external force like say a string tied to the middle of the half circle to steer it. And the rubber band is the only thing that can power it.

I hope this isn't too convoluted for you. Any help would be much appreciated thanks!!

Please note I have used the said search function and it seems my problem is fairly unique.

[CraigD]

Welcome to hypography, canucks!

If you’ve searched this forum, you’ve likely found a lot on rubber band cars, one of which had to make one sharp 90° turn. Your requirements are, I think, new to these forums.

Originally Posted by canucks13

I have to create a rubber band powered car that first has to go on a half circle (diameter on the outside is 16 feet inside is 10 feet) then make it up a two stage ramp straight away.

I think you’re describing a course that looks like this:


The best approach I can think of is to build a car with steerable wheels, similar to an ordinary auto's. That the steering need have only 2 positions – turning and straight - makes the design and build easier, as you can make the mechanism “snap” between the two positions after the car has rolled a fixed distance.

There are many possible ways to build such a scheme. Here’s a rough sketch of one that winds a length of string around a spool on the driven axle, pulling a pin to allow the steering axle to be snapped by a small elastic band from the turning position to the straight:

The drive system isn't shown, as I assume you already have a good idea how to make it.

Hopefully this is enough to give you some ideas, canucks. If and when you come up with sketches or prototypes of own, please post them or photos of them in this thread. Have fun!

[canucks13]

Yeah that diagram of the track is right on except just flip it horizontally. And yes I've seen the 90 degree post, the spool is a great idea!!! I guess one of my remaining questions is that how the elastic and pin work together. (maybe you could enlarge your diagram?) How would it pull it back into a fixed position?

Thanks though it seems like this should work, our initial designs just had a fixed axle and would then get us a score of 11/12 on a consistent basis. That is the main thing since we have to run it 3 times and they take the best 2 out of the three runs and average them. This seems like it should work though, lol if we can pull it off! Thanks!!

I will definitely post some of the sketches and such when its all said and done.

If anyone else would like to post their alternatives to the problem above please do I'd really like to see some more solutions!!


EDIT: OH also forgot to add, um what would you use to pivot the front axle?