Designing a Vehicle with Elastics/Balloons: A Hairpin Turn Challenge!

[alie77]

Hello everyone, first post on this forum and I'm really excited to hear you feed back. For my first year engineering design course I'm asked to design a vehicle that will undergo a hairpin turn (180 degrees) around a 2 by 4 piece of wood. The vehicle must only harness the power of elastics or balloons to undergo this turn (also that energy can be converted to other forms). It will travel for around 5-7 feet before undergoing the turn and then continue to move for another 5-7 feet (the track is pretty much a table split by a big piece of wood in the middle). As well, the vehicle must cost less that 20 dollars (final prototype).

The attempt at a solution

I've already come up with several good ideas with regards to powering the vehicle as well as the hairpin turn such as shifting the centre of gravity of the car to cause it to loop around the track (projectile motion). However I would really like to hear some other ideas. PS Don't be afraid to mention anything no matter how absurd, it's all part of brainstorming ;).

 

[lewando]

You should elaborate much more upon your several good ideas. You will get plenty of feedback that way.

 

[alie77]

Sure. In terms of powering the car, I would simply tape an elastic band to the body of the car and wrap it around the axle. That way, all that has to be done to wind it up is turn the wheels backwards.

As for pulling off the hairpin turn I had several ideas. One idea is using gears to have the outer tire(s) of the vehicle spin faster than the inside, thus turning the car. However I would need to have some sort of stopping mechanism and I'm not very familiar with gears so I would need you guys’ help on that.

Another idea is to have an extend-able arm that will latch onto the end of the 2x4 thus using the 2x4 as a pivot for which the car will turn around. The arm will then have to unlatch in order for the vehicle to continue on forwards.

My third idea would be to use two balloons, one pointed vertically and the other horizontally to power the car. Then, using the basic principles of projectile motion, the car will turn by controlling the air flow from both balloons.

These are the best ideas that I've come up with. Please feel free to add or comment these ideas and don’t be afraid to give some new ones two. Trust me, nothing is final yet. Thanks.

 

[CWatters]

I think I would do some experimenting. I can think of reasons why twisting the band will be better than winding them. You might also need to think about how to control the speed or risk going shooting off the end of the table.

As for steering I was going to sugest spring loading the steering so the car turns one way all the time. Then use an arm projecting out of the car (sideways about the same distance as the radius of turn?) and rubbing on the wall to keep it straight. Once it passes the end of the wall it will turn left until it makes contact again. Some considerable fiddling with the geometry of the arm will be required.

For $20 you could probably afford an electronic solution to the steering (variant of a white line follower) but perhaps not if the steering control circuit also has to be powered by elastic?

 

[CWatters]

I assume you can't just stretch a long elastic band the full length of the table, around the end of the wall and back down the table to the car

 

[alie77]

I think I would do some experimenting. I can think of reasons why twisting the band will be better than winding them. You might also need to think about how to control the speed or risk going shooting off the end of the table.

As for steering I was going to sugest spring loading the steering so the car turns one way all the time. Then use an arm projecting out of the car (sideways about the same distance as the radius of turn?) and rubbing on the wall to keep it straight. Once it passes the end of the wall it will turn left until it makes contact again. Some considerable fiddling with the geometry of the arm will be required.

For $20 you could probably afford an electronic solution to the steering (variant of a white line follower) but perhaps not if the steering control circuit also has to be powered by elastic?

Ya I'm definately going to be testing the prototypes. I really like your idea of a spring loading the steering but I would have to figure it a way of doing. The arm would definately be a bonus interms of controling the direction of the vehicle. Unfortunatly, I can't have any electronics, all power has to ORIGINALLY come from balloon or elastic. However it can be converted to say for example wind power.

I'm going to look into twisting the rubber band as I don't really understand the concep behind it. Thanks a bunch for your help

 

[alie77]

I assume you can't just stretch a long elastic band the full length of the table, around the end of the wall and back down the table to the car

Well...in terms of what the "vehicle" needs to be, there are no predefined musts. However, I think it needs to be 10x10 cm cause that's how big the final zone is. Final zone is a circle that the vehicle should stop in

 

[CWatters]

Looking online..

https://www.google.co.uk/#hl=en&sug...508c9ced339183&bpcl=35243188&biw=1009&bih=616

I see many carts have been powered using the method you proposed so it must work ok.

 

[lewando]

I strongly agree with CWatters about experimenting--early! Don't wait until the night before to realize that a component of your design is not working like you expect.

You might like to provide more detail on the area of operation (the table). Is it large enough so that you can travel in a large semi-circle?

Not sure I can visualize how you plan to latch/unlatch to/from the end of the 2x4.