Help For School Project.

[Axle]

The Teacher has asked us to make a baloon-powered Car.I've decided to make it out of Lego

[xwingyoda]

The thing that really hit me is this ;-) !! I really love the "retro" feel !!

Hope that gives you some ideas !!

*yoda*

[ApophisV]

The thing that really hit me is this ;-) !! I really love the "retro" feel !!

Erm, I think he is more talking about something like this:

;-) :-P

[xenologer]

I'm assuming that the teacher is giving everyone a standard balloon that you have to use? are they modified in any way to make an easy attachment point or a nozzle for the air to come out?

Don't even think about doing anything 'steam-engine' like. The best use of that air is as a jet, just aim the nozzle of the balloon out the tail of the car and let it go.

You're going to want the car to be as Light as possible if you're going to win any races.

So I'd definetly go with a technic frame; probably something long and narrow like a dragster shape.

With the bare minimum of bricks to attach the balloon and keep it's neck pointed to the rear.

Don't go for any wheels that have giant rubber tyres since these will add weight, stick to thin bicycle-ish ones. something like this is good:

Make sure the wheels are on long technic rod axels, with good support through the frame(the bricks it passes through should be spaced out); this should keep friction down from any rod flexing/binding.

[Jipay]

Xeno kinda explained it all. I'ed had rubber to the wheels he's suggesting though, as it will give your vehicule a good adhesion to the track.

[ApophisV]

Xeno kinda explained it all. I'ed had rubber to the wheels he's suggesting though, as it will give your vehicule a good adhesion to the track.

BUT it will increase the friction between wheels and the ground, meaning that you'll lose a lot of the power the baloon delivers due to friction forces, meaning your car would roll slower than without of the rubber!

[Brainbox]

BUT it will increase the friction between wheels and the ground, meaning that you'll lose a lot of the power the baloon delivers due to friction forces, meaning your car would roll slower than without of the rubber!

BUT rubber will stop the car sliding all over the place as would potentially happen with no rubber. You need to balance the weight (mass) of the car with the amount of grip. Make the car a bit lighter and use rubber, and you could have the same results (speeds) as having a heavier car with no rubber but with better control.

[xenologer]

Interesting discussion.

I forgot to mention it, but I probably would have added the tyres for those skinny wheels.

I figure, once the wheels actually get rolling they're fairly frictionless anyway.

[Brainbox]

I figure, once the wheels actually get rolling they're fairly frictionless anyway.

They would as long as the car was light enough to 'skim' fairly frictionless. If it was quite heavy, then it'd struggle to 'glide.'

[xenologer]

...Not entirely sure what you're saying

what I mean is, that given a rubber tyre that grips the road, if the wheel is rolling (not skidding) then there isn't any drag between the tyre and the road; the main drag would be from the axle against the car chassis

EDIT:

I just had a GREAT IDEA, sure to win the race :-D

its a "balloon powered" car, right? meaning the stretchiness of the rubber balloon is used to store energy and released to power the car.

Well, who says the energy transfer mechanism has to be air pressure?

slice the balloon into strips of rubber, tie them to make a nice rubber band

then make a pullback-motor racer

*y* advantages:

car can be Much lower profile compared to one with a fat air bag on his back; less drag

plus looks much cooler

well designed pull-back motor will translate the rubber's tension directly to your wheels; while the air pressure approach has losses due to air dispursal in uncontrolled directions, plus air doesnt have much momentum

you can focus more energy into the rubber when it is rubber-band form compared to balloon form, (the balloon form has size limits and whatnot...)

*n* disadvantages:

you Must be good at Debating, and must set fourth a good argument regarding the potential energy storage of the balloon vs kinetic energy of the car motion; and explain how the concepts of using the balloon as a rubber band are analagous to using it as an air bladder

X-D If you don't present the argument well, you might very well be disqualified

If yo Do present it well, you might get bonus points for cleverness and demonstrating understanding of the physical concepts...

[Brainbox]

...Not entirely sure what you're saying

I don't think I explained it too well. I meant that (like you said) there isn't any drag between the wheel and the road as long as the car is light enough to not 'push down' and eliminate the effect of the lack of friction.

[Axle]

Thanks for all the suggestions. I'm thinking i'll make a technic frame,add plates on the sides and have the bike wheels like said above.

And Im not very good at debating.Last time i did it was about getting a vending machine and I kinda said that........