The Problem is ...

the problem is the freedom of the ballon; if the ballon starts moving the car tends to move in zigzags. To fix this problem ...
a ) insert the balloon in net and attach net onto car
b ) create a fence around ballon to prevent it from moving

We tried both, but havent decided on which one is better ... * still in discussion

concusion - we did not do any of the ideas, we just taped the balloon securely to the car.

Combination of both cars

SOOOOOOOOOO WE FINALLY BUILT A DECENT CAR ! YAY ! :)
We put parts of our cars together to make a ballon car that works very well !
BUT the only problem is making it travel in a constant direction ; to make it travel in a straight line.
materials we used :
knex wheels with some other knex material like the sticks, BBQ sticks, straw, string, and cant forget the balloon !


P.S. this is the 4th car we SHOULD have raced with for race day.

Update on Idea One

So I've decided to totally change my whole idea since my last idea didn't work too well. So I made the body of my car out of bbq sticks and the wheels with sewing material ( the rolls ). Here is a picture of it ...

BUT this did not work either due to the wheels. So .. I think the biggest challenge is to find better wheels.