Catapult Consistency Spin Up

I was making a robot for fun, and the catapult shot perfectly with 2 discs. When I added a third to the two discs, (Same amount of rubber bands and all) the catapult did not shoot high enough. I understand it is due to the weight of the third, but what ways have people accounted for this?

1 Like

Add more rubber bands

Now for those who want a physics-based explanation,

When you increase the number of independent projectiles, the kinetic energy distributed to each projectile gets increasingly smaller. With a catapult, under the same banding adding more discs means each disc will not be shot as far/high. This is because the rubber bands only store a fixed amount of potential elastic energy, which gets converted to kinetic energy as the catapult is fired.

By increasing the number/stretch of the rubber bands, you will have more potential energy; therefore, each disc will have more kinetic energy. This means that each disc will shoot farther/higher than before.


Thank you for the explanation, but won’t adding more rubber bands make it too hard to shoot a single disc or a stack of two?

In general, a catapult should stick to shooting stacks of three, since it’s hard to make it shoot one or two while still making 3-stacks work. Don’t worry about needing three discs before you can shoot.


What do you think will happen? If I give it more power, what will happen when it’s load is decreased?

1 Like

catas will usually only ever shoot with three. im no physics expert, but more weight with the same amount of force means less distance. so just shoot with 3