Decreasing catapult recoil

We have made a catapult for Vex Over Under. Whenever we fire it, it shakes. We have added hard stops to it but there is still a little bit of recoil. Can anyone please tell me how to decrease recoil?

I can’t see clearly where the hard stop is, but it sounds like metal to metal. Try adding some padding to the hard stop with antislip mat or something else.

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I would recommend less rubber bands and instead tweaking the launch angle to make up for the distance.

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I assume you are referring to the front of the robot shaking, in that case a little more weight on the front might help but you really want to make the cata arm itself as light as possible, or take off some tension. These two suggestions will take away some of the force of the catapult, as F=ma. Also make sure that the mounting structure of the catapult is strong and secure.

I have surrounded it with griptape, do you want some more photos

Recoil is just Newton’s Laws at work.

So adding padding will not work.
But what @Foximusprime and @Micahy321 suggested will work.

In any case, I do suspect the robot is not fully built yet?
So that’s the case, just finish up the robot 1st. The additional weight will help to reduce the effect of the recoil.


Thanks, will do char20char2char20

I’d say it is less easy to understand using Newton’s Laws. Momentum is conserved. You are shooting something 0.11kg heavy at a very high speed; the recoil is just momentum being conserved and totalling 0. Therefore, the best course of action is increasing the mass of the robot (think guns), which has its own advantages and disadvantages. It is also probably not significant. The second option is to reduce catapult speed. This can, for example, be done by getting closer to the optimum 45 degrees. The third is to make the angle of the shot steeper so that the vertical component of the momentum is a higher proportion and the robot is forced into the ground. Again, there are going to be side effects. This would be a really nice thing for the notebook. Momentum is easy to calculate and there are very few terms to minimise or maximise for the desired effects. (There is a fourth option, which is setting motors to hold and thus put significant load on the power of the motor.)

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