How to get enough lift into the catapult system?

Hi Everyone!

So I have a question,

when I take apart rubber bands from my catapult system so that my gears won’t break, It doesn’t have enough tension to lift into the high goal. But if I add those rubber bands, then it will break the connection from the gear to the catapult.

Any thoughts?

Shyam B

Before we can help you, help us. Please post some pictures of the specific mechanism you are trying to fix. Everyone’s robot is difference and the solution that works for yours may not work for other peoples’.


The problem you are describing was the problem I was referring to here:

And next time I would suggest replying in the same topic instead of creating a new one.

Also, a picture would be very helpful.

However, until then here are some general tips for that type of problem. Try doubling up the beams used for the choo-choo mechanism (stack up two 1x beams). You can also try adding an axle like on Fling that stops the catapult just short of reaching the top so the force of the release goes into the axle, and not into the catapult itself. I’ve also found using brand new pins (that are stronger then old ones) to help keep it together. However, I can’t tell you which one of these things will work, if any, and that’s why a picture will be helpful.


Will get a picture shortly

Here are the photo’s:

@FRC973 Sorry for creating a new topic! I didn’t realize I had the other one. The photos are posted. Also, as you can see in the second picture, I already but the axel and I also doubled up on 1x beams but it still broke apart because of the tension of the rubber bands.

That overall looks like a really good catapult.

Have you tried using brand new pins? If you don’t have any handy, you can find some in the field in the orange pieces at the bottom left and right of the plastic pieces.

Also, try flipping around the purple pin in the green circle (and the one on the other side). And you might also try changing the pins in the red circle to 0x3 capped pins from the field (or brand new ones) and make sure the caps are touching each other inside the two beams that attach to the catapult arm.

What we are doing here is making it more difficult for the catapult to pull the pins out because they are longer and they have to pull through more holes to pop out. The idea is that you want as many holes of engagement as possible, and if you have two holes for one piece and only one hole for the second, you want to put the “one hole” one next to the cap of the pin so it can’t easily slide off. And we are using capped pins instead of the offset flange ones because by nature they are stronger.

Lastly, I can’t tell for sure that they aren’t from the picture, but make sure that your gears are aligned the same (so the catapult releases for both of them at the same time, and the force is split evenly between them).

One quick question, was it breaking at the green circle or the red circle?


green circle (20 characters)

Okay, let me know if it still is after flipping around the purple pins.

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What do you mean by flipping the purple pins? If I do that, then where is the connection from the gear to the beam?

Sorry, I meant putting the cap on the other side so they are facing the other way (i.e. the cap is now touching the gear). This should not let the gear slip off the pin as easily.

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But where is the connection then?

I think I’m not seeing the picture correctly. Can you elaborate on what you mean by the “connection”? I thought the purple pins were connecting to the gear.

Ohhhh nevermind you mean to connect the pin head from the gear that connects to the 1x beam sorry.

Yeah, I think that’s right. Post a picture when you’re done and let us know how it goes.


Sure thing! Almost done.

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@FRC973 Here you go

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Another problem arose,

Because of the tension, the gear cave outwards severely. And even then, the motors (I put 2) don’t have enough strength to make a full rotation. The 1x beams only turn a 1/2 rotation. I don’t have any capped metal axels.

Any ideas?

Shyam B

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@FRC973 Here’s what I mean

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To help with the gears flexing inwards, you could try lengthening the capped plastic shafts in the 48t gears to make them long enough to go through the yellow frame pieces. This will provide to points of support which will make it much more rigid. You might also want to put as many shaft collars as will fit on the plastic shafts to help hold the gears in place. This may or may not fix the issue where the motors are having trouble though.

Just to test it if the motors can’t spin it, try spinning it by hand and see if the catapult breaks itself when it shoots. If it is, check if the gears are aligned. If they skip teeth when it shoots, let me know and there’s some things we can try.