# Double Catapult Capabilities

To the teams that have built and used a double catapult for their robot, is there a really significant difference between firing a shot with one ball and firing two at once?

You will have more force behind a single ball since there isn’t the weight of the 2nd ball to slow down the catapult. Isn’t too crazy, but definitely not identical to a double ball shot on the same catapult.

basically what creatorthomas said

my double catapult can shoot one ball from the other end of the field (hitting the flag on the downwards arc) but with two balls it needs to be about a tile away to hit both flags (on the upwards arc)

About what angle do you guys have your double catapults set to? I just want to get an idea so we know where to start.

my double catapult starts at about 135 degrees clockwise from our tower, and ends at around 45 degrees clockwise from the tower. so about a 90 degree rotation for launch, but I’ve seen it vary a lot with different bots.

Ours launches at about a 40 degree angle from the ground and we have noticed that the starting position doesn’t matter that much. As we have changed it before and it made no recognizable difference. Our catapult fires at about 1 tile away from the flag. The most important part is the length of the catapult.

I seriously doubt that. If you draw it back from 40 degrees by only 1 degree, does it really launch comparably???

I expect you mean that past a certain point it didn’t make much difference. That can certainly be the case depending on how you have set up the elastics or whatever you’re using in their place. When you go from rotational to linear, you hit regions with little change. That can result in rotating a catapult further not stretching the rubber bands noticeably further. But that is very different from starting position not mattering much. If you run into this situation and want more change from drawing back further, try repositioning the elastic bands.

just finished a massive rebuild in 48 hours. double catapult that can hit both flags from up close (on the upwards arc) and from way back (on the downwards arc). also remember, if you change your firing range at all, you’ll also need to change your slipgear, so don’t make the gear unless you’ve locked down the firing area.

Speaking of slip gears, I saw someone using a Dremel tool on a video. Is that what most people do? I highly recommend using a wood chisel over a Dremel tool. I can cut teeth off so quickly with very little debris with a wood chisel.

a wood chisel ehh??? I have one, probably superior to my 150 grit sandpaper…

My boys used the metal files and then sandpaper it.

Guess it is still an upgrade compared to you

Oh, wow. Yes, wood chisels. Use a narrow one so you can get to one tooth nicely. It takes me a few seconds to remove one tooth, and a few seconds to clean it up. You can then sand/file it some afterward if you like. Wood chisels are less forgiving if you don’t know what you’re doing with them. I use a rubber mallet to initially remove the teeth, not to clean things up afterward.

do you hold the gear in a vice? because my vice is… uh… out of commission…

No, with a sharp chisel all I have to do is lay it on a flat piece of wood so I don’t damage the chisel when it goes through. The high-strength gears are flat enough that that works fine. I haven’t tried on the low-strength gears.

I’ve been using a small bench grinder. It’s messy, but it’s accurate and gets the job done. Just be sure to wear safety glasses.

hey, awesome I’ll have to try that! my chisels a little big and bulky, but It should work…

That’s impressive. We are attempting now to build a double catapult. It is not very accurate, and bends the metal piece we have on top to stop it even with the anti slip mat. Also, where are the rubber bands supposed to go and does how many teeth cut out on the gear actually matter that much or is it just a range?