So my team is creating a double ball catapult and we were wondering how to split the balls to make sure they don’t hit each other in the air. We are also thinking this will help us tune the catapult better, does anyone have any tips? Our catapult is about 12 holes long and our feeding system feeds the balls from the side so that we have enough room for our arm. We are using two cortex motors if that helps at all.
if you space each of the carriages well, ball collision shouldn’t be an issue. there is about 3 holes of space between our carriages, and never had balls hit each other.
In a standard double catapult, as long as it isn’t ridiculously low power, the balls should never touch mid air. The top ball is launched with more energy, and therefore has a much taller and longer arc. Until they touch the ground, both balls will continuously get further and further apart, both vertically and horizontally. For an example of a catapult in which the balls are as close together as possible, check out 1727G’s bot. Unless you stack the balls vertically (or do something else really weird) they should never collide
What do you mean by carriage.
They do not touch once in the air but since they touch each other on the catapult it changes the trajectory of both of them.
This is not necessarily true as the balls stay relatively static at the back of the catapult until the catapult is abruptly stopped - only then do they begin their airborne motion. The trajectory of the shot is more so reliant upon the length of the standoffs on the back, the work done on the balls, and the angle of the catapult at the end of the shot.
by carriage I mean the 2 little pockets that the balls sit in. your balls don’t necessarily have to touch each other, mine don’t.
We don’t really have any pockets, instead we have a 5 hole wide C-channel that the ball sit in. Could we use small standoffs to create pockets?
I mean, if you have to you can. I did. But it should work without them.
do you have a picture or a video of the catapult?
IMG_3010.zip (7.94 MB)
It doesnt seem that the balls hit each other during that video
no they do not. that is the point
But there will be some contact and some effect. You can prove it by seeing where the top ball hits when using 2 balls, vs only one ball. If it’s just one ball it will always hit a few inches higher (and also has more force I think)
the reason that one ball shots go farther has nothing to do with ball contact, its because 2 balls weigh more than one. and if you fire from close enough, and hard enough, that weight difference is trivial and won’t really effect your shots.
We fixed the earlier problem, but now we have a new problem. When we fire one ball at a time our catapult shouts accurately and consistently if in the right position. However when it fires two balls it is not consistent at all. If it hits both flags one time, the next time in the exact same position it will not hit both of the flags. Sometimes coming short, sometimes having too much power. Does anyone have any ideas?
My team has a meeting on Sunday, I can post a video or picture if needed.
odd. do the balls rest in exactly the same position each launch? pictures will be helpful
Yes the balls are in the same place every time, I can get a picture on Sunday.
One thing that might be causing a difference is that the catapult is on the side of our robot so that we have space for a lift.
alright I await the photographs