Alright guys over the months I have seen countless catapult designs each with their perks and then theres some that are just plain disappointing. Theres the forward catapult, backward catapult, the full arm catapult, forward intake catapult, backwards intake catapult. There are several more I dont remember at the moment. Which catapult do you guys believe is best and why?
I have had a catapult on my robot since the beginning of August, and I am a proponent of the backwards catapult.
- Generally requires more pistons and tanks
- makes hanging more difficult
-easier to drive and faster to use (no need to raise arm or turn around)
I believe the speed and ease of use of a backwards launcher is worth the trade off of weight and speed of hanging.
Im not entirely sure but if im not mistaken you can make the backwards catapult with 2 pistons and using 2 tanks giving an average of 12-14 good launches and an extra 2-3 decent ones.
I took some inspiration from Aaron when I built my catapult. The backward catapult is a lot easier to use, but it is much harder to create a backwards catapult that works well with 2 pistons. For most backwards catapults, you’d need 4 pistons and 4 tanks to match the strength of a 2 piston front catapult.
They both have back catapults and I have a front one so I’ll give my input. I’ve had it for a month and a half and a catapult in general is useful if built well.
The positives to a front catapult is that you only need half of everything because the degrees of motion is basically half of what a backwards catapult is. I’ve only seen backwards catapults with 4 pistons and only front catapults with 2 pistons. Does that mean if someone gets a backwards catapult with 2 pistons a front catapult would only need one? :eek: Probably impossible if you’re following the rules on pressure. The front catapult can also actually act as an assist to get big balls out quicker so you don’t have to wait for intake to spit it out or if you can’t get the ball out of your intake at all. I’ve found this to be helpful.
The negatives of a front catapult is the lunge the robot has to do in order to launch the ball (swerving back and then forward to get the ball to the back of intake). This is the only negative I see in a front catapult.
If the robot could somehow have the lunge eliminated then I would vote the front catapult as being superior.
In addition if someone has a 4/4/2 (four motor drive, four lift, two intake) setup then having 4 tanks on your robot for a backwards catapult is a lot of weight. The tanks aren’t light so keeping your robot as lightweight as possible with only four motors on drive is essential. But then again team 1103 in Round Up had a rock solid robot that weighed nearly 20 lbs. (I believe he said this in a video somewhere, don’t quote me on it) and had only 4 high speed motors on his drive. Very impressive!
Three teams in my club (mine included) are currently working to perfect our forward intake catapults which we’ve dubbed our rampapults. So far, none have had much success. The two teams that started working on them a few weeks ago have struggled a bit but I hear they’ve had some success in making them work over the break. I just got my pneumatics in the mail today so my team hasn’t built ours yet but we have it designed and ready to build, so we’ll see how it all goes once it’s built and running.
Wasabi 1492X has a 1 piston catapult, which let’s it get a lot of actuations, and doesn’t need a “lunge” either. Here’s a video for those interested- www.youtube.com/watch?v=RCzhIBXWO8c&.
Albiet my teams catapult is very different, (we have a scissor and the starting angle is 0), we have four pistons and have only a slightly farther launch. If you mind me asking, how does it work so well?
What kind of piston is it?
Are you using any elastic assistance?
This is going to cause my team to have to rethink our launcher. Wasabi is always one to impress.
wow, thats crazy distance. i’m not getting half of that with two pistons. I’m assuming its all in the angle of the piston or something?
1 (we use double-acting) piston is plenty of power. Power isn’t the issue, it’s more how the catapult is built. That’s what we think at least.
Also yeah, you want the pistons to be as perpendicular to the lever as possible (|torque| = |force X radius| = |force| * |radius| * sin(Ɵ) -> Ɵ should be 90).
For our catapult design, we actually took inspiration from Aaron and 7090 in order to create the same degree of rotation as the forward catapults, but backwards. It was also designed to only catapult large balls, as many times it was more useful to keep the buckyball and only fling the large ball. Our season has ended until March, but we ended up not having enough space to have the actual deflection we wanted (60 degrees), and went with something more like 80 degrees, which was not optimal. To add to that, the trajectory was not tuned, so the ball would go much, much higher than we intended. As a result, we just decided to throw pistons at the problem (we had 5 single action pistons, equivalent to 4 double actions), to solve it quickly before our last competition. It worked well, but obviously not as well as we wanted it to.
What I did notice, however, was that the ball had way too much power directed in the wrong direction - so I do believe that with correct geometry, a backward launcher could also be done with just 1 piston like John’s. I know it’s not clear what I mean by having a forward launcher geometry flinging backwards instead, but it’s late, so I’ll let Aaron or Ruiqi explain for me if anybody has questions.
And the biggest question of it all is how is it that they dont have to strafe backwards and forward to launch
The big ball…
Backwards launcher using 1 piston? Please explain…
Okay, so imagine a front catapult. About 70 degrees of rotation on the catapult arm, right? Now flip it around. Tada!
I believe the reason 1492 does not need to lunge is their very short big ball intakes. In my experience in matches, raising the arm to descore big balls in the high score zone is incredibly annoying. The reason I built a launcher in the first place is so I would not need to raise the arm to descore big balls.
Should the piston be perpendicular at the starting angle (resting position) or the ending angle (the position after the big ball is fired)?
Probably the starting angle to get the most acceleration at the beginning, although it shouldn’t matter too much. Just get the piston as perpendicular to the ramp as possible across the whole range of motion.
Do you think it would be possible to make a back firing intake catapult with two 393 motors? We do not have pneumatics:(.
It would be a terrible waste of motors, but yes, that would probably be possible, but you’d only get about 2 lb of force with a 15" catapult arm and 2 393 motors on high torque mode.
Not unless you use the motors to pull back a bunch of elastics and release them. I would look at the launcher on this: