8059 in SingVex 2018

The 2-ball catapult was a very interesting idea we didn’t come up with. We are going to have to prototype and see what it can do! Thanks for the ideas

I think single shooters are nicer because you have more freedom to choose your target. Also, since you’re not launching 2 balls at once, you’re less likely to miss both of them at the same time like the double ball launcher would.

Still cool tho

This 2-ball catapult can fire off with one ball too. It is not a must to have 2 balls before it fires off.
As for missing the targets, all I can say is that’s when fine-tuning and practice come into the picture.
Apart from being pushed, 8059a rarely missed their targets.

Having my teams used both single flywheels and 4-ball catapult in nbn, and now these 2-ball catapult robots that we used, I would say that multiple balls catapult might be the most efficient method to have a higher firing rate than flywheel.

But of course multiple-ball catapult is not without its own set of problems.
The force of impact is generally lesser than a flywheel or puncher.
And there is a limited distances that we can fire off the catapult, unlike flywheel, which by theory, it should have unlimited number of firing distances.

Well… I am glad that each firing methods have their own pro and con, else it will be tragic to see only flywheel or catapult at worlds :slight_smile:

Thanks. Also, if you only load one ball on the double-launcher, can you choose which position / target it shoots at or is it designed such as for instance the ball is loaded into the slot aimed at high flags first, and then the other slot.

Of course you can choose whether you want to hit the high or middle flag even with just one ball loaded.

As i know from an official meeting in HK about the rule this season, it said that you can still park on the opposing alliance platform any time, but it can be pushed by other robot same as the center platform. But you can not pushed opposing robot down from opposing platform.

As a basic idea, I like what they’re doing here. However, knowing physics well, this bothers me as it violates Newton’s 3rd law and is thus contradictory. It’s like a problem I commonly give my students: try to touch the table without the table touching you.

More importantly, it seems like it will be hard for referees to gauge. I see the intent, and sometimes it should be easy to gauge. The problem will come in when a robot is on the opposing platform and is getting pushed but has any sort of drive mechanism trying to just stay in place or any sort of mechanism that holds on to the platform. At what point is the blocking robot considered actively v. passively pushing back? It seems like the cut-off is going to be pretty vague, which means the rulings will undoubtedly vary significantly from one competition to the next.

A question regarding the 2 ball catapult-
Do you have some sort of indexer besides the ball intake to control where the ball goes on the catapult so it can choose the middle or high flag? Or is this process passive?

If it is just one ball, then that ball will always go to the far-end slot.

The driver controls which flag to hit by adjusting the distance of the robot to the flags.

The triple-deck intake roller is done with one motor. As for the loading of the ball into the catapult slots - then it is totally passive.


I am confused as to how this relates to Newton and his laws.


If Robot A pushes Robot B, then Robot B pushes Robot A with an equal magnitude force in the opposite direction. So if is legal/illegal for A to push B, then it must be the same for B to push A. It wouldn’t bother me as much with a school rule or similar, but we are talking about engineering generally using Newtonian mechanics.

thats honestly such a bad comparison to newtonian mechanics because the frame of reference is completely different int two scenarios lol

You need to learn your mechanics better.

Now, if the post was miswritten, not using the proper prepositions, that would solve the issue some of the time. But it would still leave problematic times.

Ur comparison using newtonian physics is complete non sense lmfao. Would u like to re-state your argument ?

@meng , I’ve tried to gauge what I could from the video of that wonderful two-ball catapult, but it’s so hard to tell. Are they able to adjust launch speed or angle? If so, have they checked to see if they can launch from different distances and still hit both flags? I’m thinking I might set a computer crunching some numbers to see if there might be enough leeway due to the size of the flags to make such adjustments a viable consideration.

No… they can’t adjust the speed or angle (in fact, this is one disadvantage of catapult… it is difficult to change the variables. Even more so for 2-ball catapults).

But due to the size of the flag, it does give them quite a range of distances that they can hit the flag (even without changing the speed or angle).
Guess that’s the reason it is difficult to tell from the video :stuck_out_tongue:

Maybe your misunderstanding is because you think there is a comparison. I’m not making a comparison. I’m stating that the rules are contradictory with Newton’s third law. It won’t mess up the referees (mostly), but it makes me cringe. I’ve started a new thread on this.

Makes sense. I figured the flag sizes would help a lot.

Based on your comment, I started with a different approach. It’s a pain by hand with so many interrelated pieces, but you can get the patterns well. The approach I’ve just tried is to minimize the variation in the difference between the two heights at arrival (reaching the flags) as the two balls travel some variable distance. Of course, there is the trivial solution that you launch with the arm vertical and the balls going infinitely fast. But what is most important and does it always tend toward this case? It turns out the speed part is by far the most important and the angle need not be such that the arm is nearly vertical at launch. You want to maximize launch speed and set the angle based on that. Doing so should give you the largest possible spread of distances you’re firing from to keep the balls within a limited vertical separation at arrival.

lol… my team tested their prototype in the same manner too - hands! :stuck_out_tongue:

If I am visualising it correctly, the main issue with almost vertical-arm launch is that the height gained by the ball will be minimal? If that’s the case, will the ball still be able to hit the highest flag?

But I can also imagine that this approach of yours will allow the catapult to fire off at a further distance.

Well, in this case it was math by hand. I do prefer working with piles of variables rather than have a computer crunch stuff if I can. Then I can see what’s happening before attacking it with a computer. In plasma physics this was necessary anyway since computers couldn’t solve the problems until they were simplified.

Yes, you won’t want a vertical arm. Recheck above. I noted that speed is far, far more critical than the angle, though I should have specified as long as the angle isn’t tiny. But we’re not shooting them nearly straight up. So go for as high a speed as possible. Set the angle based upon that speed and where you’d like to shoot from. Using the higher speed will give you more leeway in case you’re too close or too far away.

Sure, if you want it to. But as I noted the angle doesn’t matter so much, it works from any distance. Regardless of distance, high speed reduces the variations and so gives you more consistency, at least as far as the projectile itself is concerned.