Is a Catapult Bot Good or Bad

 My team is currently building a catapult bot using slip gears and rubber bands. We love the idea but many things keep breaking on the bot. A plus to the a catapult bot is that it will score one star in the far zone almost every launch. A major downfall is its time to reset.

In my opinion catapult robots would do really well in a competition if it is built well and the reset time is minimal. This would allow them to score from anywhere on the field and be very effective because they would score in the far zone consistently and they would be very quick shooters. Also, in skills it would be a major advantage as they will be able to score from anywhere on the field so they don’t waste time by driving to the fence each time to score.

LOL. I agree with you on that.

I understand this is a bit late, but here is my take on the catapult vs. dumper debate. Catapults are hard mainly for 3 reasons:

  1. Intake. You want to hold at least three stars and still be able to drive once you pick them up without dropping them. This kind of intake has not been built yet and if it has, it’s not been released.

  2. Upkeep. As you said, catapult parts break a lot. You can get around this with excellent build quality, but it is still difficult and I imagine it will require trial and error and lots of extra parts. Remember, stars weigh about 16 times what NBN balls did. For 3 stars/1 cube that’s 48 times the weight of a ball. That’s a lot of rubber bands. More bands = more stress on the system = more broken gears.

  3. Reset. All those rubber bands take a lot of torque to pull back down. Unless you devote more motors to the catapult, getting that torque will require gearing down your gear ratio a lot. You can get around this by having an instant reset mechanism as discussed elsewhere, but without one I don’t think you will recover from the shear amount of stars your opponents throw at you.

Conclusion: Amazing teams with catapults that have instant resets, innovative intakes, and impressive build quality will win worlds assuming their robots don’t break. As for the other 95% of us, we should probably look into other options.

I don’t know what the point is if you’re not going to try to be THE BEST. Why limit yourself if you think another design, built well, would be better?

Also, if your cutoff for who can build a good catapult robot is the top 5% of teams (though of course I know you used that percentage for example’s sake), I would argue that any team can be that good, given that they are not sorely underfunded. Last year, we experienced a big tunraround despite losing all members but myself (who had one year’s experience) and one other member (with two years of experience). With the addition of some newbies, we actually competed in what could definitely be considered the top 5% in the world (though don’t cite Skills scores on that, because we had a 100% fielding bot). I think it’s possible for anyone to build anything in VEX, given that they don’t let failure set them back and they put in 100%.

I’m not sure if a catapult is viable for even the best builders, though.

The point I was trying to make was that teams should realistic. For example, a robot that holds all 28 of the scoring objects and dumps them at the end would be unstoppable, but extremely difficult to make if not impossible (for many reasons). Some teams might be able to do it well, but with this time frame almost everyone will not have one that will work at all. If you get it to work, you will be the best, but if you don’t you will be worse off than if you built a simpler design and perfected it.

In my opinion catapults are like that to a lesser extent. So, yeah, you should shoot for the stars, but not if that means your bullet will never make it off the ground.

I do not believe that a catapulting robot is better than a dumping robot even for the top 5 % of teams but instead that the dumping robot has different strengths and weaknesses than the catapulting robot but both are equally viable designs.

If the catapulting robot was better but more risky/complex, than your team would have to decide if they need to take the risk in order to achieve their goal. For example, If your goal is to make it to state and you have made it to state several times before and believe you can do it again, it isn’t smart to take the risk.

I wouldn’t call it a “gross oversimplification”. Calling it such is what is truly “oversimplifying” it.
If someone is asking if a design is good or bad, it’s important to establish a constant in functionality and success for that design. Should you want to compare it to another design, you apply the same constant functionality to that design to ensure and equal comparison.
So, relating back to a catapult, establish a constant. What kind of success level do we want to see with the given catapult? Let’s say “regional level” in order to relate to the stage that Starstruck is currently at. So, is a catapult a good design at a regional level?
As it has been established, far zone is worth double the points. However, we’re at a stage for the regional level in which dumper bots are the norm. They’re tall - and they can block robots. Considering that we’re analyzing a catapult’s success at a regional level, it can’t be perfect. While this catapult may be able to get into the far zone, it has a low shot trajectory. Thus, at this stage in the game it isn’t essentially a “good” design. However, if you were to further the success of a catapult’s functionality beyond the norm, it then becomes a “good design” relative to others. Although it’s important to note that furthering the success of any design at this stage would output the same result.
Build at the regional level and catapult likely isn’t a strong choice. If you’re confident that you can build at a level that rises you above your competitors, go for it.

In summary, building at a mediocre level, dumper is the way. Building above average, catapult is the way.

Quotes are used to signify possible variance in the interpretation of terms used. As we haven’t defined “good”, “bad”, or “regional level”, they could be understood differently.

My pleasure - I encourage you to act similarity in your posts and interactions.

Eliminating a catapult as a viable design in all its entirety may be a bit silly. Remember, under the assumption that nobody is doing last second clears, they have to score half of what their opponents do, as far zone is worth double the point value. Pair that catapult with a blocker that will notoceably destroy the majority of dumpers and you have a team that makes it permissible for the catapult to get a large score lead early on.

Thanks for taking the time to define those terms. Of course, it is slightly impractical to set a single definition, as their meaning is relative to so many different applications.

I suggest you take a look at XLR8’s reveal posted by LEER for a good example of a catapult

Yeah, it feels like every time I say something against catapults they post something that seems to prove me wrong. Sigh. I guess the only way to see what designs are “good” or “bad” is to wait until worlds to see which of the designs, when perfected, wins out. But if we wait till worlds, we won’t have any robots! So we are stuck making guesses. Educated guesses, but guesses all the same.

Which is why my team invested in a time machine this year! ;p

Catapults are so worth it

There are design challenges with catapults, but pure catapults are also strategically problematic.

Please note: This is not criticism of catapult-making teams. This is just opinion and speculation, which many teams will probably prove wrong with their awesome designs :slight_smile:

From what I see online, catapults tend to have these strategic drawbacks:

  1. Catapults must position the robot for every shot. It is time-consuming, when compared to multi-star grouping that dumpers do.

  2. near-fence shots seem to be challenging for catapults, because they must move the stars away from the fence before shooting them (to get a launching angle.)

  3. Catapults tend to be less effective at getting stars off the fence; dumping bots easily whack the stars off.

  4. Sure, catapults get far-zone stars with relative ease, but stars are easily dumped next to the fence, where catapults cannot return as quickly. Consider this: if there were two robots, one that dumped 2 near-zone stars per 5 seconds and one that flung 1 far-zone star per 5 seconds, both robots starting with 12 stars on their side each, after 1 minute the first robot that had a higher star rate would have cleared their side. The rate at which stars are deposited is more important than the zone that the stars end up in. Since dumping designs exhibit faster star rates, they are advantaged in this way.

Again, this is, and can only be, speculation. I personally cannot wait to see the amazing innovations that the world’s teams will create.

Your right about all of that in a sense, but as a team that has a catapult robot, I can deffinitly say that depending on the design, all of the problems these points bring up can be avoided almost completely.

When I’m driving our catapult, I really only have to aim it somewhere along the 12 foot long fence, and single stars will go into the far zone. Because our robot can pick up the stars like a dumper bot, it makes it easy to position stars that are against the fence. Also a good catapult robot should be able to fire at least two stars at once, our robot has to be in the near zone to get double stars into the far zone, but that’s still less positioning than the average dump bot.

Quite right, its really annoying when the star leaves the field. I got around this problem by either throwing two stars while near the fence, or moving the single star further down the prongs by lifting the catapult so it doesn’t go nearly as far.

The angle of the fork play a major role in this one, if your fork it too steep, then its almost impossible to push the stars off the fence, but if the angle is shallow, then its really a simple matter of driving into the stars with the catapult at the correct height.

Again, as you sort of said at the bottom of your post, it does depend on the quality of the design. If a catapult can pick up stars, then it is no slower or faster then a dumper bot, as most dumper bots also have to turn around after picking up stars against the fence. However the catapult gets the advantage of guaranteeing that the stars will end up in the far zone, also if the angle of fire is high enough, they can’t be blocked. Our catapult gets a return rate of 1.8 seconds, which is the main inhibiting factor on the speed of a catapult, with the exception of the drive. If this was sped up to 1 second with a really fast moving drive, then it could probably get a single star every 3 seconds (If they’re all close together) if that same 1 second catapult could get two stars into the far zone every shot, then it would quickly outscore an equivalent dumper bot.

It probably sounds like I’m saying that catapults are better than dumper bots. What I’m trying to say is that a catapult is a effective mode of scoring, and might be able to our score a dumper bot of similar calibre. However I’m using the average dump bot as an example, no doubt there will be some really amazing dump bots built that could easily outscore almost any catapult. It remains to be seen I suppose.

Can I use it when you’re done with it? Please? :smiley:

That depends on your definition of “when”.

@Alex Baggins,
I appreciate your insightful reply; I definitely see how catapults can develop past the problems I saw earlier. I agree with what you said, especially that as far as fence-stars are concerned,

Good point! I see that hitting the stars on the fence off with the catapult is a design challenge, not an inherent feature of catapults.

Thanks for the conversation! :slight_smile:

I now think that a catapult strategy is just as feasible as a dumping strategy.

I do not think that reload time is a good way to judge which is better. Cycle time from when starting to lift scoring device to when it returns to its starting position would be better. I imagine that they cycle time of a dumper and catapult are if not the same, very close.

In the end, we have the catapults reducing their lowering time and the dumpers reducing their raising time.