Re: ball cannon???
 

FWIW, the 85 feet XXShadowXX claims he can do is a bit overkill - the field is only 54 feet long!

With the field being 27 feet wide at any given point, you really only need 14 feet on a shooter to be able to control half the field. The closer your robot is to your target, the more accurate you'll be - that much is almost a certainty. While 85 feet is definitely cool - and could come in handy with off season events and pep rallies - it not needed here at all.

Re: ball cannon???
 

We made a turreted shooter for Aim High in 2006. There is a lot of design detail in the Behind the Design Book. I highly suggest reading that entry. A couple of things you will not find in the book directly:

Ball sorting is extremely difficult! in 2006 most Hopper style designs jammed when trying to serialize a bin of balls.

We went for a single wheel to a double wheel system, because while the single wheel was accurate, the spin on the ball descored about 50% of the shots we made. Also Spin energy was significant portion of the launch energy equation, and that was with a "solid" ball. Since the moon rock is a bit more of a "hollow sphere", this will become an even larger portion of the equation.

Turret to conveyor interface is super critical. You need a feed mechanism that consistantly delivers balls to the cannon at the same speed and position in order to be accurate.

With over 1500 teams, someone will have an amazing cannon this year.

As for range: Shaddowxx please recheck your numbers. To deliver that many balls at that rate of speed will require a ton of power. Not saying it can't be done, but that will require a lot of the power motors, or a lot of stored energy.

Re: ball cannon???
 

Spray and pray? :confused:

Re: ball cannon???
 

Has your team considered actively dumping? (Dumping but with something propelling the balls out of the dumper)

Re: ball cannon???
 

Awesome, I was going to say this.

Machine guns are great and all, but a sniper puts you in constant fear. I think being consistant will be crucial.

Slow and steady wins the race, right?

Re: ball cannon???
 

Sniper relies on the accuracy, and elements of surprise and disguise. In 2006 our ball sorter would begin spinning about 1.5 seconds before the first ball fired. It ended up being a giant "HIT ME" sign for our opponents. The gorrillas on the other hand had speed and accuracy, but limited payload. They could deliver about 10 shots in 1.5 seconds, but could really only deliver those 10 and would have to reload.

Just some more food for thought? I think we are going to make a ghillie suit for our robot made out of FRP, so teams won't see us sneak up on them...:D
http://www.theghilliesuits.com/
http://video.google.com/videosearch?...um=7&ct=title#

Re: ball cannon???
 

And those that try to hit you will just slide right off. :p

Re: ball cannon???
 

I agree, pinning and dumping is more accurate:D

Re: ball cannon???
 

it may be more accurate, but the question is how easy/quick is it? For that strategy, you're assuming you can first catch up to another robot, second pin them against the wall, and third dump in them before they have a chance to get away (keep in mind that they will have more traction with the carpet border). You also have to consider how much time all of that will take - time a shooting bot will be collecting and firing balls non-stop.

There are trade-offs for both types of robots with the game design. I don't believe there is one type (shooting or dumping) that can be considered "better" overall than the other. At least, not at this point.

Re: ball cannon???
 

I see a canon as a good option, at least compared to a dumper; just because the height a bucket would have to reach for dumping along with necessary size and good stalking skills, make a dumper seem a lot riskier and less likely (according to our prototypes)...but who knows, there still are a ton of complications with the canon...:yikes:

Re: ball cannon???
 

So, a flywheel shooter is spectacular only in its mediocrity. It seems that most of your energy goes into deformation of the ball, and not into kinetic energy. Anybody having any success at throwing the ball any reasonable distances?

Patrick

Re: ball cannon???
 

We're prototyping a piston launch system. We can launch the balls about 10 feet and they can make it into the trailer.

Re: ball cannon???
 

'About 10 feet...' How do you control the distance you launch? A variable-force piston?!?

Patrick

Re: ball cannon???
 

Key word, prototyping.

Re: ball cannon???
 

words to live by......

were working on combining our harvester with our "vomiter"....so much surgical tubing so little time......

Re: ball cannon???
 

We have a good prototype/start up now, a video (of one of our not so hot rounds) is here http://www.youtube.com/watch?v=S04ub3plTSY

Re: ball cannon???
 

We finally got our prototype working up to our standards, here's a video:

http://www.youtube.com/watch?v=ZIlRWFW9jsk *

We opted for the backspin and shorter distance... first time we've made a shooter and we're enjoying the consistency when firing multiple shots in a row :) something like 3 balls/second.

*No freshmen were harmed in the making of this film.

Re: ball cannon???
 

Now, if we could only to get it to work better than our standards! :)

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Yeah, that prototype definitely proved it's possible - we could hit the trailer 16 feet away! And on top of that, what the team learned from the prototype should allow us to improve upon it and increase range and accuracy.

Re: ball cannon???
 

Good Job! and thats just the prototype :D

Re: ball cannon???
 

I think the discussion between dumping and shooting should be heavily skewed towards shooting.

After all, a well-made shooter should be able to "shoot" balls in VERY quickly from a foot or two away, nearly rivalling a "dumper".

Re: ball cannon???
 

Uh oh:yikes: beware of flying Pi's.

Re: ball cannon???
 

This is a good discussion, thanks for the videos.

Re: ball cannon???
 

Great work guys! I'm always impressed with what you come up with.

I'm not sure I understand the need to shoot 3~4+ feet. I mean, its not like in '06 where we couldn't get right up to the goal. Why not just drive right up and squirt them in?

If you think you can score from 8~10+ feet away why not just use the HP's? They'll have better accuracy than the bot.

Re: ball cannon???
 

Mostly because of the Regolith. With the new playing surface and wheels, robots won't be nearly as maneuverable. Additionally, it'll take more time to get up to speed than it has in past years, and turning will be much more difficult - especially with a trailer. When you add all that up, chasing after another robot to dump (or short range squirt) can become challenging. They'll hit the wall first, and have added traction from the carpet to get going in another direction before you can get in range. Plus, all the time spent chasing someone down is time you spend with a full hopper of balls, unable to collect and shoot more. With a longer range cannon, you're much more likely to be able to constantly fire balls, and just worry about gathering them and staying away from other players.

All that being said, our prototype shows the potential range. If the other alliance's robots are evenly distributed across the field, then there will be one within 10 feet of us a vast majority of the time.

Re: ball cannon???
 

We expect them to see us coming, and run away as fast as they can!

(always the optimist)

And we do expect to get a lot of scoring help from the PSs, but it is also going to be a bit of a challenge for them to score when the goals are over 8-10 feet away. Every bit helps!

Re: ball cannon???
 

I think there is no way that a human player can outscore a well designed turreted shooter. Think about it. A shooter can keep a constant velocity and launch angle unlike a human. Also a shooter is more consistent in calculating distance. Finally, a shooter can fire balls much more rapidly. We are aiming for ~3 balls per second.

Squirrel how much compression are you guys running. We were doing 2" and it was working very well

Re: ball cannon???
 

We've got about 1" compression at maximum. The distance is set up so that when the ball is being contacted on the holes, it just touches. If you haven't yet, try experimenting with tread on the support side of the turret in addition to the wheel...

Re: ball cannon???
 

2081s concept will be a combination between dumping and shooting. It will be able to shoot medium to short distances, however we are going to make the angle of trajectory changeable so that when we get near an opponent, we can shoot the balls at a slower speed, still unloading them quickly and aiming them horizontally, if not downwards

Re: ball cannon???
 

Our team is going after a somewhat similar idea with a cannon.
Does anyone have any idea what the angle of the camera image is?

Re: ball cannon???
 

Isn't a more elegant (and mechanically simpler) solution for range to change the speed of your shooter, instead of the angle of the shot?

Patrick

Re: ball cannon???
 

It can be very mechanically simple to change the angle. A number of teams in the 2006 Behind the Design book (and some that didn't make it) changed their shooting angle to adjust for their position relative to the target, in ways that made the rest of us say, "Why didn't I think of that?"

Re: ball cannon???
 

Sure thing -- the big winners locally in Aim High did one or the other, too.

I just noted the large team number and figured there was probably some inexperience there, so I thought I'd suggest another possibility. I think either one could work well, depending upon implementation.

Patrick

Re: ball cannon???
 

you could make the the balls feed from the back, have a large opening and have the lazy susan(or turntable) on top. Useing a shaft run up from the plate attached to the turntable and put a sproket on the shaft connected to a motor.

Re: ball cannon???
 

not at all, there is absolutely no way for a human shooter to be accurate enough to design a bot around them. if you have done any testing at all you would have realized this, unless you have some crazy good shot on your team

Re: ball cannon???
 

And you believe that a robot will shoot better?

TBH, There will be robots that shoot well, and robots that shoot poorly ... and Humans that shoot well, and humans that shoot poorly. In the end, it'll be fun to watch :D

Re: ball cannon???
 

no, i am reasonably sure that a robot will shoot even worse than a human, but i have no testing to prove this. my team is going with a dump type

Re: ball cannon???
 

We've been looking at both designs and seeing what we can get done on both sides of the equation. For the launcher we figured out how to get the camera to track colors and have a sketched out equation to calculate range based on trigonometry, however we've run into an issue on how to launch the balls. Our main design was to spin two wheels in opposite directions and accelerate the ball through them, but we can't get enough surface area between the ball and the wheels to really launch them. There is also the fact that it would be hard to get much capacity to hold balls on the robot. We figure 5 balls on the robot at one time is a stretch. The plus of a shooter would be the ability to better choose targets.

Our dumping design has just as many issues. As was mentioned earlier, really efficient dumping would mean essentially stopping both robots. Although we did find that a dumper is between 50 and 75% accurate within a foot, so if you could design a dumper that would release balls quickly you could probably do a drive by dump. The capacity on a dumper is 6 to 7 balls. Using a dumper, though, you wouldn't be as able to choose your target, and once you dropped your balls you would have to collect an entire new set.

I think the key factors are going to be time and manueverability. There are 2.5 weeks left. At some point one design may be faster to build than another and it may be more beneficial to have the extra couple days to program and fine tune than to do the other design. And, on a frictionless surface, you're going to want as much control over your bot as you can get.

Re: ball cannon???
 

This is our launcher prototype. It has a bit of a lexan "nose" that fits over it, and the aluminum version will have it completely one piece, pivots and raises.

http://www.youtube.com/watch?v=Dxqu9...eature=channel

Re: ball cannon???
 

This depends on design.

Our shooter has the capacity to hold up to 11 balls as it is currently designed and I expect that some teams will be capable of holding even more than this.

Re: ball cannon???
 

Just as an update, we upped the speed of our cannon to 3700 rpm, and the diameter of our roller is now 5" with about 1.5" compression. Here's the vid:

http://www.youtube.com/watch?v=qNH4hb7crFU

it's very consistent, we'll be testing distance controllability with varying the motor speed tomorrow (just got electronics board mounted). Gets ~10 ft and probably still around 3-4 balls per second (also need to test spin-up time).

Re: ball cannon???
 

Our team has veered from using a shooter because we figure the balls will veer because of their holes. However, I have seen designs that seem to be quite accurate. Therefore I don't know.

Re: ball cannon???
 

thats sweet!!