Re: Best Way to Shoot the Balls??
 

well they give us those super cims(thats wat our team are calling them) anyone actually know the names of those motors. Those things could probley power a scooter. But a double belt system working on one of the motors or a one belt up inside a large barrel it would be fast accurate and easy to feed, with very little fear of jamming.

Re: Best Way to Shoot the Balls??
 

If you do a two-wheeled shooter (or two belt or whatnot), you could run the wheels at different speeds to put a backspin on the ball. Not all spin has to be like a spiraled football.

Making sure you get your wheels back up to speed before putting another ball it will be huge. High RPM and low torque wheels will slow down.

Who's taking a field trip to a batting cage?

Re: Best Way to Shoot the Balls??
 

Thats only assuming you can make one of three in the same amount of time it takes another robot to get three one point goals. Speed scoring and defense will be a factor as well as accuracy.

Re: Best Way to Shoot the Balls??
 

Simple: Use two wheels (not just one like the softball launcher), but put them at a slight angle to the direction of travel - for example, the top one is canted 15 degrees to the left (CCW) and the bottom one 15 to the right (also CCW). This is how football launchers work.

I disagree, and I see no need for a 'barrel'. In a protoype I built today (see photo), the balls went very very repeatably to the same spot. The biggest variable will be the supply voltage (= motor speed), but the astute student will figure out how to compensate for that ;-)

Umm, using what energy source? A tennis ball launcher uses what is essentially a vacuum cleaner, blowing instead of pulling, and shoots the ball out of a 'barrel'. Longer barrels shoot further and flatter, and a screw-thingie on one side imparts spin. But, a 7 ball needs a LOT of air volume. Do the math with a 2' long barrel - what is the volume of the barrel in cubic feet, and how many cubic feet per minute at (60?) PSI can that KOP compressor supply? That gives you your best firing rate, BUT there is no place to store that volume of air at 60 PSI on a legal robot.

The way I see it, the only viable options are wheel-based and spring-based launchers. (A trebuchet is spring-based [EDIT: No, it is powered by a falling mass[/EDIT], and I agree, it would be soooo cool).

In the photo, that is an 8" wheel. At about 1300 RPM it launches a 7" soccer ball about 10 feet (from a table 40" from the floor), and in ten tries they all landed within an inch of each other.

The biggest issues are balance of the wheel - it wobbles a lot at 1300 RPM, it's not made for that - and the huge black marks the rubber leaves on the ball.

Don

Re: Best Way to Shoot the Balls??
 

Am I the only person thinking about ball availability? If you're on offense, and the opposing team is on defense, they have no reason to put balls in play where you can get them after you score them. So if you have 40 balls and score them all as one pointers, you get 40 points and have to wait until they give you your balls back. If you make 3's, you get 3 points. the ones you miss are still available to you if you have a ball scoop, so if you start with 40 balls you could get a max of 120 points before you've run out of balls.

Re: Best Way to Shoot the Balls??
 

I hate to call you on a technicality, but this is a bet of a pet peeve. So, for the enlightenment of all,

A trebuchet is *not* spring powered. A trebuchet derives it's energy from a falling mass. Remember the really cool looking things that threw the giant rocks from Minas Tirith in the Return of the King? Those were Trebuchets.

If it uses elastically derived energy it is another kind of catapult. So, if you use a rubber band, spring, or the bowing of wood (or something else) to throw the object it's a catapult.

To clarify, a trebuchet is a *kind* of catapult. One that uses a falling mass.

More info here (Trebuchets) and here Catapults
:rolleyes:

- Toby

Re: Best Way to Shoot the Balls??
 

haha, i was going to also mention this toby, but you got there first. but yes, a REAL trebuche would be totally awesome!

Re: Best Way to Shoot the Balls??
 

Yes, you're absolutely right and I stand corrected.

Don

Re: Best Way to Shoot the Balls??
 

to the guy saying a simple cylinder pushing a ball out... not even close to enough. i tried a 3/4in bore cylinder at 100psi pushing a tennis ball. didnt get far at all. AT ALL.
so. to increase speed use simple machines. pulleys. lever arms... i htink thats the best bet... wondering about 60psi tho.... wish they let us use higher pressure ones.and 2 tanks... not enough for multiple fires.
im gonna think about motors..

Re: Best Way to Shoot the Balls??
 

We did some experimenting yesterday and built a number or prototypes. One of which was a pneumatic direct acting system that acheived a ball velocity of 8 m/s @60 psi. Its possible, but we have some tricks up our sleeves. ;) We have a much more powerful version planned for monday or tuesday once some parts arrive.

Re: Best Way to Shoot the Balls??
 

Are we allowed to create a chamber where the air compresses safely and the chamber is a cone with the ball that rolls back into it?

----------\--------|
~~~~~O ~~~~~~ <-- Air in
----------/--------|
------ ^------^
----- Ball ---Chamber

Re: Best Way to Shoot the Balls??
 

I like the idea with two spinning wheels, like a hot wheels launcher. The important thing is that if the wheels aren't spinning at the same speed, the balls will fly off course.
Just food for thought.

Re: Best Way to Shoot the Balls??
 

I see no reason why you would need to shoot quickly if you have an accurate launching system. A barrel is probably necessary though. In my opinion, a pneumatic system would work best. There's less chance of unpredictable velocity... maybe. I donno though. I'm not the mechanical type. I just throw out ideas.

Re: Best Way to Shoot the Balls??
 

Not necessarily. If you spin both wheels at the same speed, you end up with a ball without spin coming out of the shooter. And just like a knuckleball in baseball, the ball will zig zag in any and every direction. One of the solutions we came up with is to have the two wheel mounted one on top and one on bottom. You purposly gear down the top wheel a little more than the bottom one, which results in a slight backspin. This produces a shot that is very straight, with little to no sideways curve. If you go with one wheel instead of two, i would recommend mounting the wheel on the bottom, with a solid surface above it for the ball to pass through.

Both of these ideas are direct knock-offs of baseball and softball pitching machines, so google up some images if you need a visual reference

I personally would recommend going with the two wheels, just so that you can minimize spin. With a one wheel system, whatever spin you have, be it topspin or backspin, will always be directly related to the tangencial speed of the wheel. A two wheel system has the ability to greatly reduce this relation between spin and speed.

Michael C.

Re: Best Way to Shoot the Balls??
 

There are many more ways of quickly launching balls than it first appears. There are also a lot of "side effects" that people may experience from a particular idea. Some ideas will prove better than others, depending on the hardware and software behind them and how a particular team implements them. What works for one team might not work for another.

Earliar today, I had an ingenous idea on how to shoot balls accurately and quickly into the center goal. I already have it prototyped in Vex parts, and it launches the one raquetball every second about halfway across the room by [bleep] [bleep] [bleeeeeeeep] [bleepity] [bleep] and [bleeeeping] [bleepity] [bleep] [bleepment]. It's truly amazing. ;)