Motors for ball launchers

I was just wondering how (if you’re willing to say) other teams are thinking about shooting balls to the center goal. We are leaning to a baseball shooter type machine (2 spinning wheels). We’re trying to pick the main motors, and will most likely use the new mini-bike motor. It seems to draw less power, and have a pretty decent amount of force. That type of shooter would also allow for a fairly rapid succession of shots. Is anyone thinking of any other kind like pneumatic, catapult, or something I can’t think of?

gravity powered oldschool trebuchet DUH

i dunno. need to look into the specs of each motor.

Be sure to serach the rules/strategy forum, there’s a lot of discussion on the method.

As far as motors go, you need to determine the energy needs, and pick a motor that will supply that. First, what is the mass of the wheel(s), and how fast do you want them spun up to speed after autonomous starts? Then, how much energy (think inertia) will launching a ball remove from the system, and in what time do you want that returned by the motors?

If you’re using a wheelbarrow tire, then the big CIM might be a good choice - it’ll get the tire up to speed real quick. But, it’ll be just loafing along after launching a ball, so maybe it’s too much??

Anyway,. the point is: Do the math. Make reasonable assumptions and guesses. That’ll help you decide.

As far as other ways of launching balls: other threads have discussed this, one or two wheels seems to be the most common approach.

Don

baseball launchers :smiley:

As of right now, MORT has considered a few options:
Throwing arm; probably unreliable
Dual wheel design
Single wheel design (probably prone to jamming and unpredictable spin on balls)

 The other consideration with a dual-wheel design is whether to mount the wheels on the sides or the top and bottom of the ball.
 Personally, I think the most reliable design for a shooter is one or two wheels (heavy for high momentum) on either side of the ball (horizontally). The wheels will align the ball as it feeds and the forces are balanced on either side to prevent spin.
 In terms of motors, the big CIMs have been allocated to DT, so it looks like an old CIM for the shooter.

Any comments?

A few things you need to keep in your head are:

1.) Mass of the wheel.
2.) Power needs of the motor
3.) Time between balls being launched (since the motor will slow down)

Well looking through this i guess all of those are already posted.

Good luck

Okay, if people feel like waiting till this evening, I’ve worked up a spreadsheet to tell you how long it’d take to spin up a wheel with a given motor, assuming full 12V sent to it. I’d post it now, but I originally coded it with the 3 speed Dewalt tranny in mind, but that seems slightly overkill at the moment. It makes the sheet a little messy, though.

wow guys, why dont u want spin? Hasn’t anyone ever heard of riffling, the thing that increases accuracy and distance with bullets? The correct spin repeated effectively will increase ur consistency. Geez guys, u gonna be out smarted by a red neck hick?

I’d think that the difficulty lies in the repeatablility of placing spin on the ball. I don’t think that it would create much of a noticable difference, though. :slight_smile:

In order for spin to be helpful it has to be spun correctly. Topspin won’t get you better accuracy. We thought about doing a regular two-wheeled baseball shooter except offsetting one wheel to produce some spin. But we decided it would probably take away from the overall power of the spinning wheels. Or just not work.

using rifling for a round projectile is more or less useless, as the ball spins through the air it makes a larger and larger spiral. The concept only seems to work on cylindrical objects. At the distances we will be engaging at I doubt that it will be a huge problem. The only spin that I am concerned about is through the horizontal axis.

my $0.02

Yep,

Rifling is used for cyclindrical object because the area is smaller one way. piR^2 is less than DiameterLength. For a sphere it is pi*R^2 regardless of orientation.

Basically rifling keeps the object oriented the right way to reduce drag.

In simpler thinking, It’s the reason why you wouldn’t want to drive a 18-wheeler sideways. Or why it is more fun to drive a car through the Flint Hills than my extended Aerostar van.

I’d say a CIM would be one of your best bets, although I do like the mini-bikes.

Why would you change a masterpiece jub jub??? Putting the big cims in the dt is a very um…gutsy, call, but hey, good luck with that!

It is my understanding that rifling a spherical bullet IS effective. The spin axis parallel to the direction of flight helps maintain a straighter (more accurate) path because the projectile has ROTATIONAL INERTIA. Because of this resistance to a change in rotational motion, the bullet will spin about the axis and the axis will not change direction, keeping the path straighter.

Of course, you are right in that the distances and speeds we are talking about, rifling spin will have very, very little effect on the path of the ball compared to the inital launch velocity.

-Mr. Van
Coach, 599

“The spin axis parallel to the direction of flight helps maintain a straighter (more accurate) path because the projectile has ROTATIONAL INERTIA.”

This is a valid argument, although in my personal experience the rotational inertia causes another type of inaccuracy- corkscrewing. This is especially true with barrels that are slightly bigger than the projectile, the ball bounces in the barrel and randomly bounces out of the muzzle. This action increases the “corkscrew effect”.

You also have to think of the weight of the motor, if you are planing on using the super CIM for your cannon, presuming that your cannon is near the top of your robot, that is nearly 5 pounds at the top of your robot, for each one! Center of gravity! the only way to avoid this with the Super CIM is to use a few pounds of chain and sprockets. We are leaning toward the FP motors, with ‘special’ gearbox’s.

How about mounting the motor low and using a timing belt to drive your launcher?

Our team is using the Drill motors attached to two Dryer rollers [think roller-blade wheels, but slightly larger, and made out of a much more grippy material] (we picked up two sets of the rollers that are used to keep Whirlpool and Kenmore dryers spinning). The end result is a VERY lightweight baseball-pitching mechanism that spins up in about 1.2 seconds (to maximum ball launching speed. Them suckers spin up for about 4 seconds if you let them get to it, but the balls exceed the maximum speed).