What I'm here to find out I am in the early stages of planning for a tennis ball launcher I'm doing with my group for a class project. I want to find 2 cheap electric motors that will spin fast enough, and have enough torque, so that I can attach some wheels to the spinning motors for the purpose of launching a tennis ball a few feet. (See details.) Does anyone know where I can buy such a thing? One idea I had was to purchase 2 cheap fans and take the motors out of them. But I do not know if that would work. Not sure if I could control them well enough to hit the target distance (see details), or if cheaper motors are available (see details) that would work as well or better. Details Since it's a class project, we obviously can't buy an off-the-shelf unit. However, we can base our design on any existing unit we find as long as we mention the source in our final report. The requirements are that the ball must launch 6 to 10 feet (~1.83 to ~3.05 meters). No more, no less. It can initially land at less than 6 feet and then roll the rest of the distance. But the test will be done on grass, so we can't expect much, if any, rolling distance. We have a strict $75 budget for this project. All receipts must be kept and turned in at the completion of the project. So keeping cost down is a high priority. Since this is a class project, it doesn't have to be high quality, look good, or last a long time. In fact, it only has to work twice on the day of testing. After that, it can be scrapped. :) Note: We cannot just get a long piece of PVC pipe, drop the ball in at the top, have it roll down the pipe, go up an incline, and then launch out the top. The maximum height of the entire device is limited to 4 feet, so that wouldn't work even if it were allowed. The device must have some kind of launching system but cannot use fire, chemical explosions, or steam (boiling water). We can use motors (battery powered or extension cord.) Springs and slings are also allowed, but the device must self-reset, so I think a motor driven system would be the least problematic In order to minimize unpredictability in the launch distance (due to rolling), I am thinking a steep-ish launch angle would be a good idea. That way the ball would go up in an arc, and mostly stay put when it hits the ground. I'm not sure how much velocity will be lost due to air resistance, but a preliminary calculation tells me that with a launch angle of 70 degrees, I would need an initial velocity of about 5.5 m/s to go comfortably past 6 feet without worrying about going over 10 feet. (Again, due to air resistance, that may prove to be more like 6+ m/s.) But the point is, it doesn't have to go very fast. Summarizing I'm open to any other ideas, but given the above details, and the little bit of online searching I've done, I think motors are the way to go. Since this is a popular project, I am hoping someone here has done this before and can offer some suggestions.