Ball-Shooter-Launcher-Thingy Help?

[Phoxtane]

I've been trying to build a mechanism that will shoot out Lego soccer/footballs and basketballs out at speed, but to no avail.

First, I attempted using the Piraka zamor launchers, but due to the slight difference in size of the balls, they don't get forced out nearly as fast. I then tried the two-wheels-spinning-fast method [ala Hot Wheels launchers], but it turns out that at that gearing, forcing the balls through was going to be a major problem. That and I'd rather not have to wait for the spin-up and melting of axles and wearing away of axle mounts...

That's when I turned to my collection of shock absorbers. I've got 50 of the 6.5 length shocks, all in the weakest variety. I figured that if I had a way to compress and quickly release the shock(s), it'd act as a pinball machine plunger. Multiple problems I've run into include bracing of the shock, plunger design, and the quick-release mechanism. I'm limited by the following factors:

-I need to reserve my two XL motors for the drive mechanism of the carrier vehicle. I am thus restricted to the usage of M motors. With luck, I hope to use two motors for the launcher itself and the feeder device, and another two for the pan/tilt mechanism.

-My lack of experience with building compact mechanisms of this sort.

-A general lack of any "new/interesting/rare" parts.

Any help in designing the launcher mechanism would be greatly appreciated :D

[aeh5040]

It would be hard to improve on akiyukiy's amazing construction:

[Phoxtane]

That it would. I've actually seen the video before, but it hadn't occurred to me to use a design based off his; the mechanism I was thinking of would operate in a more linear fashion. Either way, I'm working on a design right now that incorporates the lever-cam element.

[dr_spock]

Have you look at the NXT model that shoots balls for ideas? I think the instructions are online at Lego.com.

Also would using rubber tracks work?

[Phoxtane]

Have you look at the NXT model that shoots balls for ideas? I think the instructions are online at Lego.com.

I have seen those instructions. I'd love to simplify the process with a zamor launcher, but I haven't got nearly enough zamor spheres for sustained firing. The sports balls are too small to work properly with the launcher anyway :/

Also would using rubber tracks work?

Nope. You run into the same issues as with the counter-rotating wheel launcher, and the amount of torque required is much greater. I don't think I've ever seen a Lego device move tracks at that speed, in fact.

I've gotten some work done on the launcher mechanism, however! I've put together a frame that will hold the balls in a small launch track. I still haven't quite worked out the spring-loaded launcher yet or a loading device yet.

Edited May 28, 2012 by Phoxtane

[DLuders]

@ Phoxtane: You could analyze the ball firing mechanism on Brian Davis' "OGRE - A LEGO NXT Tank" See his

below and Brickshelf gallery.

While the OGRE is not a simple machine, it is basically using this simple design from Thomas Lupson-Darnell (from MOCpages). Using his Lego Digital Designer (LDD) .lxf Building Instructions file, I built his ball-shooter attachment (which has a Lego Mindstorms NXT motor connected to Power Functions, like he did), and it works well. YouTube video

http://www.youtube.com/watch?v=SC2ISxtpQww

[DLuders]

You could perhaps make a ball plunger mechanism with your Lego Power Functions Medium motors to replicate this Lego Train Piston setup (as shown on this

animation from Stiegsfeld):

The front of the piston rod could be contacting the Zamor Spheres or Lego sports balls, and the PF Medium motor could be turning a large, 40-tooth Lego Gear connected to a rod that is oscillating back-and-forth. The orange gear wheel end of the NXT Motor is doing the same thing with its ball plunger....

[Phoxtane]

It's not that easy, unfortunately.

In this image I placed a zamor sphere into one launcher and a Lego sports ball into the other. As you can see, the sports ball is slightly smaller. It's too small to go more than three inches out of the launcher, in fact.

[DLuders]

Well, then, don't use any Lego sports balls -- only Zamor Spheres in the Zamor Sphere launcher!

[Phoxtane]

Well, then, don't use any Lego sports balls -- only Zamor Spheres in the Zamor Sphere launcher!

I don't have enough spheres for that - I've got 125 sports balls, however. Not to mention that just about any vehicle with a motor-driven launcher uses zamor spheres; I'd rather do something different to make this project stand out

[DLuders]

Maybe you could have a hopper full of various Lego balls, mounted above a rotating 40-Tooth Technic Gear (on which four Technic Liftarms are attached, to form a rotating pinball-type paddlewheel). The balls fall onto the rotating paddlewheel, which spits out balls in a narrow, gate-like opening.

[Phoxtane]

Partial success; I've built a device that will launch sports balls well under half as far as a zamor launcher will send zamor spheres.

It works in the same way as the zamor launcher; balls are squeezed through until the force of the jaws forces them to be "squirted" out. While this works in the same way, it hasn't got nearly enough power to even come close to matching the zamor launcher's performance. The balls aren't clearing the gap fast enough, and the jaws have too much "grab" to them.

Edited May 28, 2012 by Phoxtane

[freakwave]

I then tried the two-wheels-spinning-fast method [ala Hot Wheels launchers], but it turns out that at that gearing, forcing the balls through was going to be a major problem. That and I'd rather not have to wait for the spin-up and melting of axles and wearing away of axle mounts...

I have built a mechanism that works with counter-rotating wheels pretty well. It consists of two stages. The feeder with a LEGO rubber conveyor belt for a constant stream of balls and avoiding chocking the acceleration mechanism. And as a second stage the acceleration device, which is a RC-Motor geared up 1:5 and using the "Tire 30.4 x 14 VR"

I does not look "pretty" in its current stage but I will look for some video I might be able to put here.

fW

[Phoxtane]

Sounds lovely, but I don't have any of the old RC parts. I assume that an M-motor wouldn't work either, unless I doubled up and geared them together.

I may be able to steal part of your feeder mechanism however ;)

[Sid Sidious]

Partial success; I've built a device that will launch sports balls well under half as far as a zamor launcher will send zamor spheres.

[snip]

The balls aren't clearing the gap fast enough, and the jaws have too much "grab" to them.

Try rubbing talcum powder on the jaws.