Double Ball Launcher

This is a double barreled tennis ball launcher that I made for my dog. It needed to have two launch tubes that would be randomly loaded so my dog wouldn't just sit at the exit of the tubes and wait for the ball to be launched into her mouth. The randomness while loading is done by the 3D printed top piece that connects the two chutes. When the ball is loaded, it bounces off the diverter in the middle of the top piece to send the ball to one of the chutes. The design as is can be manipulated to change the angle between the launch tubes, and the orientation of the 45 degree end piping.

Supplies

*I had a majority of these materials I had lying around the house from past projects. The materials costs listed above are assuming you have to buy everything required for this project. The materials I did purchase for this project where the wheels and motors.

Concept and Notes

As mentioned in the intro, the randomness comes from the shape of the y-diverter at the top of the chuting. The middle section forces the ball to either the right or left chute. The motors are ran simultaneously so whichever chute is chosen, the ball will still be launched. The two legs of the y-diverter are collared to mate with the 3" PVC piping.

The earlier concepts for this were a much smaller machine, however I decided to make the chuting 24" so it would be at a more natural height when loading. The chuting height (24" pipe sections) is mostly personal preference, so whatever height is more beneficial for your needs it can be adjusted to. There are additional motors that were added from the concept drawing as well. This helped with the stability of the ball when it was being launched at the end. The tennis balls I used when testing are roughly 2.5" diameter. If you are using smaller balls or of a different material, you may need to change the wheels on the motors to be larger or more grippy. As is, the motors are running off of 45V supplied from the 5x 9V batteries. The motors are rated to 12V ea, so I wouldn't recommend exceeding this amount, however you can go up to 48V safely if you wanted to add some more power in.

Creating the Platform

1.) Using the 3/4 plywood, cut the backing plate portion. This section is 8"x24".

2.) Using the same 3/4 plywood, cut the base plate. This section is 14"x22"

3.) The legs of the base plate will be made out of the 2x4, cutting a 22" section off. This 22" section will be cut down the middle length wise to create 2 legs that are roughly 2"x1.5"

4.) Use 4 wood screws per leg to attach the legs to the base plate. The legs will be attached at the edges of the longest section of the base plate.

5.) Attach the backing plate to the base plate using 4 wood screws. The backing plate will be attached in the middle of the shorter edge of the base plate.

Making Pipe Sections

Using the 3" PVC Piping,

1.) Cut 2x 12" sections

2.) Cut 2x 24" sections

Motor cutouts for the 12" sections of piping,

1.) 3" from either edge, mark a 2" x 4" sections roughly opposite each other. This should leave a 2.5" strip on the top of the pipe, and a 1.5" strip on the bottom of the pipe.

2.) Repeat previous step for the other 12" section of piping.

3.) Cut away the 2"x4" marked sections from both 12" sections of piping.

Assemble Piping

Print the attached STL File. I would recommend printing the attached file 1-2% bigger, as it will help with fit later.

1.) Assemble the base of the piping, putting the 45 degree section on the cut away portion for both 12" sections of piping and the 90 degree elbow on the opposite end.

2.) Attach both 24" sections to the opposite ends of the 90 degree elbow.

3.) On the backing plate of the stand, attach wiring staples 5" from the top and 1 5/8" from the edge. Repeat on the opposite side of the backing plate for the 2nd wiring staple.

4.) Put the 4" bandclamp through the wiring staple opening, and attach to the 24" section piping. Repeat this for the other section of piping.

5.) Tighten bandclamps down until hand tight.

6.) Attach 3D printed piping section at the top of the two 24" sections.

Downloads

Y-Diverter v6.stl

Making Motor Mounts

1.) Using the 2" x 4" board, cut 4 blocks that are 1"x1.5"x3".

2.) Clamp wood blocks together in pairs.

3.) Using a 1" spade bit, drill out the center of the clamped blocks.

4.) Using a 5/16" drill bit, drill 4 holes in each wood block. These holes should be .25" in from each side, starting from each corner of the wood block.

5.) Using 9" zip ties, attach the motor body to the wood block. This can be done by routing the zip tie through the top 2 holes of the wood block.

6.) After all motors are attached to all wood blocks, attach the wood blocks to each other in pairs by routing 2x 9" zip ties. Route the zip ties through the bottom two holes of one wood block, underneath the 12" sections of piping, and through the second set of holes on other wood block.

7.) Using two other 9" zip ties, connect them to the other zip ties as shown.

8.) Attach wheels to motor bodies.

Electrical

First, find the angle you want your 12" sections of piping to be away from each other. I chose to keep them at 30 degrees apart for myself.

1.) After you decide what angle you prefer. use the 1" spade bit and drill holes underneath where your motors terminals are positioned.

*I used a 1/2" drill bit to make my holes for the wiring to the motors, however I would recommend using the 1" spade bit to give yourself more room to work with when you start wiring everything together.

2.) Follow the wiring diagram as shown, using the 20g wire

Make sure the motors are wired as shown, as this makes the pair of motors spin opposite each other when mounted. You want the motors to spin clockwise on the left side of the pipe and counter-clockwise on the right side of the pipe, when looking at it from the end of of the pipe.

4.) Flip switch to on, to verify correct motor spin and power is being supplied.