Rapid Ball Juggler

Introduction: Rapid Ball Juggler

About: On my page you'll find lots of different Knex projects, from ball machine lifts to useful items. I hope you enjoy!  _______________________ Current avatar: Target of my skeeball machine Past avatars: …

Hey y'all! This is my entry into the Kinetic Sculpture Contest.

This is a kinetic sculpture that catapults ping pong balls into the air, into a basket, and back to the catapult. It runs for as long as you want it to with a motor, and a rubber band powers the catapult. A mechanism at the end allows each ball to load into the catapult one by one. It's a useless machine, but fun to watch. :-)

This machine is made to use 38mm ping pong balls.

Here's the video of the ball juggler in action:

So, let's get building! I hope you like it!

Step 1: Parts List

Here's all the pieces you'll need to make the ball juggler:

Rods: 279
  • green-98
  • white-38
  • blue-92
  • yellow-35
  • red-9
  • flexi-rod (gray rod length)-3
  • rigid tan-2
  • rigid black-2
Connectors: 225
  • dark gray-11
  • light gray-5
  • red-34
  • green-25
  • yellow-45
  • white-14
  • orange-24
  • blue-27
  • purple-40
Other: 127
  • blue spacer-51
  • silver spacer-43
  • tan clip-21
  • Y-connector-7
  • rubber band-1
  • motor-1
  • small blue gear-1
  • red gear-2

TOTAL: 631

If you have all of these pieces, then you may begin! If you don't, then you could still try, and leave some pieces out (even though it won't work as well). Tan (red rod length) or black (gray rod length) rigid rods can be replaced with red or gray rods.

Step 2: Catapult Section

First, build the catapult. There are 3 parts to build, and then you'll connect them together. This step has lots of pictures, but there are descriptions of all of them below.

Pic. 1- Build this small support.
Pic. 2- Another view, of the back side.
Pic. 3- Build the catapult. This section also includes the rubber band. I used the red rubber band from the electronic arcade Knex set.
Pic. 4- Close-up of the catapult. There are two pairs of tan clips that should be facing each other on the end of the catapult.
Pic. 5- Close-up of the spacers and the other side.
Pic. 6- Another view of the spacers.
Pic. 7- The rubber band holder.
Pic. 8- Another view.
Pic. 9- Build this small section.
Pic. 10- Attach the small section you just built to the catapult.
Pic. 11- Another view.
Pic. 12- Build the catapult housing.
Pic. 13- Another view.
Pic. 14- Another view.
Pic. 15- Close-up of the spacers.
Pic. 16- Another view, of the bottom.
Pic. 17- Get all three sections that you just built.
Pic. 18- Combine the catapult and the catapult housing.
Pic. 19- Another view.
Pic. 20- This is how the rubber band holder attaches to the catapult housing.
Pic. 21- Attach the small support. Once you do this, you are finished with the catapult!
Pic. 22- Another view.

Step 3: Gears Section

This is the gears section of the Ball Juggler. This part also includes the pusher that makes the catapult go. You'll build the section, and then attach it to the rest of the model. When combining them (starting at Pic. 8), make sure the rubber band is centered in the space where it goes. Refer to Pic. 13 for that. Again, all of the pictures have descriptions below that will guide you through the building process.

Pic. 1- Build the gears section.
Pic. 2- Another view.
Pic. 3- Close-up of the pusher. The tan clip in the middle of the two orange connectors should be facing towards the red gear (the thing that sticks out should be facing towards the red gear).
Pic. 4- The other red gear.
Pic. 5- Don't forget to build this part.
Pic. 6- Another view of the gears.
Pic. 7- Another view.
Pic. 8- Combine the gears section and catapult section.
Pic. 9- These connect like so.
Pic. 10- The gears side.
Pic. 11- Close-up of the middle.
Pic. 12- The rubber band holder.
Pic. 13- The rubber band should be closely centered on the spacers it touches. Also, the group of spacers being held in by tan clips should be centered on the axle. These things don't have to be centered exactly, but make it as close as you can.
Pic. 14- Bottom view of what you've built so far.

Step 4: Motor Section

Now build the motor section. After you build it (pictures 1-3), you'll attach it to the rest of the model (pictures 4-7). Make sure to install batteries into the motor before you put it into the machine, because it's hard to take it out once you've already attached it.

Pic. 1- Build the motor section.
Pic. 2- Close-up of the blue gear and the spacers.
Pic. 3- Bottom of the motor section.
Pic. 4- Attach the motor section to the rest.
Pic. 5- Close-up of the motor. The tan rod has no end connectors, because it won't slide out.
Pic. 6- The gears side.
Pic. 7- This connection is on the underside of the middle. You may have some trouble connecting it because of the red gear in the way.

Step 5: The Loading Track

This is the track that leads into the catapult. It also includes the mechanism for dispensing balls into the catapult. First build the loading track, which comes in four sections track (pictures 1-3), support 1 (pictures 4-6), ball dispenser (pictures 10-11), and support 2 (pictures 12-13). You'll connect those together, and then connect the loading track to the catapult section (pictures 19-21).

Pic. 1- Build the first part of the loading track.
Pic. 2- Bottom view.
Pic. 3- Another view.
Pic. 4- Build support 1, which is the second section of the loading track.
Pic. 5- Don't forget that Y-connector! You can also see the red connector and spacers, in the bottom corner.
Pic. 6- Another view.
Pic. 7- Combine the track and the support.
Pic. 8- The yellow rod should slide through the hole of the red connector.
Pic. 9- Bottom view. The green connector should be connected to the Y-connector.
Pic. 10- This is the ball dispenser, or the third section.
Pic. 11- Bottom view.
Pic. 12- Build support 2, the fourth section of the loading track.
Pic. 13- The blue rod snaps in and slides all the way to the edge, like in the picture.
Pic. 14- Slide the ball dispenser into the blue rod of support 2.
Pic. 15- Get the first two sections and the two sections you just built.
Pic. 16- Then connect them like this.
Pic. 17- Another view. On the end of the ball dispenser, turn the tan clips to face each other.
Pic. 18- Bottom view of the loading track.
Pic. 19- Get the rest of the model.
Pic. 20- Connect them like this.
Pic. 21- View of the other side.

Step 6: Basket Support

This is the support that will hold the basket. Build it (pictures 1-4), and then connect it to the rest of the ball juggler (pictures 5-7).

Pic. 1- Build the basket support.
Pic. 2- Another view.
Pic. 3- Another view.
Pic. 4- Don't forget to add that dark gray connector! It doesn't connect to anything yet; it just slides onto the blue rod.
Pic. 5- Get the rest of the ball juggler.
Pic. 6- Attach the basket support like so.
Pic. 7- A view of the other side.

Step 7: Main Track

This is the main track that leads from the basket to the loading track. There are two sections for it. Build the first section (pictures 1-3) and the second section (pictures 4-6). Then combine them (picture 7), and attach the main track to the rest of the model (pictures 8-14).

Pic. 1- Build the first section of the main track.
Pic. 2- View of the spacers.
Pic. 3- Bottom view.
Pic. 4- Build the second section.
Pic. 5- Close-up showing one end.
Pic. 6- Don't forget that small bit (light gray connector and white rod).
Pic. 7- Combine section 1 and section 2 to complete the main track. There are two connections.
Pic. 8- Get the rest of the ball juggler.
Pic. 9- Attach the main track to the ball juggler.
Pic. 10- Connections to the basket support.
Pic. 11- Don't forget to attach that small support!
Pic. 12- Connections to the loading track.
Pic. 13- Close-up of one of the connections. The dark gray connector and green rod attach to the blue connector.
Pic. 14- There are no connections here; the track just rests on the blue connector.

Step 8: Basket

You're almost done! This is the basket that will catch the balls. First, build it (pictures 1-8). Then, attach it to the basket support (pictures 9-13). The basket connects to the support in four places.

Pic. 1- Build the basket. Make sure everything is spaced out like in the picture.
Pic. 2- Bottom view.
Pic. 3- A view of the spacing of each layer.
Pic. 4- Don't forget the two blue spacers and tan clip on the edge of the yellow rod!
Pic. 5- Another view.
Pic. 6- Another view.
Pic. 7- A view of one of the ends of the basket.
Pic. 8- A view of the other end of the basket (far end).
Pic. 9- Get the rest of the ball juggler.
Pic. 10- Top view of the inside of the basket.
Pic. 11- Connections to the basket support.
Pic. 12- Another view.
Pic. 13- A view of the back.

Step 9: Get the Balls

Now get 3 ping pong balls (38 millimeter). Load them into the basket (picture 2), and they should line up at the loading track like in picture 3.

Pic. 1- Get three ping pong balls measuring 38 mm.
Pic. 2- Drop them into the basket.
Pic. 3- They should line up at the loading track like in the picture.

Step 10: You Are Finished!

Congratulations, you have just finished the rapid ball juggler! Now that the balls are in, push the switch on the motor toward the catapult side (the other side is the gear side). If you push it the wrong way, then it won't work. Have fun!

If you build it, then post a picture in the comments, and I'll add it to this step! If you post this anywhere else on the internet (pictures, video, etc.) then be sure to give me credit.

Thanks for viewing!


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Participated in the
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Question 1 year ago

Will this work with yellow gears?


Answer 1 year ago

It will if there's enough room, it looks fine to me from the pictures.


Reply 2 years ago


Aggressive ghost 132
Aggressive ghost 132

Reply 2 years ago

Also I'm going to use that as a ball lift 😂😰


Tip 3 years ago

If the Loading system is messed up because the launching arm is not far enough down get smaller rubber bands or make the arm piece on step 3 longer.


5 years ago

I built it and the first time I turned on the motor the catapult bent over to pick up the ball but didn't pick one up, can anyone suggest anything?


Reply 5 years ago

That's a common problem, try making the lever that pushes down the catapult longer. It could also be because the rubberbands are too strong. If it still doesn't work, it could be an issue with the loading track, so you'd have to make it so the track tilts more.


5 years ago

going to build it if I have the pats! ;)


Reply 5 years ago



Reply 5 years ago



8 years ago

That's awesome! I'm going to post an instructable of my own soon! :-)


Reply 6 years ago

Don't post 4 of the same comment


6 years ago

That's too bad, but you could replace some spacers with dark grey connectors or tan clips.

samet knex
samet knex

6 years ago

türk varmı

The Knex Inventor
The Knex Inventor

6 years ago

Nice! The only thing I do not have is the ping-pong balls. Once I find some, I will build this.


Reply 6 years ago

Thanks! Have you found any ping-pong balls by now?

The Knex Inventor
The Knex Inventor

Reply 6 years ago

You're welcome! :-) No ping-pong balls yet, but I'm working on it.


7 years ago

Here it is! I finished building it and it works great!