K'Nex Ball Amusement Machine


This is an amusement machine which is made almost entirely from K’Nex. The non-K’Nex components are the balls (which are made of bouncy rubber), the signs and the column labels.

There are two slots; one is for children’s use and is low down, and the other (near the top of the machine) is for adults’ use. When a ball is inserted in the lower slot, a chain hoist raises it to the level of the higher slot - it's powered by a 12-volt K'Nex motor.

Each inserted ball runs down a channel near the top of the machine and bounces down an array of pins. It then lands in one of 14 columns.

Each column can hold up to seven balls. A full column is indicated by a pink flag (in the picture below, columns 4, 9 and 10 are full). When an eighth ball enters a column, the seven balls are released into a winnings tray. The winning ball ends up in a box at the base of the machine.

If one of the three columns at the far left or far right of the machine is filled, all three coulmns get emptied into the tray.

There are some ‘blockers’ between some of the pins so that the balls end up fairly evenly distributed through columns 4 to 11. The three columns at each end are visited less frequently.

The part of the development which was most time-consuming was the design of the ball unit (there are 14 of these - it's the part which holds up to seven balls and then releases them when an eighth ball enters it). It was important that no ball was left in the column after a win, and that the bottom of the column was always closed afterwards. There would have been a lot of time wasted if, after the assembly of the machine, a flaw was found.

The balls are made of some kind of bouncy rubber (K'Nex balls are far too light for the mechanism to work). A box of 400 new balls was bought from an eBay seller. There were four different types of ball, about the same number of each. A quarter of them were slightly larger but about 20% lighter than the ones which were used, and they didn't work very well. Another quarter felt slightly tacky, and the increased friction meant that they didn't work well either. The last quarter had a surface which was more like fabric than rubber, and they tended to slide down the pins instead of bouncing on them. Anyone want to buy nearly 300 bouncy balls?

A video of one of the ball units in action can be seen here: 

If you want more photos or explanations, let me know (but I can't believe that there's another nut out there who would want to make one of these!).

If you like this, have a look at my K'Nex Fruit Machine and my K'Nex Binary Machine

Below is a PDF document describing the construction of one of the ball units, and another which describes the construction of the pinfield.
KILLERK1 month ago

not sure how I missed all of your incredible builds but wow! Just amazing work! I'm curious if you have ever seen my builds? Also if you look up KILLERK on YouTube I have a bunch of videos showing off some of my work. It would be awesome to collaborate on a build with you or at least get some input from you. Again I'm a huge fan of your work absolutely impressive and creative stuff!

Dude, you are a true knexpert, I bow down before you and awesome knowledge of knex.
J-Five2 years ago
It probably used A LOT of pieces!!!!
Elap (author)  J-Five2 years ago
Yes - each of the 14 ball units used over 500 pieces, and the 'pinfield' used over 2,000. The payout tray used quite a lot too, and so did the base...
J-Five Elap2 years ago
I'm guessing it took you a long time make?
Elap (author)  J-Five2 years ago
Between 50 and 60 hours, I reckon, spread over a few weeks.
J-Five Elap1 year ago
I'm guessing that you're wearing a mask.
J-Five Elap2 years ago
That's what i thought, it must have been fun
GASSYPOOTS Elap2 years ago
how can i get htat many peices!?!?
I believe they sell big kits in department stores
Elap (author)  GASSYPOOTS2 years ago
In England we have car boot sales where £4 can buy a large box of K'Nex. I have also bought a few very large lots from eBay.

My best purchase was 43kg from a car boot sale for £50 two years ago.
GASSYPOOTS Elap2 years ago
and 50£$2.60 O_O
Where did you get all these peices from? anyway very unique 5 stars
Elap (author)  MrShadowKnight162 years ago
Car boot sales (usually very cheap) and eBay (can be cheap for huge amounts).
KGuy Elap2 years ago
Where do you find car boot sales? Haven't seen one in years
Elap (author)  KGuy2 years ago
There are lots in England; just Google 'car boot sale' to find local ones.
Ok thanks, i have been looking for more parts.
This is so amazing and i cant beilieve you managed to build this.
jingo692 years ago
Nice! 5*
wanna beco2 years ago
I vote you ruler of the universe.... if the leader is ever chosen on Knex skill alone. I love the monster too, scary yet sweet.
If you post full instructions, you could have one of the biggest instructables ever! This machine is so unique!
Elap (author)  knexpert#108294762 years ago
Thank you for your kind comment.

I'll be explaining how the 'pinfield' was constructed, but I'll probably stop there!
aol10442 years ago
Dude! This is EPIC! what do you do with your spare time whe you`re not building EPIC stuff like this?
Elap (author)  aol10442 years ago
Thank you, kind sir!

Have a look at my interests in my profile...
frannicus2 years ago
Do you have any how-tos for this project? Looks like a fun summer activity:)
Elap (author)  frannicus2 years ago
Someone has already asked for details of the ball unit, and I will be preparing a PDF document this week.

I will also, as you're interested, explain how the 'pinfield' was constructed.

I don't intend to produce a complete step-by-step guide for the machine, but I will cover the areas which have to done properly so that the foundation blocks are there; after all, more is learned by being inventive and experimenting than by following a fixed set of instructions like a robot!

Needless to say, a machine with only seven columns would still provide a playable game and would not require a hoist for the balls - it's only because I'm a nutter that I made the machine that big.
that is awesome i am subscibing to you
KneXtreme2 years ago
Very cool. Looks like a lot of fun. I was wondering if you could get a close up of one of the ball units?
Elap (author)  KneXtreme2 years ago
I'll take some photos - give me a few days. I'll send you a message when I've done it.
KneXtreme Elap2 years ago
Great! Thanks!
Shadowman392 years ago
This is cool! Looks like a lot of fun to play, too. :-)
Elap (author)  Shadowman392 years ago
Yes - even though I say it myself, it's the randomness and chaotic behaviour that I find fascinating.
Puddock2 years ago
This is amazing!
Dr.Bill2 years ago
Pachinko !
cool knex132 years ago
Nice! 5*
Sorunome2 years ago
Cool! You just earned a subscriber! :D
make that 2,
nice job!
skiedra2 years ago
That is one inventive build!
Heh, like a mix between Plinko and Pachinko. Very cool - many kudos for such a neat build!