K'Nex Ball Amusement Machine





Introduction: K'Nex Ball Amusement Machine

About: Wacky retired chap who just can't resist going to car boot sales; a hoarder. Having retired 15 years ago after working for 33 years, he decided that he would spend the next 33 years playing.

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.



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    not only is this a masterpiece of technique, the machine looks very well and is user friendly too!

    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.


    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...

    I'm guessing it took you a long time make?


    Between 50 and 60 hours, I reckon, spread over a few weeks.

    I'm guessing that you're wearing a mask.

    That's what i thought, it must have been fun

    how can i get htat many peices!?!?

    I believe they sell big kits in department stores


    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.


    Car boot sales (usually very cheap) and eBay (can be cheap for huge amounts).


    Where do you find car boot sales? Haven't seen one in years


    There are lots in England; just Google 'car boot sale' to find local ones.

    This is so amazing and i cant beilieve you managed to build this.