K'Nex Fruit Machine




Introduction: K'Nex Fruit 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 a working fruit machine which is made almost entirely from K'Nex. It is so large that it will have to remain in the room (which has a concrete floor) for ever.

The machine pays out in balls, the size of the win being the lowest digit which appears on the three reels (so any combination which contains a zero is a loser).

During the building of it much was learned about K'Nex (Elap had discovered it at a car boot sale only a couple of months before he started) and some PDFs on K'Nex have been produced (see below).

The non-K'Nex bits of the fruit machine are the reel symbols (produced using Microsoft Word and then laminated) and the balls (meant for a child's play pit - Elap didn't have anywhere near enough K'Nex balls, and they are expensive). Also, a weight has been made from a lead-filled K'Nex cage because there were no K'Nex components which were heavy enough.

It probably took about 150 hours to build, spread over two years, and was made up as it was built - there were no plans, but Elap collects old mechanical slot machines and was familiar with the principles. There were a few areas where a redesign was necessary (for example, the handle kept falling to pieces when pulled, and the original pawl and ratchet mechanism was clunky and didn't work very well), but there wasn't a lot of reworking overall.

The return is 85.94% - quite generous for a fruit machine!

The K'Nex pieces were acquired from car boot sales (mainly) and eBay.

Here are some documents relating to the construction of the machine, and some K'Nex tips.



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    90 Discussions

    You sir, are a king among k'nex engineers. I'm not currently adept enough at k'nex engineering to re-build your machine from what you've provided, but perhaps someday I will be. If you ever produce a set of build instructions I'll be certain to hop on ebay post-haste to buy 90,000 parts so I can build one of these myself.

    2 replies

    Thank you, kind sir!
    I've made three fruit machines so far, the last two smaller than their predecessors, but I made them up as I built them, and they are so complex that it's too late to produce instructions!
    Having said that, I am wondering whether it is possible to produce a yet smaller version, for which I would produce full instructions.
    Stay tuned...

    I look forward to it. In the meantime I am going to start working on a Coin Pusher machine with a goal of 2 or 3 moving tiers. These have always been so much fun for me at the arcades.

    I am almost speechless, that is why I'm typing.. lol.. you my friend are a god... don't expect any tithes though...

    That is great i hope you complete the machine, because after looking at this im sure it'll be a great piece of ingenuity.

    Are you considering adding more instructions so someone else could build it maby using PDFs? Because this is very nice work, and took vast amounts of engineering.

    1 reply

    The problem is that I made it up as I went along and hadn't come across the Instructables site then.

    It would be too much work to explain what I did, and I've forgotten a lot of it!

    HOWEVER, I'm experimenting with a smaller version which would use K'Nex ratchets and K'Nex rubber bands and would work with K'Nex balls.

    If I succeed, I'll produce step-by-step PDFs, but to be realistic it would be the middle of the year before - and if - I completed it.

    I made it over a period of two years, spending about an hour or two a week on it on average.

    wow,The longest I ever spent building something with knex was about 2 1/2 months. I was building a ultra-lightweight helicopter that actually lifted into the air. It actually lifted about an inch. I started working on it again last week. I going to post when I finish

    This brings tears to my eyes, all those beautiful mechanisms working together. Maybe you can make a smaller version of this and post it on instructables:)

    1 reply

    The problem here is one of scale. Clearly, making a machine which was say 6" high would be impossible because of the relatively chunky size of the pieces.

    The larger the machine the more feasible it is. For example, If you want a combination of rods to be a certain length, there are far more combinations of rod lengths to try for a large-scale machine than with a smaller one.

    It would be a big challenge to make a smaller version without modifying the pieces, which of course is not allowed!

    The reason the machine is the size it is is based on constructing the smallest reels which used eight flexible rods of the same length.

    Having said all this, I have an ongoing background task running in my brain on how to make a smaller version...