**K’Nex**

This is a construction toy for children (Ted is a child at heart). It’s supposed to be the most popular construction toy after Lego. However, K’Nex is an engineering toy whereas Lego is more akin to building. Also, K’Nex tends to consist of a standard set of pieces whereas Lego very often includes pieces which are intended only for the particular model being built. This makes K’Nex very versatile.

### New Fruit Machine (Mark 3) (April 2015)

Ted’s purchases at car boot sales and from eBay have enabled him to have enough pieces to make a new fruit machine!

There is an Instructables entry here.

### K’Nex ‘Bonanza’ Amusement Machine (July 2014)

Details of the construction can be found here.

Here’s a YouTube video of it:

### K’Nex Coin Pusher (June 2014)

Details of the construction of the machine can be found here.

Yes – another amusement machine!

Here’s a YouTube video of it:

### K’Nex Fruit Machine (Mark 2) (August 2013)

Ted has finally got around to making a smaller version of his fruit machine. More details are available in the Instructables site.

This version uses K’Nex balls rather than children’s play-pit ones and has various design improvements.

### K’Nex Binary Machine (December 2012)

Ted’s K’Nex Binary Calculator (September 2010) has been superseded! Yes – it has even been dismantled! Here is its replacement.

This indispensable machine has two modes – counting and calculating.

Have a look at the Instructables entry for more details about this pocket calculator substitute.

### K’Nex Ball Amusement Machine (March 2012)

Ted has now constructed 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.

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 on the left, 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 in columns 4 to 11. The three columns at each end are visited less frequently.

More details can be found in the Instructables entry.

### Ted’s Fruit Machine as at 12th June 2011

The pay-out slide and tray have been completed, and there are now symbols on the reels! A fascia has also been added.

The size of a pay-out (in balls) is the lowest number which is displayed on the three reels.

The reel strips have been produced using Microsoft Word and have been laminated.

All that’s left now is the odd tweak – the machine is basically complete.

Ted estimates that it took about 150 hours to design and build it (but he didn’t actually design it as such – he collects old mechanical fruit machines and knew how they worked, and made up things as he progressed…).

If you would like more information, please leave a comment (if it contains an e-mail address you will receive a private reply and the comment will be deleted).

Some more pictures (click to enlarge):

### The Fruit Machine as at May 2011

Ted has been busy again. He has completed the ball reserves (there are three runs, the first of which can be seen at the top of the picture) – these will be used to supply pay-outs.

Ted has now to work out how the balls will be released; the principle is that the further the pay-out tester falls, the higher the win, and this will move levers to allow the balls to roll into the pay-out tray (not constructed yet).

The final stage will be to decide what symbols will appear on the reels.

The return will be 85.94% – quite generous for a fruit machine!

### Ted’s Fruit Machine as at March 2011

Ted has spent just the odd hour or two every now and then since January. He has started work on the slot for the ball (the machine will work with balls, not coins).

When a ball is inserted, a lever is released which enables the handle to be pulled (if an attempt to pull the handle is made without having inserted a ball, the handle will be blocked). The ball then travels to the back of the machine where it will fall into the reserve for any pay-out – this part has not been started on yet.

The pay-out tester is currently being released too early and a redesign is imminent. Attention will then turn to the pay-out mechanism.

By the way, in the photo above the handle is half way through a pull – that’s why it’s horizontal!

**Ted’s Fruit Machine as at January 2011**

He has completely reworked the clock (ie the timing mechanism for the machine). The previous version was clunky and rather unreliable and needed quite a bit of force to wind it up. The new version uses a smooth ratchet which Ted has invented (details appear in K’Nex Tips, or you may click here).

The handle has been redesigned. The old version had a slight disadvantage in that every now and then it fell to pieces when pulled. The new version is much better but, admittedly, still not perfect. The handle was returned to its starting position by a large weight at the end. This was inelegant and clumsy. The handle is now returned by a chain and weight (there are no springs in K’Nex). The weight consists of strips of lead* – ball bearings were not heavy enough – inside a K’Nex cage.

When the handle is pulled, all three reels spin round. The first reel then stops, followed by the second, and then the third. While all this is happening, the handle gradually returns to its starting position, finishing by releasing the pay-out tester (this will trigger the pay-out).

* The lead has an interesting history. When Ted had The Old Vicarage rewired in 1996, he kept all the old wiring. Whereas modern cable consists of three wires in a PVC sheath all held within a PVC covering, The Old Vicarage’s wiring consisted of three wires within a rubber sheath all surrounded by lead. You can only imagine what happened when the rubber perished and the wires touched the lead. Indeed, the first night living in The Old Vicarage commenced with a loud POP as the lights were turned on. Anyway, if the lead is cut into 6″ lengths and the wires are removed, some very useful pieces of pure lead remain.

Er… no, the dog sitting by the fruit machine is not real – it was a car boot sale purchase!

### Ted’s Binary Calculator (September 2010)

When building his Whirligig machine (see below), Ted used two ‘flip-flops’ to control the direction of the balls. It crossed his mind that the same principle could be used to work a binary counter. Moreover, the counter could be used as a calculator too!

So Ted got cracking, and after 20 hours of designing and building, he came up with this ball-operated machine:

There is one column for each power of 2 (from 2º = 1 to 2¹º = 1024), thus representing a number in binary notation. Starting with an empty machine, if a ball is inserted into the 1 column on the right it stays there. When another ball is inserted in that column, it dislodges the ball that is there and falls into the 2 column – the dislodged ball is collected in a tray at the bottom of the machine ready for reuse. There is now just a ball in the second column, representing the binary number 10.

When a third ball is dropped into the first column, it stays there because it is not already occupied. The machine now has a ball in the first two columns, representing the binary number 11.

Now the fun starts. When a fourth ball is dropped into the first column (the one labelled ‘1’), it dislodges the ball which is there and falls into the 2 column. Since that column is occupied too, the ball dislodges that ball and then drops into the 4 column – where it stays because it was empty. The machine now has a ball in just column 4, representing the binary number 100.

And so it goes on. After 1,024 balls have been inserted, there will be just one ball in column 11 – the far left column – representing 1,024 as 10000000000.

Another way of expressing the rule is that, starting with column 1 and working from right to left, the ball must fall into the first empty column it encounters, emptying each occupied column it passes over *en route*.

“So how can this machine be used to multiply numbers?” you may ask. Well, you must remember that, just as with our normal base-10 number system, the value of a digit is multiplied by 10 if it is shifted one position to the left, so a binary digit is worth twice as much if it is shifted one place to the left. For example, if you drop a ball in column 1, it is worth 1, but drop it in the column to the left and it is worth 2. If you drop it in the column which is three places to the left, if is worth 2³ = 8 times as much.

Let’s multiply 23 by 17.

First of all, express these as the sum of powers of 2: (16 + 4 + 2 + 1) x (16 + 1).

We are going to insert two balls, one in the 16 column and the other in the 1 column. We end up with the machine showing 10001. This is 17. We have 1 x (16 + 1).

We are now going to add 2 more 17s, but instead of adding two more lots of balls to the 16 and 1 columns we are going to speed things up by dropping one ball in the 32 column and one in the 2 column, *ie* as before but one column to the left. This means that we have just added twice as much – 2 x (16 + 1) making (2 + 1) x (16 + 1) altogether. The balls in the machine now represent 110011, *ie* 51 in base 10. We know it’s 51 because all we have got to do is add up the values of the columns which have a ball in them (32 + 16 + 2 + 1).

We now need to add 4 17s and so we drop one ball in column 64 and one in column 4, *ie* two columns to the left of the first balls to make them worth four times as much. The machine now represents (4 + 2 + 1) x (16 + 1).

Finally, we need to add 16 17s by dropping the balls in the columns which are 4 to the left of the original two columns, *ie* columns 256 and 16. It’s 4 columns to the left because 16 is 2 to the power 4. The machine is now showing (16 + 4 + 2 + 1) x (16 + 1).

We end up with balls in columns 256, 128, 4, 2 and 1. The sum of these is 391, and the machine has represented this as 110000111.

So now we have the result: 23 x 17 = 391 – and all we had to do was drop eight balls into the machine and add five numbers together!

A YouTube video of the machine in action can be seen here.

### Ted’s Fruit Machine (September 2010)

This is the current state of Ted’s K’Nex fruit machine which was started in July 2010. He has to improve the machine’s clock (he’s thought of a better method than the one’s he’s used) and will then be ready to tackle the pay-out mechanism (the machine will work with non-K’Nex balls and pay out 2, 4 or 8 balls depending on the winning line).

Every now and then, though, Ted gets distracted and makes something else (see above…). The target date for completion is Christmas 2011.

### Ted’s Whirligig Machine (August 2010)

Ever since he retired (damn – he’s given his age away…), Ted has wanted to build an interesting device which did a lot of absolutely pointless things. This machine is operated by a 12-volt motor which is powered by a mains transformer or from a 12″ x 18″ solar panel. It adds 1 to a counter every 5 seconds or so and lifts and releases balls for no apparent reason. These balls get sent in three different directions in the order A, B, A, C. In addition, three ‘fans’ turn, one in each of the X-, Y- and Z-planes – but why?

It is quite relaxing listening to the whirr of the motor and the clickety-clacking of the balls as they wend their pointless way around the mechanism ready to be lifted once more.

### Ted’s Binary Counter (August 2009)

Ted saw a binary counter on YouTube and built an improved version of it using K’Nex. It is powered by a K’Nex battery-operated motor. It adds 1 to the base-2 number every few seconds. It is very relaxing to hear it clunking away.

### Ted’s Clock (July 2009)

This was one of the first things Ted made after he discovered K’Nex at a car boot sale in 2009. It was dismantled in 2013.

However, because there is only a limited number of gears available in K’Nex, it was not possible to achieve (simply) a 12-1 ratio for the minute and hour hands. The clock therefore had a single hand.

The clock used a traditional recoil escapement and demonstrated how most pendulum clocks work. It was weight-driven and ticked for about 45 minutes on a single wind. There was a limit to how long the clock could be made to tick; the higher the ratio of the gear train, the heavier the weight had to be. Since K’Nex rods are all the same thickness, a heavy weight would have bent the rod which was acting as an axle for the weight-bearing pulley.

The wire for the pulley was not actually a K’Nex component. Ted used electrical wire because he wanted to use something which was to hand and which was strong and quite long. Also, the weight wasn’t all K’Nex either! Ted used some ball bearings inside a K’Nex-built cage.

Virginia, on 18/6/11 at 11:25 am said:Brilliant! I look forward to having a demo.

The website has really developed, and is looking very professional.

Brian, on 14/10/12 at 1:46 am said:that’s an awesome idea. great job at it!!!!!!