Introduction: K'nex Programmable Automaton

Picture of K'nex Programmable Automaton
A K'nex automaton with a programmable path. This alternating design was originally conceived by Heron of Alexandria.

I don't have enough string, so I could only run the short program shown in the video.

Step 1: Build Frame and Motor Components

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Step 2: Create the Program Spindles

Picture of Create the Program Spindles

Use a thin but strong string. Yarn, synthetics, or the string included with most sets will work. Two pieces of string of equivalent length are needed. The longer the string, the longer your automaton program will run. If the lengths of the string need minor adjustment, see image 6.

The program spindles are designed to be easily removable, so new programs can quickly be run by simply exchanging the spindles.

Step 3: Programming the Automaton

Picture of Programming the Automaton

Looping the string under allows moves the vehicle forward on that side. Looping the string over moves the vehicle backward on that side. To allow the vehicle to move forward, both spindles would loop under; to turn right, the right spindle loops over and the left spindle loops under, and vice versa. Keep in mind that the code runs in reverse, with the top most string layers coding for the first actions of the automaton.

To simplify programming and to allow easy distribution of different scripts, I have set up a simple coding syntax. I suggest coding in notepad so the spacing is even.

This is how the script for each wheel starts, with a L and R for the respective left and right wheels. Y is a number, and x is a unit of measurement. The Yx shows the length of the string in a particular unit. So, 8meters, for example.

Each spindle has 8 rods, so moving forward (looping the string under) one complete spindle revolution would be the following. u is for looping under, and o is for looping over. A // signifies the end of code."


The script above shows a slight left turn. A 5u signifies that a grey connector be placed on the 5th rod from the origin, with the origin being 1, and a turn of direction occurring on the 5th rod. The other side has -- to help balance out the script to make it easier to code.

An "s" signifies a stop loop around a grey connector. An example would be
This means the that on the right spindle, the string is to be looped 360 degrees around the grey connector, signifying a stop. The stop should end in the same direction it started.

That's all there is to it. On the next step I have provided some sample measurements and scripts to combine into more complex scripts.

Step 4: Sample Scripts and Measurements

All measurements are on bare floor.
-8 loops around a grey connector is equivalent to 1 full rotation on a spindle.

Snakey Path
By: The Jamalam
L/8u/5o/8u/5o// etc
R/5o/8u/5o/8u// etc
Gives a sort of Snakey S shaped path

By: The Jamalam
Goes around in circles. lol fun to watch


arrow shot (author)2008-04-23

where can i get that dual switch motor thingy? is it a knex set?

That's an All Terrain Trekker motor, I'm lucky, got 2 in newstate. It's discontinued (WHY???), so the only way to get it is to eBay it.

Really? I have an all terrain trekker set and I thought it was nothing special. When did the discontinue it?

ACtually, any sort of carnival set has motors, two way too!

crestind (author)arrow shot2008-04-23

Any motor will work from this model. That particular motor has been discontinued.

dsman195276 (author)crestind2008-05-02

i can never figure out why they stopped making that motor. it was around the best one they made.

And the cyberknex too, WHY??? And WHY??? do they create STUPID BRICKS NOW!

I totally agree.

dsman195276 (author)crestind2008-09-03


crestind (author)dsman1952762008-09-03

Yeah :D Thanks to everybody who voted.

dsman195276 (author)crestind2008-09-03

no problem :-)

The Jamalam (author)arrow shot2008-09-02


lukeD (author)2010-10-04

can you use a other motor like this or something???

Tailslvr7_7 (author)2008-05-15

I don't get how you program it.

Wow! Tails lover haha.

Yeah, when I made this account, I was OBSESSED with Tails... Back on-topic with K'nex and string program... No I didn't make it yet, but I'll find some K'nex and some string and try to make it.

Lance Mt. (author)Tailslvr7_72009-04-09

Your basically wrapping the stings so that it unravel at different intervals.. From there gears, gun and wheels may be moved, activated, cocked and what have you. -Not quite Anom delivers, Chris

crestind (author)Tailslvr7_72008-06-01

Have you built it yet? All you do is loop the strings around the greys in different patterns and it will affect the movement. No loops means it goes straight.

Foaly7 (author)2010-04-10

I'm a little confused on the programming. It just doesn't seem explained well enough.

Foaly7 (author)Foaly72010-04-10

Okay, so do you change whether it's over or under by wrapping the string around the grey connector that was added, the change it from there? As in, L/5o/8u//
After the 5o, you wrap the string around the connector at five, then go under 8, coming back to the connector at five?

crestind (author)Foaly72010-04-22

The string needs to pass 5 rods over and then 8 rods under, so on the sixth rod you would be switching to under by wrapping around a grey connector. The numbers are irrelevant for most programs unless you need something especially precise.

Foaly7 (author)2010-04-10

When I got some of the filler for my giant tub full of K'nex, (it's seriously full up.) I found a thing to make a robot in the instruction manual. I think I could build that onto this, to give it a little height.

webby427 (author)2010-02-19

No offence but I prefer Mikey13's one because it's smaller and more piece efficient but this is good 4.5* and a sub

crestind (author)webby4272010-02-19

The size of my automaton will not increase significantly with an increase in the length of the script.

webby427 (author)crestind2010-02-19

size of the robot/car

TheFoofinator (author)2009-03-17

I have had a go at making my own programmable robot, with a repetitive program however I have not uploaded it -should i post? :

Go for it, looks really cool!

The Jamalam (author)2008-12-06

I bet you hate me for straying into weaponary... but I am going to add a gatling gun to the top of this :P

crestind (author)The Jamalam2008-12-08

You could program the gatling gun to fire at specific intervals probably if you had a string pull a trigger every so often.

Lance Mt. (author)crestind2009-04-09

I loved this, never had the pieces.. i do now and i want to program it for a certian purpose. I've set several knex weapons up to cock back with one string, fire with the other.. I was having fun doing ti from a far distance but then i rememebred this.. Its dying for a shooting

Oblivitus (author)crestind2009-01-24

That would be awesome.

GMer56 (author)2009-02-16

The days of computers with punchcards are making a comeback with this instructable.

The Jamalam (author)2009-01-06

yay! you mentioned me ty lol

Miles Tails Prower (author)2008-11-07

I think you don't need special K'NEX strings. Try using a normal household string?

this is just bog standard thread

1 month ago lol

The Jamalam (author)2008-12-06

Here is a sample script: L/8u/5o/8u/5o// etc R/5o/8u/5o/8u// etc Giives a sort of Snakey S shaped path Here's another one: L/32u// R/32o// Goes around in circles. lol fun to watch

crestind (author)The Jamalam2008-12-08

Wow sweet thanks! If you want you can name your script and I'll add it.

the_burrito_master (author)2008-05-31

cool but you cant exactly program it you can only make it go strait then turn and thats it. keep it up though! please tell me if I'm wrong.

Yes this is a program. Even a simple timer that turns something on and off is considered a program. This thing will do a lot more than that. Even though the video does not show it this thing can be programmed to go straight, turn left or right and even reverse. What more does it need to do.

Vynash (author)biochemtronics2008-07-13

nothing I didntknow for sure if it did more than go strait than make a turn.

crestind (author)Vynash2008-07-13

Well, it does say programmable. And if it only went straight and made a turn, it wouldn't be programmable then :P

How can you program it? Just attach some rope? Or does it need to be attached in a special way?

Step 3.

Vynash (author)crestind2008-07-14

yeah and that comment up there was from my bro because there is a problem with Ibles so it switches over some times

Yes, I mean that's about all any vehicle can do, right? Stop, turn, go straight, and this can do all of those things.

yeah but I mean it can only go strait then do a turn not go strait ,then turn then go strait ,then turn go backwards ,then turn around ,thats what I ment.

No, you can program it to do anything. You just have to change the program. I didn't have enough string to write a longer program, which is why my automaton only went straight and turned.

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