A working Turing Machine was this week submitted to Lego Ideas, consisting of approximately 2,900 parts and a bucketload of extreme cleverness.

The original machine was devised by mathematician Alan Turing in 1936. Turing's idea was a hypothetical system that could simulate any computer algorithm.

The design consisted of an infinitely long tape with symbols that could be moved left and right, a 'head' that could read the symbols and overwrite them with new ones, a finite control that described the machine's state, and a table to link each combination of state and symbol to an instruction for what to do next.

Physical representations on Turing's model are an interesting engineering and computational challenge, and while any algorithm can be simulated, such machines are nowhere near as performant as purpose-built silicon. The Turing Machine still does, however, represent a useful model for students of computation.

Enter The Bananaman 2018 and the working Lego Turing Model.

The Lego builder first came across the concept a few years ago and, despite it being an abstract model, decided to attempt making one out of the plastic components of Lego Technic.

He told The Register: "My first few ideas how to do this would be very big and inefficient if they were ever [to be] built, but I usually stopped developing them very early. The first one that could possibly work was three years ago and I built a part of the tape with the symbol reader and a very bad unfinished prototype of the 'truth table' that would use a 32-speed gearbox instead of the 'searching' mechanism.

"Later I realized that the 'truth table' can be made way more easily (it was my fourth idea on how to build the table and it still had a dozen revisions later on), and I came up with using the registers which made everything easier. I started building the prototype last vacation, then took a break and I've finished it this vacation."

In addition to the constraints of making the device out of Lego, there was also the challenge of fitting into the limits imposed by Lego Ideas. At the time of submission, this was 3,000 parts, and The Bananaman's contraption finally managee to come in at around 2,900. The limit has since been raised to 5,000 parts.

Fans of 3D printing will no doubt be pleased to note that some of the parts (notably one of the large gears) came from a printer, but only because buying missing bits online tends to take longer and cost more. A real-world version of the model was designed and built first to make sure it worked. Stud.io was then pressed into service to create rendered versions.

The Reg wondered how robust this was. This writer has plenty of experience with Technic mechanisms exploding into cogs and pulleys after some over-vigorous cranking. The response? Bananaman told us:

"The mechanism is very precise and hard to calibrate, but because of this the base for it needs to be sturdy. I've made many redundant connections and I tried to make a good support for each mechanism. Some parts are still easy to destroy, but I'm planning to do some improvements."

How about taking the crank away and replacing it with a motor? "It was originally motorized but I've replaced the motor with a crank because it's cheaper and safer in case the mechanism gets stuck."

The Lego Turing Machine is a tour-de-force of Technic and currently has nearly 4,000 supporters. It needs 5,000 to progress to the next stage.

Should it get to 10,000 supporters on the Lego Ideas site, it will go into Expert Review, where Lego's professionals will decide if it should be approved for production. The evaluation will depend on a range of criteria, including feasibility and strength of idea.

Monica Pedersen, Marketing Director for LEGO Ideas, told El Reg: "This is indeed a very complex build with the working Turing Machine. We have previously launched the LEGO Ideas Typewriter, which also offers a complex building experience with a lot of working functions, but not completely to the level of the Turing Machine."

This is The Bananaman's fourth attempt to have his designs approved by Lego Ideas. His YouTube channel also charts the development of his skills over the years. However, we'd have to caution against falling down the YouTube Lego Technic click-hole. Plenty of intriguing projects are documented there, from a mechanical calculator to a nifty automatic drummer.

The Bananaman is still considering what project to take on next. We'd suggest a very simple CPU as the next step. Or perhaps a Lego recreation of something along the lines of the Turing-Welchman Bombe.

Or perhaps just a well-earned rest and a relaxing build of Concorde. ®

https://www.theregister.com//2024/10/05/lego_ideas_turing_machine/