Logic gates made purely of joints and levers


Originally published at: https://boingboing.net/2018/01/13/logic-gates-made-purely-of-joi.html


To quote the old song “all you need is nand.” (TTL era, you kids!) Although NOR works just as well, for those of us who did other flavors back in the day before usable CMOS.

The big problem with the lever-based approach is that the elements need power gain or the losses pile up to exceed the stress limits of the materials. That means you need something like a piezoelectric amplifier along the path now and then, and even so it’s going to be relatively slow. Offhand I can’t say whether the purely mechanical approach is faster at any given scale than the fluidic [1] one, but at human-machineable scales (visible to the naked eye) I’m pretty sure that fluidics win, especially since it’s possible to make them with lithographic techniques.

For those interested, there’s a rather readable development on 17th-century fluidics (both fiction and non) in the Ring of Fire series’ Grantville Gazettes (Flint et. al.)


one step closer to The Diamond Age


My thought exactly.


Babbage’s Difference Engine?


Fluidic (mostly pneumatic, but also hydraulic) logic is frequently used in modern industry. There are several manufacturers and not only logic gates, but also other parts like memory cells or even timers are available. If these were a bit cheaper, someone would probably assemble simple CPU from them :slight_smile:
An example of pneumatic logic parts catalog:


sure, “joints and levers” are all the rage now, but I recall back when mere string and eyelets were all we needed (“and we loved it!”)


Edmund Scientific used to sell a small programmable mechanical computer a bit like this. Could do simple binary addition and a few other tricks once you assembled it and you worked a push/pull lever to power it.

Doesn’t seem all that new or radical.


Don’t know about the current generation, but time was that there were a lot of fluidically controlled automatic transmissions. Advantages: close to bulletproof, intrinsic actuators. Disadvantages: harder to integrate with engine controls, probably on net more expensive.

Full-up fluidic calculators (per Ring of Fire) would be faster in liquid form due to speed-of-sound issues. Both would be vulnerable to contamination. Their big advantage would be that they could actually be built using 17th century technology (not the massive broad industrial support that the semiconductor type would need.)

Since the lever logics require amplifiers, there’s a tossup between pneumatic and hydraulic amps. The relative merits are outside of my field.


As for hydraulic computers, I’ve once seen MIG-29 engine at military aircraft engine testing facility. Such engine’s fuel injection maps are extremely complex, and it was completely done on hydraulic analog computer integrated with fuel pump. Such solution was totally resistant to EMP pulse. If I remember well, the pump had 49 adjustment points, and used up to 140 tons of fuel during adjustment :slight_smile:


Sounds about right. I suspect that EMP sensitivity reduction can be achieved at lower net cost; worst-case, run a modest hydraulic line to a generator powering an electronic package in a Faraday cage.


Youc an make logic gates out of pretty much anything:

To be honest, I read the headline as “Logic gates made purely out of joints and leaves” and was expecting something rather different.


Takes a big puff…I can feel the gate closing already!


Even easier: Just use tubes for all of your electronics, instead of semiconductors. Problem solved!

Way back in the wayback of 1976, Lieutenant Viktor Belenko defected from the USSR with a Mig-25 “Foxbat”; this was actually the basis for the film, “Firefox” (with a LOT of “artistic license”, mind you ^^’). You’ll find online sources that mindlessly snoot about its “primitive” vacuum-tube avionics, never once thinking about the fact that it was EMP-proof -.-’…


Yeah though EMP proofing isn’t that hard really. A steel box does a pretty good job. And beefy power transistors are still better than tubes.


Not for mobile protection. In fact, the Army gave itself fits, trying to figure that one out; Faraday cages aren’t often all that portable ^^’. It can be done, yes, but generally at a significant weight penalty, a big deal for a bomber or interceptor.


Wouldn’t a cascade of just a few levers require exponentially increasing force to work it? Kind of like how you can’t run a reducing gear backward?


Vacuum tubes are not EMP-proof. Hardier, yes – proof, no. Freaking Kettering ignitions are not EMP-proof, and vacuum tubes are nowhere near as hard to fry as points and autotransformers. The main point with EMP is keeping your loops small and give the induced EMF someplace else to go.

Thus my point earlier: optical fiber connecting metal boxes with no external electrical connections. Not reasonable in 1976 although doable with the then state of the art if you didn’t need high rate communication; the F-16’s control update rate of 4/sec would be manageable with the optoelectronic technology of the day [1]. We could have done it, but the DoD wasn’t prepared to go that radical, and that was that.

[1] Says /me, having designed some of the optical comm devices of the time.



Great for practice, or teaching the kids…

Used to be free in a browser. Now it might be free for a limited time


About 40 or so years ago there was an article in one of the electronics magazines about building logic circuits using only neon bulbs (NE-2) with resistors and capacitors. I’m still kicking myself for not having had the brains to clip that article.