Rick Fish and the Lego Adding Machine

No, I don't think Rick's adding machine was ever up on a web site. I was co-designer of the model, and I can give you a description of how it works. The "Fish/Ernest" ;) adding machine was essentially a stack of binary half-adders, powered by marbles. We got as far as designing the guts of the thing, but never made the outsides (marble tracks are sort of academic) so much of the device was hypothetical. But the guts worked. The half-adder itself starts with a hole through which a marble is dropped. This marble will toggle the half-adder with one of two possible results: 1: If the half-adder is "on" (a flag attached to the gear mechanism is up, representing a digit of 1) then the digit will turn off and the marble will proceed to the next lower half-adder as a carryover bit. 2: If the half-adder is "off" (the flag is down, representing a digit of 0) then the flag will be raised, and the marble will go into a waste chute. A stack of these half-adders can be read from bottom to top, with the top flag representing the 1's place, the second the 2's place, the third the 4's place, and so on. Each layer is about 7 bricks high, or roughly 3 1/2 inches. The whole thing is gravity-powered, and you "charge" it by dumping a handful of marbles into a holding pen at the top. You can input marbles one at a time at the top, but we also designed a set of fingers that would push marbles from lower holding racks into the appropriate digits in the machine; for example, to add nine, one could push in the "1" and "8" fingers simultaneously, and everything will fall out successfully. This was probably the neatest thing about the machine. The waste chutes were designed to conserve energy by funneling waste marbles into the holding racks for the next level. Of course, the machine had only the binary output, and could only add. But it was still pretty neat. Anyway, that was longer than I thought. Hope it's as interesting for you as it was for us. Best wishes, -James Ernest -Cheapass Games >Hi! I was wondering if you could do me a favor and as Rick Fish if he is >the guy who used to have a web page about his Lego Adding Machine at >http://legowww.homepages.com/projects/adding/project2.html? > >I am a collector of older computers, and there has been some discussion of >late on a classic computer mailing list about early mechanical computers >(such as the Digi-Comp 1). As part of this discussion, someone brought up >a Tinkertoy Tic-Tac-Toe machine, and I recalled seeing a lego adding

> >Unfortunately, the link I had is no longer valid, but a web search found >the cheapass games staff picnic page where Rick Fish is listed as having >created a Lego adding machine. Even if he is not the person who had the >above-mentioned page, I (and others) would love to hear about his