Rick Fish and the Lego Adding Machine

From: Uncle Roger <sinasohn_at_ricochet.net>
Date: Thu Jan 14 20:45:13 1999

A web search turned up a reference on the Cheapass Games web site
(apparently really good games, if you like that sort of thing) to a lego
adding machine. I thought it might be the same as the one I had found
previously (that has since disappeared) but even though it isn't, it is
very interesting. Enjoy!

>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
>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
>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
>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
>>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
>>In any case, thanks in advance!
>>--------------------------------------------------------------------- O-
>>Uncle Roger "There is pleasure pure in being mad
>>roger_at_sinasohn.com that none but madmen know."
>>Roger Louis Sinasohn & Associates
>>San Francisco, California http://www.sinasohn.com/

--------------------------------------------------------------------- O-

Uncle Roger "There is pleasure pure in being mad
roger_at_sinasohn.com that none but madmen know."
Roger Louis Sinasohn & Associates
San Francisco, California http://www.sinasohn.com/
Received on Thu Jan 14 1999 - 20:45:13 GMT

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