Bamboo computer

Dwight K. Elvey dwight.elvey at
Wed Mar 9 11:24:33 CST 2005

>From: "Jim Battle" <frustum at>
>Ron Hudson wrote:
>> If the desert island has vines you could make a rope computer, as 
>> described in a
>> Scientific American, I don't remember the issue.
>It was an april fool's issue, I believe.  If memory serves, the island 
>was called APRLFUL or something like that.  The article showed how, with 
>clever arrangements pullies, toggles, springs and such, inverters and 
>simple logic gates could be produced.  Entertaining enough.
>The problem with that "computer" is that the logic gates have no gain.
>Each gate has no power supply other than the mechanical power of the 
>input signals (ropes getting pulled).  For instance, say you pull an 
>input rope of a NAND gate one foot (OK, let's keep it metric) ten inches 
>:-) and the output rope moves nine inches, so the gain is 0.9.  Put N of 
>these gates in series and the output signal is (0.9**N) of the input 
>signal.  After half a dozen gates, very little is left at the output. 
>The rope gates had a gain much less than 0.9 -- probably 0.5.
>It is the same reason why computers aren't built of of just diodes and 
>resistors.  You can have a gate or two in series, but then the signal 
>needs to be reconditioned before being applied to the next stage.

 Relays work great. They have a lot of gain. Maybe much more
than is needed for a computer.
 I've always wanted to build a calculator using marbles that
are feed from a hopper and the addition of a manual lever
to work as a clock ( and additional power ).

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