building my own relay computer

ben bfranchuk at
Sat Feb 14 02:14:04 CST 2015

On 2/14/2015 1:05 AM, Dave G4UGM wrote:
>> -----Original Message-----
>> From: cctalk [mailto:cctalk-bounces at] On Behalf Of Dale H.
>> Cook
>> Sent: 14 February 2015 03:41
>> To: cctalk at
>> Subject: Re: building my own relay computer
>> At 08:14 PM 2/13/2015, Ben wrote:
>> The alu has never relay been a problem with relays, but what about main
>> storage? Punched tape (paper/film/card) is no longer with us for I/O.
> Punched tape is about. Check out the "green keys" list, 5-level stuff comes
> up from time to time, generally at low cost. There is some ex-CNC items on
> E-Bay at present but for silly prices. Whilst I haven't seen any on E-Bay
> there were three Documation readers advertised on the Vintage Computer
> forums.
>> Fifty years ago I got around that by building my own card reader (very
> slow)
>> for input and hand-punching Hollerith cards with a hole punch. That was
>> some years before I got access to an IBM card punch in high school. Output
>> was a set of electro-mechanical counters, and they were a real pain to
>> implement.
> Many folks have implemented photo electric tape readers, but these tend to
> be clocked off the small feed holes. I guess it wouldn't be too hard to
> build a photo electric reader that has a 3-d printed feed wheel that was
> driven by a stepper motor. In fact I am pretty sure you could even use a
> coil and ratchet arrangement, like this one here:-
> but operated buy a coil and magnet rather than a rotating cam. Some one has
> actually made a complete but operated mechanical punch card computer..
> r-1481921919
> so I don't think its hard. Getting things 3-D printed isn't hard, in fact
> most FabLabs will have one and things can be printed for the cost of
> materials. Also Hack Space...
>   I think it's the punch that's harder. You would need to harden the punch
> pins, and the would need to have a very exact fit. I guess a CNC router
> could be used to make these...

I think that needs real machine work. Strange what you could do 100 
years ago you can not do today.
Computer controlled stuff is good for may things but not that.

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