Anders said
> I've had a paper tape reader for a while but never had a punch to make new
> tapes, and the ones i've found are not only very large but also very
> expensive. So I'm toying with the idea of making an open-source punch, but
> I can't find any detailed diagrams of how the mechanism works.
>
> I'm assuming (without any data to back it up) that there is a cam, an array
> of spring-levered pins, and horizontal spacers controlled by solenoids that
> bridge the gap between the cam and each punch pin when called for.
>
> Does anyone have insight into how reliable/fast paper tape punches work?


The idea behind the paper tape punch is that the solenoids themselves don't 
supply the force to do the actual
punching, they instead set up the punch pins which are then driven by a cam by 
a motor with a lot of grunt.
I suppose it's like the mechanical equivalent of a transistor switching on by 
applying a small base current.

The once-popular Roytron punch mechanism is described in 
http://www.bitsavers.org/pdf/roytron/Roytron500_1966.pdf
and may be what you are looking for.

It's somewhat comparable to how the keyboard mechanism operates in a Selectric 
typewriter where interposers drop
into place and the cam profile on the filter shaft drives them forward. Or a 
Creed teleprinter keyboard with toothed
code bars that suspend lateral bars being moved with mechanical force.

I've also thought about a home made punch that might be built using the 
Teletype punch blocks that have been on eBay,
augmented with a bit of machining, motor and some 3D-printed parts such as the 
frame. But that's still just a bunch
of ideas at present.

As for making tape by means other than a punch, if you have a home 
vinyl/stencil cutting machine you can make working
paper tapes using my ptaf2dxf utility   https://github.com/1944GPW/ptap2dxf

It's very slow compared to a real punch and on the standard 12" x 12" cutting 
mat these machines are supplied with, there
will be a number of short tape segments cut that then need to be glued 
together. But, as a novelty, it works :)

Steve.

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