DIY Paper Tape Punch - Mechanism diagram?

[Tony Duell]

On Fri, May 1, 2020 at 4:48 PM Anders Nelson via cctalk
<cctalk at classiccmp.org> wrote:
>
> Wow, what a response! Really appreciate the docs and first-hand experience,
> this is super helpful.

I feel very greedy now. Looking arounds I have (not all working, but
all could be got to work, it's things like drive belts I need to get )

3 Facit 4070s and an N4000
A DEC PC04
Two Data Dynamics units (1130 and 1183) which are 8-level punches
3 Teletype BRPEs
A Trend Paper Tape Station (GNT 34 punch and Trend HSR500 reader in a
rack chassis)
A couple of Teletype Model 33 ASR's
A Friden Flexowriter with punch/reader
The punch from a Flexowriter on a rack chassis with its own motor.

I think there's a couple of bare-chassis solenoid-operated punches
here too but I would have to hunt for them.

And that's the 8 level ones. For 5 level (only) I have a Creed 444
teleprinter and a Booth-Willmott Model 44 Keypunch (totally mechanical
between the keyboard and the 5 punch pins so not much use for computer
interfacing).



>
> I'm also floored by the complexity of that Roytron punch! Looks like it
> contains around one hundred separate parts. I'm convinced the punch parts
> will have to be precision metal so while that's not quite "DIY" it might
> still be a reasonable bit to CNC, mill or water-jet cut.
>
> It also looks like that punch has an escapement mechanism of some sort?
> Seems like a simple way to keep regular spacing, but if course more parts
> to buy from McMaster Carr or whatever.

Some punches fed the tape with a sprocket wheel, one way to drive that
is a suitably toothed ratchet wheel and drive pawl that moves it one
tooth per punch cycle. As I said in another message, the Facit 4070
uses an accurately-machined (right diameter) capstan and pinch roller,
the capstan moves the tape one chracter spacing for a certain number
of steps (it _may_ be just one step) of the motor. I have another
punch unit here which has the crank-and-interposer mechanism to punch
the holes but has as sprocket with its own stepper motor to feed the
tape. Different manufacturers did it in different ways.

>
> Question: did all tapes have indexing holes separate from the drive

Eh? The sprocket holes _are_ the indexing holes, surely?

> sprocket holes? Also is there a source for tape with sprocket holes anymore?

Every punch I've seen (and own) can punch the sprocket holes on
totally blank tape. Some insist on doing it (there's no way to punch a
character without a sprocket hole), for others the sprocket punch is
just another pin operated by the same type of mechanism as the data
punches and you have to fire the solenoid at the right time if you
want a sprocket hole.

-tony