I'd like to say it worked first time, but then I'd have no explanation for staying up until 4AM soldering...
First all-up test of the new feed auto start/stop circuit with the rest of the machine actually connected was successful though 😅 #meccano#hellschreiber
The Meccano Hellschreiber is suddenly getting a load of interest again, which reminds me that I still haven't done a proper write up sorry!
Someone uploaded a little bit of video of it in operation at the show though: https://youtu.be/7IEC_TuKrok?feature=shared&t=572
One further improvement I made for the show that I've not talked about yet was changing the felt ink roller for one made of ribbon (velvet ribbon specifically, with the fuzzy side inwards).
That improved the legibility further as it's reduced the over-inking issues I was having, but more importantly felt fuzz was constantly accumulating on the print spindle.
Here's a photo of the improvised thread cutting machine I used to cut the printing spindle. Shown with a spare spindle in the "chuck".
The cutter is a bit of 4mm drill shank with something approximating a cutting geometry ground onto the end with a rotary tool. It is spring loaded into the work, with a depth stop on the rear to set the maximum depth of cut.
Turning the handle rotates and translates the workpiece in the correct relationship to generate the thread pitch, and the starting position was repeatedly reset to remove all but the double-helix needed.
Also a bonus photo showing the print mechanism more clearly, and the final print quality achieved 😀
And while I'm at it, a couple of photos to show the construction of the character drum.
41 wheel flanges (one for each printing character, plus a slip ring contact) have the paint removed from their outer diameter, and are bolted together in a giant stack.
The pixel pattern for each character is encoded by patches of kapton tape.
@scruss I've never even made a contact via the computer. I could never find any activity, and it's only since doing this project that I've found there's weekly nets and activity nights etc! 🤦♂️
@scruss I tuned in this Sunday and could hear the signals, but by the time I'd got fldigi installed on the shack PC and figured out the sound card settings they'd gone. I might even get the machine hooked up by next week, now that all this attention's given me a kick up the behind to get on with it 😅
@zxguesser there was a dude in Louisiana who monitored 20 metres and was always up for a F-H QSO. You could hear him worldwide - his TX power was 2.5 kW. Super clean signal (in Canada, at least)
Don't think my mini-G5RV is in any state to reach the UK now,. otherwise I'd offer
@scruss I was intending to tune in to the net and lurk quietly while I tinker about to get the machine printing signals off air to begin with. There's a strong chance that all my crude comparator circuit will do is detect band noise and print a solid black stripe heh.
If only there was a hellscreiber beacon 😆
and works just the same for messages sent from the keyboard too 😁
This is by far the best I've ever had the printer working. I cut a new print screw and re-designed the tape path slightly the other day.
@zxguesser Oh lovely - when I saw the previous posts I'd assumed it was a tape punch; I've never actually seen a hellshreiber in operation. Given that keyboard, are you going for a full enigma clone as well?
@penguin42 everyone always mentions the enigma 😆
Dividing a disc/cylinder into 26 in Meccano is beyond my ability, and I've learnt my lesson about not building anything with a billion electrical contacts for a while!
@penguin42 I semi regret building the accurate QWERTZ layout, as it's hard enough to type at exactly 2.5 characters per second as it is, without someone hiding the Y key 😄
@penguin42 lots of swearing, and dropped washers...
It's a very tight sandwich of perforated strips and washers and spacers threaded onto rods. Built just wide enough for the nuts/bolt heads of each keybar to clear the next.
I'll attempt to get a photo, but it's all fairly dense inside
@penguin42 I intend to do a full write up with lots of photos on my website some time this summer before it gets dismantled.
I'm also hoping to get on air and try to make some contacts with it if I can interface it with the rig (and the motor doesn't wipe out the whole band with RFI 😅)
@penguin42 it's essentially clone of the original machine, within the limits of Meccano parts.
Just a slight simplification of having a single rocking contact rather than two separate parts.
Otherwise it's pretty much what's shown in the excellent diagrams at https://www.nonstopsystems.com/radio/hellschreiber-the-feld-hell.htm
I could never have built it without that website
@penguin42 similarly a different arrangement of gears, but all worked out to the same overall ratio for the critical relationship between character drum and print screw.
@zxguesser Oh that's excellent; the note about marking stuff only allowed to be opened in the field is interesting; I read in a book ages ago (I think RV Jones The most Secret war?) that the Germans tended to build stuff for untrained users, because having banned Amateur radio earlier, they had less tech people in the field.