IBM Factory Clock

The third wire had a bunch of pulses every hour to reset the hour hand to "zero" just before the epoch. More interestingly (some of, maybe all?) the master clocks where spring driven pendulum jobs and would run for ages if the power was cut, upon restoration they put out enough pulses to set all the slave clocks back to the right time. mind you my Magneta PO36 system hasn't had any "dial scatter" ever.

[TonyDuell]

I once got to see inside one of those master clocks (not an IBM). It was indeed spring driven with a mains motor to rewind it. The motor also drove the mechanism that tilted the mercury switches to generate the pulses to the slave clocks (this particular system had a pulse of one polarity one minute, then a pulse of the opposite polarity the next minute and so on, so there were a pair of changeover mercury switches). If the mains failed the motor stopped running, the clock continued. And there was an complex differential gear system that 'remembered' the time when it had sent no pulses. When the motor restarted it drove said differential gear train until it had caught up, generating pulses all the time thus setting the slave dials to the right time.

[mark_in_manc]

Some of the IBM / ITR master clocks have that catch-up arrangement (mine does), and some don't. It's great fun when it's time to put the clocks back, as the thing clonks away for 11 hours worth of minutes to bring the slaves back to the right time. Perhaps it's worth noting that this is a different mechanism from that to pick up missed minutes every hour, which we have been discussing.

The mainspring on my master lasts for about an hour - it is wound by quite a clever eccentric on a 240v motor / gearbox combo, which operates a ratchet. Once the spring is wound, the ratchet 'misses', so the mainspring is not overwound.

[Nickthedentist]

Good advice from everyone, as usual! Keep it original if at all possible. Or else you'll be gutting lovely valve radios to fit DAB modules with loadsa blue LEDs, and sticking LCD panels in TV22s before you know it!

I have loads of slave clocks, run in various ways:

(1) Original, pendulum-controlled master clocks. Lovely, not necessarily expensive (I have a couple that cost about £50), but big and often noisy.

(2) The PIEXX device mentioned above. Brilliant bit of kit, beautifully made, and surprisingly affordable when I splashed out on one about 10 years ago.
https://www.piexx.com/index.php?main...6khbsib2lmigq1

(3) One of Mark Lines' clever gadgets. More versatile and less costly than the above but not quite so professionally produced. Uses separate batteries for the micro and driving the clock solenoid. I would send Mark pics of your movement and ask for advice.
http://www.electric-clocks.co.uk/Imp...ockdrivea.html

(4) A home made thing based on CMOS 4000-series chips and a quartz crystal, from designs published in the 1980s in The Maplin Mag. Scanned and posted on this site by ianm. Works well and dirt cheap, but a bit of a labour of love because you have to design your own Veroboard layout etc.
https://www.vintage-radio.net/forum/...5&postcount=26

Wonder whether the author was "our" David Church, formerly "unrealdave": https://www.vintage-radio.net/forum/member.php?u=22509 ?

Other suggestions have included a 1rpm synchronous motor with a cam and microswitch, or a quartz clock mechanism with the seconds hand operating an optointerruptor.

Good luck,

N.

as the thing clonks away for 11 hours worth of minutes

I just stop mine pulsing the slaves for an hour, or for going forwards give a once a second pulse for two minutes (and two seconds!). There is a knife switch in the case to do this, my addition.

[osx86apple]

I think it needs one of these (currently in my kitchen)

[Electronpusher0]

Originally Posted by Nickthedentist

(4) A home made thing based on CMOS 4000-series chips and a quartz crystal, from designs published in the 1980s in The Maplin Mag. Scanned and posted on this site by ianm. Works well and dirt cheap, but a bit of a labour of love because you have to design your own Veroboard layout etc.
https://www.vintage-radio.net/forum/...5&postcount=26

.

Sounds like someone needs to lay out a pcb in KiCad.......

Peter

[Radio Wrangler]

Originally Posted by osx86apple

I think it needs one of these (currently in my kitchen)

Silly thought.... you could distribute pulses from the mechanical clock via the internet and synchronise clocks all over the country all keeping mechanically-regulated time.

However, the chances of keeping a link going reliably long enough bring it all crashing down and a local program could get time from an internet time server and handle the clock easily enough. It's just the thought of a world wide synchronome/IBM/Gents system...

David

[David Simpson]

Followed Mark's advice, and right enough the wee knurled nut unscrewed off easy enough using my bronze pliers. Revealed the square shaft(aprox. 4mm or 5/32" across the flats). Yep, the hour hand seems to be a push-fit (no wee circlip or anything) but reluctant to come off. Have left it with a tiny amount of releasing oil on it meantime, whilst awaiting further advice.
Me thinks that my pal who owns the clock would definitely like to acquire an old working 2nd hand original master clock, as he has another similar slave clock(awaiting my attention). Doesn't have to be Greenwich Museum or NPL quality in accuracy or appearance. Failing that, I guess one of Mark Lines products fitted inside a nice empty period pine or mahogany lidded box might do.
The solenoid works fine off my 24V DC supply, and draws 30mA.

Regards, David

[McMurdo]

I made a little 'master clock' test box to drive the Gent system, purely for test purposes, as we used to fix the clocks for various hospitals. Not too difficult even for a dunce like me! A 555 timer, a pair of DPDT relays and a decade counter.
The Gent system used (from memory) 24V dc pulses of alternate polarity.

The cardboard box factory up the road had a slave clock system but if a clock went wrong they used to replace it with a battery operated MSF one instead. (which I suppose is a sort of master-slave clock system itself!).

[Radio Wrangler]

I'd definitely do an electrical fix using the original mechanism, David. I don't fancy your chances of finding a quartz movement with output shafts to fit those hands.

David

[David Simpson]

Right enough David, I'm now putting out feelers for a 2nd hand original suitable master clock. I know that I've praised Drew Pritchard's Restorers in the past(compared to one or two numpties on "the Repair Shop"), but I've never approved of their " always fit a quartz mechanism" procedure for factory clocks.
Have now gently removed the hour hand & completely removed the mechanism from the dial. Have completed a prolonged 24V on/off pulse procedure for several minutes, & everything is working fine. Shall now return to the bakelite case & get it nicely polished up.

Regards, David

My master clock has an interesting synchronizing mechanism, once a day a pulse "zeros" the heart shaped cam keeping the 30 second pulse house clocks set. The pulse comes from a thing I made that receives MSF (the NPL time signal), originally this signal came from the GPO at 11:00 every day. However there is a bug, it could be two seconds out if the clock was a wee bit fast so I pulse twice, once a few seconds before the epoch and then again at the hour.

Master/slave clock systems are great fun, luckily I don't have room for more than one!

[mole42uk]

I’m interested in this thread. I have the remains of a pulsed clock that I’m told was in the East German parliament (Palast der Republik) building in Berlin. I have never got around to running it but the mechanism, coils and hour & minute hands are there.....

[David Simpson]

I've put a "Wanted" thread post out. Bin given a Facebook sale link - someone down south is flogging a Master for 400 quid !
Just had a shufti on eBay - someone else has just offered a "GENTS GPO George VI Electric Pulse Master Clock" for £160(negotiable). But - would the Gents be compatible with this IBM, I question ?
My pal is hinting, after a long furlough, that all he might be able to afford is a cheapo Quartz conversion jobbie. I'm just doing a cosmetic restoration jobbie, plus testing & assessing the mechanism - bucksheesh. Cant really lumber him with significant costs. However, this has been a fascinating learning exercise for an old fart.

Regards, David

[Dave Moll]

If such a "conversion" is unavoidable, is it possible to make it reversible?

Also, if a genuine master clock isn't affordable, what is the possibility of a cheap circuit simply to create the correct pulses, which could even be hidden in the back of the clock. Adjustment pulses could be provided manually.

I would go the Arduino route with a "relay shield" such as...
https://www.amazon.co.uk/ARDU-Arduin.../dp/B076B1WBKF
https://www.amazon.co.uk/F-Mingnian-...strial&sr=1-23

They are very easy to programme and if you get the Chinese knock offs very cheap (with a two week wait). I don't bother making microprocessor boards anymore, just pick up one of these. If you need a hand with the programme just shout.

[ThePillenwerfer]

I'm not anti-quartz but the trouble with that will be either fitting the existing hands to a high-torque quartz movement or finding suitable replacements that will fit on it.

In this case I'd agree with Merlin as the cost involved in making an Arduino-based pulser wouldn't be much more than that of a quartz movement and possibly new hands.

My Arduino Uno is a knock-off that cost less than three quid - currently available from a UK seller for £4.77. The even cheaper, and smaller, ProMicro along with a Real Time Clock module would also be up to the job.

By the way, digital electronics is way out of my comfort zone too but these things are well-documented and there's help available.

[M0FYA Andy]

I'm not anti-quartz in a modern context, but I am anti-quartz when it is used to convert a perfectly serviceable historic slave clock! It is akin to using a DAB module to 'restore' a vintage radio or an Ikea leg to repair your Chippendale chair!

I'm not convinced by any argument about making a conversion reversible, we all know the likelihood is that somewhere along the line the converted clock will get separated from its original mechanism, somebody will not understand what the 'orphan' mechanism is and it will get chucked out.

A GPO Master Clock (Clock 36) would not be suitable as it doesn't provide 60 second pulses, although a relay circuit could be used to 'lose' alternate pulses. (A relay or solid-state interface circuit is in any event required, as the Clock 36 contacts aren't sized to drive slaves directly, in GPO service they operated a 'GMT34' relay unit to drive the exchange).

I believe your best answer is to use a modern circuit to generate suitable pulses to drive the slave without any modification, in the absence of a suitable original master clock.

Andy

[David Simpson]

Right enough Andy & guys, I'm on your side regarding vintage authenticity. Will do my best to persuade my pal to see sense. Early days yet, & I've had one or two encouraging replies to my Wanted post.

Regards, David