1960's Tube Train control gear in Secrets of the London Underground

[Valvepower]

Hello,

Had to think twice where to post this but I feel it’s the right place.

I was watching the Yesterday TV programme Secrets of the London Underground last night at 9:00 with Tim Dunn and Siddy Holloway looking around the hidden parts of the Tube Train network in London.

About 39 Mins into the show, they had a short piece on the development of the Automatic control equipment for the Tube Trains in the early 1960’s.

There was a great shot of the designer of the system in the early 1960’s in a train testing the equipment with what I think was an early Levell Signal generator and Advance scope.

They did very briefly describe the method of operation where tones were sent down the rails, which were recovered and decoded by the control gear.

There was some nice shots of the ‘old-school’ control gear with vitreous enamel resistors etc. From memory I think there is display in the London Transport Museum, put together by the designer.

I think it’s on again tonight at 9:00pm on Yesterday.

Terry

[Dave Moll]

Thanks for the heads-up. I meant to catch it yesterday (no pun intended), so it's good to know it's repeated tonight.

[Lucien Nunes]

If you watch the upcoming power episode you should see me demonstrating a mercury arc rectifier. My idea was to use the working glass bulb rec. to explain the operation of the big steel tank one in the museum that we were standing next to, but had difficulty steering the discussion in that direction. The steel tank rec. didn't seem to grab their interest. I've no idea yet how it has turned out.

[John M0GLN]

Fascinating series, I've yet to see Lucien and the mercury arc rectifier but I've just watched the Brompton Road Station ( closed many years ago ) episode, this also shows the work being done to extend the Central Line and build Wanstead Station, this was delayed due to WW2 when the tunnel was used as a 5 mile long factory for Plesseys to build radio equipment including R1155s, photos of the assembly line and a R1155 are shown in the episode.

John

[wireman]

I was really interested in the segment about automated trains, I didn't know how far back that went. And we are in the year when it was all to be automated..

https://www.bbc.co.uk/news/uk-england-london-17510918

I'm sure there are lots of interesting things that just don't get shown because the production company feel they would be too technical for a general audience. Connumication and signalling systems for example.

[emeritus]

My late mother worked a capstan lathe in the Plessey underground factory. When I was working at Plessey in the 1970's, one of our technicians, on a periodic visit to the scrap bins, found the original scale drawing on very grubby linen drawing cloth of the factory planning map of the tunnels, showing what was being made where: the drawing archive had obviously had clear-out. Several of us had dyeline prints made. I later contacted the London Transport museum and sent them a PDF copy: apparently they had virtually no information about the factory other than drawings of the flood doors where the tunnels go under the River Roding.

Most of it was dedicated to mechanical engineering: lathes, drills, threadmills, grinding, Pesco fuel pumps, Coffman starters for aircraft engines, Breeze machines. The only electronics activity mentioned was a small length of tunnel at Gants Hill for coil winding. Of course, actual working might not have got updated on the drawing. The pdf is too large to post here.

[its ur aerial]

I am not sure if it`s reopened, after Covid but one or two days a year, they open their Museum storage Depot at Acton to the public.
It`s a must see unbelievable interesting.

Ken, G6HZG.

[hamid_1]

Good news - it looks like the Acton depot will have a few open days this year. (The Acton depot is not normally open to the public, but there is a smaller museum in Covent Garden which is open daily.)

https://www.ltmuseum.co.uk/whats-on/depot-open-days

The next dates are 2nd and 3rd July 2022, and again on 22-25 September.

I visited the Acton depot a few years ago. It's awesome! Plenty of old electrical gear, telephones, ticket machines, historic vehicles and a library of vintage advertising posters are among some of the highlights.

I saw last night's episode of Secrets of the London Underground (featuring Blake Hall station on the Epping-Ongar branch) and noticed that some of the scenes were filmed in the Acton depot. I'll have to look out for the programme featuring the mercury arc rectifier. I was told there was one in the Acton depot but didn't see it when I visited.

[Roger Ramjet]

Originally Posted by Lucien Nunes

If you watch the upcoming power episode you should see me demonstrating a mercury arc rectifier. My idea was to use the working glass bulb rec. to explain the operation of the big steel tank one in the museum that we were standing next to, but had difficulty steering the discussion in that direction. The steel tank rec. didn't seem to grab their interest. I've no idea yet how it has turned out.

Hi Lucien,
Yes I will look out for you (nice to put a name to a face). Did the mercury arc rectifier provide DC to the 3rd Rail or were they fitted on the actual trains i.e. to convert AC from the 3rd Rail to DC for the traction motors ?
Rog

[Valvepower]

Its heartening to see all the replies – thanks.

The nearest I’ve got to mercury rectifiers was building a magnetizer using an EEV Ignitron to switch magnetizing head coil. I’ll never forget the ‘thump’ when this was contraption was fired.

The original head coil was wound on short length of drainpipe using the lathe in the workshop. From memory the CSA of the cable was 1.5mm or thereabouts. There was something like a few hundred turns.

I can’t remember the value of the capacitor bank but something like 10,000uF charged to something like 400V was needed.

This was about 30 years ago, however now the health and safety officer would have kittens and get me banned from the factory if I were to try and repeat this contraption

… Good fun though!

Lucien, I’ll be looking out for you. The word has been passed around there will be some good ‘ole power stuff in an up-and-coming episode.

Ooh, Siddy and a Mercury Arc rectifier - that's a what I call a good evenings viewing

Regards
Terry.

[Lucien Nunes]

There have been main line AC locos with on-board mercury arcs, however the tube uses DC supply. Power was distributed from the generating stations at 11kV 33.3Hz AC and transformed and rectified in the trackside substations. Early subs used rotary converters (hence the low frequency) later replaced with mercury arcs, followed by silicon starting in the 1960s.

There is a steel-tank rectifier on display at Acton, in the corner with the power switchboards. Despite its size it is hard to spot as parts of it are hidden behind other exhibits. There is a glass bulb rectifier too but neither the bulb (which is crated) nor its cabinet are on display yet. Hints have been dropped that I need to get around to checking and fitting the bulb.

[Roger Ramjet]

Originally Posted by Lucien Nunes

There have been main line AC locos with on-board mercury arcs, however the tube uses DC supply. Power was distributed from the generating stations at 11kV 33.3Hz AC and transformed and rectified in the trackside substations. Early subs used rotary converters (hence the low frequency) later replaced with mercury arcs, followed by silicon starting in the 1960s.

There is a steel-tank rectifier on display at Acton, in the corner with the power switchboards. Despite its size it is hard to spot as parts of it are hidden behind other exhibits. There is a glass bulb rectifier too but neither the bulb (which is crated) nor its cabinet are on display yet. Hints have been dropped that I need to get around to checking and fitting the bulb.

Back in the mid 60's when we were lads, we were fascinated by a strange green glow emanating from within the local telephone exchange. It reminded us of a Frankenstein film ! Later on when are started work at the GPO as a TTA, I discovered the green glow was created by a 3 x phase mercury arc rectifier providing DC for the exchange batteries.

Rog

[dglcomp]

3rd/4th rail almost exclusivly uses DC due to the skin effect, overhead uses a mixture of both but 25kV AC at 50/60Hz is really the standard, although some freight lines use 50kV and some of Europe uses 15Kv 16.7Hz as due to the previous use of rotary convertors.

One new development is to use static convertors rather than transformers for the 25kV supply as this means tehy can use all three phases and as such lower transmission line voltages can be used as they no longer have the issue with un-equal loading of phases.

[Synchrodyne]

The European use of 15.7 Hz single-phase was done to facilitate the use of AC commutator motors, which work much better low frequencies. The original choice was 15 Hz, moved up to 16.7 Hz to facilitate easier conversion from 50 Hz in motor-alternator units, although there was some generation at 16.7 Hz, as well. In the USA, 25 Hz was used, not as good as 16.7 Hz for the AC motors, but the fact that it was an existing industrial frequency at the time (c.1905) was persuasive. In the US there was some use of rotary frequency converters (that is devices with electrical, not just mechanical coupling between input and output) to go between 60 and 25 Hz for industrial purposes, although for the railways the use of motor-alternators, to go from three-phase 60 Hz to single-phase 25 Hz, was more likely. The development of 50/60 Hz single-phase electrification, early experiments aside, was essentially a post-WWII phenomenon, greatly aided by Westinghouse’s development of ignitron rectifiers suitable for traction purposes. SNCF, France, did the early “heavy lifting” in terms of 50 Hz application development, with JNR, Japan soon following. Ignitrons (and excitrons, better where regenerative braking was required), could be (just) adequate in traction service, but were rather quickly superseded by germanium and then silicon solid-state devices from the late 1950s. ASEA, Sweden, was a prime mover there.

Any more than that would probably get us off-topic, if it hasn’t done so already.


Cheers,

[Roger Ramjet]

Originally Posted by wireman

I was really interested in the segment about automated trains, I didn't know how far back that went. And we are in the year when it was all to be automated..

https://www.bbc.co.uk/news/uk-england-london-17510918

I'm sure there are lots of interesting things that just don't get shown because the production company feel they would be too technical for a general audience. Connumication and signalling systems for example.

Yes its a shame they did not go into a bit more detail. The OP mentions control tones being sent down the rails & I get that, but my poor old brain cannot get around as to how effective they would be noting the electrical noise / transients etc. generated whenever the 3rd rail sparked (as often viewed on the programme.

Rog

[stainless]

My memory of tones and the Victoria line is that they were AC magnetic fields, at the tone frequency. They were picked up fairly clearly by the replay head in a Walkman cassette player.

[Mr Moose]

Hello,
Some information on the Victoria line Automatic Train Operation system from the 1960s here:- http://www.trainweb.org/tubeprune/Vi...Line%20ATO.htm
Yours, Richard

[russell_w_b]

Originally Posted by Synchrodyne

'The original choice was 15 Hz, moved up to 16.7 Hz to facilitate easier conversion from 50 Hz in motor-alternator units, although there was some generation at 16.7 Hz, as well. In the USA, 25 Hz was used, not as good as 16.7 Hz for the AC motors...'

Would this be the origin of how 16.7Hz came to be used as a telephone bell ringing frequency until superseded by 25Hz, do you think?

[Radio Wrangler]

Originally Posted by russell_w_b

Would this be the origin of how 16.7Hz came to be used as a telephone bell ringing frequency until superseded by 25Hz, do you think?

Unlikely. Exchanges were designed to be self-sufficient from their -48v batteries. Everything had to continue without even a glitch if the incoming mains failed.

Also phone system development was at a time when mains voltages and frequencies and even coverage were not entirely uniform.

David

[russell_w_b]

Originally Posted by Radio Wrangler

Unlikely. Exchanges were designed to be self-sufficient from their -48v batteries. Everything had to continue without even a glitch if the incoming mains failed.

But back then, telephones used local batteries and local magneto signalling. Now, the two-pole telephone magneto generates a nominal peaky 16.7Hz, and hence ringing was not dependent on the exchange supply: I'm talking about a time before CB signalling was introduced.

It seems too neat an occurrence for a telephone bell and a driving magneto to operate on 16.7Hz concomitant with a handy a.c. works or traction supply being 16.7Hz also.

Sub-cycle ringers used 50Hz (by then) mains-frequency resonated at 1/3 that frequency to get 16.7Hz, which is electrically convenient, but if a heritage supply had not been available at 16.7Hz, would telephone bells have been designed to ring at 50Hz? I know the ringing isn't as pleasant as at the lower frequency but folks would've got used to it as it would be all they'd known.