Surface stock detectors

[dave1]

Can anyone tell me when these came into operation? I know that there are detectors at Finchley Road or has that been removed with the new signalling, Barons Court and Hounslow Central.

I think there were others in the past but they have been removed.

[drico]

Sept 29, 2015 10:53:19 GMT dave1 said:

Can anyone tell me when these came into operation? I know that there are detectors at Finchley Road or has that been removed with the new signalling, Barons Court and Hounslow Central.

I think there were others in the past but they have been removed.

The detector at Finchley Road has been removed, as has the crossovers between the Met & Jubilee lines.

[Nortube]

Don't know when they came in. In the normal way of only doing something after and incident (i.e. the forced platform approach speed restrictions after the Moorgate crash), I assume that it was after a big train decided it would go for a trip on the tube 

I remember when they had the mercury tubes dangling down at the entrance to platform 4 at East Finchley to stop the steam trains going attempting to go in the tunnel. Whilst a simple principle and very effective, lots of mercury spilling out over a train was probably not the best thing to happen in the later H&S era!

[hellocontrol]

Finchley Road came in 1939 and like drico has said has been removed as there is no surface stock that goes on the Jubilee.

Hounslow Central came in 1975 when the extension to Hatton Cross opened, the line was surface stock gauge up to Hounslow West east end of platforms but since then following some alterations Hounslow Central is now the limit.

Barons Court can't find a date but it was there in 1963.

I too remember East Finchley for the steam trains. I seem to remember something on the east end of the Central line but I am almost sure it was a electric train detector or something like that.

[dave1]

Thanks everyone

[railtechnician]

Sept 30, 2015 10:45:12 GMT Nortube said:

Don't know when they came in. In the normal way of only doing something after and incident (i.e. the forced platform approach speed restrictions after the Moorgate crash), I assume that it was after a big train decided it would go for a trip on the tube 

I remember when they had the mercury tubes dangling down at the entrance to platform 4 at East Finchley to stop the steam trains going attempting to go in the tunnel. Whilst a simple principle and very effective, lots of mercury spilling out over a train was probably not the best thing to happen in the later H&S era!

Ha! why worry about mercury being released from surface stock detectors, I wonder how often it happened? More worrying were the open current online relays with mercury dashpots which the AET/lineman had to keep topped up with mercury. The fingers used to dip into the pots to make contact and naturally the movement in or out had a tendency to displace mercury onto the track.

I doubt there are any around now but one never knows. The replacement relays did not use mercury at all. The last one I changed was at Earls Court rail current gap on the Picc eastbound at least 15 years ago. In my years as a signal TO I never had to top up one of the old relays but my supervisor kept a pot of mercury in the office just in case. To this day I imagine there is still plenty of mercury to be found on the job although the vast majority is in sealed glass contact units in Londex relays used to switch anything from 24vdc to 240vac and found in switchrooms, IMRs, CERs, relay rooms etc. They were very popular in the 1970s and 1980s for power changeover between LTE and LEB supplies where mains standby power was provided to maintain circuits during failure of the main supply. For new work modern solenoid controlled changeover contactors which do not use mercury from Telemechanique and other companies have been used for many years.

[hellocontrol]

I understand that the Mercury tubes have been replaced by switches on H&S reasons although they still look similar. I remember the tubes at Barons Court being hit while there was a possession on by a road railer the operator being totally unaware and the person responsible not being where they should have been. There were quite a few three penny bits and half crowns as this was on the Sunday and nobody was sure there was a spare, luckily there was.

[railtechnician]

Oct 1, 2015 10:52:01 GMT hellocontrol said:

I understand that the Mercury tubes have been replaced by switches on H&S reasons although they still look similar. I remember the tubes at Barons Court being hit while there was a possession on by a road railer the operator being totally unaware and the person responsible not being where they should have been. There were quite a few three penny bits and half crowns as this was on the Sunday and nobody was sure there was a spare, luckily there was.

Yep they were replaced years ago some years before I retired. My recollection is that some kind of flexible cable was used, something that would snap easliy along with the tube as it broke.