"special measurement system"

[rincew1nd]

Mar 10, 2015 19:49:18 GMT @aetearlscourt said:

There is a special measurement system which detects a 73 stock and thus the route to North Ealing clears anything else and the train op has to leave the cab and operate a plunger to get it to clear.

I was tempted to put this on the District board in honour of District Dave. I'm intrigued by this "special" system. Is it simply a height gauge or something more sophisticated to detect 73ts in particular, if the latter what sort of thing is it?

[bigvern]

currently S stock are not permitted on the Rayners Lane Branch, and must go to Ealing Broadway, I'm not exactly sure how it detects, but I know plungers have been put South of Hanger Lane Junction, this may be by axle counter or linked to the scanning system which occasionally fails, linked with Earls Court control room. So if any train other Than a 73 needs to proceed to North Ealing the plunger has to be operated to get the signal release required, would only apply to Engineers trains and odd stock moves, D stock can still go to Rayners Lane, but often are revered at South Harrow in recent times when this happens and the wrong route is selected.

[Colin]

It can't be axle counters as trains of different lengths could potentially have the same number of axles!!

The magic measurement is 110 metres and is as stated, to prevent an S stock being inadvertently routed towards North Ealing - there is the caveat though that anything can happen during failure conditions, so never say never. Given that its a specific distance, I would think the obvious solution is to use 110m of track and put a block joint at either end.....

[norbitonflyer]

D stock and 1973 stock both have 24 axles, and are both less than 110 metres long (109.2 and 105.7, give or take 25cm if there is a double-ender in the formation). An S7 is about 10m longer, and has 28 axles. The overall wheelbases in each case are a little shorter, which is what matters if you are detecting a train through a track circuit.

"detects a 73 stock and thus the route to North Ealing clears anything else" Surely that should be that the route clears for nothing else?

[Deleted]

Its done through the track circuits which pick up a special 73TS relay which thus allows the route to be set to North Ealing.

[norbitonflyer]

Mar 11, 2015 15:28:19 GMT norbitonflyer said:

D stock and 1973 stock are both less than 110 metres long (109.2 and 105.7, give or take 25cm if there is a double-ender in the formation).

As an aside, I note that the lengths quoted in Wikipedia make a D stock DM 25cm longer than a non-driving vehicle (trailer or UNDM), whilst on 1973 stock the DMs are 20cm shorter than a non-driving vehicle. Is that right, and if so why the difference?

D stock 18.37m/18.12m
1973 17.473m/17.676m

[Deleted]

Mar 10, 2015 22:51:47 GMT bigvern said:

currently S stock are not permitted on the Rayners Lane Branch, and must go to Ealing Broadway, I'm not exactly sure how it detects, but I know plungers have been put South of Hanger Lane Junction, this may be by axle counter or linked to the scanning system which occasionally fails, linked with Earls Court control room. So if any train other Than a 73 needs to proceed to North Ealing the plunger has to be operated to get the signal release required, would only apply to Engineers trains and odd stock moves, D stock can still go to Rayners Lane, but often are revered at South Harrow in recent times when this happens and the wrong route is selected.

Its not linked to the scanning and the only axle counters on SSL is the Chesham branch and Neasden depot

[domh245]

Mar 11, 2015 16:31:49 GMT norbitonflyer said:

Mar 11, 2015 15:28:19 GMT norbitonflyer said:

D stock and 1973 stock are both less than 110 metres long (109.2 and 105.7, give or take 25cm if there is a double-ender in the formation).

As an aside, I note that the lengths quoted in Wikipedia make a D stock DM 25cm longer than a non-driving vehicle (trailer or UNDM), whilst on 1973 stock the DMs are 20cm shorter than a non-driving vehicle. Is that right, and if so why the difference?

D stock 18.37m/18.12m
1973 17.473m/17.676m

Looking at the Rolling Stock Data-Sheet, those values do look right. As for the difference in length, I have a suspicion that it is partly down to the way in which the body shells are built (to a lay observer). With the D stock, a DM car has got all 4 doors, but with half of the section between the last door and the car end replaced with a cab unit. On the other hand, the 1973 stock seems to have had it's cab section bolted on to what would be the dividing wall between the end seating section and the end door, and because the cab door appears to be slightly smaller than the passenger door, you suddenly end up with a smaller car.

[Deleted]

Mar 10, 2015 22:51:47 GMT bigvern said:

currently S stock are not permitted on the Rayners Lane Branch, and must go to Ealing Broadway, I'm not exactly sure how it detects, but I know plungers have been put South of Hanger Lane Junction, this may be by axle counter or linked to the scanning system which occasionally fails, linked with Earls Court control room. So if any train other Than a 73 needs to proceed to North Ealing the plunger has to be operated to get the signal release required, would only apply to Engineers trains and odd stock moves, D stock can still go to Rayners Lane, but often are revered at South Harrow in recent times when this happens and the wrong route is selected.

I have seen this plunger several times with a notice saying for engineering train use only or something.

[fish7373]

Hi to your answer about this I have the information out of the traffic circular, D78 and 73 t/stock can go up the Rayners lane branch because there under or 110m, there is a measuring track circuit on the line if a long engineering trains is longer they have to operate the long train running plungers , which are position and Ealing common platform at signal WM22 two hand plungers one at schoma loco cab height and other one at battery loco height, next set is at signal WM20/21 two the same as signal WM22 but with extra one at ground height, there is no track wheel treadles or plungers, the S7 are not signed off to go up the Rayners lane branch my interfere with the signalling on the line, it’s in the traffic circular but cannot publish it, so hope you can understand this, thanks FISH7373

[Deleted]

Through past experience the S stock does not interfere with the current signalling but LU like to be double safe and has declared its not compatible with certain signalling equipment.

[rincew1nd]

Thanks fish7373, so the "special" system actually is only a train length measurer. I was envisaging something that measured length, counted axles and checked for height. So an S7-1 (if one existed) would be able to happily trundle through, only stopped by the professional at the front, but an engineering train has to stop and press a button.

[domh245]

Is this similar to the system used at Edgware road during the changeover period from C stock to S stock?

[Tom]

Similar, but not identical. Edgware Road used a track circuit and a position detector to define the train measuring section, at Ealing Common it was three track circuits, with the middle one being occupied with the ones either side being clear.

The measuring system is primed by a train in the platform at Ealing Common. On departure the measurement is made and the result is then 'stored' in the signalling system until the train concerned has passed the junction signal at Hanger Lane, at which point it is forgotten about.

When the concept was originally considered my preference whould have been for the measuring circuit to inhibit an auto route call on WM21, thus allowing the signaller to override the measuring arrangement, but that would have involved considerably more work to design and install.

[Tom]

Mar 11, 2015 14:12:54 GMT Colin said:

The magic measurement is 110 metres and is as stated, to prevent an S stock being inadvertently routed towards North Ealing - there is the caveat though that anything can happen during failure conditions, so never say never.

I think the track length in the end was something like 108.5m, but it was near enough! The caveat is quite true - with a failure of one of the track circuits it is possible to wrongly measure and we did prove this during the testing.

[Tom]

Mar 12, 2015 18:47:27 GMT @aetearlscourt said:

Through past experience the S stock does not interfere with the current signalling but LU like to be double safe and has declared its not compatible with certain signalling equipment.

Actually, it was Bombardier's recommendation. They say the traction package can affect any track circuit operating below 100Hz, which is why the 50Hz track circuits on the Wimbledon branch also had to be replaced.

[Deleted]

It never made a difference running over 33 1/3hz when they sent one to Upminster in cancelled Engineering Hours one night