towerman
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Post by towerman on Oct 22, 2005 20:00:05 GMT
When new C & 72TS had speed sensing which stopped the deadman operating below 4mph,at the time it gave a lot of trouble.Is it still fitted or has it been removed?
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Deleted
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Post by Deleted on Oct 22, 2005 20:53:34 GMT
The C stocks certainly still have speed sensing, although I've personally never had any problems with it!
The C stock (I think) is set at 7mph. If the train is below 7mph, the TBC can be released in Rheo 1 and hold (all other positions will still cause a loss of train line air).
Occasionally I've had a C stock where I've let the TBC go at about 5mph and it's still broke the circuit, therefore came up in a heap, but that's not a real problem, as long as I can release the deadman once the train is stationary!
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solidbond
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Post by solidbond on Oct 22, 2005 23:37:08 GMT
Hmm - interesting Towerman. As far as I am aware, on C stock, the speed sensing wasn't linked to the Deadman until the stock was refurbished in 1991 - 1994. Certainly when I worked on them from 1988, there was no connection with speed sensing and the deadman. I also have some articles from the Evening Standard, from the early 80's, about a problem with the deadman not always being operative, and there was talk about a strike, or guards riding with the driver. The problem was that, in Rheo 1 & Hold the deadman did not operate at any speed. The work-around that was introduced was the 'I'm breaking the rules with a naughty word-it' switch, which has been discussed before. It's official name was the Traction Control Cut-out Switch. Basically, when the TCCOS was cut in you could motor, but not release the Deadman in any position without losing air, but when it was cut out, you could release the Deadman in Rheo 1 & Hold, but the motors wouldn't work!
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Post by Christopher J on Oct 24, 2005 1:29:24 GMT
Does Speed Sensing calculate the speed of the Train by the speedo/spinning of the wheels?
I was just thinking, if the wheels of a C stock (or 72) lock at (for example) 35mph, the speedo will drop to 0mph - could you then technically drop the handle in Rheo & Hold 1 and not blast all of the Trainline out of the Deadmans Valve if the wheels are locked?
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Colin
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Post by Colin on Oct 24, 2005 1:51:55 GMT
Does Speed Sensing calculate the speed of the Train by the speedo/spinning of the wheels? I was just thinking, if the wheels of a C stock (or 72) lock at (for example) 35mph, the speedo will drop to 0mph - could you then technically drop the handle in Rheo & Hold 1 and not blast all of the Trainline out of the Deadmans Valve if the wheels are locked? Wheels lock at 35mph? - now that's a serious defect!! ;D ;D I can only speak for C stock: If speed sensing is lost for any reason, the train will assume it is doing a speed higher than 7mph - therefore if the deadman is released in rheo1 & hold, the trainline air will be lost to atmostsphere. Sorry, not sure where speed sensing get's it's info from. |
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towerman
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Post by towerman on Oct 24, 2005 2:51:08 GMT
I believe it's linked in with the speedo.
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Post by q8 on Oct 24, 2005 6:54:30 GMT
Does speed sensing on the 'A' stock work in the same fashion as 'C' stock?
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Colin
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Post by Colin on Oct 24, 2005 20:28:56 GMT
Well, it works in a similar manner on D stock - in that if speed sensing is lost, the deadman will work in service1 under 7mph.
On that basis - I would assume that all stocks work on the same or similar principal.
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Deleted
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Post by Deleted on Oct 25, 2005 2:43:20 GMT
Solidbond has tried to educate me on how this works several times, but I have a memory like a sieve! ISTR there is something on the axle from which the speed sensing gets its information, but for the life of me I can't remember what it's called!
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solidbond
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Post by solidbond on Oct 25, 2005 7:11:01 GMT
Solidbond has tried to educate me on how this works several times, but I have a memory like a sieve! ISTR there is something on the axle from which the speed sensing gets its information, but for the life of me I can't remember what it's called! There is a perception head, which is located on the cover for the driving wheel cog. It is this that detects the speed, and sends the information to the speed sensing unit. It is possible, and has happened, for this to become loose, which will cause the speed sensing unit to receive no information, thus thinking the train is not moving, even when it is. In that situation, it is possible to release the deadman in Rheo 1 & Hold, without losing air, as the train still thinks it is stationary. The clue that this has happened is that the speedo reads zero the whole time, and when you release the deadman in Rheo 1 & Hold there is no loss of air. |
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Deleted
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Post by Deleted on Oct 25, 2005 10:36:24 GMT
Now, this happended to me a few months ago. Leaving East Putney going west the speedo wouldn't budge off zero and stayed like that until Wimbledon. I had to go back to Edgware Road (other end OK), then down to Earls Court with it still broken before the TT met me. He got down on the track and seemed to just give it a whack!
It never occurred to me to try releasing the deadman, but isn't this quite dangerous? If the deadman were released in Rheo1 & Hold at 40mph it would take a long time for the train to stop. But the DISI says "train to be withdrawn from service if Train Technician cannot rectify" which I read as "keep going in service until the TT meets you", which is what I did. Not sure I'd do that again now!
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