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Post by countryman on Aug 3, 2020 8:23:30 GMT
I'm not sure this is the best location for this. Please move if necessary. I accidentally came across this this morning. It is an article about runaways on the Underground. I certainly wasn't aware of these, and I don't remember seeing anything about this on here. hydeparknow.uk/2019/02/10/runaway-tube-trains/ |
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class411
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Post by class411 on Aug 3, 2020 8:38:57 GMT
Weird.
I'd always thought that trains were designed so that the brakes were naturally full on, and were released by air pressure.
Thus, unless the driver forgot to discharge the air pressure (although one would have thought that turning of the master switch [or whatever it's called on a train] would cause this to happen automatically, this sort of thing would be all but impossible.
Having said that, I've often wondered why the pressure gauge visible in carriages indicates higher pressure when the brakes are activated.
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Post by Dstock7080 on Aug 3, 2020 9:48:02 GMT
Weird. I'd always thought that trains were designed so that the brakes were naturally full on, and were released by air pressure. Having said that, I've often wondered why the pressure gauge visible in carriages indicates higher pressure when the brakes are activated. On conventional Stock, those without SAPB Spring Applied Parking Brakes, the gauge in the train car was the brake cylinder pressure, higher pressure = harder brake. On rheostatic brake trains, motor cars the pressure will initially rise then fall away as the rheostatic brake takes over. The first point is answered by, if the compressors fail or stop topping up the train brake system, the brakes will eventually leak off. (fails to mention the District R Stock at High Street Kensington!) |
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Deleted
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Post by Deleted on Aug 3, 2020 10:42:19 GMT
Fails to mention about the motorised trolley incident on the Met either late 80’s or early 90’s where members of staff were killed around Choleywood i belive it was
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Post by countryman on Aug 3, 2020 11:18:03 GMT
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Post by greggygreggygreg on Aug 4, 2020 18:31:23 GMT
Weird. I'd always thought that trains were designed so that the brakes were naturally full on, and were released by air pressure. Thus, unless the driver forgot to discharge the air pressure (although one would have thought that turning of the master switch [or whatever it's called on a train] would cause this to happen automatically, this sort of thing would be all but impossible. Having said that, I've often wondered why the pressure gauge visible in carriages indicates higher pressure when the brakes are activated. As a previous poster stated more modern stock has spring applied parking brakes. Older stock (at least on the mainline - not sure if the Underground was the same) has manual parking brakes which had to be manually applied. The brakes on older trains worked by having equal pressure in the brake cylinders and the brake pipe. So if there was compressed air in the cylinder and normal atmospheric pressure in the brake pipe, then the brakes would apply. Thus if the train came apart, the brake pipe would vent to atmosphere and the brakes would apply. If there was compressed air in both the cylinders and brake pipe, the brakes were released. If both were at atmospheric pressure, the brakes were released. So when a train was off the juice, the cylinders would eventually leak their pressure, causing a train to run away if there was no handbrake applied |
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Post by spsmiler on Aug 4, 2020 22:35:06 GMT
Having read the pages I was surprised to learn that there was sufficient material for the two pages. I did not realise there had been so any run-aways!
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hobbayne
RIP John Lennon and George Harrison
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Post by hobbayne on Aug 4, 2020 23:14:02 GMT
I knew the Piccadilly Line Bag-on-the-handle driver very well. He was at Northfields.
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Post by philthetube on Aug 6, 2020 1:19:53 GMT
with older stock, none still around, the brakes would leak off over time when stabled, so if left on a slope would run away.
This was mitigated against bynusing scotch blocks and/or rail anchors, A scotch block was a wooden chock placed under the wheels and a rail anchor clamped to the track and attached to the front of the train.
I will be surprised if someone does not produce a pic shortly.
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roythebus
Pleased to say the restoration of BEA coach MLL738 is as complete as it can be, now restoring MLL721
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Post by roythebus on Aug 7, 2020 0:23:45 GMT
His article doesn't mention the runaway on the W&C in BR days when they ran a single car train in the off-peak. One was brought into service, the brake didn't work at Waterloo, the train continued down the slope, up the other side, then back and forth until it eventually came to a stand in the bottom of the tunnel.
The brake rigging had been disconnected for repairs and had not been reconnected but was allowed back into service. After that they stopped using single car trains. I believe the driver was Bill Stone.
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class411
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Post by class411 on Aug 7, 2020 7:38:00 GMT
His article doesn't mention the runaway on the W&C in BR days when they ran a single car train in the off-peak. One was brought into service, the brake didn't work at Waterloo, the train continued down the slope, up the other side, then back and forth until it eventually came to a stand in the bottom of the tunnel. The brake rigging had been disconnected for repairs and had not been reconnected but was allowed back into service. After that they stopped using single car trains. I believe the driver was Bill Stone. Sorry, this is going to seem a really stupid question to those who already know, but, if there was a driver on board, why could he not have used the motors against the direction of travel? |
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Post by underover on Aug 7, 2020 14:20:29 GMT
Weird. I'd always thought that trains were designed so that the brakes were naturally full on, and were released by air pressure. Thus, unless the driver forgot to discharge the air pressure (although one would have thought that turning of the master switch [or whatever it's called on a train] would cause this to happen automatically, this sort of thing would be all but impossible. Having said that, I've often wondered why the pressure gauge visible in carriages indicates higher pressure when the brakes are activated. On older stock with separate brake handles, generally speaking there is a value to dump the air. If done too quick, it is possible to leave air in the system. You can't just leave the handle in emergency (quickest way to dump air) as if you were swapping ends, you would not be able to go as you would still have an emergency brake application on the train. |
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Post by philthetube on Aug 7, 2020 16:15:16 GMT
His article doesn't mention the runaway on the W&C in BR days when they ran a single car train in the off-peak. One was brought into service, the brake didn't work at Waterloo, the train continued down the slope, up the other side, then back and forth until it eventually came to a stand in the bottom of the tunnel. The brake rigging had been disconnected for repairs and had not been reconnected but was allowed back into service. After that they stopped using single car trains. I believe the driver was Bill Stone. Sorry, this is going to seem a really stupid question to those who already know, but, if there was a driver on board, why could he not have used the motors against the direction of travel? I would imagine this would destroy the moving parts on the train, though someone else will be able to answer better than me, imagine banging a car in reverse to stop it rolling forwards, there would be bits of metal everywhere. Nobody would be 100% sure of the result of trying this. Once it was decided that there was no imminent danger then the sensible thing to do would be to wait. |
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Post by croxleyn on Aug 7, 2020 16:38:25 GMT
In theory it could be done but it very much depends on the design. Years ago I built a controller for a battery operated engine for the Watford Miniature Railway, but didn't get the prototype quite right. Upon trying to reverse drive, the electronics vapourised! The second version needed a motion sensing interlock as being series configured the motor would effectively regenerate into a short-circuit, locking it solid!
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class411
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Post by class411 on Aug 7, 2020 16:42:03 GMT
Sorry, this is going to seem a really stupid question to those who already know, but, if there was a driver on board, why could he not have used the motors against the direction of travel? , though someone else will be able to answer better than me, imagine banging a car in reverse to stop it rolling forwards, there would be bits of metal everywhere. Nobody would be 100% sure of the result of trying this. I really don't think that's the case. An electric motor is completely different to an internal combustion engine and its transmission. The motor simply applies torque. Having said that, a train control system and its motors are not the same as a simple A/C mains motor (which definitely will slow down a reverse motion before inducing forwards rotation), so if no one knew for sure, your comment below certainly makes sense. |
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Post by afarlie on Aug 8, 2020 18:58:08 GMT
I'm not sure this is the best location for this. Please move if necessary. I accidentally came across this this morning. It is an article about runaways on the Underground. I certainly wasn't aware of these, and I don't remember seeing anything about this on here. hydeparknow.uk/2019/02/10/runaway-tube-trains/Did any of these incidents show up in 'official' reporting to RAIB (or it predecessors at HMRI)? |
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