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Post by noddymac on Sept 7, 2024 22:58:04 GMT
I noticed yesterday that trains were running a bit slower than usual between Newbury Park and Leytonstone on the west. I found out that the reason for this is trains will be auto-coasting to avoid putting strain on the motors and causing more issues. A pretty good idea that could work. At first I thought it may have been the train losing codes or some kind of technical issue, but no, it’s auto-coasting which is the same as normal coasting in manual operation.
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Post by xtmw on Sept 7, 2024 23:08:41 GMT
Sounds like the coasting vectors are finally being used?
ATO on the Central Line has never been able to coast, unless the coasting vectors are switched on. IIRC this is done from Wood Lane.
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Post by Dstock7080 on Sept 8, 2024 3:59:37 GMT
Implemented from 6 September 2024.
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gefw
Gone - but still interested
Posts: 201
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Post by gefw on Sept 8, 2024 16:22:49 GMT
Interesting move - last thing I heard no one really knew much about the "coast" facility design, what (if any) options there were & the affects on how the ATO drove the train - but well worth a try (for various possible effects regarding Energy consumption, rail noise & motor wear).
It gets to the Trainborne ATO controller from the Central system via the non safety control systems when berthed in a platform (so presumably applies for the next whole interstation run & perhaps until told otherwise (or ATO mode deselected)). But the operation/consistency of this path/mechanism has been a bit patchy (eg with Hold visuals & brake rates).
I was told ATO would never "coast"; it always wanted to be in either "motoring" or "braking" mode and some reasonable level of demand had to be set - so likely not to be a true "freewheel" just a bit less focussed at keeping very close to the Maximum Safe (allowable) Speed (given by the ATP codes). - But this will perhaps become clearer now it is being tried.
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Tom
Administrator
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Post by Tom on Sept 8, 2024 20:14:08 GMT
I knew there were plans to introduce it (I'm supposed to be involved in some of the work) but not that it had been introduced!
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Post by xtmw on Sept 8, 2024 23:41:01 GMT
... After so many years!
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gefw
Gone - but still interested
Posts: 201
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Post by gefw on Sept 9, 2024 15:11:15 GMT
If it is only in use in one area/direction it is probably a trial to ascertain the affects (needed to seek agreement for wider implementation).
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Post by Dstock7080 on Sept 9, 2024 16:53:39 GMT
It’s across the whole Line.
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Post by croxleyn on Sept 10, 2024 13:12:55 GMT
The idea of coasting for a system which has the motor permanently linked to the wheels (unless I'm mistaken) is somewhat strange. The velocity of a "non-powered" train will depend on the rolling resistance, any gradient and the mass (including passengers!). I'm wondering whether the "coasting vectors" are actually a set of rules/algorithm to predict the optimum speed to travel at given the distance to a train in front, and timetabling requirements. That would certainly provide the greatest efficiency: regarding motor wear, an induction motor has no slip rings unlike the good-old parallel- or series-wound DC motors whose brushes obviously wear out.
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Post by t697 on Sept 10, 2024 15:49:51 GMT
But of course currently the Central line 92TS still have dc motors with commutators and brushes. The long delayed CLIP project brings the induction motors.
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gefw
Gone - but still interested
Posts: 201
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Post by gefw on Sept 10, 2024 16:40:33 GMT
True that coasting will not reduce the number of revolutions the motors do (and hence basic wear).
The thought is probably that the deterioration of the brushes/commutators is influenced by the Heat & current at the brushes and possibly also by aggressive and regular switching between motoring & (regen) braking particularly when near the "speed limit" and hence "calming down" ATO driving technic may well help.
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Post by spsmiler on Sept 10, 2024 20:48:54 GMT
might reduce the leccy bill too - as its better to coast than either accelerate or brake
btw, maybe that is why I had a slow start to my journey when leaving Leyton westbound?
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Post by xtmw on Sept 10, 2024 21:38:04 GMT
It shouldn't affect trains acceleration/deacceleration
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Chris M
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Post by Chris M on Sept 11, 2024 1:47:57 GMT
True that coasting will not reduce the number of revolutions the motors do (and hence basic wear). The thought is probably that the deterioration of the brushes/commutators is influenced by the Heat & current at the brushes and possibly also by aggressive and regular switching between motoring & (regen) braking and hence "calming down" ATO driving technic may well help. It might also be theorised that it will reduce wear on other components. I recall that the aggressive and rapid cycling between braking and accelerating was speculated to be a possible causal or contributing factor to the 1996 stock cracking issues (although I don't remember if this was confirmed correct or incorrect) |
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gefw
Gone - but still interested
Posts: 201
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Post by gefw on Sept 11, 2024 7:53:27 GMT
It shouldn't affect trains acceleration/deacceleration Would be interested to get some feedback of your CL experience (as a Train Op) Concur that the braking/stopping for station is unlikely to be affected when the ATO has "coast" set. Not so sure about the acceleration phase - Logically the acceleration may be the same when well below the "speed limit" but may ease off earlier when near speed? Does the speed in ATO drop/fluctuate noticeably less than the "speed limit" on the long uninhibited runs? Does ATO always get/employ the "coast" command - or only when on time or early or train ahead? |
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Post by zbang on Sept 18, 2024 0:55:49 GMT
The idea of coasting for a system which has the motor permanently linked to the wheels (unless I'm mistaken) is somewhat strange. regarding motor wear, an induction motor has no slip rings unlike the good-old parallel- or series-wound DC motors whose brushes obviously wear out.
FWIW, it's common in many systems for trains to coast, I can't see that the p-way conditions around London would be any different. (And, of course, there's both dynamic and regenerative breaking, where the wheels are driving the motor; that's fairly well accepted.)
As for the second part, induction motors don't have slip rings unless they do - the "wound-rotor induction motor", AKA a "slip-ring motor"; used to be common for some industrial uses; granted that AFAIK they've never been used in railway applications.
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Post by brigham on Sept 18, 2024 7:38:18 GMT
Coasting has been part of normal railway operation ever since the low rolling resistance of iron wheels on iron rail, and long before electric traction was ever dreamed of.
In my part of the world, the power unit on mineral trains would be disconnected from the first waggon, trot round tho the back of the moving train, and jump onto the last one.
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