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Post by jamesb on Jan 2, 2012 18:56:57 GMT
I got a train from Roding Valley heading towards Ealing Broadway via Hainult earlier today.
The driver announced that the train was going out of service on the approach to Hainult, because 'we were running on half motors' and the train would be going extremely slow and they couldn't risk going into a tunnel with it.
Do you think that mean that the back half of the train didn't have any motors at all, or that every other axel wasn't motored on the whole train?
What could cause this to happen? The train was obviously considered safe and serviceable to be driven with passengers from Woodford to Hainult. Could it be some sort of fuse that blew? Or shoe gears falling off?
It happened some time in the early afternoon, after or around 13:00.
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Colin
Advisor
My preserved fire engine!
Posts: 11,317
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Post by Colin on Jan 2, 2012 19:33:05 GMT
So many questions!!
There can be a number of things that will cause motors to not work - fuses, MCB's, missing shoes, motors cut out, etc, etc.
The term 'half motors' can mean several things. I dunno what the exact set up is on 92ts (well apart they're obviously motored on all axles), but it can mean half the axles on a single car, half the axles on a two car unit. It might even be a single motor on an eight car train, or it could be one of the two traction circuits and the train really is on half motors.
Generically, almost all motor defects are referred to as 'half motors'.
Now depending on the circumstances, its usually desirable to get the train off the railway as less than full motoring capacity means that not only will the other motors be more strained, but potentially the defective train will lose time compared to other trains around it. And of course the defect needs fixing.
In your case it wouldn't have mattered on the quiet branch from Roding Valley to Hainault, but once you get down to Leytonstone it could become a bit of an issue. As there's a depot at Hainault it would make sense to put the train in there and get it fixed.
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Post by dagdave on Jan 2, 2012 21:18:02 GMT
Apart from running slower and delaying the service there would be no reserve capacity in the remaining motors if they also developed a problem. Not a good idea to carry on in service through the city with a known motor fault.
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Post by jamesb on Jan 2, 2012 22:32:19 GMT
Sorry for all the questions... I'm inquisitive like a child!
Thank you Colin. It makes more sense to me now... I couldn't see how literally half the motors on the train could fail. If there are 4 axles per car, that means 32 axles per train, so does that mean 32 motors per train?
If just one out of 32 motors wasn't working, would it really make that much difference to the performance of the train?
Does the failed motor slow the train down by preventing that particular axle attached to the failed motor from 'coasting' meaning it is turning against some resistance?
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Post by auxsetreq on Jan 2, 2012 23:14:29 GMT
The trains are two car unit based. Every unit has it's own traction logic controlling it's motors. A traction fault on one unit will mean a loss of eight motors. A loss of just one motor on a unit isn't possible. It's either all or nothing. Half motors would mean two units - sixteen motors, half the train's compliment, would not be working. It could remain in passenger service until it's changed over asap as it will be rather slow. Also it's halfway to a sit down. There are many reasons for traction faults, but the common ones are - Auxiliary supply problems, frequency monitors, blocked blower filters and other usually electronic based faults that are assessed by a bloke with a special key who can open up all manner of secrets on the train's on-board diagnostics via the DTS.........
If a unit is not motoring, it's coasting, and braking on friction only...........
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Colin
Advisor
My preserved fire engine!
Posts: 11,317
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Post by Colin on Jan 2, 2012 23:16:00 GMT
If there are 4 axles per car, that means 32 axles per train, so does that mean 32 motors per train? On a 92ts, yes. If just one out of 32 motors wasn't working, would it really make that much difference to the performance of the train? One on its own probably wouldn't - but it all depends on how they're set up on a 92ts. It may be the case that they work in pairs (ie, per bogie) and so it could be that you'll lose a bogie per 'motor'. Generally speaking the decision to take a train out of service will depend on a combination of how the train is performing, what the trains computer is saying along with location of the train and the mobile fitter's advice (if they've met the train). If the defect was confirmed by the Leytonstone mobile fitter at Stratford westbound but it's only one axle......you'd probably just change it over at West Ruislip (or Hainault next time round). If it were the same scenario but approaching a peak it would definitely go to Ruislip depot. If you had a whole car or more out you'd be looking to get rid of it as soon as possible - that could even mean putting it in Holborn or Marble Arch sidings and bringing it out much later in the day, when its less likely to bug ger up the service, for depot attention. There's never a definitive answer!! Does the failed motor slow the train down by preventing that particular axle attached to the failed motor from 'coasting' meaning it is turning against some resistance? No - a failed motor isn't working, therefore it's having no effect whatsoever!! The reason the train may run slower is simply that it's not got the full power of all the motors moving it along - a fully loaded train with only 80% of it's motors working is gonna accelerate from platforms slower than a fully loaded train with 100% of it's motors working.......multiply that over 40 stations..... |
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