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Post by Deleted on Jan 2, 2012 19:32:16 GMT
I haven't been in UK for a while but I recall that when a train left a station and for any reason had to abort accelerating there was always a big bang, and after the bang the PCMs probably returned to starting position and as the situation allowed for increasing the speed again the PCMs would start as if the train would start from stand still i.e. "stepping up" until the PCMs reached the notch the driver has set. Was this due to the contacts of the PCMs not able to withstand opening under current?
When the driver choose to abort the acceleration and would reverse the controller back to zero, would the main contactor (or whatever causes the big bang?) open immediately or will it open when the handle reached zero?
Did the PCMs always rotate in "same direction" -- i.e. when the acceleration was aborted, did the unpowered PCMs return the "same way", or did they go forward through the rest of the "notches".
[Sorry -- posted in totally wrong section]
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Post by eurostarengineer on Jan 3, 2012 13:21:57 GMT
PCM's? Do you mean RPA? Rotary Pneumatic Accelerator? The big bang is the Line Breaker opening.
Depending on stock, when they line breakers open you put the master controller/power controller at OFF and then go through the same shunt, series, parallel routine.
I think.
EDIT: Oh you're talking about the 73 stock... My bad.
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Post by 1018509 on Jan 3, 2012 20:26:49 GMT
The RPA would return to its rest position turning in the reverse direction.
The loud bang is from the line breakers. They always part with a large bang due to the current passing through them which is at its greatest during a pull away. The bang is more noticeable at slow speeds because the ambient noise of the train is less.
Such is the current drawn through the line breaker tips they are changed at slightly under yearly intervals. 100% change. 16 copper tips per uiit (1973 stock).
RPA tips are changed as required 84 per unit (1973 stock).
There's also the 32 tips per unit (1973 stock) of the G contactors and the 8 tips per unit (1973 stock) of the PB contactors.
Not to mention the hundreds and hundreds of auxilliary contactor tips ............. shall I go on?
I speak for 1973 stock only when I say drivers do not notch up to a certain position these days.
It's normally pull away with handle in full parallel and coast when line speed or whatever limit is reached.
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Post by 1018509 on Jan 3, 2012 20:29:54 GMT
Another thing about the RPA it notches up to its fullest position in Series and then notches back to its rest position to reach Parallel.
It's then ready for Rheo braking.
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metman
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5056 05/12/1961-23/04/2012 RIP
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Post by metman on Jan 3, 2012 23:23:36 GMT
Do A stock have an RPA?
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Post by eurostarengineer on Jan 3, 2012 23:29:04 GMT
Yes, A stock do.
I reckon this is a thread for Tecchy to reply to. Bloke is a goldmine of information.
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Post by Deleted on Jan 4, 2012 6:54:04 GMT
What I still wish to know is the moment the line breaker opens: Does it open the moment the driver starts to notch down, or the moment the driver has returned the handle to zero position? Thanks for replies. I'm a foreigner/tourist so terms and classes are mainly all greek to me. Sorry for using wrong terms. I tried to google the correct terms but found surprisingly little info about the rotary contactors -- or whatever they should be generally called. No photos came my way either. The rotary contactors (ok?) I recall listening while travelling in a motor unit with apparently two sets of such devices (series and parallel set?) under the transverse back to back seats -- listening the clicking first under other seat and then under the other. I do recall that there was a hands-on demo of the driver's controller and the rotary contactors at Covent Garden years ago (late 70s or early 80s?), but I just cannot recall how it actually worked or did I ever try it (it was a busy attraction  . Thanks for moving the thread into correct "folder" I did try to insert it here but probably finger slipped  pekka |
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Post by Deleted on Jan 4, 2012 12:56:23 GMT
Hi "Engineer", Excellent -- all I wanted to know (for now that is )! pekka |
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Post by tubeprune on Jan 4, 2012 15:49:32 GMT
Actually, the arc is extinguished as the line breakers open by a magnetic field generated by a "blow out" coil at the back of the arc chute.
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Post by tecchy on Jan 4, 2012 16:28:47 GMT
tubeprune has got it, although when you say the 'arc' is extinguished that should read that the circuit is opened. The arc is a bi-product of the situation. The electrical arc is permitted to happen at the line breakers as the environment the copper contacts are located in does not let the spark travel anywhere but inside the fire resistant covers. Hence the line breakers take the large current beating and the RPA doesn't. Line breaker tips are changed regularly because of the arching that happens.
Air is not blown across the contacts. As tubeprune says, it is driven by a magnetic valve.
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Post by Deleted on Jan 4, 2012 16:58:19 GMT
Apologies for error - incorrect information removed. Old age and early onset of senility to blame, must give up.
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Post by Deleted on Jan 9, 2012 12:03:09 GMT
...and from London Transport Museum I learned that:
"-- The simulator was built by staff at Golders Green and was on display in the Museum from when the Museum opened in 1980 until 1993. When the Museum was refurbished in 1993, the simulator was removed. The PCM unit was taken away and it has been used to provide spare parts for our 1938TS operational heritage train. What remains of it is still at the LTM depot. The driver's cab was cut down in 1993 and was on display as a simulator between 1993 and 2005. When the Museum was last refurbished in 2007, the cab simulator was refurbished and replaced and is still a popular activity in the Museum.--"
pekka
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Post by tubeprune on Jan 9, 2012 15:22:31 GMT
...and from London Transport Museum I learned that: "-- The simulator was built by staff at Golders Green and was on display in the Museum from when the Museum opened in 1980 until 1993. When the Museum was refurbished in 1993, the simulator was removed. The PCM unit was taken away and it has been used to provide spare parts for our 1938TS operational heritage train. What remains of it is still at the LTM depot. The driver's cab was cut down in 1993 and was on display as a simulator between 1993 and 2005. When the Museum was last refurbished in 2007, the cab simulator was refurbished and replaced and is still a popular activity in the Museum.--" pekka That reminds me of a little job that I got to do for the original display in 1980. I had to frig the equipment so that it would respond to a 240 volts domestic supply. |
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Post by Deleted on Jan 9, 2012 17:13:29 GMT
That needs some kind of overhaul, the brake lever looks melted from peoples sweat acid and the controls are unresponsive sometimes!
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Post by tubeprune on Jan 10, 2012 7:21:21 GMT
That needs some kind of overhaul, the brake lever looks melted from peoples sweat acid and the controls are unresponsive sometimes! Realistic then  |
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Post by Deleted on Jan 10, 2012 17:15:53 GMT
That needs some kind of overhaul, the brake lever looks melted from peoples sweat acid and the controls are unresponsive sometimes! Realistic then Haha you could say that! But even for realism its far too often that im stuck motoring or braking! |
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