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Post by psi on Aug 31, 2018 7:14:25 GMT
We visited London this February and I was over the moon when I found out that there still is stock with RPAs in use (Bakerloo line 1972 stock).
I asked about the controls of RPAs (that I wrongly addressed as Pneumatic Camshaft Mechanism) some time ago, and got almost everything answered. There are still some things I'd like to ask. Again, I'm sorry for asking daft questions and not using the correct terminology or grammar:
1) How many "notches" there are in the controller of 1972 stock (or any old RPA controlled stock)? What are the notches called (neutral, 0 , inch, series, parallel, weak field or what)? I understand that it is not a good plan to run the train having resistors connected, and that driver should always move the handle towards full series or full parallel (or weak field) notches. So, are there intermediate notches between inch and full series or full series and full parallel in the 1972 or any (say, from 1938 stock) controllers?
2) What if the driver first throws the controller flat out (to full parallel), and then, quite soon, realises, that full series is enough: can he return the handle to full series to prevent all the cars still notcing at series RPA from going past the full series and prevent the cars entering to parallel RPA?
Or is there a danger that, if one of the cars has already gone ahead and be already notching the parallel RPA would, in this case, stop on a reistor notch causing danger of resistors overheting?
3) Provided that the stopping of RPAs notching ahead up by returning the controller to lower notch is not possible, will the line breaker act the moment the driver starts to return the handle towards '0', or the moment the handle hits '0'?
4) Could someone, please explain how the rheostatic braking is controlled on 1972 stock? From Trainweb-tubeprune I've learned that RPAs are used, but wouldn't the braking current rise so high that notching down under heavy current braking would cause excessive wear to contactors? I understand that switching from series to parallel is not an easy thing to do either, and that several methods are used to prevent curent spikes and jerkiness of driving. Has anyone found any (public!) shematics of rheostatic braking on 1972 stock? How many notches? How does the air brake come along, are there extra notches like "apply", release" etc, in case the rheostatic is not working?
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Post by PiccNT on Aug 31, 2018 9:03:29 GMT
The 1973 stock on the Piccadilly Line also has RPA's. I don't know the technical details of how it works but Fish7373 will probably have the answers.
On both the 1972 and 1973 stocks, You have an "Off and Release" position and then "Shunt", "Series" and "Parallel". Once in Parallel, you need to go back to off and release and then to series to bring it down to just series. On the 1973's, we have a separate weak field switch on the offside of the cab that is permanently cut in.
On the 72's, they have the EP brake + Rheostatic 1 & 2 (plus Westinghouse) and on the 73's we have Westcode + Rheostatic. The rheo's operate approximately if you start braking between 21 and 51 mph (max line speed is 45) and drop off at about 8mph. They are obviously only on the 4 motor cars.
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Post by Deleted on Aug 31, 2018 9:54:44 GMT
I am pretty sure I read somewhere that if a driver tries to apply too much power too quickly the motor will overload causing the clunk sound and the motor cutting out that sometimes occurs. To rectify it the driver needs to apply power a bit slower until a certain speed. Am I right?
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Post by PiccNT on Aug 31, 2018 11:04:02 GMT
The clunk sound is either the door interlock circuit breaking when a door opens slightly as the train pulls away thereby cutting out the motors (need to go back to off and release and then power again - aka restroking) or going over a rail gap shortly after pulling away. There is also an overload relay that prevents surges from damaging the motors and this can cause a bit of a jolt.
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Post by brigham on Aug 31, 2018 11:19:13 GMT
... There is also an overload relay that prevents surges from damaging the motors and this can cause a bit of a jolt. Equivalent to the 'canopy switch' in tramway terms, then?
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Post by philthetube on Sept 1, 2018 12:45:50 GMT
Setting off in full parallel shouldn't cause problems unless there is a dodgy door interlock on the train, and is the normal way to drive.
The RPA is there to regulate the power provided to the motors, thus avoiding both damage and wheelspin.
Series tends not to be used much, usually parallel or coast.
Can someone please say what RPA stands for please, I am ashamed to say that I cannot remember.
Doh, just seen the thread title.
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Post by MoreToJack on Sept 1, 2018 13:25:23 GMT
Can someone please say what RPA stands for please, I am ashamed to say that I cannot remember. Doh, just seen the thread title. Don't worry, I did exactly the same and was about to administer a reminder, before noticing the thread title myself... oops!
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Post by fish7373 on Sept 2, 2018 15:13:09 GMT
Can someone please say what RPA stands for please, I am ashamed to say that I cannot remember. Doh, just seen the thread title. Don't worry, I did exactly the same and was about to administer a reminder, before noticing the thread title myself... oops! Rotary Pneumatic Accelerator Stands for.
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Post by Chris M on Sept 2, 2018 15:16:13 GMT
Rotary Pneumatic Accelerator Stands for. If it's standing for Mayor of London it'll get my vote!
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Post by psi on Sept 3, 2018 6:46:57 GMT
Asking one thing leads to another -- I'm sorry! 0) In my older message: Pneumatic Camshaft Mechanism (PCM) operation I asked about " Pneumatic Camshaft Mechanism - PCM". I was told to use the term " Rotary Pneumatic Accelerator -- RPA". It appears that both exists/existed. From RS Info Sheets 4 Edition.pdf I learned that there is only one camshaft mechanism in 1972 stock: "-- A.E.I. Traction pneumatic single camshaft, resistance controller with series/ parallel grouping and 2 stages of weak field --". How come? What is the difference between PCM and RPA -- except spelling, of course ? 1) On Tubeprune Photos - C Stock Driver's Cab I found a photo "Fig. 3: C Stock Combined Traction/Brake Controller (CT/BC)" which gives me good idea of the "Combined Traction/Brake Controller (CT/BC)" positions/notches in C stock: A- Parallel B- Series C- Shunt D- Off and release E- Rheostatic 1. and hold F- Rheostatic 2. and ep.application min G- Rheostatic 2. and ep.application nor H- Rheostatic 2. and ep.application max I- Lap J- Service application K- Emergency L- Shut down These do match with the reply I got earlier from PiccNT, many thanks! So, what was ommitted or added to different stock (1972 / 1973 etc)?
How many "notches" there were in different stock PCMs/RPAs? 2) RPAs will continue to full parallel even though driver would move CT/BC from A "Parallel" to B "Series" or C "Shunt". 3) The Line breaker will blow at D "Off and release". 4) The brakes are all rather confusing, really: I have now the impression that the different brake systems work with these CT/BC positions/notches: Rheostatic brakes:- Applied at E or F (F,G & H are the same?) - Released at D Electro-Pneumatic EP-brakes:- Applied at F,G or H - Released D Westinghouse brakes: - Applied at J - Lapped at I - Released at D NEW QUESTION: What is HOLD? I have thought (possibly wrong again) that "Direct air brakes" have: - Release - Lap - Application " Westinghouse brakes" has: - Release - Running - Lap - Application - Emergency and " EP brakes" has: - Release - Service 1, 2, ... - Emergency so, what is " Hold" and what is " Lap" in CT/BC? _____________________________________________________ SUMMARY OF TODAY'S QUESTIONS 0) What is the difference between "PCM - Pneumatic Camshaft Mechanism" and "RPA - Rotary Pneumatic Accelerator". How many per motor car? 1a) How do "Combined Traction/Brake Controller (CT/BC)" positions of C stock differ from other stock? 1b) How many "notches" there were in different stock PCMs/RPAs? 4) what is "Hold" and what is "Lap" in "Combined Traction/Brake Controller (CT/BC)"? pekka __________________________________________ PS: I'm afraid this may go on, and on, and on...
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Post by Dstock7080 on Sept 3, 2018 8:02:58 GMT
Asking one thing leads to another -- I'm sorry! SUMMARY OF TODAY'S QUESTIONS 0) What is the difference between "PCM - Pneumatic Camshaft Mechanism" and "RPA - Rotary Pneumatic Accelerator". How many per motor car? 1a) How do "Combined Traction/Brake Controller (CT/BC)" positions of C stock differ from other stock? 1b) How many "notches" there were in different stock PCMs/RPAs? 4) what is "Hold" and what is "Lap" in "Combined Traction/Brake Controller (CT/BC)"? pekka __________________________________________ PS: I'm afraid this may go on, and on, and on... 0) no difference; each time you visited the Railway Training Centre the other acronym was always in vogue! So, you’d say “PCM” and were told it now “RPA”, next visit it was reversed!! One unit per Motor car. 1a) C Stock and 1972 Stock TBCs were very similar in appearance and identical in operation, both trains fitted with Westinghouse brake. 1967 Stock were slightly different in positions and the way the Deadman device worked. 1973 Stock doesn’t have pure Westinghouse brake. 1b) notches in PCM; used to be a Motormans exam question! There were many, unfortunately forgotten by myself - although “1, S and 7” was possibly the answer: what contacts are made in ‘shunt’? 4) HOLD; is EP brake hold; ie just enough brake to hold a train at a station platform, the TBC could be released in this position. Rheostatic brake is not operative below 6mph. LAP; is no ports in the Westinghouse rotary valve are open, (this being mounted directly under the TBC), the Westinghouse brake air will equalise throughout the Train Line pipe. Used after Westinghouse brake application and during brake testing.
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Post by fish7373 on Sept 3, 2018 18:28:21 GMT
Q = RPAs will continue to full parallel even though driver would move CT/BC from A "Parallel" to B "Series" or C "Shunt". Answer = Full Parallel move to Series will notch down to Series move to Shunt will Notch down to shunt, Full Parallel To OFF RPA Will Not Notch Down just drop out. just run back to off.
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roythebus
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Post by roythebus on Sept 3, 2018 19:18:43 GMT
I'm sure I was taught that RPA was Rapid Pneumatic Accelerator back in 1970. Same bit of kit as the PCM surely? What is HOLD?
I have thought (possibly wrong again) that "Direct air brakes" have: - Release - Lap - Application
There's no direct air brakes on tube stock that I know of. Direct air brakes are used on locos and allow air directly from the loco air brake valve to enter the brake cylinder, not fail safe!
"Westinghouse brakes" has: - Release - Running - Lap - Application - Emergency
Correct. Some Westinghouse brake handles have release/running and charging position. Release position gave a slightly higher air pressure to release the brakes more quickly. Some steam locos have release, running and charging positions as 3 positions, lap and emergency if I remember correctly.
and "EP brakes" has: - Release - Service 1, 2, ... - Emergency
There's been several types of EP brake on LT; the Q stock had the A typre EP brake which like the Westinghouse had a "lap" position, so the motorman would move the handle from release/running/charging to EP application, once the train had started to slow to his requirements, he'd put the handle to EP lap, which would de-energise the ep application valve and hold the constant brake cylinder pressure. Later stock had the d type EP brake where it was self-lapping; brake pressure was variable automatically by moving the brake handle further round. On C stock and later I think that was similar to the D type and was self-lapping. Not sure about later stock, but on BR they went over to Westcode EP brakes which only have 3 steps of brake, poor, not quite so poor, and you might stop where you want if the WSP lets you.
so, what is "Hold" and what is "Lap" in CT/BC?
"hold" holds the pressure as someone has explained, and the Westinghouse positions have been explained.
I've worked as a guard /emergency motorman on LT and a secondman and driver on BR so have had experience with most types of brakes up to 1988. _______________
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Post by fish7373 on Sept 3, 2018 20:13:00 GMT
ROYTHEBUS release/running/charging to EP application, once the train had started to slow to his requirements, he'd put the handle to EP lap, which would de-energise the ep application valve and hold the constant brake cylinder pressure. Later stock had the d type EP brake where it was self-
On EP There is no running or charging and LAP is only used when the train is stopped
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Post by Colin D on Sept 4, 2018 2:03:21 GMT
I'm sure I was taught that RPA was Rapid Pneumatic Accelerator back in 1970. Same bit of kit as the PCM surely? When I first saw this thread I sure it was, as you say, we were taught at White City Training Centre that RPA=Rapid Pneumatic Accelerator. For me that was in 1967.
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Post by psi on Sept 4, 2018 7:05:44 GMT
Well -- It's all rather confusing, really. 0) So the thingamebob, according to " What does Series and Parallel mean" may be: PCM - Pneumatic Camshaft Mechanism
- Pneumatic Camshaft Modified
RPA - Rapid Pneumatic Accelerator
- Rotary Pneumatic Accelerator
- Rotator Pneumatic Accelerator
and prior to 1959 it was always PCM. in " What does Series and Parallel mean" peteuxb said: To my understanding (based on 1955 built, MetroVic controlled Helsinki trams driver's manual and young kids general observation of trams) staying on an intermediate notch is not a good plan, as resistors may overheat. Thus it seems odd that the controls allow (allowed) this. Yes, I do understand (i.e. I do NOT know this for a fact!) that the inch/shunt is a series notch with all resistors in use. In " First day at Northfields" solidbond said: So which classes used single camshaft and which used two separate (series and parallel) camshafts in PCM/RPAs?
1) No intermediate notches between inch/shunt and series or series and parallel in Controller. Ever during MU resistor control? When did "Inch" notch became "Shunt"? 2) According to Wikipedia's article " London Underground 1938 Stock" (no, Wikipedia is not authoritative, I know) i learned that : Was the 1938 stock the only class that had the PCM/RPAs not able to reverse under load? Ever? 3) The Line breaker will blow at "Off and release". This is now a fact, no? 4) Roy: yes I should not have mentioned direct air brakes in this context So, there has been variations in the number and meaning of brake notches from class to class.
In C (and 1972 etc) stock was the rheostatic brake action the same at EP brake nothes min, med and max?
Does the rheostatic brake use "line" to supply for motor field and no batteries? In case of line failure the rheostatic brakes will drop, no?
The " Diagrams, Instructions and Other Scans" area here is a well of information. There seems to be all sort of drawings of stations and rolling stock (suitable for modeller) but very few schematics for someone trying to understand what actually happens... And sadly so many links to actual data has rotted... Unfortunately I have not come across electrical schematics of power control that would show the controllers and the PCM/RPAs of resistor controlled trains. Are there any public schematics anywhere? Can someone point the correct direction to find them? pekka
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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 Sept 4, 2018 9:00:13 GMT
ROYTHEBUS release/running/charging to EP application, once the train had started to slow to his requirements, he'd put the handle to EP lap, which would de-energise the ep application valve and hold the constant brake cylinder pressure. Later stock had the d type EP brake where it was self- On EP There is no running or charging and LAP is only used when the train is stopped Yes I'm aware of that. On the D type EP release on EP also is also release, running and charging the Westinghouse. Same on BR Southern Region EP stock. I thought I was clear with the A type EP brake, motorman puts handle to EP application, then returns it to EP lap to hold that pressure. Westinghouse lap was further round than the EP application position. One problem with using Westinghouse only on Underground stock was that if the EP was isolated for some reason you only got about 28psi in the brake cylinders as the mercury arc retarders were switched out as well. Somewhere in my book collection I have THE book on the RPA/PCM equipment which somebody at Waterloo lent me many years ago. If ever I find the book I'll have a look through it and see what it says. But yes, it was possible to run up to parallel and hold parallel by putting the controller back to series for drive comfort on the older stock. Personally I found the C69 unconfortable to drive, maybe because it was rather alien having to drive left-handed! Luckily I didn't do that very often. On the older SR stock the same applied with the deadman/controller, run up to parallel/weak field, handle back to series for comfort! On the later BEP/CEP/CIG etc stock they had different master controllers with full weak field back towards the driver. EP brake could be simply switched off and as there were no mercury retarders, Westinghouse gave the full 65psi in the brake cylinders. But, we only had 3 applications of the Westinghouse before the auxiliary reservoirs ran out of air!
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Post by fish7373 on Sept 4, 2018 19:26:04 GMT
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Post by Dstock7080 on Sept 4, 2018 21:46:06 GMT
hope some of this helps? 1967, 1972 mkI, 1972 mkII Stock AEI double pneumatic camshaft 1973 Stock AEI single pneumatic camshaft 1983 Stock Kiepe electric camshaft A Stock AEI single pneumatic camshaft C69, C77 Stock AEI double pneumatic camshaft D Stock GEC single pneumatic camshaft (ps. i failed earlier exam question i see, as "1, S and 7' are "off" !)
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Post by philthetube on Sept 5, 2018 2:41:20 GMT
Somewhere in my book collection I have THE book on the RPA/PCM equipment which somebody at Waterloo lent me many years ago. If ever I find the book I'll have a look through it and see what it says. note to self.
Do not lend books to Roythebus
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Post by psi on Sept 6, 2018 12:58:07 GMT
fish7373 and Roythebus: thanks for the explanation and prints of the brakes. The EP brake handle is really a mechanical marvel combining handle position and brake pressure into electrical contacts. I'm impressed!
Dstock7080's: The Image of the notches just wetted apertite but alas gave very little.
I have seen camshaft diagram and schematic drawing of a tram's series parallel bridge transition system, but there the sets of resistors were closely tied to each of the two motors. As the controller advcanced from zero to full series, more and more contacts from both reisistor banks were bridged, until all resistors were bridged, and the transition took place. Then, during the magical series to parallel transition movements, all resistor bridging contacts were released and they were closing again as the controller advanced from transition to full parallel. In your diagram the camshaft unit contacts are forming a mirror image around transition, and that seems rather odd...
Another thing: Looking at "camshaft position" column, it seems like the rotary camshaft changes direction at transition. Is that the thing 1018509 tried to tell in " Pneumatic Camshaft Mechanism (PCM) operation" when he said: or am I completely lost?
Do you possibly have the other Fig 5 images as well (the 5-viii figure mentioned that the Fig. 5-x should be the motor and resistor side of the circuit).
I found Q stock control schematic links from " Q STOCK CONTROL CIRCUIT". No camshafts there, the schematic only shows the resistor contactor's coil side or controller side, right?
pekka
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Post by psi on Sept 7, 2018 5:51:25 GMT
Dstock7080: I must have long wires and dim light in the attic. Last night the lamp got light: I realised why the resistor contacts on camshaft unit did not form a triangle but a ramp. It is the idea of controlling the resistors by "sort-of-tapping" instead of "sort-of-shunting"
CONTROL BY "SHUNTING" RESISTORS A B * C-> * * D * * * E * * * * / / +--o-o--+--o-o--+--o o--+--o o--+ | | | | | o-+-WWWWW-+-WWWWW-+-WWWWW-+-WWWWW-+-o IN R1 R2 R3 R4 OUT
CONTROL BY "TAPPING" RESISTORS A * B * * C-> * * D * * E * * IN o-+-------+-------+-------+-------+ | | | | | o o o o o / | | / / o o o o o | | | | | o-+-WWWWW-+-WWWWW-+-WWWWW-+-WWWWW-+-o OUT R1 R2 R3 R4 OUT P S
Due to this it is possible to have parallel resistor contacts as a mirror image of series resistor contacts, just by changing which end of the resistor chain is used as output (OUT-P instead of OUT-S in above), and reversing the direction of rotation of the camshaft. In addition to this there is of course the bridge switching from series to parallel and whatnot. To most of you this must have been trivial but not for me. Boy - I feel so clever now
BUT: How it is done in case one has separate series and parallel camshafts, like in 1972 stock, not to mention Rheostatic braking?
pekka
Edit: Apparently ascii art should not be done using (code)...(/code) tags, as this way the ascii art won't won't work using Android phone. I wonder how it should be done? I'm not that clever after all
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Post by psi on Sept 11, 2018 14:40:19 GMT
Dstock7080:
Have you (or anybody?) got both a"Sequence Chart" and a "Power Circuit" of Single and Double Camschaft system that has rheostatic braking as well?
This way I could hopefully(!) understand what is happening during acceleration, transition and rheostatic braking.
I have Pierce Connor's "The London Underground Electric Train", but it does not give all the answers.
pekka
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Post by Deleted on Sept 11, 2018 20:10:04 GMT
If you don't get a reply in a few days time, I will get some drawings for you.
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Post by fish7373 on Sept 14, 2018 1:17:26 GMT
Dstock7080:
Have you (or anybody?) got both a"Sequence Chart" and a "Power Circuit" of Single and Double Camschaft system that has rheostatic braking as well?
This way I could hopefully(!) understand what is happening during acceleration, transition and rheostatic braking.
I have Pierce Connor's "The London Underground Electric Train", but it does not give all the answers.
pekka
One from the 1960 Tube Stock
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Post by psi on Sept 14, 2018 6:47:30 GMT
Fish7373: Thanks for the schematic and sequence table of 1960 stock. The stuff across motor armature must be for spinning sensoring mentioned on Wiki page " London Underground 1960 Stock": What I'm still after is the sequence table AND power schematic of single and double camschaft systems that also has rheostatic brakes:
- Single camschaft w. Rheostatic brakes (1973 or D78 stock)
- Double camschaft w. Rheostatic brakes (1967, 1972 or D69/77 stock)
It is the Double camschaft w. Rheostatic brakes (1967, 1972 or D69/77 stock) that I'm most intersted in!
I know this is rather specific. I'm sorry for asking, but I have this obsession of wanting to know why and how the "ticking" goes the way it does from under one seat to the other...
pekka
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Post by fish7373 on Sept 14, 2018 12:12:52 GMT
1972 Traction diagram
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Post by fish7373 on Sept 15, 2018 15:35:45 GMT
1973 SEQUENCE chart
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