Standard Stock Technicals

Thanks for that Tubeprune. I'm reading Mr Agnews Electric Trains Vol 1 on this at the moment and just trying to get my head around the contactor sequencing. This book is one of the best purchases I've ever made. Thanks for the recommendation.

Were both axels of the motor bogie motored? I can't remember off the top of my head.

Yes, both axles on the drivers end bogie were motored but the accelerating relay coil was only in circuit with one. This wasn't a problem when the motors were running in series and the resistances were stepped out one at a time. There were six resistance steps with the last two being cut out simultaneously. However, in parallel when the first resistance was cut out this was not in the motor circuit with the accelerating relay. As a result the accelerating relay switched over almost instantaneously cutting out a further resistance in it's motor circuit.
This meant there were only three stages of resistances to cut out in parallel compared to five in series.

Ah! You are quite correct in the sequence of contactors dropping out TP but my understanding is the speed in which they dropped out the resistances in parallel is quite different to how they dropped the resistances out in series. In series they were dropped at an equal rate, in parallel one would drop out first on motor 1 closely followed by motor 2. In essence I would of thought motoring up in series you would have heard an even number of single clacks upto five on acceleration, a doulble clack for transistion, but once in parallel there would have been a double clack (one for each motor) for each resistance cutout upto two (RR1+R1, RR2+R2).With RR3+R3 comming in together this would sound like one single clack before full parallel . Page 115, steps 9 and 10, second paragraph.

Not really sure. We had no speedos on the trains. I would guess it would be around 15 mph.

Sorry, can't do any better than that. However, if you left the handle in series, it might build up to 20ish. I was thinking more of a stright run up to full parallel. Once all the resistance is cut out the motor still accelerates.

Thanks TP,
I noticed that the Standard Stock DM's were labelled A and B end and only the very last of the Standard Stock was labelled A and D. Do you know when this happened and what was the reason behind the labelling change.
Darren.

The "A" and "D" indentification system was first introduced by an "Instruction to Shops" issued to the workshops at Acton Works in March 1932 where axles were to be lettered A, B, C and D, west to east or north to south. As Ben says, A car with the cab at the "A" axle end was an "A" car, a car with the cab at the "D" axle end became a "D" car. The north side of the train was the No 1 side and the south side No 2. Thus a wheel would be, say A1, or C2. A double-blocked A1 wheel would have one brake block called A1A and the other block A1D. No one has come up with a better identification system and it survives to this day.

Thanks for the info TP and Ben. This is proving really useful.
I have numbered the DMA's 3000 upwards in even numbers and the DMB's 3001 upwards in odd numbers. The trailers 5000 upwards and the Control Trailers 7000 upwards. Is this the correct numbering scheme for this era stock.
Here are some pics of the stock with the latest textures Richard Scott has applied and by god does it make you hair stand up. You can even make out the rivets with the bump mapping.

I've seen pics of the weak field raised aswell. A small thing on a long arm, offside cab window, yellow and black lines on it.

Wasn't it a new feature introduced on the 1931 (or 1934?) stock then retrofitted?

The Piccadilly extension stock did indeed have a week field flag and the rest was retrofitted to the 1923-27 stock on the Central for the long runs into Essex. When was the 1927-29 stock on the Picc retrofitted with field flags (at the same time as the older trains?) as they wouldn't have kept up with the 31-34 batch? The 1931/4 DM looks great as does the 1925 control trailer, remember the later control trailers (1927-9) had marker light boxes rather than the shutters.

Great job keep it up!

I read in one book that the new picc stock was designed for 50mph running and had a weak field. This source could have been incorrect, I've been routing through my Tube stock Underground File to find out. There is a picture of a UCC car with a field flag up (and ep brake sticker) on the Bakerloo at Wembley Park with a 1904 Met saloon stock train on the other platform so it must have been around 19381