Great Western Coffee Shop

Sideshoots - associated subjects => Heritage railway lines, Railtours, other rail based attractions => Topic started by: grahame on April 10, 2020, 04:12:43



Title: Front of the bubble [DotD 10.4.2020]
Post by: grahame on April 10, 2020, 04:12:43
This brings back memories though the picture is only 9 months old.  It's the cab of a bubble car - though the layout looks just the same to me as other first generation units.

Anyone car to describe what each of the controls and displays does?

(http://www.wellho.net/pix/bubblecab.jpg)


Title: Re: Front of the bubble [DotD 10.4.2020]
Post by: martyjon on April 10, 2020, 08:45:41
This brings back memories though the picture is only 9 months old.  It's the cab of a bubble car - though the layout looks just the same to me as other first generation units.

Anyone car to describe what each of the controls and displays does?

(http://www.wellho.net/pix/bubblecab.jpg)

Left side handle power control (Accelerator)

Blob with the button cancel AWS

Next gear selector

Far right brake control handle in fixture on windscreen

Large dial speed

Middle dial vaccum brake and reserve


Title: Re: Front of the bubble [DotD 10.4.2020]
Post by: Western Pathfinder on April 10, 2020, 08:52:27
At the base of the windscreen central pillar,is the AWS Sunflower indicator, in front of that to the slight right is a round black object ,which is the train brake control,missing its operating Handel.
Which would lead me to think that the unit is being driven from the other Cab.


Title: Re: Front of the bubble [DotD 10.4.2020]
Post by: bobm on April 10, 2020, 08:56:18
You mean Graham wasn't driving at the time?

And I suppose the white circular thing at the edge of the shot is the steering wheel   ;D ;D


Title: Re: Front of the bubble [DotD 10.4.2020]
Post by: martyjon on April 10, 2020, 09:27:23
This brings back memories though the picture is only 9 months old.  It's the cab of a bubble car - though the layout looks just the same to me as other first generation units.

Anyone car to describe what each of the controls and displays does?

(http://www.wellho.net/pix/bubblecab.jpg)

Left side handle power control (Accelerator)

Blob with the button cancel AWS

Next gear selector

Far right brake control handle in fixture on windscreen

Large dial speed

Middle dial vaccum brake and reserve

Having looked more closely the 2 large dials are as I said speed and engine revs

Key equivalent to ignition key

Switches front lights, cab lights, 1st gen DMUs had oil tail lights responsibility of the guard


Title: Re: Front of the bubble [DotD 10.4.2020]
Post by: rogerw on April 10, 2020, 09:32:48
The big white wheel is the handbrake


Title: Re: Front of the bubble [DotD 10.4.2020]
Post by: martyjon on April 10, 2020, 09:40:46
This brings back memories though the picture is only 9 months old.  It's the cab of a bubble car - though the layout looks just the same to me as other first generation units.

Anyone car to describe what each of the controls and displays does?

(http://www.wellho.net/pix/bubblecab.jpg)

Left side handle power control (Accelerator)

Blob with the button cancel AWS

Next gear selector

Far right brake control handle in fixture on windscreen

Large dial speed

Middle dial vaccum brake and reserve

Having looked more closely the 2 large dials are as I said speed and engine revs

Key equivalent to ignition key

Switches front lights, cab lights, 1st gen DMUs had oil tail lights responsibility of the guard

Somewhere there is a press button to acknowledge the guards instructions

Can't remember what 4th dial was

Starter button on left side not shown on piccy which started all engines on unit together. Individual engines were started alongside the unit from ground level

No fuel gauge in cab all tanks had a gauge on the tanks themselves


Title: Re: Front of the bubble [DotD 10.4.2020]
Post by: martyjon on April 10, 2020, 09:49:10
Oh I forgot there is a switch for the windscreen wipers which also had a variable speed control and that reminds me that the 4th dial was the air pressure dial for the cars engine needed to operate the windscreen wipers


Title: Re: Front of the bubble [DotD 10.4.2020]
Post by: martyjon on April 10, 2020, 09:57:04
Finally for my two pennyworth there is a toggle switch for the two tone air horn

Have I missed anything ?


Title: Re: Front of the bubble [DotD 10.4.2020]
Post by: Witham Bobby on April 10, 2020, 09:57:56
What you cant see, to the left, is the stack of blue lights.  There were three vertical columns of lights.  The columns to left and right indicated, when lit, that the engine it reported was running.  The central column of lights indicated that the final drive was engaged correctly.  In a single car DMU, only the top three lights across the stack would be relevant.  A 3-car, with two cars powered, would show the top two rows.  There was a limit (six power cars??) on how long a DMU train could be.  I don't know if this related to the number of lights, or whether some technical limit decided the length of the train and this in turn affected how many lights there were.


Title: Re: Front of the bubble [DotD 10.4.2020]
Post by: grahame on April 10, 2020, 09:58:44
Many useful bits of information and reminders there.  Looking to correlate that ...

(http://www.wellho.net/pix/labelcab.jpg)

A Accelerator
B AWS Cancel button
C Gear Change
D Vacuum Brake
E Manual Brake
F Rack for gear brake handle and gear level handle
G AWS - most recent status indicator
H Speed indication
I Engine Revs
J Vacuum pressure
K Air pressure
L ?

Now ... a little lost as to which switches are which ...
M
N
O
P


Title: Re: Front of the bubble [DotD 10.4.2020]
Post by: martyjon on April 10, 2020, 10:28:40
I think the red button (P) is engines stop


Title: Re: Front of the bubble [DotD 10.4.2020]
Post by: grahame on April 10, 2020, 10:35:21
I think the red button (P) is engines stop

Yes - that makes sense. 

There are two switches just above "P" (part of the "P" group).  Lots of switches mentioned - which were those?


Title: Re: Front of the bubble [DotD 10.4.2020]
Post by: grahame on April 10, 2020, 10:48:51
What you cant see, to the left, is the stack of blue lights.  There were three vertical columns of lights.  The columns to left and right indicated, when lit, that the engine it reported was running.  The central column of lights indicated that the final drive was engaged correctly.  In a single car DMU, only the top three lights across the stack would be relevant.  A 3-car, with two cars powered, would show the top two rows.  There was a limit (six power cars??) on how long a DMU train could be.  I don't know if this related to the number of lights, or whether some technical limit decided the length of the train and this in turn affected how many lights there were.

I've looked through my pictures and found an image that went a bit off to the left - please excuse the awful quality as I've had to play with the colour profile to get it to show at all.  Also the rest of the control panel - the bit the driver can't reach from the driving seat.

(http://www.wellho.net/pix/leftcab.jpg)

(http://www.wellho.net/pix/rightcab.jpg)


Title: Re: Front of the bubble [DotD 10.4.2020]
Post by: Electric train on April 10, 2020, 11:32:15
What you cant see, to the left, is the stack of blue lights.  There were three vertical columns of lights.  The columns to left and right indicated, when lit, that the engine it reported was running.  The central column of lights indicated that the final drive was engaged correctly.  In a single car DMU, only the top three lights across the stack would be relevant.  A 3-car, with two cars powered, would show the top two rows.  There was a limit (six power cars??) on how long a DMU train could be.  I don't know if this related to the number of lights, or whether some technical limit decided the length of the train and this in turn affected how many lights there were.

I've looked through my pictures and found an image that went a bit off to the left - please excuse the awful quality as I've had to play with the colour profile to get it to show at all.  Also the rest of the control panel - the bit the driver can't reach from the driving seat.

(http://www.wellho.net/pix/leftcab.jpg)

(http://www.wellho.net/pix/rightcab.jpg)

Top photo are the engine and control air indication lamps 3 per power car outer ones are engine run

The lower buttons outer ones are engine start the centre (black) i think was the lamp test.

Fault finding this was a challenge given to us apprentices at Reading DMU

Second photo

Red device the emergency vacuum brake

the single silver control is the car and train light control, buttons for car lights only centre leaver train lights

Next are the Smiths Heater control for this car, each car had its own set.  Smiths heaters used diesel fuel for combustion and were very effective at filling the car with smoke  ;D


Title: Re: Front of the bubble [DotD 10.4.2020]
Post by: Fourbee on April 10, 2020, 11:40:24
I think this link was originally posted on this forum somewhere. The DMU in the video is not identical to the images posted, but some of it might help with the gaps if you search in it:
https://www.youtube.com/watch?v=2VgB3Uwx6oI

If you've got 18 minutes to burn, you could watch the whole thing of course!


Title: Re: Front of the bubble [DotD 10.4.2020]
Post by: Western Pathfinder on April 10, 2020, 11:51:54
This may also prove to be of interest
https://m.youtube.com/watch?v=bS5xiM0LYtA.


Title: Re: Front of the bubble [DotD 10.4.2020]
Post by: Fourbee on April 10, 2020, 12:56:03
This may also prove to be of interest
https://m.youtube.com/watch?v=bS5xiM0LYtA.

That was the link I meant to post!  :-\


Title: Re: Front of the bubble [DotD 10.4.2020]
Post by: eightonedee on April 10, 2020, 16:16:04
Brought back happy memories of a footex gift from my mother in law, taking a DMU up and down the Wensleydale from Leeming Bar to Castle Bolton. There is something satisfying when you (think?) have got the hang of balancing the throttle, gears and brake. Recommend it to anyone,


Title: Re: Front of the bubble [DotD 10.4.2020]
Post by: Trowres on April 10, 2020, 23:13:50
Many useful bits of information and reminders there.  Looking to correlate that ...

(http://www.wellho.net/pix/labelcab.jpg)



A Engine power controller - idle and 4 power positions; incorporates deadman's device
B AWS Cancel button
C Gear Change - 1,2,3,4,neutral. There is also a slot under the circular part of the handle into which a brass forward/reverse lever is placed when the cab is in use. This lever is mechanically interlocked with the gear change handle.
D Vacuum Brake
E Manual Brake
F Rack for vacuum brake handle and forward/reverse handle
G AWS - most recent status indicator
H Speed indication
I Engine Revs
J Vacuum - "duplex" gauge - two indicators; brake pipe and release pipe
K Control air pressure
L Brake cylinder reservoir vacuum - only "bubble cars" had these. Due to having only 2 brake cylinders on the train if a single-car, it was especially important to know if the vacuum above the brake piston was being maintained correctly.

Switches are a problem as the layout varied between DMU types. Here's my attempt:-

M Communication buzzer and either demister blower or cab heater
N Control circuit key and ??? did these things have a screenwash?
O Route indicator light switch; two switches for marker lights - each with red/off/white
P Switch to select whether the tachometer is looking at engine 1 or engine 2. Red light to indicate control circuit is energised (i.e. a key is inserted in one or other cab and no fuses have blown); other switch is either demister blower or cab heater fan.


On the indicator panel to the side of the cab, the outer lights indicate engine running; the central light is "air and axle" - it was illuminated only if both final drives on a power car were in the correct direction for running as indicated by one of a pair of air pressure switches (one for forward, one for reverse).

The three black buttons were LH engine start / all engine stop / RH engine start (the red test button was a feature on re-engneered panels).

The drivers cab had a heater fed by engine coolant. A switch was provided to control an air circulating fan fitted to the heater. The demister, however, was fed (if I recall correctly) by air from the Smiths heater warming the passenger saloon. It wasn't terribly effective.

The Smiths heater burnt atomised diesel fuel. A glow-plug provided initial ignition. The start-up sequence was originally a clockwork timer but this was eventually replaced by an electronic unit (as in the bubble car photo) that included a 741 op-amp. Another 741  op-amp was used in an interlock circuit that de-energised the starter motor circuits when an engine reached sufficient rpm to run.

Remember that vacuum brake gauge with the twin indications? Releasing the brake required sucking air out of the train pipe until 21" Hg registered on the train pipe gauge. As the mechanical exhauster wasn't very rapid at doing that sucking, a large tank (about the size of an oil drum) was provided on each car, linked by a "release pipe" with about 30" vacuum. Into this went the air from the train pipe in order to release the brake quickly.

In fact, as the vacuum exhauster was belt-driven off the gearbox input, as soon as the driver put the unit into 1st gear to start from a station, the exhauster stopped. If there wasn't sufficient vacuum in the release reservoirs, the brake would never be released!

The compressed air supply was used for horn, wipers... and engine and gearbox control. The throttle and gearbox controls were just big rotary switches energising a selection of wires down the train. These linked (via relays) to electro-pneumatic valves that operated an air-motor for controlling the engine governors and more pistons to select gears and forward/reverse.


Title: Re: Front of the bubble [DotD 10.4.2020]
Post by: grahame on April 11, 2020, 07:20:11
Huge "thank you" to everyone who's helped me fillin what all the nobs, dials and levels do - Trowres, Martyjon, Electric Train, Witham Bobby, Rogerw, Western Pathfinder, Bobm, Fourbee and Eightonedee. 

You correctly identified that the original picture was of the trailing cab during a journey - three vital elements missing to operate the vehicle from this end. Here, from earlier in that day, is a further picture with those three emenents shown:

1. The handle on the vacuum brake (on item D)
2. The forward / reverse level (fitted under the gear change on item C)
3. The driver - physically larger that any of the controls and blocking much of the view in the bottom left of the picture.

(http://www.wellho.net/pix/drivencab.jpg)


Title: Re: Front of the bubble [DotD 10.4.2020]
Post by: eightf48544 on April 11, 2020, 11:53:29
If I recall correctly the Rev counter acted as a gear change indicator, There being a yellow crescent round the top of the dial as the revs increased the needle moved round when it reached the end of the yelllow band it was time to change gear.

It then crawled round again until after a painfully long time you got to fourth gear and 70mph!

Modified to add round.


Title: Re: Front of the bubble [DotD 10.4.2020]
Post by: bradshaw on April 11, 2020, 12:24:43
Especially when the panel located between the door and the left hand window showed one or more engines out!


Title: Re: Front of the bubble [DotD 10.4.2020]
Post by: Electric train on April 12, 2020, 07:20:50
The gear box on DMUs is a 3 speed epicyclic, fourth gear being direct drive.  The coupling to the engine is a fluid fly wheel.

The original driving technique was in first gear take the train to the speed that the engine tacho showed change up, where the driver would change gear with out dropping the engine revs off.

It was soon found that this cause excessive where to gear box brake bands and over heating of the fluid fly wheel.  The driving technique was changed, the driver when a gear change is needed drops the engine revs off change gear and the apply engine power.

The final drive on the driving axels has a sliding dog to provide reversing .  One of the checks that had to be done on a power car that had a final drive change was to check the axel turned in the right direction, get the pneumatic lines crossed and the dog would engage in the wrong direction  :o :o


Title: Re: Front of the bubble [DotD 10.4.2020]
Post by: Trowres on April 12, 2020, 22:10:39
Compared with today's mess of incompatible trains, most heritage DMUs had a remarkable degree of compatibility (identified by a coupling-code symbol on the cab ends). Most units had the "blue square system" that used four jumper cables connected down the length of the train. No fancy computers or change-end reboots. A clever staggering of connections on the power cars (e.g. pin 1 at one end connects to pin 2 at the other end of the coach) was all that was required to ensure that the leading driving cab could monitor the status of engines on six power cars.

Forward and reverse was managed with similar simplicity. Selecting "forward" in the leading power car was correctly interpreted as backwards by any power car in the train that was pointing in the opposite direction. All done by the way the jumper cables were wired. The only use of relays was to ensure that each power car supplied the current to work its own electro-pneumatic valves, with a relatively small current from the leading power car operating all of the relays down the train.

I came across one class 108 2-car unit in which engine coolant from the power car was used to provide water heating in the toilet in the trailer car (via flexible coupling pipes between the coaches). I have no idea how commonplace this was and have never seen the practice described in any manuals or historical notes.


Title: Re: Front of the bubble [DotD 10.4.2020]
Post by: Fourbee on April 13, 2020, 09:51:31
Forward and reverse was managed with similar simplicity. Selecting "forward" in the leading power car was correctly interpreted as backwards by any power car in the train that was pointing in the opposite direction. All done by the way the jumper cables were wired. The only use of relays was to ensure that each power car supplied the current to work its own electro-pneumatic valves, with a relatively small current from the leading power car operating all of the relays down the train.

On class 483s (so not comparing apples with apples) the unit coupling was needed the right way round, observing the letters on the cab ends; presumably you end up with an intra-train tug of war otherwise!


Title: Re: Front of the bubble [DotD 10.4.2020]
Post by: TonyN on April 13, 2020, 16:37:38
Quote
The central column of lights indicated that the final drive was engaged correctly

These where added after an early incident when one power car in a set did not reverse and tried to fight against the rest of the train. This resulted in overheating and a fire fortunately the car was empty at the time.


Title: Re: Front of the bubble [DotD 10.4.2020]
Post by: Reading General on April 13, 2020, 17:57:43
This is an interesting thread, I'm learning a lot from it. These trains took me many places when I was young. I distinctly remember riding on one from Reading to Henley (when the branch train was a through train from Reading) with my Dad where the blinds were up in the drivers cab at the Reading end of the train. We got to see the line view going backwards through Sonning Cutting and then watch the Driver and see out of the front from the reversal at Twyford. A wonderful experience for a small lad.


Title: Re: Front of the bubble [DotD 10.4.2020]
Post by: Oxonhutch on April 13, 2020, 21:12:35
A wonderful experience for a small lad.

Indeed. Daring to sneak into an empty First Class for a journey towards St Annes-on-the-Sea just so I could watch out the front.


Title: Re: Front of the bubble [DotD 10.4.2020]
Post by: CyclingSid on April 14, 2020, 06:55:26
Used to enjoy going from Reading to Basingstoke in summer and watch the rabbits on the line. They had obviously sussed out these large things that invaded their space and had timed getting out of the way perfectly.


Title: Re: Front of the bubble [DotD 10.4.2020]
Post by: eightf48544 on April 14, 2020, 10:46:27
Managing to get near the front of a set of 117s on an Oxford Northampton excursion via East West and the Bletchley flyover. Interesting to watch the stagger on the overhead.


Title: Re: Front of the bubble [DotD 10.4.2020]
Post by: Umberleigh on April 27, 2020, 18:00:26
Once travelled in one of a pair headed from Barnstaple down to Exeter. I appreciated the view out of the rear cab but not so much the bucking and swaying at speed, which could be quite alarming!


Title: Re: Front of the bubble [DotD 10.4.2020]
Post by: Ralph Ayres on April 27, 2020, 21:06:16
Once things return to some sort of normality I'd strongly recommend a visit to the Ecclesbourne Valley Railway, which has a particularly good collection of traditional DMUs. Their Railcar weekends, with a varied mix of types and the occasional towed goods van, are excellent. On a quiet trip we were treated to an explanation of the various coupling codes and some of the tricks which can be used with care to join different combinations, so long as you understand which commands will or won't be sent along the train. We also had a demonstration of how a trainee driver who doesn't notice that one car hasn't gone properly into gear can make a bit of a mess of the gearbox, but that's a different story...


Title: Re: Front of the bubble [DotD 10.4.2020]
Post by: Trowres on July 04, 2020, 00:09:45
I came across this set of photographs of DMU cab interiors. Some rare long-gone examples in the set. Wrap-round windows on the class 124 forced a significant rethink on the layout of indicators!

http://www.dawlishtrains.com/cabs-dmu-heritage.html (http://www.dawlishtrains.com/cabs-dmu-heritage.html)



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