Why isn't manual transmission used on railway vehicles?

puffernutter wrote:
> On 4 Jul, 12:32, ab...@cam.ac.uk wrote:
>> On 4 Jul, 11:26, thagor2...@ wrote:
>>
>>> Manual gearshifts are popular with trucks because they're fuel
>>> efficient compared to automatics. How come their not used on the
>>> railways as far as I know? Is it the extra complexity of having bogies
>>> that rules it out or the huge clutch that would be required especially
>>> with locomotives or is there another reason?
>> Firstly because most diesel locomotives are electric transmission.
>>
>> Secondly, because the size of the gearbox on DMUs / WR diesel
>> hydraulics is a damn sight larger than a cars
>>
>> Thirdly, if they had manual transmission, how would you change gear on
>> a power-twin DMU or larger? Signal box sized levers and rodding?
>>
>> I expect it's a complexity thing. Can you imagine pulling away from
>> The Cross being sent every which way by the points whilst also
>> changing up gears?
>>
>> Manual gearboxes are used on small diesel mechanical shunters -
>> especially historic narrow gauge ones. I've had a lot of fun with a
>> four-speed air-shift gearbox on an old mines Hunslet diesel. In
>> addition, the simplese type of motive power, the Motor Rail Simplex
>> has two big levers, forward-reverse and first-second gears.
>
> IIRC the heritage DMUs had manual gearboxes with a centrifugal clutch
> (Leyland engines?). These could quite happily be run in multiple with
> all the gear changing initiated from the leading cab. Some of the
> Rolls Royce engined units, whilst automatic still had a manual change
> so that they could be used in multiple with other (manual) units. I do
> have a rev counter from an old DMU that has "UP" and "DOWN" marked to
> aid the driver to know when to change.
>
> I of course stand to be corrected as I was nobbut a nipper at that
> time :-)
>
> Cheers
>
> Puffernutter

The speeds were also laid down in the drivers manual. 1st gear was 0 -
15 mph, 2nd was 15 to 27, 3rd was 27 to 41 and 4th did the rest.

Brian.

In message <5OaUrkbN3VcIFwNu@nemesis.as15758.net>, Pyromancer
<pyromancer@beeching.stormshadow.com> writes
>Wait for engine revs to drop to minimum, change into 2nd gear. Wait
>five seconds. Open throttle.
There was a yellow band on the rev counter positioned between 10 o'clock
and 2 o'clock which was the working band. The engine revs were allowed
to drop to the bottom of the yellow band the next gear was engaged, the
top of the band being the maximum governed engine speed, 1800rpm rings a
bell somewhere. Further as part of the bell code, the driver replied
with two "peeps" on the guards buzzer before taking any action at all,
this was to ensure that the driver had the right instruction which the
guard would change if not properly understood.
--
Clive

Pyromancer wrote:
> From what I remember, the operation (based on observations of the Class
> 126 Ayrshire units, which didn't have a through air line, in the very
> early 1980s) was:

That matches my recollection of the DMUs on the Hayfield branch. And
there was a duplicate deadmans handle on the right-hand side of the
drivers compartment, it was used when the tablet was picked up at the
New Mills Tunnel End box and when the tablet was dropped off at Hayfield.
Bruce

Clive wrote:

> Further as part of the bell code, the driver replied
> with two "peeps" on the guards buzzer before taking any action at all,
> this was to ensure that the driver had the right instruction which the
> guard would change if not properly understood.

This was, and is, the rule, but on the Buxton line 104s it
was not necessarily followed to the letter....

I spent many journeys behind the driver on these units,
fascinated by the driving technique and the signalling.
The best time would be rolling down the hill
from Middlewood to Hazel Grove at sunset, seen in
its full glory from the embankment overlooking Manchester,
and sometimes coasting at just a tad over the unit's
70 mph maximum.

For a very large part of the downhill Buxton - Stockport
journey the engine would be idling, with the rev counter at
0.

And what the DMU drivers in those days, especially the
ex-steam ones from Buxton shed, would have made of the
painfully cautious approach to the buffers at Piccadilly
we get these days, is probably unprintable.

Charlie

In message <dp6dnYWkpeXb7-_VnZ2dnUVZ8gydnZ2d@posted.plusnet>, Mortimer
<me@> writes
>I've never driven a car without synchromesh, but I thought that the
>technique was to get the engine/input shaft rotating at the correct speed to
>enmesh with the output shaft for the gear about to be selected, rather than
>to attempt to engage with the engine idling.
Yes, when I drove Bristol/ECW Loddeckas, the box was as in all boxes
since the 30s where all gears were in constant mesh (overlooked by a lot
of contributors) but gear changing was done by moving the dog clutches
in the gearbox, allowing for a fast up change but for a down change the
engine had to be put into neutral revved until both shafts were the same
speed then the dog engaged, something that modern motorists couldn't
imagine but basic and easy once you got the hang of it. A lot of
people called it double declutching because it took clutch to neutral,
flash of gas, then clutch to the next lower gear.
--
Clive

On Jul 7, 8:15 am, "Mortimer" <m...@> wrote:
> "Roland Perry" <rol...@perry.co.uk> wrote in message
>
> news:eC9WFkfSekbIFAwR@perry.co.uk...
>
> > In message
> > <7115a734-d7e6-4288-bdcc-e3de98825...@y21g2000hsf..com>, at
> > 04:00:33 on Fri, 4 Jul 2008, MIG <googles...@doreenbird.co.uk> remarked:
> >>Weren't the "heritage" DMUs kind of preselect?
>
> > Something like that. I remember sitting on them while they ground their
> > way up through the gears on the slow trains out of Paddington. Rarely
> > finding the next set of teeth on the first attempt.
>
> I remember the same on the heritage DMUs that used to operate the line
> between Aylesbury and Marylebone. The transmission required a very strange
> driving style (by car driving standards, anyway!) in that the driver always
> let the engine revs drop to idle between disengaging the old gear and
> engaging the new one, so each gear change took several seconds to complete.

I remember the very slow gear changes as well, and I wonder if they
could ever get up a steep hill if they tried to change out of first.

Very different from the modern hydraulic units which seem to change
instantaneously, but that would be a very different system. Speed of
gear change alone could account for a huge leap in performance.

What I can't remember is whether the hydraulic heritage DMUs that ran
out of St Pancras had gear changes more like modern units or more like
other heritage units.

The message <gTegnOBEQocIFw$H@yewbank.>
from Clive <Clive@yewbank.> contains these words:

> A lot of
> people called it double declutching because it took clutch to neutral,
> flash of gas, then clutch to the next lower gear.

We used to call double-declutching a "racing change", presumably because
that's how the old(1920s/30s) racing/sports cars had to be driven. Once
you'd got the knack it was easy, and it certainly impressed the females.
However, it didn't do the synchromesh gubbins any good, and it doubled
the wear on the clutch. The other trick was "hell-and-toeing" -
operating all three pedals at once... Never did manage to get that one
right very often.

--
Dave,
Frodsham

In message <D62dncnh2tKVZ-7VnZ2dneKdnZydnZ2d@posted.plusnet>, Mortimer
<me@> writes
>"Clive" <Clive@yewbank.> wrote in message
>news:gTegnOBEQocIFw$H@yewbank....
>> In message <dp6dnYWkpeXb7-_VnZ2dnUVZ8gydnZ2d@posted.plusnet>, Mortimer
>> <me@> writes
>>>I've never driven a car without synchromesh, but I thought that the
>>>technique was to get the engine/input shaft rotating at the correct speed
>>>to
>>>enmesh with the output shaft for the gear about to be selected, rather
>>>than
>>>to attempt to engage with the engine idling.
>> Yes, when I drove Bristol/ECW Loddeckas, the box was as in all boxes since
>> the 30s where all gears were in constant mesh (overlooked by a lot of
>> contributors) but gear changing was done by moving the dog clutches in the
>> gearbox, allowing for a fast up change but for a down change the engine
>> had to be put into neutral revved until both shafts were the same speed
>> then the dog engaged, something that modern motorists couldn't imagine but
>> basic and easy once you got the hang of it. A lot of people called it
>> double declutching because it took clutch to neutral, flash of gas, then
>> clutch to the next lower gear.
>
>How did you manage the "flash of gas"? Was the aim to apply exactly the
>right amount to make the two shafts match in speed and then lift the clutch
>quickly,
Yes.
> or did you apply slightly too much and then pull the gear lever
>gently but steadily so that the dog clutches will engage when the shaft has
>slowed down to just the right speed, as you'd do with a clutchless change?
No.
>
>How long did it take to master getting just the right amount of throttle to
>match the speed
At a guess about 10 hours driving time
>- what proportion of the time did an average driver get
>things wrong?
Once used to it, you didn't think about it, it just worked, I presume by
knowing your speed and engine speed.
> I can usually manage a clutchless gearchange in both
>directions (although some gearboxes such as Hondas are more difficult to do
>it in than others such as Peugeot and VW), but that's with synchromesh.
I've tried it in cars but normally the balk rings cause you grief.
> Mind
>you, it takes some mastering and "usually" isn't good enough so I don't
>normally bother: the penalties for getting it wrong (graunching sound,
>possible/probably damage to gearbox) make it not worth it.
Listen to a Mekydro transmission changing gear, you'll never worry about
the dogs in your gearbox again.
>As a matter of interest, don't synchromesh gearboxes also move the dog
>clutches? I thought the difference was that before the clutches engaged, a
>sping-loaded cone on the shaft rubbed on a conical depression on the
>dog-clutch to "persuade" the input shaft to get to the right speed a
>fraction of a second before the lever was moved further and the dog clutch
>engaged.
Correct
> Or do synchromesh gearboxes do away with the dog clutch altogether
>and rely solely on the synchromesh cup/cone to transmit all the power?
No, you were right first time.

--
Clive

"David Jackson" <dijackson@zetnet.co.uk> wrote in message
news:313030303337333348729C9B67@zetnet.co.uk...
> The message <gTegnOBEQocIFw$H@yewbank.>
> from Clive <Clive@yewbank.> contains these words:
>
>> A lot of
>> people called it double declutching because it took clutch to neutral,
>> flash of gas, then clutch to the next lower gear.
>
> We used to call double-declutching a "racing change", presumably because
> that's how the old(1920s/30s) racing/sports cars had to be driven. Once
> you'd got the knack it was easy, and it certainly impressed the females.
> However, it didn't do the synchromesh gubbins any good, and it doubled
> the wear on the clutch. The other trick was "hell-and-toeing" -
> operating all three pedals at once... Never did manage to get that one
> right very often.
>
> --
> Dave,
> Frodsham
If you tried that on a lot of modern vehicles, you'd fall foul of the
'traction interlock'....
Regarding changing down on a semi-automatic box- a friend was on board a
Bristol RELL which did a top (13th?) to 1st change when coming down-bank
from Bristol to the Severn Bridge- it was a good thing that everyone was
sitting down.
Brian

In message <J-idnWglCPiUOe_VRVnyhgA@posted.plusnet>, Mortimer
<me@> writes
>"Clive" <Clive@yewbank.> wrote in message
>news:mT4hHjDc9ocIFwep@yewbank....
>> In message <D62dncnh2tKVZ-7VnZ2dneKdnZydnZ2d@posted.plusnet>, Mortimer
>> <me@> writes
>>>"Clive" <Clive@yewbank.> wrote in message
>>>news:gTegnOBEQocIFw$H@yewbank....
>>>> In message <dp6dnYWkpeXb7-_VnZ2dnUVZ8gydnZ2d@posted.plusnet>, Mortimer
>>>> <me@> writes
>>>>>I've never driven a car without synchromesh
>
>>>How long did it take to master getting just the right amount of throttle
>>>to
>>>match the speed
>> At a guess about 10 hours driving time
>
>As little as that? Thinking about it from a perspective of never having had
>to do it, I'd have thought that it would be the single main skill that a
>non-synchromesh learner would have to acquire, significantly lengthening the
>time that it took to become proficient compared with a driver of a
>synchromesh gearbox.
Agreed, but you are learning one skill, not the multitude of skills
needed to confront traffic in an ordinary car.
>I presume it took a lot longer to change gear with double declutching
>because the
> simple clutch-down/change/clutch-up process becomes clutch
>down/into-neutral/clutch-up/blip-throttle/clutch-down/into-gear/clutch-up.
Correct.
No, it's just one of those things one does without thinking about it,
when was the last time you looked at a rev counter and thought now or
later is the time to change up? It comes with practise and after a few
hours driving time you just do it without a thought. Remember the
brain is much more powerful than the best computer you can buy.
>>>- what proportion of the time did an average driver get
>>>things wrong?
>> Once used to it, you didn't think about it, it just worked, I presume by
>> knowing your speed and engine speed.
>
>And that was without an engine rev counter and a corresponding output-shaft
>needle to match up on the rev counter ;-)
>
>Am I correct in thinking that modern DSG gearboxes achieve their very smooth
>and fast gearchanges partly by having an auto-throttle which performs this
>matching of shaft speeds to avoid bring the clutch up with the gearbox and
>engine sides of the clutch going at different speeds?
No, what man do you think could instigate and complete a gear change in
8 milliseconds?
I think you've made a mistake, a fast change is not a smooth change and
the throttle doesn't enter into it, it's just a solenoid changing from
the 1,3,5 ratio to another clutch between the 2,4,6 ratio. Next F1,
Germany in a fortnight listen to the gear changes, no man on earth could
change a gear that quickly.
--
Clive