Why isn't manual transmission used on railway vehicles?

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?
>
> Just curious.
>
> B2003

Weren't the "heritage" DMUs kind of preselect?

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.

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

> Matching load and revs in some sensible manner, which manual selection
> of gears is generally very bad at due to deficiencies in the component
> connected to the top of the gear lever.

As an advocate of automatics, my experience --- out of the half-dozen
or so we've run --- is that a manual is more efficient on paper, but
you never get the fuel consumption it claims. An auto is less
efficient on paper, but that's the fuel consumption you get. The
grand-parent posting's claim that an auto is `always' slipping the
torque converter isn't true, of course: every auto gearbox of the last
twenty years has had lock up on the top, and most on the top but one,
gear, and as autos get more epicyclic ratios more of them can be run
with a lockup. I don't know about the six-speed VAG `traditional'
auto, but I suspect that the top three or possibly even the top four
ratios run with lockups.

Anyway, this is all beside the point. Get yourself to a car dealer
and drive a VW/Skoda/Audi with the `DSG' gearbox. Two layshafts, two
oil-bath motorcycle clutches. One shaft has R, 1, 3 and 5, the other
has 2, 4 and 6. The computers then select the appropriate next gear
in advance (ie if you're in fourth and accelerating the other shaft
will have lined up 5, decelerating it'll have lined up 3) and blend
the drive over when you reach a change point. The shifts are
effectively instant, as the drive is never broken. Banned in F1 (it's
roughly the `twin clutch' design McLaren used five years ago), the
only loss is that it's about 5kg heavier than the manual equivalent.
If you believe your skills with the ratios are a sign of your manhood,
you can have it with a hideous flappy-paddle thing on faux-sportive
cars, but on my cooking Skoda estate it's driven just like an auto.
But it gets 50 to the gallon. Around town it's not quite as smooth as
the best slushpump autos, but it's perfectly acceptable. A beautiful
piece of engineering.

ian

thagor2008@ 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?

I read that the new DMUs ordered for West Midlands are going
to have mechanical transmission, IIRC for the reason you
suggest.

Epicyclic gearboxes, though, I would imagine, not a
clutch-based system.

Charlie

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?
>
> Just curious.
>
> B2003

It's about control. With electrical transmission of the power, using
traction motors on the bogies, it's possible to deal with wheel slip
very effectively. This means that each axle can transmit the power
that its adhesion can justify - if you use a mechanical transmission,
then traction on all axles is limited by the axle with the lowest
adhesion.

It's also possible to use the traction motors as part of the braking
system, either with power storage or by dissipating the energy in
resistances. This reduces brake wear and maintenance costs while
providing good control over wheel slide when there is poor adhesion.

It's also easier to design for good bogie dynamics when the power is
transmitted over flexible cables than through a solid shaft with
universal joints at each end.

Scaling clutch technology to operate in the rail environment is also a
challenge. I've had two clutch springs break and I've worn out one
other clutch in 110,000 miles in a low-power car. Over the 23 years
I've had the car, that's not so bad, but even pacer units would cover
this in rather less than two years - and would require considerably
more power to be transmitted.

It would certainly be possible to design a mechanical transmission to
handle the power required for rail vehicles, but electrical
transmissions are more efficient and offer so many other advantages
that nobody bothers.

Rob

Andrew Robert Breen wrote:
> In article <Ndsbk.140837$312.137628@newsfe12.ams2>,
> Charlie Hulme <info@davenportstation.org.uk> wrote:
>> thagor2008@ 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?
>> I read that the new DMUs ordered for West Midlands are going
>> to have mechanical transmission, IIRC for the reason you
>> suggest.
>>
>> Epicyclic gearboxes, though, I would imagine, not a
>> clutch-based system.
>
> "Automatics", in other words...
>

I thought "Automatics" changed gear automatically?

If the new units work like the 1950s DMUs they will
have a handle which the driver uses to change gear by
operating the epicyclic gearbox..

I'm probably out of my depth here...

Charlie

> I used not to be a fan of automatics, but we've had our Octavia with the
> DSG for two years now, and ... I like!

My parents had a trip in mine, test-drove one the following month and
bought one soon thereafter. They're awesome. Diesel autos are thin
on the ground, and it's a perfect pairing. My parents' 2.0 16V
diesel is a lot more refined than the 1.9 8V in mine. My wife's Saab
9-3 (94-01 shape) auto (standard GM part) is nicer to drive, but
that's mostly down to the awesome last-of-them-made 150bhp light
pressure turbo engine...for Mr Breen's benefit, the last engine in the
direct lineage from the Ricardo modular V8 that gave us the Stag, the
Dolomite and the Saab 99.

I had mine sight-unseen: there weren't any DSG testers available and
the 05 Octavia estate was only at that point available in LHD, so mine
was on of the first off the boat. So the first trip I had in a DSG
car was driving home with it once it had been delivered to the office,
and I'd never seen one of the cars irrespective of transmission other
than in a photograph. It sounded like a neat idea, so I just had it
on the ``if banned in F1, then you want it'' argument: see also ABS,
stability control, etc. I reckoned that at worst I just wouldn't like
it much, and my wife being prepared to drive my car while having the
economy of a diesel (40 miles per day motorway commute) was worth any
unpleasantness --- company cars are only for four years and decouple
you from any maintenance gremlins.

ian

> Semi-auto options remain
> (and grow in popularity) 'cos in auto mode they generally
> do better than manuals and in semi-mode they allow the proud
> owner to pretend they're the Stig (I speak, here, of
> cars of course..)

Except the Stig himself knows that electronics do it better. The only
reason F1 cars have flappy paddles is because the full-auto option is
banned. Barnard did the semi-auto for his Ferraris in the late
eighties, because powered shifting and automatic clutches were enough
of a problem, but rapidly other teams realised that the real win was a
full auto, and Benneton and Williams were both running fully automatic
gearboxes by the early 90s.

Remember, the great F1 car that never was: the Williams of 1993 with a
CVT gearbox, tested by Hill and others. It was two seconds a lap
faster, straight out of the box, with the engine not yet tuned to take
advantage of the fact that with CVT a power-band 1 rev wide is just
fine. It was banned instantly, and criminally, mostly on the grounds
of the bizarre noise it made and a fear of a transmission arms race.

Full-auto gearboxes were banned in the post-Senna hysteria, and hence
the rise of the flappy paddle. But it's bollocks to think that's a
good thing for your Stag about town: it's a regulatory issue, which
stops the teams doing the faster thing.

ian

On 5 jul, 01:20, a...@aber.ac.uk (Andrew Robert Breen) wrote:

>
> Semi-automatics, then.
>
> Plenty of epicyclics + automatic clutched boxen,
> some with hydrokinetic drives to avoid having a
> low bottom ratio, some without (from memory, the
> delightful Citroen C-matic had a h/k drive, the
> Porsche sportmatic -

Had one of those (Porsche Sportmatic), couldn't sell it fast enough.
NM