puffernutter

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