Re: Dead hauling QR diesels

[Trevor Gibbs <xdford@start.com.au>]

Aus loco discussion mailing list

Hello there

There are I guess pros and cons to having a loco idle while being
towed, but the concept of being bad for Traction motors should not be
one of them. THe only consideration would be any voltage that could be
generated while the loco is being moved having "nowhere to go" because
it is 
disconnected through what are known as recirculating currents. This
would be minimal as a loco to get any real form of excitation for
Dynamic Braking had to be placed in the equivalent of Notch 4 speed to
work. LatMore modern locos can excite their traction motors as a fuel
conservation measure at a much lower rev rate so there might be a
slight problem there.

Otherwise there is little heat at the brushes because current is not
running through them apart from friction (minimal as the carbon
compound was self lubricating against the copper surface). When I was
at Mile End, I had a long discussion with Alf (the Email brush man
Alf... but I can't remember his surname)re wear on brushes while
engines were being towed, and it was universally recognised that next
to no wear occurred 

THere might be a case in dusty territory for the blower being on and
pressurising the motor commutator area and keeping dust out but the
rotation would act as a fan anyway. However the Old CR often towed
locos across the desert for balancing purposes many times the whole
distance to Kalgoorlie from Pt Pirie or vice versa.

Peter, you are correct about the long distance QR trains having a loco
midstream. I photographed one at the Roma St Yard in 1974 and it was
common place apparently ( although I only witnessed it a few times and
then at night) There is also a picture of one such working in
"Destination Sth Brisbane". Could it have been a hangover from steam
working when engines had top be separated for weight working on
bridges by a carriage or two on certain lines? 

Be interested in any other feedback here... Justin... just what do you
do at MPC???


Cheers


Trevor


Original message from: "PETer and susAN Cokley" <petan@powerup.com.au>
>
>Aus loco discussion mailing list
>
>Interesting statement re dead haulage of diesels on Australian
Railway
>Rollingstock Mailing List.
>
>David Bromage wrote >>>>
> [ snip of preceding material, see "ausrollingstock mailing list"
for
>complete message in context]
>
>Dead hauling a diesel electric is bad for the traction motors. Even
if
>you're double heading but don't need
>all the horsepower, it's wise to have the second loco idling and
offline.
>The blowers keep the traction motors cool and dry, and you can easily
switch
>the second loco in if the first one fails.
>
>**************************
>
>My understanding of dead haulage of QR locos is that they are in fact
>switched off and frequently hauled part of the load and not always
attached
>to the hauling locos, thus can be back in amongst the wagons forming
the
>load being hauled.  I also understand that this is a regular event
and over
>some quite long distances.
>
>Some feed back please?
>
>Cheers
>Peter Cokley
>
>
>_____________________________________________________________________
_
>To unsubscribe, write to Ausloco-unsubscribe@listbot.com
>---------------------------------------------------------------------
-
>Advertisement:
>Workstation with Monitor under $800!
>So, you just heard that you need to add how many new workstations by
>the end of next week? Check out the bundle below. It includes
>everything you need to get everyone up and running quickly.
>http://www.listbot.com/links/cdw5
>



__________________________________________________________________
Get your free Australian email account at http://www.start.com.au


______________________________________________________________________
To unsubscribe, write to Ausloco-unsubscribe@listbot.com
----------------------------------------------------------------------
Advertisement:
Workstation with Monitor under $800!
So, you just heard that you need to add how many new workstations by
the end of next week? Check out the bundle below. It includes
everything you need to get everyone up and running quickly.
http://www.listbot.com/links/cdw5