Re: [SA] Booster engines in 500 Class Steam Loco's

["John Lacey" <jlacey@zeta.org.au>]

"Booster" engines were  auxillary engines fitted to some USA-and other-steam
locos  to increase their tractive effort on starting and in climbing steep
grades.

They were typicaly fitted to the rear trailing axle-or to a tender in some
cases-but in the case of the 500s this would have made the axle load too
high so the new 4 wheeled truck was installed.  The booster added 8000lbs to
the tractive effort rating of the 500 class.

When the booster assistance was not required, a spring gear held the wheels
out of contact and thus no parts of the booster engine or gearing were in
motion.  This occurred once a predetermined speed was reached.

The 500B class were allowed 540 tons as the winter load on the line to
Mt.Lofty, with 500 tons for the 500 class ( all 500s were converted to
500B).

John Lacey

----------
In article <39C0D6A6.F1B4B51@ozemail.com.au>, Jonathan Lau
<jonlau@ozemail.com.au> wrote:


> I have read that the 500 Class 4-8-2 loco's of the South Australian
> Railways were rebuilt as 4-8-4 type, with a Booster engine fitted in the
> trailing truck allowing increased tractive effort.
>
> Can anyone describe this booster engine and how it works?
>
> Thanks,
>
> Jon Lau
>