Re: DL531 Alcos

["Steve Palmano" <steve719@GTE.net>]

Aus loco discussion mailing list


My understanding is that the Alco DL531 model benefited from having an
electrical system, and particularly traction motor capacity that was quite
generous in relation to the engine power output.  Thus, for any given gear
ratio (and therefore top speed capability) the continuous speed was quite
low.  The sources to which I have access quote a continuous speed of 6.1 or
5.8 mile/h for the 830 class, according to build year, and a maximum speed
of 60 mile/h.  Circa 1957, when the DL531 was first released, that was a
pretty good ratio.  Couple that with the low power to axle load ratio that
Melanie has already mentioned, and it figures that the DL531 should be a
good candidate for extended working full out at low speeds without burning
up its electrical system or losing its feet.  It seems that in this case,
practice reasonably matched theory!

Actually, in 1957 Alco appeared to have a competitive advantage with the
DL531, particularly for narrow gauge railroads.  It was dimensioned to fit
tight clearances, had a light (<12 long tons) axle load, but a good adhesion
weight in relation to its power.  At that time, GM did not have a 6 motor
version of its G8, and wouldn't have for a few years.  I don't know whether
GE ever offered or built a U9C, but even so, using basically a U12C chassis,
it would have been somewhat heavier.  (Conversely, GE's high power 12
cylinder offering of the time, the U18C, was noticeably lighter and more
tightly profiled than Alco's 12 cylinder models.)  In 1957/8 EE would have
had to use its 8 cylinder engine for locos in the 1000+/- hp class; it would
probably have been a tight squeeze to get this and 6 traction motors into a
unit weighing less than 72 tons.  (The MRWA G class, at 75 tons, is
indicative.)  GM and EE eventually introduced even lighter locos in this
power class (GL8C/QR1700 and RSE92C/QR1600 respectively) although both of
these used light weight and therefore lower capacity traction motors.
(E.g., the EE 540 TM, first used in QR1600, is 450 amps continuous, whereas
the 537 is 635 amps.  By the way, I don't have numbers for the 548 and 558.)
Their continuous speeds are slightly higher than that for the DL541.

Anyway, back to the DL531, it's interesting that despite its apparent narrow
gauge design leanings, most of the units sold in Australia were for standard
and broad gauge applications!  In part, I suppose, none of the ng roads had
a specific need for a 12 ton axle load loco; for their light lines they
wanted really light axle loads, around 10 tons, and it was into the 1960s
before decent 6 motor locos in this class appeared.

Cheers,

Steve Palmano

----- Original Message -----
From: ben scaro <bscaro@hotmail.com>
To: <Ausloco@listbot.com>
Sent: February 22, 2000 07:48 PM
Subject: DL531 Alcos


> Aus loco discussion mailing list
>
> I don't want to get involved in a flame war re the merits of the Alcos,
but-
>
> In Tasmania I've heard crew comments that the units could haul if in good
> condition (most weren't), but cab comfort\visibility left a lot to be
> desired, and thus drivers did not like them, preferring EEs.  I am not
sure
> what the opinion was in the shops, but Tasmanian fitters must have been
more
> used to their EEs.
>
> I understand on the Eyre Peninsula the 830s are liked for their lugging
> ability compared to the NJs, but I've not heard anything re the relative
> merits when it comes to crew comfort and visibility.
>
> What was the view of SAR\AN broad gauge crews ?  They had to work in 830s
in
> fairly hot conditions, and had the comparison of EE 800s and 500s, which I
> understand were fairly popular units, though not much used on main or
> branchline runs in later years (except for the odd grain\super run on the
> northern broad gauge and on the Naracoorte-Kingston line.
>
> Cheers
>
> Ben
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