To start this list off I would like someone to clarify the of found
cionfusion with the term "Mallet" and specifically the differences between
simple and compound mallets.
Best regards

Stefan Lerche'
Duncan, B.C. Canada

At 18:50 28/04/99 -0700, you wrote:

From: "Stefan" <stefan@seaside.net>

To start this list off I would like someone to clarify the of found
cionfusion with the term "Mallet" and specifically the differences between
simple and compound mallets.
Best regards

That might send us scurrying for our reference books. I was 'taught' (by
whom I can't remember) that a Mallet was, by definition a compound. I've
just reached up for my large Collins' dictionary and it says "Chiefly US -
a very large powerful steam locomotive with a conventional boiler but with
two separate articulated engine units". No mention of 'compound' but I
think the definition is suspect anyway because I know of a 2-4-4-2
(compound) Mallet preserved here in NZ which is neither very large nor very
powerful. In fact, it is downright cute.


Nelson Kennedy, Christchurch, New Zealand
Ferrymead Trams, 0 gauge NZR trains and a little Espee H0 are at:
http://DownUnder.Railfan.net

At 02:18 PM 4/29/99 +1200, you wrote:

That might send us scurrying for our reference books. I was 'taught' (by
whom I can't remember) that a Mallet was, by definition a compound.

This is why SP's big AC's were "articulated consolidations" as opposed to
true Mallets, which reuse the steam for the second set of drivers, correct?
The same can be said for UPs Big Boys and Challengers. Were the Garratts
classified as simple articulateds as well?
Best regards

Stefan Lerche'
Duncan, B.C. Canada

At 21:51 28/04/99 -0700, you wrote:

From: "Stefan" <stefan@seaside.net>

This is why SP's big AC's were "articulated consolidations" as opposed to
true Mallets, which reuse the steam for the second set of drivers, correct?

Yep, that's how a compound works. High pressure from the boiler to one
engine and the exhausted lower pressue to the other. That raises a
question for me - how did the loco deal with any imbalance of supply from
one set of cylinders to the other? Were they designed so there would
always be a surplus of steam from the exhausts of the high pressure
cylinders with any excess being vented to the atmosphere once the inlet
valve had closed?

Were the Garratts classified as simple articulateds as well?

The New Zealand ones certainly were and I don't know of any compound
Garrats. Maybe they would have been Mallets if they were compound or was
the term mallet reserved for two engines following 'elephant style'. I
think the norm for Garratts was 'back to back' style.




Nelson Kennedy, Christchurch, New Zealand
Ferrymead Trams, 0 gauge NZR trains and a little Espee H0 are at:
http://DownUnder.Railfan.net

At 05:02 PM 4/29/99 +1200, you wrote:

The New Zealand ones certainly were and I don't know of any compound
Garrats. Maybe they would have been Mallets if they were compound ...

I believe this is the caseie: true mallet is = compound
Best regards

Stefan Lerche'
Duncan, B.C. Canada

Nelson Kennedy wrote:

From: Nelson Kennedy <nelsonk@chch.planet.org.nz>

At 21:51 28/04/99 -0700, you wrote:

From: "Stefan" <stefan@seaside.net>

This is why SP's big AC's were "articulated consolidations" as opposed to
true Mallets, which reuse the steam for the second set of drivers, correct?

Yep, that's how a compound works. High pressure from the boiler to one
engine and the exhausted lower pressue to the other. That raises a
question for me - how did the loco deal with any imbalance of supply from
one set of cylinders to the other? Were they designed so there would
always be a surplus of steam from the exhausts of the high pressure
cylinders with any excess being vented to the atmosphere once the inlet
valve had closed?

Volume/pressure is self-regulating. In the original design, the
high-pressure and low-pressure cylinders are made to proportions which
will represent the desired match - usually half the pressure in the l-p
system as in the h-p, but if there were an imbalance, the actual working
pressure in the l-ps would simply rise or drop to equalize with the
volume . . . no problem.

Were the Garratts classified as simple articulateds as well?

Like Nelson, I can't recall an instance of a compound Garrett . . . I'm
not sure about Fairlies, though (the ones which were two complete
engine/boiler assemblies joined at a single cab with single controls) I
seem to recall seeing one with mismatched cylinders but can't remember
where.

In a message dated 4/30/99 12:10:56 AM, HOsteam@onelist.com writes:

<<
Volume/pressure is self-regulating. In the original design, the
high-pressure and low-pressure cylinders are made to proportions which
will represent the desired match - usually half the pressure in the l-p
system as in the h-p, but if there were an imbalance, the actual working
pressure in the l-ps would simply rise or drop to equalize with the
volume . . . no problem.

Some Mallets could also be started by directing high-pressure steam into the
low-pressure cylinders.

Perhaps the plumbing necessary to accomplish that function was helpful in the
conversion of these Mallets to simple articulated late in the career of those
locomotives.