two questions about steam

[nw-mailing-list at nwhs.org]

Thanks to Dave Stephenson, Bud Jeffries, and Bill Sellers for their superb answers to this newbie's questions.  Bud, here I thought the empty tender weight was heavy, but it turns out it was light relative to other railroads.  Bill, thanks for the great explanation of automatic stokers.  With Dave turning up the 1947 N&W study on the steaming efficiency of sized coal, both questions seem to have pointed out just how well N&W had their act together.

Tom Leuthner

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Message: 4
Date: Wed, 01 Mar 2006 23:00:31 -0500
From: nw-mailing-list at nwhs.org
Subject: Coal Size
To: nw-mailing-list at nwhs.org
Message-ID: <3.0.6.32.20060301230031.00bdb3f8 at pop.charter.net>
Content-Type: text/plain; charset="us-ascii"

To the gentleman asking about the size of coal in a tender.  As a former locomotive fireman, the size of coal lumps was of no consequence.  They
varied from egg-sized up to nearly the size of a football.   Using a Standard
HT Type stoker,  a lump of coal falls into the coal trough in the floor of the tender where it comes into contact with a screw or auger powered by a twin
cylinder steam engine to begin it's   12 to 14 foot journey to the jet plate
located in the firebox just below the butterfly door.  As the coal is forced through the round chute by the auger, it is crushed into smaller pieces much ;like meat going through a meatgrinder.  When it reaches the entrance to the firebox all of it is reduced to about the size of marbles as it falls on the jet plate where  air pressure blows or distributes these pieces of coal to various locations in the firebox determined by vertical "wings" on the jet plate. The fireman  determines how strong the pressure is on each section of the jet plate
with the use of   6  valve handles positioned in  a  "V" shape just below the
main stoker valve that controls the speed  at which the stoker engine operates.
The biggest headache in using a  Standard HT Type stoker is wet coal, that falls on the jet plate as so much mud.  This tends to build up a hard crust on the jet plate which is loosened by a tool on the engine known as a jet pick.
It is curved similar to a fish hook, and the fireman opens the fire door and
pulls the point back toward him to loosen this  residue buildup.   In the
case of a shovel fired locomotive,  a tender full  of egg -sized coal is perfect to fire a locomotive.  Again, to answer your question, on a stoker fired
locomotive coal size is of no  consequence.   Bill Sellers.