IMPROVEMENTS IN STEAM ENGINES AND BOILERS APPLICABLE FOR ROAD LOCOMOTIVES, STEAM TRAM CARS, AND OTHER PURPOSES
Year: 1877

page_text: PROVISIONAL SPECIFICATION left by Harold Wilhelm Widmark at the
Office of the Commissioners of Patents on the 20th December 1877.
HAROLD WILHELM WIDMARK, of 13, Tamworth Place, Redland Road, in the
City of Bristol "IMPROVEMENTS IN STEAM ENGINES AND BOILERS APPLICABLE
FOR ROAD LOCOMOTIVES, STEAM TRAM CARS, AND OTHER PURPOSES."
This Invention has mainly for its object to provide propelling apparatus for tram
cars which shall require but little attention and the expenditure of a small amount
of steam, and shall also get rid of the noise caused by the exhaust steam issuing in
puffs, when set free by the slide valve, and escaping from the cylinder at a higher
pressure than the atmospheric pressure.
By the following arrangement the steam pressure will be so much reduced before
the steain is allowed to escape that it will be near the atmospheric pressure, and
consequently will escape without the distinct puffs before mentioned; the steam
also will be expanded to the atmospheric pressure instead of being allowed to
escape at high pressure, and this expansion will give more power out of the same
quantity of steam. The boiler required will therefore be less, and the weight of the
tram engine reduced.
In some steam trams constructed, the steam has been made to escape first into a
reservoir where it has partly expanded before going into the chimney, but even
then the escape has not been continuous, and the final pressure in the cylinder has
been lost for power.
I propose to provide on the engine to each cylinder another large cylinder on the
compound principle. This cylinder might either be in the same line as the small
cylinder, and have its piston on the same rod on the continuous expansion
principle; or the large cylinder might be in another plane with its piston rod, in
connection with the crank axle by a separate connecting rod. Or I provide only
one large cylinder for the two small cylinders to expand into. Then there will also
be a separate connecting rod and piston rod. Or I have only two cylinders, one
large and one small, the large one taking steam only from the small cylinder.
Then the respective cranks will be set at right angles. In any case I provide a
valve on the valve chest of the large cylinder, or a valve on each end of the

page_text: cylinder, to open inwards and admit air behind the piston if the pressure should by
expansion or by less admission into the small cylinder havo fallen so low that in
further progress of the piston the pressure would be less than the atmospheric
pressure. A partial vacuum would without these valves often occur, and would
create a pressure on the piston in the wrong direction. By these valves the
pressure in the cylinders can never be lower than the atmospheric pressure.
When the piston turns and progresses on the return stroke, the mixture of steam
and air escapes through the exhaust port into the chimney in a continuous stream
without noise.
By the means above described, less steam will, as before stated, be required for
driving the engine, and if a boiler is provided having a great quantity of water over
the fire-box and tubes, and a large surface to the water, the water level will not fall
rapidly when the engine is working, nor will great attention for feeding be necessary.
The driver, acting also as stoker, will therefore be enabled to leave the boiler during
the trip, and only attend to stoking and feeding at the ends and during stoppages.
With a great quantity of water in the boiler the pressure will also during the
working be more constant.
Also, as there can be no blast from the exhaust steam, the pressure of which has
been reduced, it is necessary that the flue or tube areas of the boiler should be
large, so that they do not much abstruct the products of combustion, rising only
through the natural draught by means of the chimney.
To gain these objects I use an upright boiler with an internal fire-box. The
upper portion of the shell I enlarge, and make a smoke-box, as a ring, to go all
round the lower part of this enlarged portion. From the upper part of the internal
fire-box tubes go radially and in several rows as to the height; their outer ends are
fixed in the enlarged shell, where the ring smoke-box receives from them the
products of combustion, which afterwards are led into the chimney by pipes or by
another set of tubes returned into the fire-box, into an upper compartment divided
off by fire-bricks from the lower portion. From this upper compartiment an internal
tube takes the products into the chimney.