Components
[ Home ] [ Up ] [ Evolution ] [ Mallet vs Articulated ] [ Mallet vs Conventional ] [ Builder Specs ] [ Components ]

 

Baldwin Mallet Specific Components

The first Mallet locomotives were designed to meet conditions prevailing in Europe, so features common to European practice were carried out in their design.  The majority of smaller European Mallet locomotives carried side tanks eliminating the need to carry a separate tender.

This Swiss Mallet is typical of small European Mallets with its side tanks.

Click photo for a larger image.

Weights of European Mallet engines typically range from 25 to 110 ton.

Given their much larger size US Mallets required a number of innovations to deal with an engine that is typically twice the size of its European counterpart.  Some of these innovations are reflected in the material in this section.

As the following drawings show, Mallets articulated around a single hinge point midway between the two driver blocks.

This drawing shows a top, bottom, and side view of the hinge connecting the two driver block frames in the 1906 Baldwin GN Mallet.

Click photo for a larger image.

 

This double hinge connecting both the upper and lower bars of the driver frames is simple yet extremely strong, a necessary feature for a 335,000 pound locomotive.

The bearing slides on which the front part of the boiler rests are cast steel with the upper part rivited to the boiler and the lower part bolted to the frame of the low pressure engine.

The top half of the bearing slides back and forth along the slots 1/3 the way up the support, allowing the boiler to move back and forth along the center line as the Mallet takes curves.

Click photo for a larger image.

Thrust springs and their bearings are placed ahead of the bearing slides.  Their purpose is to regulate the side movement of the forward engine.  The springs center the boiler once the engine is back on straight track.

In this drawing the thrust springs and bearing are shown that regulate the movement of the front engine relative to the boiler.  

Click photo for a larger image.

The receiving pipe is easy to access for adjusting and packing.  It is not terribly complicated with only one ball joint and one sliding joint.  The exhaust pipe is similar, but has one additional ball joint.  Given they carry low pressure steam or exhaust steam they require little attention and have only a minor tendency to leak.

Receiving pipe connecting the rear high pressure cylinder's outgoing low pressure steam to the front low pressure engine.

Click drawing for a larger image 
Exhaust pipe discharging exhaust steam from the front low pressure engine.

Click drawing for a larger image.

In order to save room and restrict locomotive height to limits imposed by tunnels and other railroad features that constrain maximum height, an innovative steam dome was constructed combining the functions of the throttle and cast steam dome.  The valve box rests in elbows leading to the outside steam pipes.  

Cast steam domes containing throttle and valve box.

Click drawing for a larger image.

The reversing gear is operated by compressed air allowing the engineer to easily handle the locomotive and adjust the cut-off without physical effort.  Reversing can also be accomplished by hand should air pressure be unavailable.  The steam chest valves are operated by Walschaerts valve gear.  Walschaerts valve gear is extremely advantageous on this locomotive because the eccentrics for a Stevens valve motion cannot easily be placed under the firebox which is directly above the rear group of wheels.  Starting can be accomplished if necessary by admitting steam directly to the low pressure cylinders through the receiving pipe through a direct connection to the boiler.  This valve is closed as soon as sufficient steam is available from the high pressure cylinders.

 

(c) 2007 Iron Horse 1:29