Sutton's Locomotive Workshop British Railways Sulzer Type 2 Operating Manual - page 18
How a real locomotive operates
To simulate the sounds of a diesel-electric locomotive successfully, you will need
some idea of how and why they sound as they do. The most important aspect to
know is that the diesel engine itself does not propel the loco directly. The engine
drives a generator, which provides the electrical power for the traction motors. It
is these electric motors that actually turn the wheels via gears. This means there is
no linear correlation between diesel engine speed (or sound) and track speed, and
explains why some models sound so unrealistic.
For example, with engine idling, there is sufficient power to move a light locomotive
(without train). Releasing the brakes is often all that would be needed to move off.
Put a few hundred tons on the hook, and the loco will need a lot more power to get
its train moving, even slowly. That’s two different ‘power’ sounds needed for the same
speed. Now imagine a heavy train on an upward incline. It may be going slowly, even
decelerating, but the engine will be providing maximum power. On the descending
gradient, the engine may well be at idle, with the loco travelling at speed or even
accelerating, effectively being pushed downhill by the weight of the train behind it.
In the real world, these effects are created by gravity, mass and inertia. In the
‘model world’, sound projects have to simulate them. We have gone to great lengths
to bring you the correct sounds and necessary controls to get as close as possible.
It’s now down to your skill and knowledge to simulate any eventuality!
Prototypical brake application
On a real locomotive, acceleration, speed and deceleration are under control of the
driver. He will use his experience of the locomotive type, the train weight and
knowledge of the route to anticipate the control movements required to achieve the
required performance and safety. Deceleration is often achieved by reducing power
only, allowing the locomotive to ‘coast’ down to lower speeds. Typically, the brakes
are only used to fine tune this rate of deceleration or make a halt at a specific point.
At other times, strong braking will be required, even at high speed, such as in an
emergency brake application.
A feature notably lacking in all other programmable decoder brands with
British sounds, is the ability to apply a variable braking force to increase the rate of
deceleration when desired. This makes stopping a heavy train at a signal or station
platform more difficult than it is on a real loco. Without brake force, the locomotive’s
dynamics are only partially modelled. There is no point in having the sound of brakes
being applied if the rate of deceleration is unaffected!
Working closely with the decoder manufacturer’s software engineers, we have
designed and incorporated a revolutionary new ‘Brake Force’ feature. The objective
is to simulate the real driving experience as closely as possible. It will require you to
SLW Class 24 Operating Manual
Page 35
Page 34
SLW Class 24 Operating Manual