42Modern Railway Modelling | Summer 2005

‘TRACTOR’ SOUND FXHow to install ‘plug and play’ DCC sound to recreate ‘Tractor’ thrash. Photography MRM Studio.

PROJECT

It’s an early start, an early diagram and

you discover that your train has a Class 37

allocated to it. Collecting your kit bag and

pulling on your high visibility vest, you wander

out from the bothy into the early morning mist

and over to your assigned locomotive. After the

usual checks, it is time to start the engine and

leave it to warm up for about ten minutes or

so. The whine of the starter motor is followed by

the reassuring firing of the English Electric diesel

which chugs away amidst clouds of clag from

the cold exhaust ports. After a short time, the

engine settles down as it warms through and the

exhaust thins out. Compressors are running and

air pressure is up. Time to ease the brakes off

and move the locomotive off the stabling point.

Another day, another diagram, another train.

However the difference here is you are at

home, in your railway room and with a DCC

throttle in your hand. For with DCC and Lok

Sound, to start your Class 37, leave it to warm

up and then move it off with full and authentic

sound including the release of the brakes has

to be one of the most exciting developments

for UK outline modelling since DCC first

appeared. Strictly speaking, it is not new to

overseas modellers because Roco has offered

models with installed sound for a while now

whilst Kato makes provision for speakers in its

new HO scale models.

However, the Class 37 sound recordings in

Lok Sound decoders is a UK first for the Class,

made possible by the efforts of Steve Weeks

at South West Digital. There was a hiatus in

availability as Lok Sound released its Lok

Sound 3 decoder and then delayed with the

programmer. Since November 2004, this has

been resolved and Lok Sound with Class 37

sounds is available by mail order once again.

The quality of speakers has improved too

and a variety are now available in different

shapes and sizes for Lok Sound decoders

including a fairly beefy 20 x 40mm oblong one

which will fit in a Bachmann Class 37. Perhaps

the two barriers to the onward development of

sound for UK outline diesels is cost (the South

West Digital programmed Lok Sound decoders

will more than treble the value of your average

RTR loco) and that the producers of UK outline

models, such as Bachmann, are filling its

products with so much metal that there is barely

room for a normal mobile decoder, never mind

speakers. The Bachmann Class 20 is a case in

point.

Nonetheless, the Bachmann Class 37 is a

good choice and this project shows how to

install both decoder and speaker into the latest

version; the Class 37/0. As you will discover the

actual installation from an electronics point

of view is very simple. Less straightforward is

ensuring that sufficient room is available inside

the model to allow the free operation of both

decoder and speaker. The Lok Sound decoder

is supplied with a 23mm diameter speaker

which would, under normal circumstances

be adequate for the job. However with a little

modification to the bodyshell it is possible to

fit the larger 20mm x 40mm oblong speaker

into the boiler compartment end and gain the

benefits of better sound as a result.

Only simple tools are required to complete this

project including tweezers, pliers, insulation tape,

double-sided adhesive tape, a sharp scalpel and

soldering iron. A soldering iron is only needed if

you intend to replace the round speaker with the

larger oblong version – the original should be

unsoldered from the two decoder leads and the

new one soldered in its place.

The same rules apply to the fitting of sound

decoders as they do to conventional mobile

decoders. Be sure not to place any pressure on

any component when re-fitting the body, do not

let any part of the decoder come into contact

with metal and do not wrap the decoder in

insulation tape. Always test the installation of a

decoder on a programming track by obtaining

an address read out on CV1 before placing

the model on your layout and exposing it to

full power. Programming power is sufficient to

detect any fault in the model without running

the risk of damaging the decoder. It is also

worth noting that the model should be in good

running order and any servicing completed

before a decoder is installed.

The photographs on the next two pages

demonstrate the installation process.

OperationOperation is about as close to real driving as

is possible in 1:76 scale. Assuming your model

is stationary, you can thumb function button

F1. Remember, your running lights are still

controlled by F0. The model ‘starts up’ and then

idles until you open up the throttle (in whatever

manner your hand-throttle works). The brakes

will release and the model will move away

with the appropriate engine power sounding

through the body. When bringing the model

to a stand, the action is accompanied by the

squeal of brakes and the return to idling.

Other functions are used for other sounds:

functions F2 to F4 are for a variety of horn

sounds. F5 offers a shunting mode which is

quite effective. Function mapping can be used

to allocate other lighting effects to function

buttons F7 and F8.

In all, to hear a Bachmann Class 37 move

away with the classic English Electric engine

sounds and exhaust beat is quite an experience.

To simply ‘drive’ the locomotive with sound is

fun. It makes you think about correct operation

and that is fun in its own right.

Engines idling, EWS Class 37/4s return from the Far North with a train of Safeway intermodal boxes and loaded VGA/VKA vans. Normally a Class 66 diagram, 37 406 and 427 do the honours on November 1, 2004. Photographed at Clachnaharry, the sound of both locomotives powering up after the 10mph PSR at this location was impressive, as always. This can be done in 4mm scale with Lok Sound 3 decoders and programming by South West Digital. Brake squeal and basic horn sounds are all programmed into the decoder.

42-45-noisy tractors.indd 42 11/4/05 9:35:09 am