If you are planning to use a sound trailer on an end to end layout, where trains frequently reverse, then check out the notes here
You can even use a four wheel van as a sound trailer. The soundcard is mounted on the battery and speaker. The speaker points downwards and holes have been drilled in the floor. Phosphor bronze wipers pick up off the wheel backs and it all just fits....although you will need to choose the battery carefully. We suggest the CTB40 replacement battery for Uniden cordless phones.
Once the soundcard settings have been set, for the type of loco which will pull the trailer, then you are ready to go and your guests will never realise that the sound is not coming from the loco but from immediately behind it.
Before fixing the major components to the coach floor, it is necessary to organise an electrical pickup from the track for the soundcard. In this case, phosphor bronze strips were purchased from the local hobby shop and were glued in place inside the bogies so that they were in contact with the back of all eight wheels. This ensures a continuous contact when the train is passing over points, etc.
Wires were then soldered to the phosphor bronze wipers and were threaded up through the bogie pivots. These wires should be very thin and flexible so that they do not restrict the movement of the bogie and cause derailments.
The soundcard, speaker and a 3.6 volt NiMiH battery were fixed to the coach floor using double sided tape and the track inputs from the bogies were soldered to the M1/M2 terminals of the soundcard. You may want to paint the battery and other components matt black before installation so that they are not visible through the windows.
The battery has a Panasonic connector and has been plugged directly into the soundcard. This avoids the need to solder the leads from a live battery and risk a short circuit during soldering.
If you are using DCC then a simple decoder, with at least one function output for the whistle or horn, will need to be connected between the track and the soundcard. You then set the address to be the same as the loco which is pulling it so that the sound matches the loco.
In many instances, installing the soundcard in a locomotive is not viable. There may be insufficient space in the locomotive. Or perhaps you have so many locomotives that it is just too costly to install a soundcard in every one.
A better option may be to install the soundcard in a sound trailer which can then be easily run behind whatever locomotive you choose at the time. Parcels vans, container wagons, brake vans, 4 wheel vans or any similar rolling stock, which would commonly be seen behind the locomotive, would all be suitable. The picture below shows an installation in a Hornby Full Brake Coach.
