A gimmick of model railway locomotives of today is on-board sound effects. This high tech digital electronic sound is in most cases impressive to hear but it can in some instances double the cost of an originally expensive model. Don't think that sound equipped locomotives are an invention of the digital era though. Way back in 1963 and for one year only, Tri-ang Railways offered one locomotive, an R55 Transcontinental series F7, with the added attraction 'now with diesel engine noise'.
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    The R55 Diesel Loco is as old as Tri-ang Railways themselves and appeared in their first public catalogue in 1955. The loco went through a number of transitions with the colour changing from all over grey with a bottom band of maroon to one of a grey body with a red cab and red bottom band. The greatest change was in 1959 when Tri-ang Railways made what was the most significant update of all time, the introduction of the standard Mk.3 tension lock coupling. No doubt by 1963 sales of this model were beginning to fall off and something new was necessary to revive sales. To achieve this, the F7 locomotive was fitted with "Diesel Engine Noise". How does it work? Being a product of the clever people at Margate, it worked very well.
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    The sound equipped locomotive was the regular model that had been in production since the 1959 update but instead of being marked 'Tri-ang Railways' it now carried the marking 'Transcontinental'. An additional motor, an X04 type was fitted in the body but it was not intended to drive anything. This additional motor was wired in parallel with the propulsion unit but it was more ingenious than that. In series only with the noise motor was a wire wound resistance. As current flowed through this resistance it warmed up and its resistance increased.This meant that when cold the noise motor started up quickly but as the power to the locomotive increased the voltage diminished slightly and the motor did not over speed. When testing the model with the body off, the sound did not impress but once the body was fitted it acted like a sound box and the sound effect was transformed. So what does it sound like in action on the line?
    As the throttle is increased the noise motor starts up well before the propulsion motor and the effect is surprisingly good with a deep diesel growl emanating. On applying more power to the locomotive it then starts to move and the combined growl of the noise motor and propulsion motor becomes most convincing. I know the idea of it all it seems bizarre but it is true. Remember at this time model railways were viewed as toys and were intended to be played with and much more importantly, enjoyed by all.

    It certainly still gives the latest hi-tech models of today a good run for their (lots of) money.