Wednesday, April 23, 2014

Drewry supplied pre-WW2 diesel-mechanical shunter on NZR

 

Number 32 from 1939, a two axle Tr (tractor) class is seen in Henderson in 1964.  Originally it had a Parsons petrol (gasoline) engine, but in 1958 this was replaced with a Detroit Diesel 4-71 series engine developing 78 kW (105 hp) at 2,000 rpm, with the power train via an Allison torque converter.  The remains of this particular loco, one of 16 similar ordered by NZR from Drewry before WW2, are stored in the Tokomaru Steam Museum.

As electric motors have much better torque than mechanical ones, diesel-mechanical transmission on railways world-wide has been almost completely confined to low speed, low tractive effort needs in yards or to railcars.

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