Thus two makes and four types of engine, arranged one or two per motor car, and in trains made up of differing proportions of motor cars and trailers, can cater for every performance requirement whether for low density, high density, or inter-city trains giving power/weight ratios from 4.6 to 11.0. Such being the case, and having regard to the need for reduction in variety, the further alternative presented by the Paxman power unit, giving 450 H.P. in a single engine per power car, although successful on trial, can not be justified, on either cost or performance, in comparision with the use of two 230/238 H.P. engines per power car.
On the other hand, there is no data based on actual experience in service on British Railways yet available which would support immediate choice of one make of engine to be exclusion of the other as between B.U.T. and Rolls-Royce. And similarly there is not enough experience yet to choose between gearbox and torque converter transmission. Retention of both required, however, that each should be able to multiple one with the other, and this problem is in process of solution.
4. Recommendation
For all diesel multiple unit trains, of whatever kind, having underfloor engines, it is recommend that -
(a)
only 3 basic types of power car to be adopted -
(i)
230/238 H.P.
One Engine 57' vehicles
(ii)
300/360 H.P.
Two Engines 57' or 63' 6" vehicles
(iii)
460/476 H.P.
Two Engines 63' 6" vehicles
(b)
Only 2 makes of flat underfloor diesel engine be adopted -
(i)
B.U.T.
150 H.P. and 230 H.P.
(ii)
Rolls-Royce
180 H.P. and 238 H.P.
(c)
Only 2 types of transmission be adopted -
(i)
Wilson Gearbox
(ii)
Torque Converter
(d)
Only 1 type of control be adopted, capable of operating both makes of engine and both types of transmission.
(e)
Selection as between the above alternative be made on the basis of -
(i)
Usual commercial considerations of first cost and delivery.
(ii)
Overall financial justification for scheme of which a given order for diesel multiple units forms part.
