My traffic Officers have expressed a good deal of apprehension about
the low power of the forthcoming Derby vehicles in relation to weight
and certain tests have been carried out with Derby alloy cars with
tail loads calculated to produce a power/weight ration of about 4 3/4
to 1. These tests have shown that the acceleration of the 63 1/2 tons
cars will be markedly slower than the types we have already and that
the timings of stopping services may in some cases be not so good as
the present steam timings.
My Area Board heard something about these matters and are pressing me
to try to secure improvements on steam performance whereever possible.
While the original purpose of these units was of course to secure
economy rather than dramatic improvements in timings, I am really
forced towards the conclusion that a unit with the power/weight ratio
of less than 5/1 is not going to be good enough, especially in
comparison with the much better performance that will be put up by the
earlier alloy cars or even by the Metropolitan-Cammell productions.
Since we are confined at the moment to A.E.C. 150 h.p. engines, I think
the right course is to build the forthcoming batch of 50 units for the
Eastern Region to the length of 57' instead of 63 1/2'. The weight
would almost certainly be no more than the Metropolitan-Cammell unit
and might be a shade better; at any rate performance would be about
the same and the two types could be used interchangeably.
I quite expect that if Derby Works have been laid out to produce
63'6" cars there might be some initial inconvenience in changing to
57' underframes, but I am quite satisfied, from the point of view of
this Region, that I ought not to accept units weighing as much as 63 1/2
tons.
I wonder, therefore, whether you would be good enough to look into the
situation and let me know what would be involved in turning out my 50
units to the shorter length?
