V4s or B1s – which locomotive was the better?

IN ISSUE 276, Wesley Paxton queries the relationship between the Gresley V4 and the Thompson B1 designs. There are many more important reasons for the proliferation of the latter than any personal prejudice (for which there seems little serious evidence).

They were substantially different concepts. The engineer and writer AF Cook described the V4 as a Rolls Royce for the job of a Ford.

The V4 was designed just at the start of World War Two as a locomotive of maximum power with a low enough axle load to travel over the majority of LNER lines. It had three 15in cylinders (with Gresley valve gear) which would give it a ‘smoother’ power output with six pulses of power per wheel revolution, thus a bit better on starting and climbing than the two larger 20in cylinders of the B1. The extra cylinder however, made it more expensive to build and maintain.

The other advantage of the V4 was its 2-6-2 wheel arrangement. The trailing wheels gave more lateral stability at the rear, so produced a better ride for both crew and track and crucially allowed the use of a wide firebox, but with a slight negative effect of taking some adhesive weight off the rear driving wheels when accelerating.

The leading pony truck steered adequately into curves and has been used worldwide, though the swing link version originally used was not optimal on poor track. To keep the weight down quite a lot of the V4 components were made of specialised alloys. It was an excellent locomotive for lines such as the West Highland.

There is no doubt that the B1 was a ‘Ford’ – but it was required and designed well into the war when it was obvious that quantity production was the essential priority. No special steels and less maintenance made it the deservedly better choice. Even with its narrow firebox, the boiler performance was excellent and its riding, until worn, acceptable.

Keith Parkin, email