DYNAMIC AUGMENT. The latest issue of Railway includes an article on reckoning horsepower and related topics. A sidebar compares steam with diesel power calculations.

In the BR steam era, the improved drafting and valve-setting arrangements on locomotives such as A4s, 'Princess Coronations' and 'Kings' enabled peak performances often well exceeding 2,000 dbhp and steam locos could therefore, with decent coal and a good crew, out-perform early diesel-electric designs such as the 2,000 hp English Electric Type 4s (Class 40s).

The joys of Not Invented Here. Imagine:


That's a GP7 knockoff demonstrating in Scandinavia.

When the first 6,000 hp diesels rolled out of Erie and London, Ed King noted in Trains that 1,000 hp per axle had been achieved with steam before 1920 with the Pennsylvania E6 4-4-2.

The Railway sidebar continues

Although magnificent, Gresley's A4s would never be able to meet the constant intense 125 mph all-day running of todays HSTs or Class 91s, however much we may like to dream. Track force levels would also be a problem with steam traction at high speeds.

The maintenance of good permanent way is also essential for 100mph-plus operational speeds.

On The Milwaukee Road, which had steam power capable of sustained running at such speeds (and keyboard ferroequinologists continue to research that), the Roadmaster asked engineers to not exceed 100, and the Fast Fifteen and its successors were much easier on the tracks while permitting similar timings.

The main article notes that brake horsepower (or shaft horsepower) is not determinative of power at the rails.

Traction control technology has revolutionised the haulage power of locomotives -- the Class 59 demonstrated very effectively this technique, outperforming much heavier, higher-powered diesels when introduced in the early-1990s.

The concept scales up: put the guts of an SD70MAC in a shell that fits the British loading gauge.


They make impressive models too, here on Invergeachy at the recent Gauge O Guild exhibition.