Classes C12 & C12A 4-Cylinder Compound
Designed by Karel Belčamin in 1913
Very soon after the appearance of his B16 Atlantics in 1912, Belčamin started to explore other avenues of development to exploit the power and potential of their new wide-firebox boilers. It seemed logical enough to install three coupled axles with smaller driving wheels in place of the large four-coupled wheels of the B16 and thus reap an increase in adhesive weight of 50%. The two-cylinder compound drive was abandoned in favour of the more common four-cylinder von Borries layout. The first draught design, seen above, used the cylinders of the B15 4-4-0, with inside valves and Stephenson valve gear. In keeping with current practice, Belčamin produced an alternative design, shown below, with outside Walschaerts valve gear for the outside cylinders:
The higher running plate and outside valve gear lend the engines a much more modern appearance, strongly reminiscent of Doncaster practice, although technically there would have been little to choose between them. In the event, both these designs shared the fate of the 2-6-0s of three years earlier, condemned by the dislike of the civil engineer for the single leading axle, especially since it was mounted in a simple Bissel pony truck.
Text and graphics © Norman Clubb 2012