Re: Limiting factors for speed on any narrow gauge

Properly designed steam locomotives on good track were capable of rather high speeds on narrow gauge track. In 1985 I paced a SAR class 23 4-8-2 north out of Kronstadt at speeds that varied between 115 kph and 120 kph (74 mph). This was on a 3'6" gauge electrified double track main line. With 63 inch drivers, 120 kph is a rotational speed of 397 rpm. Using 450 rpm as a practical limit, the class 23 should have been able to achieve 84 mph or 136 kph. The SAR speed limit at the time was 95 kph, so I've no idea what maximum speed was achieved by a 23.

The class 16E poppet valve 4-6-2's had 72" drivers and were claimed to be the fastest narrow gauge steam locomotives in the world. At 450 rpm the speed would be 96 mph. I have heard it claimed that one reached 100 mph but I've never seen an actual speed figure published, so this should be taken with a grain of salt.

Michael Allen