Confusing the hell out of the White Notation

The White Notation is a means of describing different types of engine but I've been exploring some more of A E Durrant's works on obscure steam railway engines and found a very curious pair that defy classification according to their wheel arrangement.

Wheel arranging sounds suspiciously like flower arranging to me but is really a very serious business involving weight restrictions, chassis flexibility and maximising adhesion. Most engines can be classified very simply and the White system quickly allows an impression of the engine to be formed, whether it's a humble 0-4-0T or an express 4-6-2.

The French, being the French, had to be different and used their own system that counted only the wheels you could see from one side, so a 4-6-2 became a 231 - perfectly logical but determinedly different.

However, neither system copes perfectly with some engines.

Look closely between the middle and trailing driving wheels and you'll see an extra pair of carrying wheels. To my eyes, these appear to be vestigial limbs but they were critical to successful operation (Photo: The Steam Locomotives of Eastern Europe by A E Durrant)

The first one is a Turkish 2-6-0 or mogul with an extra pair of carrying wheels between the middle and trailing driving wheels. These engines were very successful across the Turkish system but for the lightly laid Chemin de Fer Ottoman Anatolie (CFOA) their axle loading was too heavy. This line was built with French capital and was originally to a narrow gauge of 1100mm. It was subsequently widened to standard gauge but the civil engineering works imposed a 15½ ton axle load. The solution was to spread the weight of the engine with an extra axle, thanks the long coupled wheelbase on these moguls.

Using the White notation, Durrant classified them as 2-6-(2)-0, which is a good compromise. The French might therefore call it a 13(1)0. As it's something more than a Mogul perhaps we should call it a Rajah. With the extra wheels, the axle weight fell to 13½ tons.

This is a six-coupled pannier tank with a similar pair of carrying wheels. This magnificent O gauge model was built by Dennis Allenden and looks like it came out of a steam punk novel. (Photo Model Railways)

A similar arrangement was used on the Etat Belge and a lovely O gauge model by Denis Allenden (a Brit living in the US modelling French railways) featured in Model Railways magazine in 1974, from which these pictures are taken.

I was fascinated by this engine as a boy, not only because of its extra carrying wheels but also because it's an 0-6-0 pannier tank and, until I saw this, I thought pannier tanks were unique to the GWR. This engine was designed by Alfred Belpaire who gave his name to the distinctive square topped fireboxes featured on so many famous engines in the latter days of steam. The square chimney bothered me a bit but what was almost frightening to my youthful preconceptions of what an engine should look like was the pair of extra carrying wheels nonchalantly inserted between the driving wheels.

Magnificently weird, these engines were built in 1873 for fast suburban services between Brussels and Ottignes and were derived from an earlier design of tender engine. The extra weight of the pannier tanks meant the axle loading would have been excessive if these extra wheels hadn't been inserted. (Photo: Model Railways)

That's just where they were needed, though, and their inclusion made the civil engineers sleep better at night.

Weirdest of all Mallet locomotives and a tribute to complexity, this locomotive's wheel arrangement defies description. (Photo : Florisdorf)

However, I humbly submit that this engine confuses the hell out of any wheel classification. It's a rack and adhesion Mallet locomotive built by the firm of Florisdorf (flower village?) for the 760mm gauge Bosnia-Hercegovina Railway in 1906. Ostensibly an 0-4-6-0 locomotive, if you look closely what appear to be wheels are actually cranks that drive the rack mechanism within the frames. Further inspection reveals two undriven carrying wheels at either end of this bogie, which has no adhesive power.

I suppose that makes it a 2-2-6-0 but shouldn't the rack mechanism receive some recognition for its contribution to motive power, even if it is only occasional?

This engine is so weird I want to take it home to marvel at its oddness and look after it although in reality this layout didn't make much sense. This class of engine remained isolated and didn't run for long. Durrant says they lasted for 30 years and that the best means of describing their wheel arrangement is to use the German system, which would be 2zz+C.

The German system is a mystery to me.

I think it should be the exception to every attempt at classification and remain steadfastly unclassifiable and unclassified.