The Kitson-Still Steam-Diesel Locomotive.

Updated: 9 Dec 2008
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Left: The Kitson-Still steam-Diesel locomotive

The Kitson-Still Locomotive was an attempt to combine the fuel economy of the diesel engine with the high starting torque of the steam locomotive, in order to remove the need for a gearbox for the Diesel part. It was intended for mixed traffic. Steam from the oil-fired boiler was also to be used in overload conditions, for running the locomotive auxiliaries, and for train heating. The actual engine was a horizontally opposed 8-cylinder design; the 4 inner cylinders (nearer the crankshaft) were steam-powered, with Hackworth valvegear, while the 4 outside cylinders (furthest from the crankshaft) were Diesel. The crankshaft was geared at a ratio of 1.88:1 to a jackshaft between the front and middle driving wheels, and this drove the connecting rods. The Diesel exhaust was passed through extra boiler tubes to make use of its heat.

Above: Section of the Kitson-Still locomotive.

Note the small-diameter boiler set very high, above the considerable bulk of the steam-Diesel engine. Its small size led to a lack of steam, when tests began in April 1928. There were many problems; poor boiler performance was only one. The loco did its last test runs in 1933, the economic climate of the time meaning that there was no chance of selling an unconventional locomotive, and indeed very little chance of selling a conventional one.

Above: A contemporary drawing with the Kitson-Still as built in the foreground.

Behind it is a most interesting machine with four vertical cylinders and rocking-lever drive. This may have been an alternative concept- at any rate it certainly never saw the light of day, and I have never found any reference to such a machine anywhere. It certainly has a boiler (though a rather small one) but there is no actual confirmation in the picture that it used Diesel as well. Bizarrely, it has something labelled as a radiator at the front, when one would have thought that any spare heat would have been used for heating water. Possibly it was supposed to be a lubricating oil-cooler.

Left: A rare photo of the Kitson-Still with indicator shelters fitted.

The Kitson-Still was tested on some of the more severe routes in Britain, including Wakefield to Bradford via Ardsley, which included a 1:40 gradient. Other test routes were Bradford-Leeds and Leeds-Wakefield.

Left: Inside the boiler.

The working pressure was 200 psi, but apparently this would drop to 135psi on starting; I am not an engine driver, (IANAED) but that seems to me an awfully big loss of pressure, indicating that the boiler was of quite inadequate size. The locomotive would change from steam to Diesel operation at an engine speed of about 30 rpm.

Here are the vital statistics:

Wheel arrangement2-6-2Boiler pressure200psi
Driving wheel diameter5 ftOil burner heating surface563 ft2
Front & rear pony wheel diameter3 ftExhaust gas heating surface508 ft2
Coupled wheelbase14ft 3inWater tank capacity1000 gallons
Total wheelbase28ft 3inOil tank capacity400 gallons
Length over buffers39ftTotal weight (full)87 tons
Max internal combustion IHP950HPAdhesive weight59 tons
Max combined combustion IHP1300HPAdhesion ratio*4.7 to 1
Starting tractive effort at 80% boiler pressure28,000 lb

* The adhesion ratio or factor of adhesion of a locomotive is the weight on the driving wheels divided by the starting tractive effort. A common rule-of-thumb for a steam locomotive states that a good factor of adhesion equals or exceeds 4, but not by much. A factor below 4 will show a tendency to wheelslip, especially on starting. A much bigger factor than 4 implies that the locomotive is either unnecessarily heavy or underpowered. (The number 4 is the inverse of the coefficient of static friction for steel on steel)

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