Steam diesel hybrid locomotive

A steam diesel hybrid locomotive was a railway locomotive with a piston engine which could run on either steam from a boiler or diesel fuel. Examples were built in the United Kingdom, Soviet Union and Italy but the relatively high cost of fuel oil, or failure to resolve problems caused by technical complexity, meant that the designs were not pursued.

Kitson-Still system

In 1926 Kitson and Company, Leeds, built an experimental example for the London and North Eastern Railway, using as their model the Still engine already in use for stationary and marine applications. It was on trial until 1934, but then scrapped. It was designed because a steam engine offered a high starting torque—a tractive force of 25,450 lbf (113.2 kN) was available—while a diesel engine offered a better fuel efficiency, and it was an attempt to combine the benefits of both in one machine.

Construction

In outline, the machine resembled a conventional 2-6-2T steam locomotive, but it had four pairs of horizontally opposed cylinders (13.5 in (340 mm) bore × 15.5 in (390 mm) stroke) mounted longitudinally above the frame and driving a crankshaft placed between them, with the further drivetrain powered by gears. The cylinders were made double-ended, with the rod end of each cylinder for steam and the closed end fitted with a diesel injector. (Some drawings, published in contemporary magazines, show only two pairs of cylinders and it seems that this was one of the design features that was changed during development.) The boiler, with a diameter of only 51 in (130 cm) and a small internal firebox, was mounted above. The "regenerator", capturing heat from the exhaust, was integral with the boiler and had 38 tubes totalling a heating area of 508 sq ft (47.2 m2). The driving position was in the usual place behind the boiler, and tanks—400 imp gal (1,800 L) for fuel and 1,000 imp gal (4,500 L) for water—were mounted on the frame at the rear, one above the other.