Egyptian Steam-Motor Locomotive

A steam motor is a form of steam engine used for light locomotives and light self-propelled motor cars used on railways. A steam-motor locomotive typically has a relatively small multi-cylinder steam engine which is geared down to the driving wheels. Doubling the speed of a given engine doubles its power output if everything else remains constant; alternatively, you can have the same power output from a smaller and lighter engine. 
Four of these steam-motor locomotives were built by the North British Locomotive Company of Glasgow in 1937, in association with Sentinel Waggon Works Ltd, for hauling passenger trains that were supplied to the Egyptian State Railway at the beginning of of 1938. They were outside-framed 2-4-2 tender engines that were propelled by two Sentinel steam-motors, independently powering the two driving axles. These motors were already proven to give low maintenance costs and favorable consumption rates for steam and lubricating oil, as well as even torque. The boiler was a conventional locomotive-type, unlike other Sentinel designs that favored vertical boilers and chain drives, and was built by the North British Locomotive Company, who also provided the frames and tenders. 
Each steam motor was a fully enclosed two-cylinder double-acting single-expansion design. The two cranks were set at 90 degrees as usual to avoid dead-centre problems. The motor housing was supported at the front on the locomotive framework, by a beam with rubber shick absorbers, and at the rear by the driving axle. Power transmission from the roller-bearing crankshaft to the driving axle was by gears inside the steam-motor housing. Each motor produced 200 hp, the twin cylinders having an 11in bore by 12in stroke. The valve gear was a modified Hackworth design, having piston valves of 5.5in bore. Roller bearings were fitted on the crankshaft, but all other bearings had plain bushes with forced oil lubrication.
It is believed that these locomotives, with their fully enclosed machinery, were ordered specifically because conventional exposed coupling rods and valve gears suffered severe wear from the sand of the Egyptian desert environment. They were described as "not very successful" since their machinery was inadequate and proved no more resistant to sand than conventional designs, and once the sand had got in, it was harder to get it out again. They were soon taken out of service but wartime motive-power shortages saw them in use again in 1943. Their exact fate is unknown but all four were presumably scrapped sometime after the events of World War II.
== Gallery ==
File:Egyptpic1a.jpg
File:Egyptpic2a.jpg|No 277 at Cairo Main station
File:Stegypt1a.jpg|No 278 at Cairo Main station
File:Egypt2a-2.gif
Category:Scrapped steam locomotives
Category:Egypt
Category:Egyptian Locomotives
Category:North British locomotives
Category:Steam locomotives
Category:Tender locomotives
Category:Scrapped locomotives
Category:Locomotives
Category:2-4-2 steam locomotives
Category:2-4-2 locomotives
Category:Sentinel Wagon Works Ltd
Category:Built in 1937
Category:Passenger locomotives
Category:Steam-Motor Locomotive