All Western Class 52 locomotives were fitted with two engines driving two transmissions. The equipment associated with these was duplicated in each end.

When running the Maybach MD655 engine (13) rotates the Engine to Transmission cardan shaft coupled to the transmission. Using internal gears, two smaller cardan shafts mounted on top of the transmission rotate the dynostarter and hydrostatic oil pump for the cooling fans (1). The dynostarter provides 110 volts for the electrical systems operating on the locomotive and acts as the starter motor for the diesel engine. The hydrostatic oil pump works constantly and a small electrically operated valve diverts oil to the fans to turn them as required. For clarity these two items are not shown on the diagram below.

When the driver selects the direction for movement the transmission (9) convertor 1st stage (gear) fills with oil and the diesel engine now begins to rotate this oil, rather like a ships propeller in water. Face to face with this 'propeller' is another similar 'propeller' which begins to rotate too and this is coupled to another cardan shaft leading to the bogie mounted Intermediate gearbox (7). In this gearbox a combination of bevel and wheel gears transmit the drive downwards. From there cardan shafts (8) transmit the drive to the axle mounted final drive gearboxes (5).

As the locomotive moves forward gaining speed the converters change (1st to 2nd; 2nd to 3rd), each convertor decreasing in physical size until the 3rd convertor is used. This, the smallest of the three converters, then drives the train forward in the speed range between 63 and 90 mph.

Class 52 Western Diesel Hydraulic Type 4 C-C Locomotive in section

The driving position in a Western cab is quite compact with everything a driver needs to perform his duties with ease. The gauges on the desk angle show the air pressures in the brakes for both locomotive and train, road speed and that end engine speed in rpm. A group of five fault lights in front of the driver indicate the general health of the locomotive (Blue = normal / Red = warning).

To the drivers left are the train brake handle and locomotive brake handle, centrally in front of him are the AWS acknowledgement reset button and warning horn, to the right are the master switch direction selector and power handle. The AWS 'Sunflower' yellow/black indicator is in corner of the left windscreen. This is a visual reminder of the last signal - All black indicates a clear aspect, yellow/black indicates a caution aspect.

A selection of photos around the cab of D1015 from 2002, during 'The Western Sunset' railtour. Thanks to EWS for allowing access.

If the power controller looks familiar this is probably due to it being a standard Brush type as seen on Class 47 Diesel-Electric locomotives although with a different end piece. The direction controller positions are slight different, the standard being four positions: Forward, Engine Only (EO), Reverse, Off. On a Western there are five: EO, Forward, Off, Reverse, EO. The additional EO positions allow the driver to select EO without the transmission reversers throwing into neutral from the selected direction.

The power handle regulates the engine speed by air pressure to the engine governor, this type of system is referred to as 'infinitely variable', giving the driver total control over the engine speed rather than having electronic equipment or 'notches' with pre-designated settings like modern class 66/67's.

New Equipment

In order to comply with current regulations D1015 has undergone several modifications and upgrades:

Following dual brake modifications under BR, if the 'A' engine shut down on any Thousand the electrical feed to the big compressor was lost and the loco was unable to create enough air pressure to work air braked trains. On D1015 the compressor wiring circuits have been modified to allow 'B' engine to electrically feed the big compressor if 'A' engine fails, thus improving reliability.

Why Two Engines?

When the bigger diesel hydraulic locomotives were designed technology was still being developed. Although the Westerns were built from 1961 onwards the transmission design went back to the middle 1950's. At that time the maximum 'input' (the power from the diesel engine) that any single transmission could manage was around 2,000hp. Therefore to have a locomotive more powerful than 2,000hp required two smaller transmissions, each with its own engine.

The twin engine 'reliability' was more by default than design. By the time that the Westerns were actually built technology had overtaken them and transmissions with a bigger capability were already being constructed. Just like today when you buy your new computer, it its already out of date by the time its on the shelf!

What does a 'Tooth on Tooth' button do?

When a transmission changes gear the physical connection between the transmission and final drive to the intermediate gearbox is momentarily broken by a clutch known as a 'dog' clutch. This clutch has a 'male' and 'female' side and to 'mate' properly the teeth on one side need to fit inside the other. On occasions the teeth will try to mate face to face (tooth on tooth) and the operation of this button pushes the clutch around until the teeth fit inside each other properly.

Sometimes in your car you misjudge the gear change and you hear that awful grinding of gears. If your car was a hydraulic you could press the tooth on tooth button and the gears would mesh correctly, instead you just dip the clutch and try again!

Forwards or backwards!?

Did you know that when a twin engine diesel hydraulic locomotive moves forward the rear transmission is in reverse! This is because the Maybach diesel engine rotates clockwise when running at the flywheel end. If both transmissions were in forward the locomotive would try to pull itself apart! Gear changes between the two transmissions also take place at different speeds. The leading transmission changes first, followed by the trailing one. This is to reduce the risk of the locomotive causing a 'snatch' in the train and breaking the train couplings.

Why is there black smoke from the engines when starting away?

No, the engines are not sick! The turbo charger that compresses air and pumps it into the cylinders, along with the fuel, is driven (rotated) by the exhaust gases from the engine itself. When the engine takes power from idling the turbo blower is 'lagging' behind (turning slowly) and the fuel / air mixture is more in favour of fuel until the turbo charger speeds up and pumps the air in faster. Once the turbo charger is rotating faster the fuel / air mixture is corrected again and the exhaust emissions clear. This is called 'turbo lag'. You can clearly hear the turbo charger working hard on a Maybach, it's the whistling sound as the engine revs pick up.

Why do we preheat engines?

In order to aid starting a Maybach diesel engine the coolant water is warmed to 110°F (around 43°C). This warms the cylinder heads and helps combustion of the diesel fuel oil. The combustion of the fuel and air mixture takes place inside a chamber within the cylinder head and then expands into the cylinder itself, forcing the piston downwards. The characteristics of this engine type doesn't lend itself easily to cold starting. Warmed engines start more easily, should run cleaner with the added bonus of reduced wear and deposits (carbon etc) associated with cold starting of any diesel engine.

There are a number of unique advanced features incorporated in a Maybach MD series diesel engine such as pressure oil cooled two piece pistons, roller main bearing crank shaft, quadruple overhead camshafts, six valves per cylinder head (3 valves air inlet and 3 valve exhaust gases) and a individual pump / injector unit per cylinder.

The engine coolant is warmed by a small preheater, located in a compartment behind the cab side doors at each end. The preheater only runs prior to starting or when the engines are shut down and are getting 'cold'. You can hear them running sometimes when we shut down the engines at stations. It carries out the same purpose as glow plugs do in modern diesel engine cars.

Although it is possible to 'cold-start' a Maybach engine it is not recommended.

Why are tour starting point departures always rather sedate?

Some sites on the internet have held articles about tours from Paddington always stating that the departures were always sedate. Well, there is in fact a very good reason for this policy. The coolant system on a thousand gets very hot very quickly and storming out of Paddington on full power on a relatively 'cold' engine would cause the coolant water to heat up quickly and expand (water expands when heated and this creates the pressure) and there is a risk that the coolant pressure relief valve could 'lift' and the coolant would be thrown out. This means that the engine would then probably fail with low coolant and we would either spend the rest of the trip operating on one engine or become a total failure until the coolant could be refilled.

In BR days of course the locos engines ran constantly and this was not too much of a problem. Once the engine coolant has had time to fully circulate around the system then full power can be applied. It normally takes around four or five minutes for this to happen.

Did you know ... ???

The technical design of the Western diesel hydraulic locomotives was taken from a German Railways built C-C locomotive type ML3000. This locomotive was a stretched V200 B-B locomotive giving 3000 hp and weighed just 101 tons.

So why were Westerns heavier at 108 tons?

Well, originally it was envisaged that the Westerns would be more powerful versions of the Warships with the same internal layout, ie. engines behind the drivers cab. This did not meet with approval from the drivers and unions as the constant noise and vibrations from having a diesel engine thrashing away directly behind you made driving Warships a very noisy occupation.

In order to remedy this the engines were placed in the middle of the body with the cooler groups behind the drivers cab. This meant that the frames in the middle of the locomotive had to be thicker and stronger to take the weight of the engines. Even so the designers put a bend upwards in the frames, and this bend straightens when the engines are mounted. Therefore when a Western has its engines removed the loco bends upwards like a banana! The deflection upwards is around 3 inches, making an empty Western out of gauge for running on the main line!

BRITISH RAILWAYS CLASS 52 DIESEL HYDRAULIC TYPE 4 LOCOMOTIVE
Click the graphic for full view with Key, or click here for a PDF version

Note: The large air compressor added during air-brake fitting is located in place of '21' at B-end only

Weights and Measures