Diesel electric

Can someone explain please how diesel electric locomotives work? I understand the basics, such as diesel engine driving a generator to produce electricity for the motors, but I get a bit lost when we get on to fuel racks, load regulators, governors etc.

All help gratefully received!

 

Firstly I think a copy of the British Railways book "Diesel Traction (Manual for Enginemen)" would be useful, it covers most of the basic information about how diesels work and how they are integrated with the locomotives and DMUs.

Each cylinder of a diesel engine has an injector; the injector is basically a device that sprays a charge of fuel into the cylinder at a given time. The injector is connected to a pump by a high-pressure pipe; the pump is fed by fuel from the diesel tank. The pump ram has a helix cut around its side so that as the ram is rotated the amount of fuel pumped is varied. The ram is rotated by the control rack that is connected to the governor via a mechanical linkage. The pump ram is worked by a cam on the cam shaft of the engine (the same cam shaft that operates the inlet and exhaust valves).

As Jordan says the governor is basically a very much updated and more finely engineered version of the type of thing you see on a showmans locomotive or traction engine. A pair of weights that are rotated by a drive from the diesel engines crank shaft; the weights (due to centrifugal forces) will move out the faster the shaft is rotated, by connecting the weights to the fuel rack you can governs the speed of the engine. The engine can then be made to go faster and slower by setting the neutral position of the weights with an external force. In a car this is your right foot, on a diesel locomotive it will be either a pneumatic or hydraulic piston.

On the smaller engines (DMU, bus, car, etc) the fuel pumps, the governor and the control rack will be built together into a single unit and mounted on the side of the engine, this combined unit will be driven directly off the engines crankshaft. On the larger engines (i.e. Sulzer’s – Class 33 or 47, English Electric – Class 37 or 50, etc) each cylinder will have its own pump next to it with the control rack running the length of the engine with the governor as a separate unit at one end.

I sorry if the above is a bit wordy and not very easy to visualise, I may see (if I can find the time) if I can scan in some of the drawings from the book above as it will help a lot. The book, by the way, also covers lots of other subjects like DMU epicyclic gearboxes, how electric traction changes gear (i.e. traction motor field diverters), braking systems (both vacuum and air), etc, etc. It is the diesel locomotive equivalent of the “Handbook for Steam Locomotive Enginemen”.

Hope this helps.

 

Thanks! Very much appreciated. I have to admit to having given away my copy of the Diesel Traction Manual, being a stricly 'Black Book' man. How short sighted... But at least I can still borrow it back!

 

Just an add on to the above. The governor doesn't only control the engine speed, but it also reacts to load imposed on the engine. On the BR/Sulzer type 2 (D5000s, later class 24) for instance - and I'm doing this from 40 years of recollection - notch 1 applied power to the traction motors without any increase of engine revs. This loading would pull down the engine revs but the governor senses this and opens up the injector pump racks to compensate and restore the engine to its normal idling revs in this controller position. These locos, and I think on all other Sulzer engines as well, the controlling method of increasing engine revs was by air pressure acting on a diaphragm in the governor housing.

Besides the basic mechanical governor as described, there were hydraulic ones too which I think that Sulzer and the Deltics had. Woodhead, I think was one manufacturer of these. On a smaller scale, CAV had a hydraulically governed in-line injection pump used on commercial vehicles. These were standard on Foden 2-stroke engines, and I have seen occasional applications of them on AEC and Leyland ones.