Diesel Trains and Diesel Cars

The Diesel Engine on a train is only working as a generator to provide electricity to the Electric motors which provide the mechanical energy to the tracks. They are very large Hybrids. The engine in an automobile is connected to the road mechanically via the transmission/differentials, and in turn needs to operate as we are all familiar.

So is a diesel train the same as a diesel-electric train?

As far as i know all diesel trains built today are hybrids. Every train i see running down the tracks are driven with electric motors powered by a diesel power-station. Although i could be wrong as i am not a (train driving) Engineer.

I'm pretty sure practically all diesel locomotives are diesel-electric, but if I'm right railcars (as they're called in UK, but perhaps not elsewhere) with engine under the passenger compartment have mechanical transmission.

Can anybody confirm (or correct)?

Codey

for more information: http://en.wikipedia.org/wiki/Diesel_locomotive

Old habits die hard. In olden days, the lubricating oil used in locomotive diesels was naphthenic, with very low viscosity index. If one allowed the engine to get cold, the oil was too thick to lubricate effectively. Naphthenic lube oils were preferred because the 'carbon' it forms is soft and easily blown out the exhaust port and also did not clog up the piston rings or form hard carbon around the piston lands that would rapidly wear the cylinders.

Modern railway diesel engines and lubricants do not need to be kept hot all the time to prevent lubrication problems. Lube oil base stocks and additives are vastly superior to even 10 years ago, as are fuels used. Keeping the engine idleing when not needed to move the train is no longer practiced by many railroads. In fact, extensive tests have shown that prolonged idleing contributes to 'bore-polishing' and very high oil consumption, which means shorter time between overhauls in modern engines with today's lube oils.

Glad someone who actually knows what he is talking about has chimmed in.

I worked as the assistant engineer or "oiler" on a ship that used large diesel Caterpillar engines like those used in locomotives. Starting these engines required pre-lubricating the bearings and purginig of old fuel from the cylinders. This was accomplished by running a pressurized lubrication system and manually opening valves on each cylinder and then cranking the engine. Old fuel was blown out the valves. All the valves were closed and the engine could then be started.

I suspect engines are kept running on trains only to keep accessories like air conditioning going, batteries charged, and because the engines once shut down take some time and effort to re-start.

Semipro,

I don't know of any current production EMD or GE locomotives that have an auxiliary means of pre-lubing I think the best we could do is roll it over with the rack cut out. I do believe it is a mechanical practice to plumb in a unit to circulate oil on initial startup coming out of storage.

In the Chicago area commuter trains are a life line. They often are running as you noted to maintain hotel services. Batteries are important because they provide emergency lighting and back up to certain vital systems that will ensure safe operation should normal 480 VAC be lost while en-route.

From the stand point of some one who maintains locomotives for a living the answer may come from two directions. First we use no anti-freeze as a general rule in the jacket water, only rust inhibitors. From October to April any unit in service will most likely run constantly. Second, if the locomotives are tied onto a consist the air generated by the compressor is needed for the brakes.

It is true many newer high horsepower locomotives have an automatic start/stop system and many older ones have been retrofitted.

When I was working at an Oldsmobile dealer, there was a training guide that showed a locomotive automatic transmission being assembled. There was a clutch pack being loaded into the transmission case. The clutch pack appeared to be about 6 feet across. and was being loaded with a gantry crane. The year was 1973, or 74.

Hi,

The diesel powered rail car or independant locomotivehauled train rely upon the the motive power unit to provide not only the tractive energy, usually electricity, but also the on-board envirommental support services,eg lighting, ventilation , heating and cooling as long as the train is in service. The engine also has to maintain the compreesed air supply used for the train braking system and all the essential services around the powerplant such as the large air blast coolers for the dissipation of jacket heat .This load can run into tens or even several hundred kilowatts and is beyond the capacity of all but a large back-up battery and inverter unit. Therefore the train engine(s) is started before anyone boards the train to get the carriage environment to a tolerable standard or maintained at that level between journeys whilst waiting at the platform.

You can therefore readily appreciated that shutting down the only source of energy even for brief spells could result in either overheating within the engine's 'life support' systems and,or, a general loss of power causing problems else where in the carriages.

Remember that the output of the generator is then fed via a sophisticated control system to the bogie mounted electric motors; if this is a hybrid system then there will be some form of short term energy storage which will usually be chemical ie Battery of some form. Hitachi are developing a version of this system it also benefits from the ability to convert kinetic energy produced during braking into reusable electricity rather than being wasted as heat. The penalty is a lot of additional weight to be dragged around and overall higher life cycle costs.

Interestingly the high powered diesels used in either locomotives or the power cars seen on the likes of the UK intercity 125s are typically started using compressed air delivered at high pressure to an air motor. Older engines used direct air supply to the cylinders to 'motor' the engine but as this version requires an extra valve in the cylinder head it is not popular today.

Diesel rail car units with engines under most if not all vehicles are similar to the above but may use mechanical transmiision with torque converters and auto change gear boxes to power the driven axles.

Large diesels as well as requiring pre-start lubrication also require continued oil supply to the turbo charger for a period of time after the engine stops to dissipate heat from the bearings.

Overall I think you will see that there is a world of a difference in these industrial scale power plants in comparison with the automotive version although with ever increasing demands being imposed on it there will be a tendency to adopt or devise similar safeguards and back-up systems no doubt.

I hope this helps.