ken@ihuxq.UUCP (ken perlow) (12/14/83)
Well, how do they work? I ride the Chicago & NorthWestern
a lot (the one that drives on the left), & it seems that the
power is not directed through a fixed set of gears. If they're
1-speeds, how do they generate & couple the torque to get started,
& how come the revs sound relatively high? A lot of
freights have 2 or 3 engines coupled together. How do they
synchronize them?
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JE MAINTIENDRAI ***** *****
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ken perlow ***** *****
(312)979-7261 ** ** ** **
..ihnp4!ihuxq!ken *** ***darrelj@sdcrdcf.UUCP (Darrel VanBuer) (12/15/83)
Diesel locomotives have no transmission as such. Instead, the diesel drives a DC generator which drives a series-wound electric motor which is coupled to the wheel trucks. A series-wound motor at very low RPM has very high torque (and very high current consumption) so has very good starting characteristics. The truck motors can also run as generators for braking and send the electricity to an extremely large "toaster". Strings of locomotives depend on the use of accurate speed governors to run all locomotives at close to the same speed out of a set of about 10 speeds. Also, the electric motors are fairly good about load sharing. (Steam locomotives were almost never ganged because there was never a way to do good load sharing; that's why they're so big).
tag@tty3b.UUCP (tag) (12/15/83)
Well, if memory serves me correctly, they don't have a transmission
per se. The prime mover drives a generator, and there are electric
motors on each powered axle.
The trick is that in "first gear" the motors are in series, with a
dropping resistor; in "second gear", in series with no resistor; in
"third gear", the motors are in parallel, with the resistor; in
"fourth gear", parallel with no resistor.
Tom Gloger
Teletype Corporation
Skokie, Illinois
ihnp4!tty3b!tag
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Tom Gloger
Teletype Corporation
Skokie, Illinois
ihnp4!tty3b!tagdavid@iwu1a.UUCP (David Scheibelhut) (12/16/83)
They do not have transmissions. The engine drives an electric generator producing about 600V DC. Power is then distributed to electric motors connected to the wheels. Generally there are twelve motors--one per wheel. This setup takes up less space than a clutch and transmission and produces high torque over a large range of speeds. David Scheibelhut
hyder@hammer.UUCP (Paul K. Hyder) (12/16/83)
My understanding of railroad engines was always that the diesel
was used to drive electric generators and that the resulting
pull was from electric motors. Has this changed in recent times?
This form of diesel use gives smooth operation and makes multiple
engines easy. The result is a 'one-speed' transmission of sorts.
Someone out there want to clarify this?
Paul Hyder {tektronix!tekecs!hyder}jj@rabbit.UUCP (12/16/83)
Hmmmm. The little baby GE yard engine we used in a coal yard went like this. 1) Two deisel engines, on governors, running at constant speed, throttle varied by governor automatically. 2) big control in cab varied the PRIMARY current in generators connected to each engine. This varied the amount of voltage/ current that was generated by each generator. 3) Generators were connected directly to traction motors, with a HUGE contactor to reverse things or stop things. The control was, I thought, done most reasonably in the lowest power part of the machine. <i.e. using a generator as a gain device with a mechanical power input.> Braking in the yard engine was strictly by shoes on wheels, and by car brakes (cursed baby compressor! Took DAYS to get 50 cars pumped up!)) I don't have any experience with bigger engines, but the system seems really nicely adaptable. The addition of a big "toaster" for braking seems reasonable enough. Comments? How do road engines work? (It seems to me that, since current in a motor and torque <at any given speed> are a more or less monotonic and linear function, controll of multiple engines in the D.E. style is trivial, you just set each for equal traction motor current, this just about guarantees equal loading and tractive torque.) -- -Diogenes stopped here- (allegra,harpo,ulysses)!rabbit!jj
avsdT:willett@avsdS.UUCP (12/17/83)
* * It is my understanding that a diesel uses electro-mechanical means for transmitting power. The big diesel engines power a generator with the potential being varied by the control of the engineer. The power output of the generator is then wired to the truck under the locomotive which contains the fixed ratio gearbox and electric motor. By changing field winding potential of the generator, the generator puts out less or more power. The field winding can also have the polarity changed to reverse the potential to the motor to make the motor run in the reverse direc- tion. The large diesel engines have a very small RPM envelope and would require an infinitively changing gearbox. Since that is not practical, an electro-mechanical means of torque conversion is practical since mo- tors have a much larger RPM envelope than the big diesel engines, great torque, and can keep the diesel engine at a relatively unchanging speed. By no means an only answer, Michael Willett Ampex Corporation Redwood City, Ca.
jpg@sdchema.UUCP (12/17/83)
In the US, diesal locos have no mechanical or
hydralic transmission (some are made in Europe though).
The diesal engine drives a generator that provides electricity
to electric motors mounted on the axles. Hence the term "diesal electric".
This is also the reason why the GM division that manufactures diesals
is called the "Electro-Motive Division"filed01@abnjh.UUCP (H. Silbiger) (12/27/83)
Almost all US diesel railroad prime movers are diesel-electric. Thus, the engine is direct-cuopled to a generator, usually DC. The wheels are driven by electric traction motors. The operator conrols the power the same way as though he were controlling an all-electric, by means of a controller. The diesel throttle is operated by demand sensing. Multiple operation is thus easy, as it is all electric. In Europe, diesel mechanical and diesl hydraulic transmissions are also used. Some of these hydraulics were used on the Southern Pacific about 20 years back, made by Kruass-Maffei. The Budd RDC (Rail Diesel Car) uses a mechanical transmission. Herman Silbiger AT&T-IS Morristown