Triffen,

The reason a Diesel locomotive used an "electric transmission" was that it was impossible to make the necessary 16 speed mechnical transmission. Can you imagine the size and number of gears to handle a 2000HP engine and the problems of shifting the gears. Imagine the drive shafts that would be needed to connect the transmission to the wheels of a locomotive. How big would a clutch or torque converter have to be? How much easier is it to flip electric switches than change gears?


At the time the Diesel engine/electric transmission locomotives came out, they were tripled the fuel efficiency of the steam locomotives, thru the greater efficiency of the Diesel engine. I'm sure the railroads were very happy with than let alone the maintenance that was much easier and more cost efficient on the Diesels locomotives.

P E H

83-240D,

Aren't all Diesels stratified charge engines?


P E H

if i remember correctly from my long ago high school physics class the conversion of electrical to mechanical would be a loss of 10 to30% of the energy. i think that a mechanical transmission would be less than 5% loss.

the honda insight is a standard transmission car with electric assist with a storage battery charged by the motor being activated as a generator under decelleration to charge the storage battery. the prius is an automatic, perhaps a constantly variable type (i'm not sure). having driven both i found the insight with stick, to be engaging to drive and it reminded me of a 240d but faster with a torquey feel. the prius was totally devoid of any feel of control, rather like running a video game.

that said, the type system that the insight has seems a logical derivation of current mechanical and electrical technology that will probably become pretty universal on all vehicles that are driven in stop and go mode... i dont see it being on over the road trucks or road graders where braking is not a big part of the picture.

i am not sure why the train engines all are diesel electric. control? perhaps a rail buff can fill us in on that.

__________________
[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.

If the engine is disconnected from driving the wheels directly, you will have conversion losses driving the wheels with electricity alone. The automotive hybrids have the electric motor on the same power train, so it can be used as a regenerative brake, and store energy to assist acceleration.

A locomotive is configured the way it is to take advantage of the low rpm torque characteristics of DC motors, and no transmission is then necessary. Think of how many gears would be needed to directly couple a diesel engine to a locomotive -- I ain't gonna clutch that thing!

__________________
'83 240D with 617.952 and 2.88
'01 VW Beetle TDI
'05 Jeep Liberty CRD
'89 Toyota 4x4, needs 2L-T
'78 280Z with L28ET - 12.86@110
Oil Burner Kartel #35

http://i16.photobucket.com/albums/b1...oD/bioclip.jpg

Some locomotives do have a form of regenerative brake called Dynamic braking. "The electric current generated by the motors in the dynamic-braking mode is a waste product and is dissipated as heat in banks of resistors located in the locomotive carbody." It's not turned into power the train can use to get moving but it does take massive braking effort off the wheel brakes.

Almost all modern locomotives are now made with AC traction motors (see AC TECHNOLOGY vs. DC HERE )

Aha, dissipating the brake energy in resistor banks as heat is not regenerative braking. Regenerative braking is storing the energy in cap banks or batteries. Locomotives use dissipative braking.

__________________
'83 240D with 617.952 and 2.88
'01 VW Beetle TDI
'05 Jeep Liberty CRD
'89 Toyota 4x4, needs 2L-T
'78 280Z with L28ET - 12.86@110
Oil Burner Kartel #35

http://i16.photobucket.com/albums/b1...oD/bioclip.jpg

t walgamuth,

Read reply #16.

P E H

Ultimate Hybrid ??
Bio-diesel hybrid electric ..

http://hybridiesel.blogspot.com/

still curious thou ..

Would a VW TDI (90hp) engine consume more
fuel per hour @ 60 mph vs running a generator
that was keeping charge on a bank of batteries
of an EV going at the same 60 mph speed ???
Which use would consume less fuel ??

Triff ..

And which would produce less harmful emissions (including manufacture of batteries)

__________________
"If anyone knows other lessons I need to learn, please tell me. I'm tired of learning them the hard way".
by JerryBro

The Glow Plug Wait: This waiting period is a moment of silence to pay honor to Rudolph Diesel. The longer you own your diesel the more honor you will give him". by SD Blue

My normal daily life; either SNAFUed- Situation Normal... All Fouled Up, or FUBARed- Fouled Up Beyond All Repair

62 UNIMOG Camper w/617 Turbo, 85 300SD daily driver- both powered by blended UCO fuels

OK .. you win ..

I'm getting one of these

http://www.primepedalkarts.com/reflex.html

Triff ..

As "82 300TD" commented, many of the mainline diesel locomotives have what is correctly called Dynamic braking. As was covered there, the braking energy is dissipated in an air cooled resistor grid. True regenerative braking has been used on locomotives, but they were straight electric. In that case when in braking mode the energy is returned to the overhead DC catenary wire and into the distribution system.

One additional system that has had moderate testing in this country but has not been accepted, was use of a diesel engine with hydraulic transmission of the power to the wheels. This system has been used in Europe but did not stand up to the rigors of American raillroading. Units were supplied by ALCo and Krauss Mafei of Germany.

__________________
1961 190Db retired
1968 220D/8 325,000
1983 300D 164,150