Sry, is there really a wikipedia page about trains versus semis?  

I'm well aware electric motors make massive torque, and do it from 0RPM.  You should find some of my posts relating to electric cars and hybrids.  I'm not uninformed in this area.

I'm talking about fuel efficiency.  Not being a mechanical engineer, and also not being a dumbass, I would surmise that straight diesel engines in a locomotive couldn't be geared to get proper torque at low speeds, thus the diesel electric system's advantage is that it allows the diesel generators to run at a constant speed while electrical current is throttled to control torque.  

That's probably reason enough to use a diesel electric system in a train, but I had always had the impression that it was more fuel efficient as well.  I could be wrong on that.  

and again, if there's a Wikipedia page comparing the relative fuel efficiency of both systems across both applications, I'd love to see it.

That doesn't stop the Greenies - the comment I heard on NPR was that the rules don't go far enough because they don't require hybrids.  Apparently being a hybrid is the magic formula that will save the polar bears.

Yes, but if the government made sense they would measure pollution for cars in terms of miles driven.  Instead they use mass of pollutants per mass of fuel consumed.  This causes bizzarre consequences when more fuel efficient engines are banned because they can't get that last bit of NOx out of their exhaust (Ref 96-97 VW TDI engines)

Sorry to have wasted your time by making you explain things I already understand.   (inertia, torque, mass, etc etc)   Obviously I won't bug you to get into specifics about available torque over broader speeds that semis encounter that trains do not, because of course trains just get up to speed and don't stop or slow down for thousands of miles.   Or whether or not given a particular load at a particular speed if a diesel electric system can provide the torque needed with lower fuel consumption than a straight diesel system.    

*sigh*

Diesel electric is expensive, but can be more efficient.

It's a good upgrade for tracks and armored vehicles...

Didn't we just have a thread started by someone who thought he was the first person to ever think of a diesel electric car/truck?

I can't wait to see how the testing is done, every truck is different and will need to be tested. Wait till people have to pay for that.

This might be the final nail in the coffin for America's loggers.

Why do you say that?

Do you think the engines, generators and motors would be the same size if the system were used in a semi?

First off, they could use much smaller motors for traction, since the vehicle and load are both much smaller.  The generators could be much smaller, too, considering the size and weight of the vehicle and it's load would be lighter.  

I'd bet a diesel electric system conversion in a semi wouldn't come out to more than maybe a couple hundred pounds heavier than the diesel drivetrain that's in there now.  



It's about scale, dude.  The system would be scaled.  If scaled appropriately, I want to know if a diesel electric setup in a semi would be more fuel efficient than a straight diesel setup.

You don't seem to know, so you're not answering anything.

What do you think?  They won't be able to afford the higher costs associated with these new regulations.



 

How much higher will those costs be?  I'm curious.  The industry is claiming $1,000/vehicle for a one ton, with $7,200 in life cycle savings.  Thats about $500/yr.  Which means the difference will pay for itself in two years (leaving aside finance costs).

So it is a cash flow issue.

Correct?

That number is complete bullshit thrown out to give the press something to write.

We don't even know how they plan to do the test, it might be a computer simulation for big trucks, and dyno test for little ones.

Those numbers are wrong.  They will be considerably higher, plus cost of upkeep.  This is a regulation that is not needed and will put more people out of work.



 

Lots of people saying what it is... I'm inclined to take my info from industry rather than a poster on a forum.

Ask yourself this, if they can increase fuel efficiency 20%  for only 1k per vehicle, why the fuck don't they do it? Customers would easily pay the extra money, they are already paying a lot more than that for electric and hydraulic hybrids.

Yup



 

In 1998, Ford asked their suppliers for ideas on ways to drop weight.  They received 200 submissions at an average cost of 50 cents per pound and implemented none of them. Their margins are razor thin and they weren't willing to risk it.

You want me to tell you why American automobile manufacturers are dumbasses?

No shit?  That's what we call a clue.



 

The truck industry is a lot different from the car industry.

And your experiences in the US automotive engineering field is?  



Ever hear of gasoline direct injection engines?  They have been slow to reach the market in the US, mostly due to the EPA.  



 

Ok, I'll answer.

No.

Geared drivetrains are very efficient in transmitting power at the flywheel to power at the wheels - in excess of 90%.  Replacing the transmission and differential with a generator and motors, while it allows for the engine to run at a constant rpm where it has it's highest BSFC, gives it back up in converting mechanical energy to electricity and then back again.  A straight electromotive transmission in an OTR truck would not be markedly more efficient than a mechanical transmission system.

So, why are they used in locomotives?  Guess what - it's NOT because they are more efficient than other systems.  When diesel-electric engines were first introduced, they were used almost exclusively for yard jockeys and low speed operations, because they were LESS fuel efficient than steam engines.  The reason the railroads pushed into long haul diesels was because they required less maintenance and fewer personnel to run.  They were willing to take the hit in fuel to reduce personnel - given the strength of the RR unions you can see why.  Another reason for using electromotive transmission instead of mechanical is the torque multiplication levels in a train are orders of magnitude higher than in an OTR application.  The gearbox alone would be a monstrosity.  

Wait, you say - what about braking?  Locomotives use the motors as generators and dissipate the train's kinetic energy as heat.  Sure - but why do this on a truck?  It adds fans and resistor banks (there goes your comparable size) and trucks typically don't brake for the distances trains use.  What about regenerative braking?  That's where the "big" efficiency gains in hybrid drives come from, at least using Toyota's system.  But it comes at a cost - batteries.  Which means weight.  Implementing regenerative braking in an OTR truck blows the size/weight budget right out of the water.  Now the system is a LOT bigger and heavier than a conventional transmission.  Is that an overall problem?  Maybe not.  But it's no longer as simple a matter as you propose.

Great points on diesel-electric locomotives.  Another benefit to diesel-electric locomotives is slip detection/prevention  D-E have nearly infinite torque multiplication ratios, even an automatic transmission with torque converter would probably slip wheels at shift points.  



Now if they could make a CVT for a diesel locomotive, it might work.  But seeing how automotive CVTs are either for very small engines or are horribly unreliable, D-E will continue to be used.  Not even a dual sequential gearbox would work in a locomotive.  



Finally, D-E provides weight which is tractive effort.  Weight isn't needed in a semi-tractor trailer rig.  Part of the load (which is why they are called semis) provides weight which provides traction.

bahahahaahahahahaha
there's NO FUCKING WAY

Just moving to the 2010 emissions regulations changed engine prices by over 10,000 dollars (that's right, 10 grand more) on big motors and over 2 grand on little trucks (3/4T, 1T) and reliability and miles went down
so now, wave your magic wand and increase mileage by 30% and it only costs $1000????????   GTFOH