Why not diesel electric trucks?

jdc1 wrote:
I think the OP was thinking along the lines of a Chevy Volt or Honda Clarity. Use the EV drivetrain, and a diesel engine as a generator. Makes PERFECT sense to me.

Chevy Volt is a completely different animal and designed to serve a different purpose, even if some of the parts superficially are similar.

It uses batteries most of the time for daily commutes while being charged at night. Only on longer trips does the ICE kick in to supply power allowing for effectively unlimited range. Effectively for most people 80-95% of miles it's a battery electric vehicle and it suffers less than ideal efficiency when the motor does kick in but for most that's a good trade off.

A diesel-electric locomotive doesn't use a battery bank for propulsion. If it's moving the ICE is providing the power, just transmitted via electrons.

PS: I believe Ford has a Plug-In-Hybrid F-150 which is similar in purpose to the Volt.

To answer the OP’s question directly…

Sure thing. Pretty easy to boot, but the solution will take much space

Take a Model 3 and say it’s battery/motor is a 50KW system

So just take a gas or diesel 50KW generator of the correct voltage and the fuel tank system to keep it going.

All the parts are readily available at most any hardware store…except for the DOT fuel tank. Junk yard would be the best source, or if money no problem…order a brand new one from any OEM

Then find the space to mount all that & the cabling/controls to manage it all

Maybe toss the battery’s to boot, but they would be needed for regenerative braking…or toss the batteries and use resisters to absorb the regenerative braking power & reject it as heat.

Hey !…maybe we’ve just solved Tusk’s Semi problem !!! :B

schlep1967 wrote:
If a single diesel electric locomotive can pull 27,000,000 pounds, why has it not been scaled down to pull 20-40,000 pounds yet?

I think the OP was thinking along the lines of a Chevy Volt or Honda Clarity. Use the EV drivetrain, and a diesel engine as a generator. Makes PERFECT sense to me.

JRscooby wrote:
I always thought the idea was traction. Steel on steel is pretty slick. Can you imagine what driveshafts would look like if used them to drive all the wheels?
Years back, sitting around a campfire, burning some illegal substances we discussed driving a pump with engine, to power hydraulic motor on each wheel. Would not have the regen of electric, but hydraulic motor lighted than electric, pump lighter than generator. And with valving, the engine could run idle, or most efficient RPM. As speed increase some motors freewheel

Yes, I can imagine the drive train...look the last steam engines ever built. They were wildly complicated systems of gears, axles and shafts...and even there not all the wheels were powered. Steam engines do have the advantage that they can put out peak torque from zero RPM similar to electric motors.

I believe hydraulic has been used on some smaller railyard engines but it's not as efficient.

There is no "regen" with diesel locomotives. The available power is what the engine is putting out right now. If the engine puts out more power than the electric motors take up, it's wasted but since trains spend 95%+ of their time running at a steady speed, it's not a big deal.

Turtle n Peeps wrote:

Why has it not been scaled down to pull 20-40,000 pounds yet?

Because of this pesky problem.

Trains don't do this for fuel efficiency. They do it for reasons Ben stated. If you have 4 engines pulling a train it would be a nightmare to get all 4 to dump the clutch at the same time! :B

This is the reason.

The electric in diesel-electric locomotives is acting exclusively as a transmission.

To build a mechanical transmission capable of absorbing thousands of horsepower and then smoothly meshing it across 4-5 locomotives would be massive, complicated and expensive.

Using a generator and some electronic controls to feed electric motors in place of a transmission is dramatically simpler and allows much easier means of meshing across multiple locomotives.

It's actually slightly less efficient if you compared it to a mechanical transmission once the train is up to speed but getting the train up to speed is a huge issue.

On the other hand for trucks putting our just a few hundred horsepower with no need to mesh with other trucks, a mechanical transmission is comparatively small and simple (keep in mind, simple is a relative term).

I always thought the idea was traction. Steel on steel is pretty slick. Can you imagine what driveshafts would look like if used them to drive all the wheels?
Years back, sitting around a campfire, burning some illegal substances we discussed driving a pump with engine, to power hydraulic motor on each wheel. Would not have the regen of electric, but hydraulic motor lighted than electric, pump lighter than generator. And with valving, the engine could run idle, or most efficient RPM. As speed increase some motors freewheel

Poor efficiency. Although I would like the idea of skipping the transmission.
Direct connect on the highway and use electric at low speeds around town.
Continue with the electric power boost at speed and regenerative for braking or descending speed control.

These guys are trying, but wether they make it….
https://www.hyliion.com/erx-page/

BenK wrote:
Electric motors, especially DC motors, can have over 300% torque at ZERO RPM

No ICE's can do that and getting it going from a dead stop requires that. As all ICE's have no torque at zero RPM

That's why they use a transmission with a clutch or torque converter.

My Hybrid car uses a system much like a diesel-electric locomotive, at low speeds, the ICE engine powers a generator that (along with the battery) powers the electric motor to drive the wheels. At higher speeds, the ICE engine can be coupled to drive the wheels mechanically.

All ICE's use an electric motor to start it because an ICE can NOT develop torque until it gets RPM

While most ICE engines needs some sort of starter motor (not always electric, sometimes air, sometimes a crank, etc), some air start systems inject compressed air into the cylinders to turn the engine for starting so no starter motor required.

But more interestingly, some ICE engines can start with combustion alone, Mazda's Skyactive start/system system knows which cylinder to fire to start the motor by injecting gasoline and firing the spark plug:

https://www.mazda.com/en/innovation/technology/env/i-stop/

But even those have a starter motor for cold starts, and to handle the case where the cylinders didn't stop in the right position for restart.

Why has it not been scaled down to pull 20-40,000 pounds yet?

Because of this pesky problem.

Trains don't do this for fuel efficiency. They do it for reasons Ben stated. If you have 4 engines pulling a train it would be a nightmare to get all 4 to dump the clutch at the same time! :B