[Shepherd777]

Originally Posted by Blue Angel

I will start by stating that I have no direct experience with the mechanical efficiencies of heavy truck transmissions. Having said that, I would imagine that everything is fairly relative, meaning that from a % loss standpoint shouldn't a car's drivetrain be roughly the same efficiency as a heavy truck?

What you are proposing to do would be similar to what GM does with the Volt when it is running in it's "Range Extending" mode (gasoline engine running a generator to drive the electric motor once the main battery is depleted). The generator runs at fairly steady speed to generate the power required to drive the vehicle.

One thing the Volt does, however, is directly couple the engine to the drive wheels through a simple transmission linkage at higher speeds. This is because there's a lot of loss involved in converting mechanical energy into electrical energy and then back into mechanical energy again.

I would think your concept would work really well if you were able to couple it with a transmission and differential gearing that allowed a 1:1 transmission ratio while cruising to minimize losses. This way the electric motors could be used around town and geting up to speed, and once on the highway with the cruise control set the engine could couple directly to the wheels for maximum efficiency.

As another poster commented, I don't think the diesel locomotives use electric propultion for its efficiency, but more for the low end torque characteristics of the electric motor, getting a train moving from rest. Some large ships have used this method as well, but many that do have done it to adapt rotatable "pods" that house the drive motor and propeller. These pods are directable, allowing the ship to steer based on the direction of the propeller's thrust, making navigation in tight spaces much easier. There's a slight efficiency payback with not having to steer by dragging a rudder through the propeller's wake as well.

Absolutely brilliant work, by the way!

Hi Blue Angel -

You said: "I will start by stating that I have no direct experience with the mechanical efficiencies of heavy truck transmissions. Having said that, I would imagine that everything is fairly relative, meaning that from a % loss standpoint shouldn't a car's drivetrain be roughly the same efficiency as a heavy truck?"

Yes, I generally agree with your thesis here. But remember, Class 8 trucks usually have TWO monster differentials

"What you are proposing to do would be similar to what GM does with the Volt when it is running in it's "Range Extending" mode (gasoline engine running a generator to drive the electric motor once the main battery is depleted). The generator runs at fairly steady speed to generate the power required to drive the vehicle."

Yes, exactly correct. Being an old Chevy guy, I could do no less. I may ruffle some feathers here, but I believe GM usually has the best technology. I mean except for the angular, sharp, faceted body of the 2014 Vette, of course. Still, I'd give my left one, to own one of those.

"One thing the Volt does, however, is directly couple the engine to the drive wheels through a simple transmission linkage at higher speeds. This is because there's a lot of loss involved in converting mechanical energy into electrical energy and then back into mechanical energy again. I would think your concept would work really well if you were able to couple it with a transmission and differential gearing that allowed a 1:1 transmission ratio while cruising to minimize losses. This way the electric motors could be used around town and geting up to speed, and once on the highway with the cruise control set the engine could couple directly to the wheels for maximum efficiency."

Most all proposed and test versions of Class 8 hybrid trucks use this configuration that you are referring to. As you are probably aware, this is called a Parallel Hybrid Architecture. And all of those folks use your basic premise for this stating "there's a lot of loss involved in converting mechanical energy into electrical energy and then back into mechanical energy again." I completely agree with this statement. But there are also ways to mitigate, or even negate, these losses. Honest.

But, the Parallel Hybrid configuration is also vastly more complicated, costly, and heavier than a Series Hybrid. And the ICE has to have enough torque to operate an 80,000 lb. rig. So in a Parallel Hybrid, the ICE is a full-size 13-15 Liter diesel engine.

One drive-train manufacturer is even proposing a Dual-Mode Hybrid configuration. But again, extreme complexity, cost, and increased weight are my main issues. And they require a full-size 13-15 Liter ICE.

I told one of the very senior engineers and Vice Presidents at one of the drive-train manufacturers that they were doing their Class 8 hybrid projects like it was the Manhatten Project. I just feel that their architecture complexity and weight is not warranted. Not to mention the cost. I believe I can do better. Time will tell.



AFAIK, nobody is proposing a pure Series Hybrid configuration in a Class 8 truck except me. I really can't elaborate why I believe in Series Hybrid, when all of my competitors believe in Parallel Hybrid or a Dual-Mode Hybrid. But I do believe my reasons are absolutely valid. Like Bruce Willis / John McClane said in the first Die Hard movie, while speaking with Sergeant Al Powell on the terrorists two-way radios, "Listen fast. This is a party line, and the neighbors have itchy trigger fingers."

The large Class 8 OEM's (the terrorists) monitor this site, and I do not want to divulge any more ideas and concepts to them than I already have with the previous truck.

"As another poster commented, I don't think the diesel locomotives use electric propultion for its efficiency, but more for the low end torque characteristics of the electric motor, getting a train moving from rest."

I was always under the assumption that diesel electric locomotives used this method because nobody (at least at the time when diesel electric architecture was introduced in the 1950's) could build clutches and transmissions that could handle the ever increasing post World War II payloads. But one of the truly great by-products of electromotive propulsion is efficiency.