HEMTT-A3 Heavy Expanded Mobility Tactical Truck
I’ve always wanted to get a big monster truck. Huge tires, sits really high off the road, good visibility, don’t have to worry about road obstructions like pot holes, goes in the snow, even take it off-road. The problem is that these big monster trucks don’t get very good gas mileage.
Well now Oshkosh Truck Corporation is manufacturing a truck using Diesel Electric Hybrid technology that increases fuel efficiency 20% over the truck it replaces. The HEMTT A3 truck is being built for the military, which is pretty demanding about reliability and performance. The truck has a 400 HP Cummins ISL Diesel Engine with a 305 KW electric generator. The generator charges a 1.5 MJ ultra-capacitor. The capacitor feeds power directly to electric motors mounted on the wheels. The vehicle can work off-road, climb a 60% grade, and achieve 65 mph on secondary roads. The truck weights 3000 pounds less than its conventional predecessor, but still can carry a 13 ton load.
The capacitor is the heart of the drive system. It stores the equivalent of 0.42 Kwh, or equivalent to 0.035 gallons of gasoline (4.5 ounces). You can’t get very far on that amount of power so the vehicle does not work as a home plug-in. The capacitor does buffer the power from the engine allowing the engine to always run at an efficient speed. The capacitor provides for bursts of power when the vehicle accelerates and can capture the power from regenerative braking. That is what gives the vehicle its improved fuel economy.
The real point to discussing this vehicle is that this drive train technology could also be used on more conventional vehicles like cars or utility trucks. A capacitor in a car could allow for a smaller, lighter engine to be used. It would be optimized to run at peak efficiency. You can eliminate heavy parts like the transmission. More of the car becomes solid-state electronics which are very reliable. The capacitor also recovers the energy from braking. The number of cycles on the capacitor should be almost unlimited so it won't degrade over time like a battery. Assuming a 20% increase in efficiency, a 30 mpg car becomes a 36 mpg car. If every car on the road today used this technology, we would save about 1.9 million barrels of oil each day, along with a reduction in greenhouse gas emissions. You also could add a battery to this design to create a plug-in vehicle. The battery would not need the capacity to power the entire car (making it cheaper). It would only re-charge the capacitor; sort of like how a battery on a camera charges a capacitor that powers the flash. You might never need to run the engine just traveling around town.
I was thinking that if you painted the truck a little better color, maybe black with lightning bolts or flames, it would be a really cool machine to drive around. You can get it with armour plating if you drive in a rough neighborhood. Put a camper on the back, put the family yacht on a trailer and you would be ready for a week-end camping at the lake. The truck can also work as a stand-alone electric generator so there would be plenty of power for the hot-tube and plasma TV. As a hybrid electric, I was wondering if they would let me use the HOV lane to drive to work. My wife pointed out, that people would see me coming and just get out of my way! I’m not planning on getting one anytime soon though. It would be a bit of a problem to park and I haven’t figured out how to get it into the garage, although maybe I could put the garage on the truck.
Comments
Is this really in production? I know they built two but thought the project was canned once one a key supplier ceased operations. How any are they going to make and when?
Oshkosh claims that the HEMTT A3 is production ready now, but the army has not ordered any. The Army did recently order for 233 of the HEMTT A4, which has the more traditional drive train. The price of the vehicle could be an issue.
Some more information about the vehicle; the capacitor can add about 190 hp to the vehicle for 10 seconds or 19 hp for 100 seconds. This surge of power for a short period of time would provide for excellent acceleration characteristics. This would probably be more meaningful in a car where you could get excellent acceleration performance with a very small engine.
Hi John,
Caught your article on Seeking Alpha.
One thing that is not quite clear and I would like clarification is the truck exclusively driven by electric motors, with power boosts supplied by the utlra-caps? Or is the vehicle normally driven?
What it sounds like is a locomotive, the diesel turns a generator, the electricity from the generator then turns motors that turn the wheels and other reading has it the vehicle also captures the energy of the vehicle during braking.
Some other site notes this sort of vehicle may really pay off for vehicles making frequent starts & stops.
Marcus, This truck is driven by electric motors just like a diesel-electric locomotive. The diesel-electric locomotive has been around for 30+ years. They use the diesel engine to power a generator which provides power to the electric motors. This eliminates the need for a huge gearbox and clutch on the locomotive. Electric motors produce tremendous torque, especially at low speed, which is perfect for accelerating a very heavy train. Slipping the clutch would not be as good. Electric cars have the potential for tremendous acceleration because of this, if only the power supply can produce enough current.
The idea behind the capacitor is to buffer the power from the diesel engine so that the engine can always run at the most efficient speed. The capacitor can also capture the energy from braking to increase the overall efficiency.
The current high cost of the capacitors severely limits this from currently being a practical solution, but EEStor is working on a new capacitor that might make this technology a practical reality. A very large battery could also be used in this application like GM is planning with its Chevy Volt.
Does anyone know what the actual mileage rating would be on one of these things? It's 20% more efficient than an equivalent vehicle, but it's hard to imagine an equivalent. I'm pretty impressed, but I'd really like to get more detailed specs.
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