• May 15, 2006

The primary job of the US military's ground forces isn't to haul fuel, but you wouldn't know that by looking at the mix of cargo that it lugs around the battlefield. Approximately 70% of military vehicle cargo is fuel, which is no surprise considering that a large off-road truck may only get 2-4 MPG. Add everything up, and cost of getting that fuel to the front lines can top $600/gallon. 

Oshkosh has a solution, however - the Heavy Expanded Mobility Technical Truck, or HEMTT, fitted with the company's ProPulse hybrid drive system. The system uses a diesel motor to spin a generator in a series hybrid configuration, where no mechanical connection exists between the IC engine and the drive axles. Ultracapacitors are used instead of batteries to store energy. The ProPulse system packs 300 kilowatts (just over 400 HP) of electrical power - enough to lug 13 tons of cargo around, over, or through just about any terrain. Used as a stationary generator, the HEMTT can power several houses in event of a power outage.

The packaging of the hybrid drivetrain leads to better operator comfort, vastly improved serviceability, and a center of gravity that's lowered by over a foot when compared to a conventional drivetrain.

The system is currently in the prototype phase, and there is no definitive date for the system to enter active duty. The cost of the system is also unknown at this time. We just want to know when we can pick one up at a surplus auction.

[Source: AP via Yahoo!]



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  • 8 Comments
      • 8 Years Ago
      A young Ferdinand Porsche designed the 1898 Lohner with a serial gas-electric hybrid drive, including wheel hub motors. Transmissions were very primitive then, and this was a way around them. In WW1, Porsche designed amilitary vehicle similar to the Oshkosh to carry large field cannons and ammo, also a gas-electric serial hybrid. The lead "tractor" had the engine and generator, and the subsequent 2 to 3 trailors all had wheel hub motores. This allowed the units to ford a stream one at a time, with the electric cables extended between them. Very clever.
      • 8 Years Ago
      Capacitors are a perfect system for trucks, as a capacitor bank can easily store most of the energy collected from regenerative braking long enough for it to be effectively reused while not costing much in terms of size or weight. Batteries have a major drawback in that they're heavy, costly, and otherwise not designed for long high-cycle lifespans. For a diesel-electric generator hybrid, batteries make less sense than capacitors, as the charge/discharge cycles will be far more regular and quite intensive. And in terms of capacity, modern capacitors can store as much as a good battery, but with the cost of longevity. The stored energy will "decay" with time.

      Also, as was mentioned, capacitors can *rapidly* charge/discharge, which is quite important for accelerating a multi-ton vehicle to cruising speed.
      • 8 Years Ago
      Ever since BMW’s cap hybrid X3 concept a couple years ago, I’ve been wondering if it would be feasible to make a capacitor-based hybrid race car. Their advantages over batteries have been pointed out above, mainly weight and charge/discharge speed. If you look at driver inputs in to a typical race car, there’s a lot of time spent at full throttle and threshold braking. Regenerative braking could quickly store some of that lost energy in caps when braking for a corner, and then reuse that energy to boost acceleration when exiting the corner and on the straights.

      I don’t see cost being a big factor, since racing isn’t as cost sensitive as the consumer market, but the two big questions would be, does it make the car faster and is it reliable. The quickness factor quickly boils down to weight. Could the added weight of the hybrid bits be countered by reducing engine size and brake size? Even if the hybrid car is a bit heavier, could it still lap a track faster due to the increase in horsepower. I guess another hurdle would be finding a series that has flexible enough rules to allow something like this, although Audi’s diesel R10 has paved a way for alternative propulsion in LeMans racing. Maybe, just maybe.
      • 8 Years Ago
      The Prius is actually both a series hybrid like this truck and partly a parallel hybrid, like Honda makes. The Prius has two motor/generators and a gas engine combined in a planetary gear system. When the gas engine is running, about 2/3 of the power goes directly to driving the wheels and 1/3 is used to generate electricity in one motor that is used in the other motor to drive the wheels. So the Prius is actually a hybrid hybrid :-)
      • 8 Years Ago
      David, the first gen Prius had such a setup.
      • 8 Years Ago
      I've often wondered why this approach to hybrids, an IC engine acting only as a generator for an otherwise electric propulsion system, hasn't been used in cars. Are there problems with it that make it unsuitable for automobile and truck applications?
      • 8 Years Ago
      Oshkosh has a rep as being the WORST truck builder in this hemisphere. If it wasn't for the arm-twisting of the military's truck buyers that this company does, they would have been out of business DECADES ago. Yet, somehow they have come up with a fairly advanced hybrid system (I believe I read an article here, or in a magazine that said BMW was working on a hybrid system that also used caps).
      I find the line that "there is no definite date for the system to enter active duty" to be quite telling. It reminds me of the movie REMO WILLIAMS where a company got a ton of money to build a weapons system for the military and then engineered an "accident" that destroyed it...just as it was about to be tested.
      I wouldn't be surprized to find out that Oshkosh got a ton of government money to build this prototype...with a non-competitive bid contract.
      • 8 Years Ago
      Sounds alot like the Diesel Electric Trains that have been in use for the past fourty years?