What It Is
A regenerative drive system based around a hydraulic pump/motor and a pair of accumulators. Eaton Hydraulics has been down this road with its Hydraulic Launch Assist (AD&P, April 2002, p. 28), but Permo-Drive Technologies, Ltd. (Ballina, Australia) is working with the U.S. Army, the largest truck fleet operator in the world...and garbage truck fleets.
What It Does
A reversible pump/motor is attached to the driveshaft via a clutch, and connects to a pair of accumulators (one high- and one low-pressure) filled with a combination of nitrogen gas and hydraulic fluid. Under braking, the hydraulic fluid flows through the pump/motor unit into the high-pressure tank. It is released back through the driveshaft on acceleration. In military applications, the Permo-Drive unit can be used to accelerate the vehicle with the engine off, which reduces its noise and heat signature.
Why People Are Interested
According to U.S. Army figures, 70% of the bulk tonnage required to sustain a military force in the battlefield is fuel. That’s about 600,000 gallons of fuel/day at an air freight cost of $600/gallon. Testing of a Permo-Drive-modified Army FMTV (Family of Medium Tactical Vehicles) at the military’s Aberdeen Proving Grounds in Maryland shows a 26% to 33% improvement in fuel economy, a 7.5-second reduction in 0-60 mph times, and a 450-foot reduction in stopping distance from 32 mph when fully loaded. Permo-Drive says spare parts are readily available, the components are robust, the technology is mature, and the units can be retrofit to existing vehicles. The technology also appeals to garbage truck fleets who perform $10,000 brake overhauls on each truck as often as once a month. Permo-Drive says it can extend this interval to once every six to eight months.
A system for Class 6 trucks is under development. It has a target weight of 330 lbs., produces 340 hp and 995 lb/ft of torque, operates at 5000 lb/in.2, and is 18-in. long by 9.5-in. wide by 12-in. high. Prototypes will be ready in the fourth quarter of 2003, with production scheduled for the second quarter of 2005.
Check it out at: www.permo-drive.com