Mower Uses Water As Hydraulic Fluid

A group of Purdue University undergraduates have built an industrial riding lawn mower that uses water instead of petroleum-based hydraulic fluid.

The students have created what is thought to be the first vehicle that uses water in all of its hydraulic systems, including power steering, power brakes and transmission.

Recent advances in water hydraulic systems have allowed them to perform as well as petroleum hydraulic systems. Because water offers several environmental and economic advantages over petroleum hydraulic fluid, the students teamed up to demonstrate that such a vehicle is now possible.

May graduates Jason Brown, Dan Sellers, and Dan Pitstick worked through their final semester at Purdue to build the machine. Nathan Schoonover, who will graduate in December, also worked on the project.

Although the mower was redesigned to prove a point, it does have a practical purpose. Mowers leak some hydraulic fluid, and on golf courses that fluid can kill grass on greens that often cost tens of thousands of dollars to construct and maintain.

Jacobsen, a division of Textron Inc., donated the Greens King IV mower, which is a 31 horsepower, front wheel drive mower with three sets of gang mowers that are raised and lowered hydraulically.

Gary Krutz, professor of agricultural and biological engineering and the students’ advisor, says water hydraulic systems only would be practical in vehicles that use high pressure systems, such as heavy equipment used in construction, agriculture, forestry and mining. Automobiles have hydraulic brake and steering systems, but these are not typically highly pressurized.

Using water in hydraulic systems now costs twice as much as using petroleum products, but that could change as more applications are found for water hydraulics.

“If all of the research and development were done, all of the major companies would be using water instead of hydraulic fluid,” Krutz said. “Because the industry is in its infancy, mass production hasn’t lowered the cost. But once you start mass producing the necessary parts from ceramic, fiber reinforced plastic or stainless steel, the prices will drop.”

Research at Purdue on water hydraulic systems focuses on hydrostatic bearings, which would be used in cars or industrial or agricultural equipment. “These would work well with cars in the future that use fuel cells, because you would be able to use the water in the fuel cell and in the gear box,” Krutz said.

Water, Water Everywhere

The water used in the mower isn’t straight from the tap; ordinary city water contains too many minerals and impurities and could cause build-up and corrosion. Instead, the system uses distilled water that has been de-ionized to remove any electrical charges that could cause corrosion. Corrosion also is the reason parts for water hydraulics systems have to be made of stainless steel, plastic or ceramics. But the more expensive parts would prove their worth as using water in hydraulic systems makes machinery more energy-efficient, saving money, Krutz said.