A zero-turn riding lawn mower (colloquially, a z-turn) is a standard riding lawn mower with a turning radius that is effectively zero. Different brands and models achieve this in different ways, but hydraulic speed control of each drive wheel is the most common method. Both commercial duty and homeowner models exist, with varying engine power options, size of cutting decks, fuel type (gasoline or diesel), and prices. A z-turn mower typically drives faster and costs more than a similarly sized conventional riding mower that has steerable front wheels.
Most current models have four wheels: two small swiveling front tires and two large drive tires in the back. Bush Hog mowers sometimes come with a small, pivoting fifth wheel mounted in the center behind the driver. Instead of controlling the swiveling tires to steer the machine, the large drive tires rotate independently of each other based on the driver's input. They may rotate in opposite directions. The mower can pivot around a point midway between the drive wheels (the classic z-turn), or it can pivot around either one of the drive wheels if one is stationary, or it can turn in a circle of any radius. Reversal of the direction of travel can be accomplished by causing both wheels to rotate in reverse.
Steering controls differ on z-turn mowers. Instead of a steering wheel, most z-turns have two throttles that control the rotational speed and direction of each drive wheel. The throttles are typically moved by a seated driver who operates levers mounted waist to shoulder high. The mower's engine throttle is controlled separately, if at all. Some zero turn mowers are steered by a joystick or a steering wheel, the advantage of either one being the location of the hands may permit less fatigue during prolonged mowing and the use of a single hand for steering.
In 1949, Warrensberg, MO resident Max Swisher invented the very first commercially available zero-turn mower and called it the "Ride King". It was a three-wheeled machine - one wheel in front and two in the rear. The patented system utilized the front wheel as the drive wheel that also was able to turn an amazing 360 degrees. The wheel was driven by the motor in the same direction 100% of the time. In order to reverse and/or utilize the zero turn capabilities, you simply turned the steering wheel 180 degrees and the mower would reverse course. In 1963, John Regier was an employee of the Hesston Corporation, a manufacturer of farm and agricultural equipment. The company had recently engineered a device called the swather, which, propelled by a series of belts, cut hay, alfalfa and other farming materials and laid them out in windrows. The way the belts and pulleys operated allowed for counter- rotation—a process which particularly struck Regier. An idea came to him one day: What if he could incorporate the same technology into lawnmowers?
"So he went home and invented this thing that was able to operate on the zero-turn radius," says Ken Raney, advertising manager at Hustler Turf. "He began selling them, but they weren’t really taking off the way he wanted them to. Nobody knew the technology then, so nobody wanted to buy it." Regier's patent was eventually sold to Hesston, which would eventually become Excel Industries—parent company of Hustler Turf. The mower was called—appropriately enough—the Hustler.
"We were the first company to offer mowers with zero-turn technology," says Paul Mullet, president of Excel Industries. "After Regier sold us the patent, he came to work for us and the rest is history." Excel Industries is the parent company of Hustler Turf Equipment, Inc., which manufacturers Hustler Turf and BigDog Mowers zero-turn mowers.
In 1969, Grasshopper Mowers introduced the first commercially viable zero-turn mower, and in 1974, Dixon coined the term "zero-turn radius" with their entrance into the mower market.
In 1997, Robert D. Davis Jr. obtained United States Patent 5644903 for a new steering control he had invented for a zero turn radius mower, based on eight previous patents.
Currently, there are more than three dozen zero-turn mower manufacturers offering a range of mid-mounted and out-front mowing deck options and accessories.
For most zero-turn mowers today, steering is simply changing the speeds of the drive tires. The tire speed is controlled by two levers that protrude on either side of the driver and typically extend over the lap. It is not that different from steering a shopping cart. When both levers are pushed forward simultaneously with the same force, the mower moves forward; when both levers are pulled back simultaneously with the same force, the mower moves backward. Push one lever more than the other and the mower makes a gentle turn. Push one lever forward and pull the other back and the mower pivots from the drive wheels, creating a zero-radius turn.
Zero-turn mowers can use steering wheels but must be designed much differently. Husqvarna is one of the few zero-turns to use a steering wheel by connecting the back wheels to an axle. The axle is mounted in its midpoint to the body of the mower.
Zero-turn mowers are designed to cut so closely around obstacles that there's virtually no need to trim. These mowers pivot through 180 degrees without leaving any uncut grass. Maximum lever movement means maximum fluid flow, which translates into a rapidly turning wheel. If one drive wheel turns more rapidly than the other, the machine moves along a curved path. If both wheels turn at the same speed, the machine follows a straight path. If one wheel stops and the other turns, or if the wheels turn in opposite directions, the mower pivots.
There are a number of different attachments that add to the versatility of zero turn mowers. One popular attachment is a bagging system that allows you to collect grass clippings. There are many bagger options available for zero turn mowers including two- and three-bucket designs. You can also add a mulching kit to the deck to mulch clippings back into the lawn instead of having the grass discharge from the side chute.
Adding a hitch to the back of a zero turn mower allows use of a variety of different attachments, including a dump cart, spreader, plug aerator, lawn dethatcher, roller or sprayer. Some zero turn mowers also accommodate front-mounted attachments such as a snow blade, snow blower or brush for clearing snow or debris.