Preventing Overturns With Zero-Turning-Radius Mowers

Richard L. Parish  |  12/18/2004 1:31:52 AM

A ROPS and seatbelt are important for protection from overturns.

Zero-turning-radius mowers are often used to mow ditches, pond banks and other slopes. Operators need to be aware of safe practices to prevent overturns, and machines should be equipped with a rollover protective structure (ROPS) in case an overturn does occur.
 
Zero-turn mowers are somewhat different from conventional tractors, and safe practices to prevent overturns are different in some cases. Zero-turn mowers tend to have low centers of gravity. They are fairly stable, but their short wheelbases and narrow wheel spacings can contribute to overturns. A ROPS and seatbelt should always be used with any zero-turn mower, even the smaller models. A folding ROPS should always be locked in the upright position unless it is necessary to lower it temporarily for loading into enclosed trailers or driving under low-hanging obstacles. Raise the ROPS as soon as you move out from under the low obstacle.

Side Overturns
Side overturns are not common with zero-turn mowers, but they are possible. The wider the deck, the less chance of a sideways overturn, since a deck out beyond the tires will help stabilize the machine. It is always desirable to mow up and down slopes with a zero-turn mower rather than across slopes to reduce the risk of a side overturn. If it is absolutely necessary to operate on the contour of a slope, the operator should be prepared to take emergency action if an overturn seems imminent.
 
The correct emergency action is different for mid-mount and front-mount mowers. With a mid-mount mower, the drive wheels are at the rear, so the operator should always turn downhill if a side overturn is sensed. Front-mount mowers have the drive wheels at the front of the tractor unit. Even though they have a deck out front, many decks can tilt up, providing minimal overturn protection. It is best to turn a front-mount mower uphill if a side overturn is sensed (assuming the front-mount mower has two rear wheels; on models with a single rear wheel, the operator should turn downhill as with mid-mount mowers since the single rear wheel design is less stable).

Front/Rear Overturns
As noted above, the dynamics of mid-mount and front-mount zero-turn mowers are different. Mid-mount zero-turn mowers should be backed uphill and driven downhill. That keeps the drive wheels and the weight of the engine on the uphill side so the torque reaction of the drive wheels will be counter to an overturn. With front-mount zero-turn mowers, the drive wheels are at the front of the "tractor" portion of the machine. If the front-mount mower has two rear wheels, it is best to drive uphill and back downhill to keep the driving axle uphill. This is probably not best with front-mount mowers having only one rear wheel; they are less stable, and the single wheel should probably kept uphill -- and extra caution used.

General Safety Suggestions
It is always a good idea to avoid jerky maneuvers. On flat ground, jerking the steering levers will tear up the turf, shorten tire life and stress the hydraulic system, but jerking the levers while on a slope can result in a mower turning over on top of you. Avoid steep slopes with a riding mower; use a walk-behind mower (operated across the slope) or a string trimmer. All zero-turn mowers should have a ROPS. If your mower has a rollover protective structure and a seatbelt, be sure to wear the seatbelt; the ROPS is useless unless the seatbelt is fastened.

Zero-turn mowers are generally stable, but you must still use reasonable caution to avoid overturns. Good driving practices that are desirable on level ground will help you avoid overturns. A ROPS is important to protect you in case an overturn does occur.

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