Greens on golf courses are mowed early in the morning — when the turf usually is slippery from dew or irrigation — and a greenskeeper must be able to drive a mower anywhere on and around the green without losing traction or damaging the turf. However, many riding mowers will slip during turns in the sculptured trim area around the green or when climbing minor grades on the green.
In the traditional greensmower design, hydraulic motors on each driven wheel are piped in parallel. But this configuration means that when one tire slips, all the motors stop. Another issue is that cutting reels are self supporting on the ground, so the weight on the front wheels is minimal during mowing, adding to the possibility of slippage. As a result, even minor rises can be difficult to climb straight-on and impossible to negotiate on a diagonal line.
To solve this maneuvering problem, The Toro Co., Bloomington, Minn., has designed and patented a hydraulic traction circuit that enables a groundskeeper to easily manicure golf greens with the speed and convenience of a riding mower. The traction arrangement on Toro’s Greensmaster riding mower has a triplex configuration, with two drive tires in front and a steering tire in back. Its hydraulic circuit plumbs the front wheel motors in parallel with each other, then adds a third motor at the rear wheel and plumbs it in series with the front two. The rear motor has twice the displacement of each front motor, and the tires mounted on all three wheels are the same size to maintain the correct speed ratio.
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With Toro’s circuit, the machine will continue to move on wet or uneven turf until one front tire and the rear tire slip. Traction while climbing grades, especially on a diagonal line, is significantly improved compared to 2-wheel drives or simple parallel 3-wheel drive systems, because Toro’s rear wheel will continue to push even if a front tire loses traction. In addition, rear-wheel traction is improved because weight transfers from the front wheels to back when going uphill.
It is difficult in almost any drive configuration to maintain the correct speed ratio between the front and rear tires during turns. The tricycle layout of the Greensmaster means the rear wheel must turn faster than the average of the two front wheels while turning. In the patented Toro system, an overrunning clutch allows the rear tire to overspeed during turns to maintain gentle, even traction.
Toro designers also paid extra attention to protecting the turf from hydraulic leaks. The Greensmaster has fewer hydraulic lines, monoblock connections, and a centrally located bulkhead mounting. These machines also are ready to accept bio-friendly hydraulic oil if the user chooses to install it.
Another patented Toro system, Turf Guardian, monitors the hydraulic oil level. A miniature hydraulic tank sits atop the main tank. Should the level in the small tank go down, an alarm signals the operator to stop the machine. By following this procedure, leaks usually are limited to a few ounces.