Pull-behind wide-area rotaries
Until recently, you have not had a wide array of equipment from which to choose for mowing large-turf areas. Agricultural-type rotary mowers pulled behind a tractor were your only choice. Today, you have better options of self-contained, wide-area rotary mowers. Recent design advancements in turf-type, pull-behind, wide-area rotary mowers make them a more attractive option than the mowers historically used in agriculture. Traditional manufacturers of large PTO-drive rotaries have turned to the robust turf market in recent years as a new sales avenue for their products. In addition, new manufacturers have introduced product innovations of their own.
PTO-drive pull-behind mowers Pull-behind PTO-drive wide-area rotaries are multi-deck units designed to trail behind a towing tractor, which also provides the power to operate the mowers through its rear power take-off. Creating a mowing swath 10 to 22 feet in width, one unit can cut up to 80 acres of wide-open turf per day. To duplicate that workload without a large, multi-deck unit, you would need several operators on smaller machines. Because labor is the largest cost in any turf-maintenance operation, maximizing productivity of your employees through proper equipment selection is key to a profitable and efficient operation.
A three-deck design is the traditional configuration of PTO-drive rotaries, with main transport frame and transport wheels. You raise and lower the decks hydraulically for over-the-road travel or between mowing areas. The maximum deck width is typically 72 inches. Units with large deck sections are suitable for wide-open, level turf areas but will tend to scalp turf if the terrain is undulating. Therefore, it is important that you match the mower-deck size with the terrain that you will be mowing. The large deck sections on the 15- to 22-feet models make them suitable for parks, athletic fields, school grounds, golf-course roughs, airports or other relatively flat, open areas.
What makes a turf-type rotary? One of the distinguishing characteristics of the new turf-type rotaries is the multiple-blade deck. The multiple blades provide a finer cut. The older agricultural-type mowers had fewer, very long and heavy blades (often 0.5-inch thick or more) to maximize their torque and brute strength for mowing tall turf and shredding thick stalks. The after-cut appearance wasn't a major concern, as long as the machine cut the turf and the underside of the decks didn't clog.
Turf-type wide-area rotaries were developed by equipping decks with multiple-blade spindles, reducing the length of each blade and creating a high-lift "sail" on the back of each blade for a clean cut. Depending on the design of the decks, engineers added baffling or chambering under them. This maximizes air velocity created by the spinning blades to help the grass stand up for a cleaner cut, while also mulching the clippings. This internal baffling also directs the clippings for proper discharge and dispersion from under the decks for a good after-cut appearance.
Wheel function Merely adding more and smaller blades did not answer all the challenges of creating a good turf-type mower. Large decks still tend to scalp turf surfaces that are not flat. Manufacturers have added multiple caster or gauge wheels and anti-scalp rollers to make them suitable for mowing a wider range of terrain. Two basic wheel-types exist and perform different functions. * Caster wheels support the decks via constant ground contact. You use these wheels to set the height of cut. They are full-swivel, part-swivel or fixed-position wheels. * Gauge wheels, by contrast, sit slightly off the ground so they only contact undulations in the turf. They serve to raise the mower deck slightly before the blade has a chance to scalp the turf. Anti-scalp rollers (usually located in the front or rear center of each mower deck) perform the same function. Occasionally, the deck shell itself houses the anti-scalp rollers.
Many manufacturers, in efforts to minimize scalping and maximize flotation, have introduced smaller (8 to 10 feet wide) rotaries with narrower deck sections. However, no innovation has affected wide-area mower design as dramatically as the concept of individual mower decks for each blade (See photo, page C 18). This, in effect, links many push-mower decks together with a common frame and drive system. The result is a "floating" mower with the high-capacity productivity of the traditional wide-area rotaries, but with the flotation, discharge and after-cut appearance of individual push mowers. Suddenly, golf-course superintendents and managers of corporate sites with hills, berms or undulating terrain had a relatively economical choice for high-capacity turf mowing without fear of scalping.
Smaller versions of this floating-deck design mount on out-front rotary mowers, as well as engine-powered, self-contained models and pull-behind PTO-drive multi-deck mowers of various configurations and drive systems.
Another innovation aimed at enhancing the after-cut finish of wide-area rotary mowers is the mulching deck with a counter-rotating-spindle design. Circular, under-deck baffles house each blade to contain and mulch clippings-minimizing clumping and unsightly discharge. The unique aspect of the design, however, is that a series of four smaller blades are positioned above the main blade on a counter-rotating section of the blade spindle (see figures, page C 18). By rotating in the opposite direction, these smaller blades create additional air turbulence within the deck baffle to help keep the clippings suspended while further shredding them for minimal discharge. As with any type of mulching deck, you should wash the under-deck sections frequently to keep them free of buildup. This buildup reduces the available air volume within the blade baffle and causes improper cut and discharge.
First things first Proper equipment selection for any large-scale site includes a few important steps: * Survey the terrain you need to mow, taking note of undulations, obstacles and any bridges or other transportation challenges, etc. * Determine the quality of after-cut appearance you want. * Determine which machine will render the results you desire. * Inventory your existing equipment and analyze your budget to determine your need and ability to purchase a large pull-behind mower.
Self-contained and PTO-drive units Self-contained wide-area rotary mowers offer the advantages of relatively small deck sections (typically 44 to 60 inches) for good flotation over ground contours and excellent after-cut appearance. Because the front-mounted decks cut the turf before the traction wheels run over it, these units reduce scalping and increase maneuverability for mowing around trees and other obstacles. This has a price, however, as most self-contained wide-area rotaries are expensive. Therefore, you must have a regular and sizeable need for such a machine to justify its cost.
PTO-drive wide-area rotaries are economical alternatives, especially if you already have a tractor with which to pull and power them. Even if you must buy both, a tractor-mower combination usually costs less than the self-contained units due to the competitive nature of the agricultural-tractor market. The advantage of going this route is your ability to utilize the tractor for other tasks (such as spraying fertilizers or pesticides).
PTO-driven units have a downside. Due to their position behind the towing tractor, most pull-behind rotary mowers do not provide as good after-cut results as a front-mounted mower. Additionally, trimming around obstacles is difficult. Often, a tractor-mower combination requires the presence of another operator on a small out-front mower for trimming. You must not forget that expense-figure it into any cost calculations you make.
What to look for Once you decide that you require a pull-type wide-area rotary-mower-and-tractor combination, you'll want to make the best choice among mower units. Features to consider include: * The width of the mower should be appropriate for the site you are maintaining and compatible with the horsepower of the tractor you have or want to purchase. * Most mowers require at least one hydraulic valve and remote hydraulic outlet on the tractor. * Wing decks must individually raise via the tractor-seat controls for transport or trimming in tighter areas. * Caster wheels (as many as needed-preferably four for each deck section) must support mower decks. Units should have an adequate number of gauge wheels or anti-scalp rollers as well. * Deck wheels must be semi-pneumatic or otherwise puncture-proof. * Deck sections must suspend from the transport frame in such a manner as to allow side-to-side and front-to-back flotation, and allow the wing decks to flex up and down while in use. * Deck sections must have sufficient overlap between them to avoid skipping (leaving strips of uncut grass) in tight turns. * All blade spindles and pivot points on the mower frame must have easily accessible grease zerks. * Deck-drive belts must have automatic tensioning by spring-loaded idlers. * Height of cut must be easily adjustable, preferably in 0.25-inch increments. * All other things equal, a mower with a high blade-tip speed usually provides a higher quality of cut than one with a slower blade speed.
Maintenance and speed Mowers built with standard agricultural and industrial components (belts, bearings, etc.) are more economical to maintain over the long haul because service parts will be locally available at less cost than specialized-proprietary parts and components.
Don't be seduced by claims of mowing speeds faster than 4 to 5 mph. Every mower has a speed limit above which it will not cut or discharge properly. Generally, 4 to 5 mph is the best range for a good quality of cut. Furthermore, at faster mowing speeds, you subject your mower to extra wear and tear from the inevitable and increased bouncing and jostling that occur.
Properly selected and utilized, pull-behind wide-area rotary mowers provide an economical and efficient means of maintaining large areas of turf.
Peter L. McCormick is president of TurfNet Associates Inc. (Skillman, N.J.).
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