Tech Solutions: Wheelin'

Carts are the backbone in the greenhouse industry for moving plants. They are available to meet almost any grower needs: transport, shipping, display or customer service. There are carts available to handle almost any material, bulk, bags, flats, pots or nursery stock.

All sizes of greenhouse operations can benefit from carts. They increase labor efficiency by allowing one person to move more material at one time than could be carried by hand. They also reduce fatigue.

During the past few years, manufacturers have developed carts especially for plant-handling operations. Today, you can purchase carts that:

• Fit into the narrow aisles between benches.
• Tow behind a garden tractor or electric cart, creating a train to carry several hundred flats.
• Have tilting shelves so that the plants are more visible at the garden center.
• Fold or disassemble for easy transport when empty.

In the greenhouse, carts and wagons can serve several purposes. They are convenient for moving bulky materials, such as bales of peat moss, bags of growing mix and boxes and bundles of containers that are difficult to move by hand. Carts are also excellent choices for transporting planted containers from the headhouse to the greenhouse growing area. A typical multi-shelf cart holds 40 to 60 flats.

More carts are now used for shipping. At least one container handling can be eliminated by loading the plants in the greenhouse, rolling or fork-lifting carts onto a truck and unloading and pushing the carts into the garden center. A hydraulic tailgate is convenient for the unloading operation.

Cart selection
Carts should be designed to be operated by one person. Capacity, size, weight and rolling resistance are of prime concern when deciding on a model.

For handling large, bulky items, such as bales, boxes or large nursery containers, a flat bed and large wheels are desirable. Four-wheeled carts are more stable than three-wheeled ones. Swivel wheels increase maneuverability in tight quarters.

Transport carts should be designed with flexibility in shelf spacing. Shelves should be easy to add or remove to accommodate different sized plants. Some manufacturers offer folding or knock-down carts to save on back-haul space. In some, the shelves are removed and stacked onto one cart and the bases stacked onto another. In others, the shelves are removed and the rack folded to a narrow width. A 22-inch-wide cart is convenient as it holds the standard flat and fits into narrow aisles in the greenhouse.

Construction
Purchase a cart that is lightweight but well-built. A welded frame of square steel tubing will take abuse better than a frame that is bolted or fabricated from pipe fittings. Carts that are loaded with a fork lift need to have extra bracing and support in the base. Perforated steel, aluminum or magnesium may be used to reduce the weight.

The cart bed or shelves should be made of a lightweight material that is strong enough to carry the load without sagging. Shelves are usually made of galvanized expanded metal, or heavy wire mesh with angle iron rails. Carts for shipping and display at the garden center are available with shelves that can be tipped for visual impact.

Operating conditions
If the carts are to be used in a greenhouse, check on the aisle and door widths and space needed to turn corners. A 6-inch clearance is needed for easy maneuverability.

Carts work best on a fairly level surface. Ramps with a slope no greater than 1:12 should be installed between greenhouses or work areas that are at different levels.

The larger the wheel diameter, the easier it is to move a cart. It takes about 20 pounds of force to push a 1,000-pound-cart on a concrete or asphalt surface and about 40 pounds on hard-packed gravel.

Tire size should be at least 2 inches wide by a 5-inch diameter for use on paved floors and 2¾ inches wide by a 10-inch diameter for use on unpaved areas. Hard, rubber wheels are common on carts used for shipping. Pneumatic tires are best on unpaved areas. Wheels or casters with sealed roller or ball bearings do better than sleeve bearings. Greaseable bearings are desirable.

Caster placement
The location of casters or wheels is important for smooth cart operation and ease of movement. Fixed casters make straight-line movement easy and should be placed on one axle of most types of carts. Carts with four caster wheels are difficult to maneuver. At least one set of casters should be lockable to prevent rolling.

Fixed casters in the center of a cart with swivel casters near each end allow the cart to be turned within its own length. If swivel casters are slightly smaller in diameter than the fixed ones, maneuverability is increased as a slight tilting action shifts the load to one end.

For towing multiple carts, a tow bar that attaches to one end is needed. It can be removable or hinged to keep it out of the way when not in use.

Cost
Carts vary in price from about $200 for a flat-deck cart to about $700 for a delivery cart that holds 50 flats. Extra shelves are $40 to $50. To prevent the loss of carts sent to garden centers, they should be color-coded or have a laser-cut nametag. Some are now using bar coding that can be identified and tracked with a hand held scanner. Cart leasing services are common in Europe.

Maintenance
Carts will give many years of satisfactory service if given regular maintenance, including lubrication of the bearings and pivot points. Check pneumatic tire pressure frequently. Make repairs to frames and shelves when needed. Maintain a reasonable stock of maintenance parts.

Carts make a great low-cost tool to reduce the cost of plant handling. Their flexibility and long life can help all size growing operations.

John Bartok is a regular contributor to Greenhouse Management and an agricultural engineer and emeritus extension professor at the University of Connecticut. He is an author, consultant and a certified technical service provider doing greenhouse energy audits for USDA grant programs in New England.