MAY 2010
                                        

Choose the right casters for carts and containers

You wouldn’t think of throwing away your collection truck just because it had a flat tire. But that’s exactly what people are doing when they throw away a recycling collection cart, bin or container just because a caster has failed. Whether the caster failure is due to an excessive payload, a collision with a curb or tailgate or another cause, the failure often damages the cart’s base as the caster tears away from the cart and risks injuring staffers while also leaving a hospital, hotel, office or other facility strewn with empty bottles, crushed cans and dirty newspapers.

Since the plastic container itself often remains in fine condition and ready for more work, replacing failed casters and repairing the cart bases, if necessary, may return the cart to service.

Some collection carts feature a six-caster arrangement that enables it to easily roll up and over curbs and tailgates without damaging the cart.

Though not the most challenging tasks your maintenance team will face, caster replacement and its associated repairs take considerable amounts of time and the cost for parts and labor quickly becomes quite substantial while leaving carts and containers out of action slows productivity. “Replace and repair” as an operational mantra simply invites inefficiency and ensures your staff is constantly diverted from their productive responsibilities.

Specifying the right caster in the first place to match the cart or container, the intended payload, the likely flooring and other operating conditions – without over speculating – minimizes the risk of caster failure and extends operational life while promoting optimum, smooth performance at the lowest cost.

To determine the type of caster required for peak performance in your operation, a basic understanding about caster construction is recommended. A caster typically comprises a wheel set within a fork attached to a bolt plate. This is where the caster is attached to the base of the cart or container via bolts, screws or other fasteners. Casters may be rigid, meaning they roll only forward and backward or swiveling, meaning they rotate 360 degrees to maneuver in all directions. They are typically manufactured of steel for maximum strength though aluminum and plastic are also used for light-duty applications. Wheels are manufactured in a wide variety of materials to accommodate different types of flooring and other factors. A huge range of bearings with a variety of properties ensures the wheels roll and swivel smoothly in any conditions while a range of brakes and other accessories may be added.

The most important consideration in specifying the ideal caster is to determine how much weight is to be transported. Moving and hauling bulk forklift container loads of crushed glass demands a far stronger, sturdier caster than catching shredded office paper in a plastic bin and rolling it for consolidation into a larger container. The crushed glass has a high bulk density and places ample weight per given area whereas the shredded paper contains a high volume of air (a low bulk density), until densified, and, therefore, places far less weight per given area.

Once the weight is determined, the required load bearing rating of the caster may be calculated. For example, if 600 lb. payloads of paper are to be collected then we recommend specifying four casters, each providing a caster load rating at 200 lbs. for a total load bearing capacity of 800 lbs. But isn’t that over speculating? It isn’t because the four casters would only bear an equal amount of the weight when the load is equally distributed within the cart and when the cart is standing on a flat, level surface.

Since collection carts are routinely pushed up and down ramps, we recommend accommodating load bearing requirements due to shifting contents by taking only 75 percent of the caster load rating to arrive at the total cart load rating. In this case, total caster load rating of 800 lbs. x .75 = 600 lbs. This helps ensure that even if payloads shift inside the cart during transport, the caster would more than likely be able to accommodate the increased demand without fail.

The primary factor in determining the right wheel is the flooring surface on which it is to roll. If a collection cart is to be used indoors over carpeting or tile and noise needs to minimized, such as in a hospital or hotel, then soft tread wheels are recommended. Polyurethane is among the most durable and long-lasting materials, but if the carts are rolled outside in a parking lot or in a maintenance area with concrete flooring, the wheels are likely to pick up tiny pieces of metal, gravel, sand or other debris.

Soft rubber rolls even more quietly than polyurethane though it costs more. For hauling scrap and other materials where the flooring is rough and dirty, such as on and off trucks, around scrap yards, in industrial areas and for curbside recycling containers, we recommend hard rubber tread wheels.

Of the group, hard rubber stands up to the most punishing handling and weather conditions for the longest length of time before wearing without marking clean, indoor floors and at the lowest relative cost.

Many people don’t recognize the difference between swiveling and rigid casters until they try to maneuver a bellman’s cart to their hotel rooms and wonder why it either won’t turn or won’t move in a straight line. Swiveling casters add 360 degree maneuverability, which is critical for rotating carts and containers inside a trailer or box truck. Workers typically spin, slide and drag carts inside the trucks to make efficient use of the space but pay little attention to whether they are pushing carts fitted with swiveling or rigid casters.

Easy rotation offered by swiveling casters makes it slightly more challenging to maintain a straight line when pushing or pulling. This is why the caster configuration selected is important in achieving the desired performance and longevity.

The classic bellman’s cart features two swiveling casters at the corners of one end, from where it is to be pulled and steered, and two rigid casters at the corners of the rear end. This configuration combines both tracking and control with a stable platform that distributes loads evenly among the four casters. In cases where greater maneuverability is required, four swiveling casters may be specified. These four swiveling casters may be placed at the center of the front and rear and at each side in a diamond configuration for even more maneuverability, though stability may be reduced. Light weights to be moved in tight quarters call for this type of caster configuration.

The recycling industry quietly runs on millions of casters. At a time when commodity prices have tumbled and companies are struggling for profitability, cutting cash outlays for replacement parts, ensuring your staffers are spending their time on productive tasks and eliminating day to day headaches are vital to your survival. Making sure your recycling carts and containers are fitted with the proper casters is an easy first step.