This is the second part on how to identify and solve ergonomic issues in the field. We will talk about caster rigs (or forks and swivel sections as they are also called). I will share with you what I look for in solving push/pull issues in the manufacturing environment?? It is important when making proper application decisions to understand the underlying “forces” that impact caster functionality. At Caster Concepts and in my experience the most challenging push/pull issues arise on carts with capacities of 1000-2000 pounds. Carts of this size and capacity are found in a variety of manufacturing settings and are most prevalent in automobile assembly facilities.
Let me first summarize the three types of swivel sections.
- The first is a kingpin version. Kingpin casters are the oldest style caster available in the market. A kingpin style caster is assembled and tightened around a “kingpin” in the middle of the caster rig and is best suited for a rough application. When side load is a concern, a king pin style caster may be considered. However, if a primary concern is with the ease of pushing this cart, a kingpin version may not be your best choice.
- The second is a kingpinless style. Until recently, this was the solution for all ergonomic issues. A kingpinless style caster swivels on ball bearings in a hardened raceway resulting in a very efficient caster with good ergonomic properties. Preventative maintenance (greasing) is required to insure the predicted life of this caster.
- The third variation and the newest concept to hit the market is the precision sealed ball bearing swivel section. This caster is a safety manager’s dream come true. The caster swivels around a precision sealed ball bearing which insures consistent performance over the life of the caster. A major benefit of this type of swivel section is the fact that the swivel section is maintenance free. No preventive maintenance is required at scheduled intervals. This will extend the life and keep push and pull results consistent for a prolong period of time.
Now that we have discussed the types of swivel sections, let’s talk about a couple common application errors I see in the field.
- First, an undersized caster rig. Typically when price is a concern, an undersized, imported caster rig will be selected. This may make purchasing happy, but the added cost is going to come during the life cycle of the caster.A caster with too small or inconsistent swivel section will progressively be more difficult to push. Once this happens, the potential for back injuries become more common and the rate of caster replacement increases. The best advice I can give is to select a caster and then choose one size bigger for your application. Or you can contact me below and we can choose together. (Yes that was a shameless plug J!!)
- Second, and equally as important, a caster does not work well with a swivel lead that is too small. Swivel lead is the distance between the center of the swivel section and the center of the wheel. I would suggest a caster with any pushing and pulling required should have at least a 2 ½” swivel lead. The longer the swivel lead the more leverage is created and the easier the caster is to push and pull. However, one side note, the swivel lead and capacity of the caster have an inverse relationship. Swivel lead goes up and capacity goes down. Please be sure to consult with an engineer when adjusting swivel leads.
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