While this information was first printed in 2016, it is still relevant for fleets today.
When it comes to spec’ing fifth wheels, you might not think that having a multitude of choices could simplify a decision. “However,” says Rob Nissen, director, field services, SAF-Holland, “experience shows that more choices can simplify the process by making it easier to pinpoint the right specifications.”
SAF-Holland (www.safholland.us) is a global manufacturer of trailer and truck suspensions, fifth wheels, landing gear and coupling products.
Nissen notes that while there can be some overlap, most tractor trailer combinations can be classified as one of three types:
- Standard duty – 100 percent on-road and a gross combination weight of less than 95,000 lbs.
- Moderate duty – Less than 10 percent off-road and a gross combination weight of less than 115,000 lbs.
- Severe duty – More than 10 percent off-road and a gross combination weight of more than 115,000 lbs.
Main considerations
Because each classification calls for unique capabilities in a fifth wheel, Nissen says these key factors must be considered:
- In what type of operation will the tractor be involved?
- Will that operation vary from time to time or over the life of the tractor?
- What will be the maximum towed vehicle weight?
- What will be the maximum drawbar load – the highest safe horizontal pulling force?
- What will be the maximum vertical load to be carried – the highest safe down force on a coupling device?
Once those questions are answered – and there may be more than one answer to any of them, depending on the complexity of the operation – the most appropriate fifth wheel capacity can be selected.
There is one common factor that is of the utmost importance, stresses Nissen. “No matter the vehicle size or application, it always pays to spec a fifth wheel for a somewhat higher capacity than you need. The extra margin can avoid safety issues and maintenance headaches down the road, and ultimately lead to lower cost of operation.
Tips
Nissen highlighted these spec’ing tips:
- The extreme demands of off-highway applications call for a high-capacity fifth wheel.
- A lightweight aluminum top plate is a good option for an on-highway application where fuel economy and load capacity are top considerations.
- A heavy duty, on-highway fleet is a good candidate for a low-lube top plate. A no-lube option is ideally suited to a standard duty on-highway application. Both options can reduce maintenance costs and downtime.
- A no-tilt mount is ideal for side-dump and frameless end-dump applications. A locking bar can be removed to allow articulation as the situation warrants.
- A fully-oscillating fifth wheel provides the best performance on tractor trailers that operate in applications such as mining or logging where rough and uneven terrain is common (where the center of gravity of a loaded trailer must be below fifth wheel bearing surface).
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