A. COUPLERS

The coupler on the trailer fits over the ball on the hitch which is permanently attached to the tow vehicle. The coupler (Figures 4.1 to 4.3) is often incorrectly referred to as a hitch and clarification is usually in order for most conversations. Couplers, like hitches, are manufactured in four weight classifications, generally accepted as standard today, which are: 

Class I – 2000 lb. gross – Figure 4.4

Class II – 3500 lb. gross – Figure 4.4

Class III – 5000 lb. gross – Figure 4.5

Class IV – 8500 lb. gross – Figure 4.6 

The gross weight must include the trailer itself AND its cargo. For extremely heavy duty applications-over 8500 lb-few ball and coupler connections are strong enough. A lunette eye, Figure 4.5, should be used with the pintle hook shown in Figure 4.6. Whatever your application, it is important to know the eventual gross load and the coupler’s stated rating. 

The coupler or lunette eye must be securely attached to the tongue. This can be accomplished in a variety of ways. Couplers are available to fit angled or straight tongues. The 50° angle which accommodates a triangular or V-tongue is available in all capacities. Remember that I have found this angle to encourage tongues shorter than appropriate for the best towing configuration, as discussed in Chapter 2. But since little else is available, adjustments should be made. In my opinion, a coupler with a shallower angle (say 40°) would make it easier to build a long tongued trailer. Couplers with straight slots of 2-in channel width and 3-in width are designed to fit a straight tongue of channel or tubing of that size. A built up piece of material can also be used. Some of these couplers slide onto the tongue from underneath, others from above. Three inch channel couplers fit the 40° Step Neck TM, also mentioned in Chapter 2. A coupler used by many rental yards which is reportedly designed to fit a variety of ball sizes, is pictured as E in Figure 4.1. 

There is a large assortment of couplers on the market-those shown here are only a few. How the coupler attaches to the tongue can affect the height of the trailer, which in turn may influence not only your choice of coupler but also your choice of axle; hence, the trailer’s center of gravity and ultimately the trailer’s performance. Don’t treat this choice lightly. Chapter 2 discusses the attachment of couplers and the results and should be understood before you make a final selection of coupler. Selecting a coupler of adequate capacity and configuring the trailer to provide the highest performance will repay you in many miles of pleasant towing.