Suspension Hitch–Air Cells or Air Springs?

Suspension Hitch-Air Cells or Air Springs

Air Springs used w/suspension hitch
When the first air suspension hitch was introduced it used air springs which have long been used to improve the ride in trucks, trailers, and equipment.  They are a very efficient method to get good results given there are so many different configurations of air springs.  There is virtually nothing that can not be suspended on air springs.  However, there are some draw backs.  In order for the air spring to work properly it must be installed correctly, have the correct amount of inflation and most importantly, the load must be able to move when the carrying vehicle hits the bump.  Being able to move, the energy that comes from the bump is then dissipated.  In commercial applications it is usually not an issue to have the necessary equipment and items that is needed such as  an air compressor, controls, tubing, fittings, and an electrical source for the proper installation for an air spring suspension.  However, for vehicles without an air compressor it is an added expense to install one on the truck.  Another advantage to air springs is that they are readily available in many configurations.  One of the largest suppliers is Air Lift Co.  The industry standard warranty for air springs is only one year as the rubber in time will deteriorate.

Air Cell used w/air hitch
The use of closed cell polyurethane air cells came to the market place about 10-12 years ago as another method for carrying constant loads, e.g. vehicle with a snow plow. In 2008 after having been out of the suspension hitch manufacturing business for 8 years I came across this new product called an Air Cell. After reading the description on its use I called the company and explained to them I wanted to use the cell for a suspension hitch for 5th wheel trailers. They wouldn’t say one way or the other whether it would work, but they agreed to send me a few to play around with. A few months later I had made my first prototype suspension hitch using the closed cell urethane air cells. Keep in mind, my goal was to fabricate an new style of hitch that would weigh less, cost less, and give the trailer an equal ride to the air spring hitch I had been making since 1999. In that time we had just started using the hitch in pickup trucks and we were having a difficult time getting the hitch to give the pickup a smooth ride. It made the truck ride very bouncy (is there such a word). When I sold the company we still had not accomplished the task of a smooth ride in the truck.

On the virgin trial run I knew I had stumbled onto something great. I was towing a 40′ trailer with a 1 ton dully truck. I was on an interstate highway that was very old and not in even fair condition. What amazed me from the get go was the ride in the truck. I literally did not know the trailer was behind me, it was so smooth. From that point on I never made another hitch using air springs. Unlike air springs there are some limitations with the air cell. The load can not exceed the capacity of the air cells, unlike an air spring, you can add more air. It takes more air cells to carry the same load. Load designing is more critical for the air cells, however, when starting from scratch the design can be accomplished to fit the air cells. They do not need the air compressor, tubing, fittings, electrical connection, etc. They also carry a life time warranty.

During our observance of how the new hitch worked we found surprisingly new differences between an air cell suspension hitch and an air spring suspension hitch. For example, the rate of speed at which we hit the “bump” with the air spring hitch was directly related to the amount of energy transferred to the tow vehicle. However, with the air cell hitch the rate of speed at which we hit the bump made little difference in the ride of the truck. We found that with the air springs, the greater the speed, the greater the energy, the greater the movement of the trailer. Another discovery we made was with the air spring air hitch when we encountered several bumps in a row the ride was for more jolting in the truck. With the use of the air cells very little difference in the ride quality of the truck was noticed with the rate of speed and also little difference when several bumps in a row were impacted and the trailer movement was much less than with the air springs. In conclusion; with the air springs the trailer must move to dissipate the energy from the bump. When the bump is encountered, the air springs expand and move the trailer in an upward motion until the energy has dissipated, and then it returns to the home position. If another bump is encountered before the trailer has returned to its home position the energy hits the air spring and now the air spring must stop the downward movement of the trailer before it can reverse its direction to again dissipate the energy. The air spring hitch will not react quick enough to have the energy dissipated so the energy is transferred into the truck frame and results in a bucking action in the truck.

With an air cell suspension hitch we found that with the construction style of the air cells they actually absorb the energy when a bump is encountered so the trailer does not have to move to dissipate it. That is why speed has little effect on the ride as does hitting several bumps in a row. While I prefer air cells over air springs for an energy absorbing hitch, air springs seems to work very well in the axle suspension for trailers.