The word “trunnion” comes from the french word “trognon”, which in turn comes from the old french word “estroigner”. In context, the word translates to “core”, symbolizing how the trunnion was an essential part of cannons and siege guns used by the french in the late 1400s. The obvious question being, how did this word come to be associated with trailer hitches?
In simple terms, a trunnion is a precision bearing mount used for revolving fixtures. When it comes to a cannon, the trunnion is the circular object on the side. It is circled in red on the right-hand side.
Though the term did not exist at the time, this was a creation of mechanical engineering that would become central in many years to come after the late Medieval era.
The revolving nature of the trunnion allowed for cannons to be easily transported, and this technology was later adapted into car suspensions and other heavy machinery in the modern era. For example, did you know that the AK-47 actually uses a barrel mounted to a trunnion?
Trunnions are used on guns, bridges, cars, and so much more. In the context of trailer hitches, our goal is weight distribution. This is accomplished via chains or spring bars.
Spring bars help keep your trailer in line with the towing vehicle. Without spring bars, the trailer sway would make it hard to drive well.
Spring bars can be tightened to be made taut, which ensures the trailer is kept firmly behind the vehicle.
Spring bars come in two basic forms. Either round bars, or trunnion bars. For more information on the difference, see our accompanying article: Round Bars vs Trunnion Bars.
Whether you choose round bars or trunnion bars, they both accomplish the same purpose. They are both spring bars, which exist on WD hitches for the purpose of redistributing the tongue weight of the tow vehicle and trailer. For a simple illustration, see the image below.
Because round bars and trunnion bars both accomplish the same purpose, there isn’t much reason to prefer one style over the other. Trunnions usually have more clearance and can come in higher tow capacities, but both hitches provide weight distribution, and many times have built-in sway control, like the Fastway’s e2 trailer hitch. It comes in both trunnion and round bar styles and provides safer, more comfortable tow. So no matter what you’re most comfortable with, the e2 hitch is right for you.
