By Loren Sackett
Much to my dear mother’s horror, I loved breaking things as a kid. Now, as an engineer, I sometimes get paid to break things—though not as often as I’d like.
Recently, Alpine Engineering & Design worked on the development of a product called the Link Lock, which makes it easy to adjust trailer safety chains. As part of its development, we had to test its breaking strength. After all, if a trailer disconnects while driving down the highway, the safety chains are the only thing keeping it attached to the truck.
Why Safety Chain Length Matters
Most lightweight trailers (under 20,000 lbs) attach to a truck using a hitch ball near the rear bumper. If the trailer detaches from the ball, safety chains (or cables) prevent it from becoming a runaway hazard. However, chain length is critical:
- Too long? The chains drag on the road, wearing down and weakening over time.
- Too short? They interfere with turning and could cause an accident.
For safety, chains must be just the right length—but adjusting them is often a hassle. Link Lock solves that problem, making adjustments quick and easy. Of course, for Link Lock to be effective, it must be strong enough to handle the extreme forces of a trailer disconnecting at high speeds.
Putting Link Lock to the Test
SAE International (formerly the Society of Automotive Engineers) sets industry safety standards, requiring that each safety chain and its attachment points (hooks, bolts, etc.) must have a breaking strength equal to or greater than the trailer’s Gross Vehicle Weight Rating (GVWR). Since Link Lock is the attachment point between the trailer and chain, it needed to meet this requirement.
To verify its strength, we conducted a series of breaking tests. The process was simple in concept:
- Pull on the chains with extreme force—hard enough to break something. A hydraulic cylinder was used to apply an increasing amount of force.
- Measure the exact force required for failure – using a laptop, load cell and specialized electronics the applied force was easy to measure and track.
Identify the weakest link and improve the design if necessary.
When Things Go Boom
As we refined the Link Lock design, we performed multiple rounds of testing. In one particularly violent test, the pin failed explosively. The sudden break jolted the laptop—but fortunately, it survived to test another day. (Personnel were behind a protective barrier).
With that data, we reinforced the pin so that the entire Link Lock assembly was stronger than the chain itself.
The Fun (and Importance) of Breaking Things
Ensuring that components can handle their intended loads is critical—people’s lives depend on it. While some engineering calculations can be done from the comfort of a cubicle, sometimes there’s no substitute for real-world destruction testing.
And honestly? Breaking stuff in the name of safety is a lot of fun.
Alpine Engineering is an engineering company that specializes in designing and engineering trailers and trailer equipment. Alpine Engineering also provides un-biased trailer expert witness testimony in legal disputes.