Brake actuators provide solid stopping power for a concrete mixing trailer

I’ve posted about towing a cement mixer and the various types of couplers. In the larger models of concrete mixing trailers (Cart-Away’s CMT-100 and CMK-175, Trailer Haul's MT125, Concrete Titan, etc) I’ve mentioned the brake actuator, but never explained what that does and why one doesn’t see them on the smaller mixers. Smaller cement mixers, sometimes called portable contractor mixers, vary in size but are rarely large enough to require brakes.

That’s why the couplers are simply bolted or welded to a tow bar and have no actuator: they don’t need one. Portable concrete mixers of one yard or higher capacity do require brakes and that’s where the actuators come in. A brake actuator is a device that activates the brakes. Why they didn’t call it an activator instead is beyond me; they just didn’t. The most popular actuator in the rental industry for this weight range of trailered cement mixer is the surge brake type.

A surge brake system is a ‘wet’ system. That is, it uses brake fluid pumped by a master cylinder to wheel cylinders through hydraulic hard lines. This system may sound familiar, and it should. The auto industry has been putting them on all of our cars for decades. And the surge brake system on your trailer works just like the brakes on your car. When stopping your car the action of pushing down on the brake pedal pushes a rod connected to the master cylinder. This forces fluid from the fluid reservoir through the brake lines to (depending on how old your car is) either squeeze your brake pads against the disk or push the brake pads outwards against the drum. The friction of the pads against the disk or drum slows the vehicle.

The brake system on a cement mixer trailer works the same way, but the foot that’s pushing on the trailer’s brake pedal is the trailer’s own weight. As you begin to stop the towing vehicle, the trailer is still going at the same speed. Once the vehicle speed is less than the trailer’s speed the trailer begins to surge forward slowly (hence the name surge brakes). As the trailer moves forward the part of the actuator connected to the coupler, called the slide assembly, begins to slide backward and pushes a rod connected to the master cylinder.

The process from there is the same as in your car: The master cylinder sends fluid to the wheel cylinders and slows the trailer. The harder and faster the towing vehicle brakes, the same will happen with the trailer after only a moments hesitation.

With safety on the road a high priority, the modern brake actuator provides solid stopping power for the concrete mixing trailer.