I frequently get asked by contractors looking to upgrade their fleet if they should spend the extra money on a reversible plate compactor. My answer is always the same: it depends entirely on the width of your trench and the depth of your lift. To understand why, you have to look under the hood at the mechanical "heart" of these machines—the exciter assembly.
A standard forward-moving vibratory plate compactor utilizes a single eccentric (off-center) weight mounted on a shaft inside the exciter box. As the engine spins this shaft via a V-belt, the centrifugal force of the unbalanced weight creates the vibration. Because of the way the weight is timed and positioned, it naturally throws the machine slightly forward with every hop. It’s a simple, bulletproof design. But if you are working down in a 600 mm [approx. 24-inch] wide utility trench, a forward-only plate becomes a nightmare. Once you reach the end of the trench, you physically do not have the room to turn a heavy machine around. You end up having to drag it backward by hand, which will destroy an operator's lower back by noon.
This is where the engineering of the reversible plate compactor shines. Instead of one eccentric weight, a reversible plate has two synchronized eccentric shafts spinning in opposite directions. The operator controls a hydraulic lever on the handle that alters the phasing (the timing) between these two weights. By shifting the phase, the operator can direct the net centrifugal force either forward, perfectly straight down (for "spot compaction"), or backward. This allows me to guide a 400 kg [approx. 880 lbs] piece of iron down a narrow trench and simply pull a lever to reverse out, without ever breaking a sweat. Reversible plates also deliver significantly higher impact force, allowing you to compact thicker lifts of material. It’s an investment in productivity and operator ergonomics.
