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Efficient High Speed Drive

EHS, or efficient high speed drive, provides extremely high tractive effort or very quick travel speeds, adjusting automatically depending on load and terrain conditions.

EHS is similar to the field-proven and revolutionary hydrostatic drive system that Tigercat initially developed and released in 1996 with the first 630 series skidders.

Like Tigercat’s standard hydrostatic drive system, EHS consists of two variable displacement motors as inputs to the Tigercat transfer case. Front and rear output shafts are connected directly to the front and rear axles.


Tigercat 632E skidder with EHS drive system

While the standard electronically controlled hydrostatic drive system performs exceptionally well, EHS is capable of providing the tractive effort of the deepest gear ratio offered in Tigercat’s standard transfer case as well as the top speed of the shallowest gear ratio offered in the standard transfer case.

This is accomplished with more sophisticated computer logic and the ability to take one of the drive motors offline when high tractive effort is not required. In this case all pump flow is directed to one hydraulic motor, increasing both travel speed and motor efficiency.

When operating conditions demand high tractive effort, both hydrostatic motors are working. When tractive effort requirements are reduced — for instance, when traveling empty or loaded on flat terrain — all of the pump flow is directed to one motor for higher travel speeds.