Variable Transmissions Information

Variable transmissions are a broad category of products applying to any industrial transmission powering machinery. Variable transmissions are used in industrial applications to alter the speed of an output shaft.  Many have integral power packages, such as electric or hydraulic motors, or they may be an integral part of driven components.   The most important performance specifications to consider when searching for variable transmissions include output shaft speed, output torque, and continuous output power.  The output shaft speed is the no load rotational speed of output shaft at rated terminal voltage.  Output torque describes the torque capability of the transmission under constant running conditions.  The continuous output power is the mechanical power provided by the transmission output.

Configuration Options

Important configuration options to consider for variable transmissions include output shaft position, shaft orientation, and mounting.  The output shaft position on hydraulic variable transmissions can be horizontal, vertical up, or vertical down.  In order for a shaft to be orientated in a vertical position, considerations need to be made regarding lubrication.  Shaft orientation choices include in-line, offset parallel, and right angle.  In an in-line orientation the input (driving) shaft and the output (driven) shaft can be connected with an imaginary axial line through the center of each shaft at 0° angle.  With an offset parallel orientation the input (driving) shaft and the output (driven) shaft are parallel, however they reside in the gearbox at different heights above the horizon.  A right angle orientation has the input (driving) shaft and the output (driven) shaft perpendicular to one another. This is most common with worm gear speed reducers.  Mounting choices are base or flange.  Base mounted transmissions are mounted at the base with the use of external hardware (screws, bolts, rails, etc.).  These are sometimes referred to as foot mount.  Flange mounted transmissions are equipped with integral flanges so that it can be mounted with the use of external hardware (screws, bolts, rails, etc.).


Common features for variable transmissions include integrated motors, integrated gears, continuously variable, c-flange adapters, hollow shafts, speed feedback, and reversible construction.  Variable transmissions can have an integrated motor in a packaged configuration.  The "packaged" transmission consists of the adjustable speed section and an electric motor.  The unit may also include a geared reducer.  They can also have integrated gears.  The "packaged" transmission consists of the adjustable speed section and a geared reducer.  The unit may also include an electric motor.  Continuously variable transmissions provide an uninterrupted range of speed ratios, unlike a normal drive or transmission that provides only a few discrete ratios.  C-flange adapters are supplied for connecting customer supplied motors.  Variable transmissions with hollow shafts have output shaft with a hole or bore that can accept a shaft.  Outputs with collets for tool bits are one example.  A transmission equipped with speed feedback has indication of the rotational speed of the output shaft.  Feedback may be magnetic sensor, tachometer, potentiometer, encoder, or current.  Reversible transmissions have output shafts that can rotate clockwise or counter-clockwise.