Shaft mounted reducer is a helical gear reducers designed for mounting
directly on the drive shaft. A torque arm provision is made to avoid
overload failure and can be mounted on the cylindrical shafts or
spherical shafts. They allow considerable cost reductions and provide
maximum positioning flexibility with easy installation and maintenance. The shaft-mounted type has two variations. One is truly shaft mounted, in that it is supported entirely by the input shaft of the drive machine, with torque reaction absorbed by a special link. The other is mounted to the driven-machine housing so the input shaft does not absorb reducer weight or torque reaction.
They are used in almost all applications within aggregate industry. Drums are trunnion driven through shaft mounted reducers by electric motors.