Engine shaft size

Most of the time, PTO clutch/brakes are mounted directly on the engine shaft. If the installation is not on an engine shaft, please make sure that the tolerances are close enough to provide a snug fit between the bore of our clutch and the shaft. (All engine manufacturers should produce shafts within the required tolerances.) Also, a standard rule of thumb is that the minimum diameter of the shaft, for one piece designs, is also the minimum amount of shaft engagement. (Two-piece designs would require shaft engagement in both pieces.) The engine shaft step radius needs to be smaller than the chamfer on the clutch or the clutch will not seat properly. If interference occurs, a spacer with the proper chamfer is required. Some of our clutches have a small bearing carrier (it looks like a taper). The shaft should be short enough so it does not make contact with this internal piece.

Direction of rotation

We manufacture our units for either clockwise or counter-clockwise rotation. They can be mounted with the pulley toward the engine or they can be mounted with the pulley away from the engine. This mounting is critical because this determines which direction the leaf springs are orientated. If springs are not run in tension, they could suffer premature failure because they will be running in compression. If the torque required from the clutch is low enough (less than 75%), and vibration and inertia are low, it is not as critical that the springs be mounted in the correct configuration.)

All PTO clutch/ brakes have to operate with the pulley being the output. In no case can a PTO clutch/brake be installed with the pulley as the input. If you require a pulley input design, please use a general purpose clutch.

Backing plate restraint

If the installation uses a pin or a flat going through the slot on the backing plate, approximately 1/16″ of movement should be allowed in both the radial and axial direction. Various other options are also acceptable such as a plate contacting one of the flats of the backing plate as well as clevis pins or cables. In all cases, a good way to check is after the clutch is completely installed, you should be able to feel movement in the radial direction back and forth. In heavy vibration applications, greater surface contact should be used to help prevent notching of the backing plate and the restraining piece.

Key length and height

In many of the clutches, the key does not go all the way through the clutch. Therefore, the key length can only be as long as the keyway length within the rotor. Please check this before installation. In some clutches, the bearing inner race may be exposed on the top of the keyway. In this case, the key needs to be slightly undersized in this area so it does not force itself against the bearing inner race.