Mechanical Linear Actuator Specifications

[Chuck - Raymarine - Moderator]

For the benefit of others who may view this thread, torque refers to a rotational force, whereas linear drives exert force in linear fashion (i.e. thrust / extraction). The force exerted by a linear drive specifies the amount of force which will be exerted by the drive's ram when pushing or pulling. When attached to the boat's tiller arm or quadrant which is in turn attached to the rudder post, the linear drive will exert a rotation force on the rudder post. This rotation force will be equal to the specified force of the linear drive multiplied by the length of the tiller arm.

Example: Given that the Type 2 Short linear drive exerts a force of 480 kg and should the tiller arm be 10" (25.4 cm) long, then the torque exerted on the rudder post would be 480 kg x 25.4 cm = 12192 kg - cm. Should you need to convert kg - cm to N-m (or other units), there are web based utilities such as the one found here which may be used to do so. In this case, the maximum torque exerted to the rudder post would be 1195.6 N-m. The Type II Mechanical Linear Drive is designed for use with a longer tiller arm. Given that the Type 2 Long linear drive also exerts a force of 480 kg and should the tiller arm be 14" (35.56 cm) long, then the torque exerted on the rudder post would be 480 kg x 35.56 cm = 17068.8 kg - cm, or 1673.9 N-m. As you may see, the listed maximum rudder torque values for the Type II Short and Long Mechanical Drives are very close to these calculated values.