Originally Posted by Winf
Looking at installing a ray marine
type 2 rotary drive autopilot
Can these be installed direct onto the rudder
shaft and if so how do I calculated the correct gear
Install under the pedestal is going to be a pain - the drive unit will be in the engine
bay and will need a lay shaft installed so trying to avoid if possible.
Short answer: NO! They do not have the torque to drive the quadrant directly. That's why they make a linear drive
. (a great piece of kit, by the way!)
As an option, you can put a length of chain in the existing cable and use that with a couple idler sprockets to connect to the output of the AP chain drive.
But, if you are DETERMINED to connect to the quadrant,
Calculate the gear ratio you would use to connect to your wheel
Now calculate how many rotations of the AP output shaft that is going from lock to lock.
Figuring your rudder swings 45deg each way, you need to rig up gearing so you get that many rotations of the AP drive with a 90deg swing of the rudder.
On my boat
there are 6 full rotations of the 3 inch diameter AP drive sprocket from lock to lock. You would need a gear ratio of at least 24 to 1 to get 6 rotations of the AP drive in 1/4 rotation of the rudder shaft if you are connected directly to the quadrant. That's a drive sprocket of 72 inches (Yes, 6 FEET) in diameter. Sound practical to you???