Autopilot Motor

[serini]

I have just taken delivery of a Whitlock motor to mount below-deck and act as the drive (via a sproket and chain) for an autopilot system for my wheel steered - Shearwater 39. The problem is that the clutch supplied with the system only disengages the motor and not the gearbox so, as I see it, I will now have a lot of extra drag in the system when the autopilot is not on. Apart from the fact that I think I will lose 'feel' on the helm my main worry is that I use a wind vane much of the time and I think that the Whitlock motor will just ruin its performance. Has anybody any experience of these motors? Why on earth did they design it so that the clutch is between the motor/gearbox rather than at the final drive? Anybody any experience of alternative motor/clutch combinations? I am (or hoped to be) running it with a Navman pilot system.
Thanks

 

[hightech]

The clutch is ut at the motor end as t is the point of least torque, but maximum hold. So you can have a clutch that is small and needs little current to operate. put it at th other end and it woul need to be large and use lots of current.

If the designer has done their job and the assembler theirs, the backdrive should be minimal, then with the mechanical advantage of the rest of the steering, little load should be observed.

Whatever pilot electronics you end up with, just make sure that they can handle the current requirement of both the drive and clutch.

 

[serini]

Thanks for your reply - understood point of least torque but with a drive reduction of about 20 to 1 then with the motor not running the wheel has to overcome a gear running at 1 to 20. If I compare this with the windlass I have - the clutch on which uses low current - then when the clutch is disconnected the gear runs free and surely the torque requirement on the windlass is much greater than on the pilot. Average drive current on the Whitlock motor is 4 Amps, Autopilot will drive 20 but I have considered putting in a revesing solenoid. Thanks for your Help.