Autopilot for Rack and Pinion Steering - Page 2 - SailNet Community

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  #11  
Old 03-21-2007
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There's a problem with using a "ram-based" autopilot connected to the steering quadrant.

You'll be turning the steering wheel along with the quadrant. It will be geared-up by the rack ratio. This is not an efficient use of autopilot driving power.

It may work fine, or it may not. A moving steering wheel might be unfriendly to people in the cockpit. A _locked_ steering wheel could cause all kinds of trouble for the ram.

I can see several ways around the problem:

1. Use a pilot that drives the wheel, and mount it in the cockpit. I know you don't like that idea, but it may be the simplest thing to do. It's possible to build a pivoting mount for the drive motor (or a tensioner for the drive belt) that would let you disconnect the drive belt when not using the autopilot.

2. Put a cogged-belt pulley on the steering wheel shaft, underneath the covers ( between steering wheel and rack). Mount the autopilot motor under the covers, and run a belt between the motor and the steering shaft. You'll need some way to freewheel the belt (or a motor that turned freely when not powered). The motor and belt would be protected from weather, and invisible. The mounting details for the pulley would have to be worked out.

In either case, you'll have to think about lock-to-lock time, which should be about 15 seconds for good autopilot performance.

If you could lift the pinion off the rack and free the quadrant from the wheel, _that_ would let you use a ram on the quadrant. But unless the builders allowed for that possibility, it won't be easy to do.

I may be an old lady about this; driving the quadrant directly, and turning the wheel through the pinion, might work fine.

How heavy is the boat, and with what kind of rudder? That's crucial info for sizing the drive motor.

FWIW, I love my CommNav (ComNav?) 1420. I'm using a hydraulic pump, not a motor, but the control unit should be happy either way.

Charles
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  #12  
Old 03-21-2007
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Quote:
Originally Posted by witzgall
The boat is 47" (custom), but the wheel is not attached to a pedistal, so a wheel pilot would not work - at least not without running it to the cockpit side, which I would not want to do.
What is it attached to? Can you access the other end of the wheel's shaft?
I think most wheel mounted autopilots are a bit weak for a 47 footer. So you may need an internal actuator anyway.
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