Autopilot above deck install for hydraulic cylinder drive

[brianb]

To avoid having to crawl into a narrow space to repair and disconnect an AP in a choppy sea way, and to avoid the cost of expensive installations I have chosen a different approach. I believe I have an approach that is robust, is self contained and easily repaired at sea, and occupies what is really unusable space that the tiller arm swings through.


As you can see in the photos the tiller arm rests on the hydraulic cylinder (the boat stern is simulated by a pair of ice chests, a J 35 tiller, and a paint can). What is not shown is a stainless drive plate that contains a bearing slide attaching the tiller to the cylinder. You can also see a small gear that drives a precision potentiometer within the box through an O ring seal. This serves as the rudder position reference avoiding the purchase of an expensive position sensor.

The hydraulic pump and cylinder are normally used in twin engine power boats. The cylinder is of heavy construction but of the same travel and thrust as that found for sail boat applications. The pump is simpler since it does not need the clutch function. This is provided by the sailor as he/she simply lifts the tiller arm an inch to disengage from the hydraulics.

In all the investment is $447 for components, box, epoxy, glass, and associated bits. This compares favorably to the $2800 quotes I have seen for similar function uninstalled. The project is nearly complete and I hope to have it ready for the Three Bridge.

Your insightful commentary encouraged.

Brian

[Paul Elliott]

These aren't insights, just questions from a non-expert:

* You mention a bearing slide on the tiller. Is this used to provide fore-and-aft motion as well being a pivot? I assume this is what you are planning, but if not, with the piston hard-secured to the cockpit wall you will need two degrees of freedom or the piston/cylinder will bind as the tiller pivots. You could of course pivot at both ends of the piston/cylinder.

* Does the tiller support the cylinder? If the cylinder is what is keeping the tiller from drooping, there may be too much side-load on the cylinder (or there may not -- like I said, I'm no expert).

* Why not support the cylinder from the cockpit, and connect the piston to the tiller? Then you won't have to deal with flex and stretch in the hoses, and there will be less weight on the tiller and/or piston (which may not be an issue).

* If you disengage by lifting the tiller off the hydraulics, do you then have to continuously hold the tiller up? Will this be comfortable?

For what it's worth,
Paul
S/V VALIS

[brianb]

* Yes, two degrees of freedom. It is a slide, or groove made from two delrin blocks. A bearing rides along the delrin grove.

* The cylinder is supported at both ends and is bolted to the stern area on a support structure about 10" in front of the rudder post. Side loads are handled by a plate that rides on a delrin bearing and attached to the hydraulic cylinder. Side loads are carried by the delrin bearing surface.

* Ah, the traditional approach. It gets in the way and the hoses get in the way.
The hoses and cylinder are made precisely for this style of installation. Typically used on power boats to drive multi engine outboard installations.

* For a quick disengagement you lift the tiller. The delrin track slides out of the way if your going to steer manually for a prolonged period.

Thanks for the comments. Getting very close to trails.

Brian

[cr1]

Hey Brian,

Thanks for sharing. Always appreciate new ideas and of course saving money.

Rich Hillman
Horizon - Contessa 26