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Discussion Starter · #1 ·
(I'm cross posting this from another site; I'm the author; trying ot get more input).

The orthodoxy of below-decks autopilots is that the linear drive be connected to a separate tiller arm that is attached to the rudder post, and not to the existing radial drive.

For those of you not familiar with this setup, I am referring to boat that have vertical rudder posts that are steered with Edson wheel steering, using a circular, cable-driven fixture called a radial drive - like a quadrant that simply goes all 360 degrees.

Edson's recommended bronze tiller arm is a whopping $417! That's the direct price, and for the C-36 unit with 2.860" bore for rudder post, there is no machining charge.

Edson warns against attaching to the radial drive, but gives no compelling reason.

"In no case should the autopilot be attached directly to the quadrant or radial drive wheel!"

I think it's just because they want to sell tiller arms! One purported reason for the tiller arm is that in the event of a steering system failure, the autopilot provides a backup. But, with the linear drive on the radial drive, which is directly connected to the rudder post, there seems to be nothing in the path to break except the radial drive itself, which seems quite robust.

I can only imagine that the radial drive is strong enough to be driven by the linear drive, especially since Edson puts a rudder stop right on the top outside edge of the drive, which can presumably absorb the rudder force in that condition.

As a matter of fact, that rudder stop might be a good place to attach the linear drive, and then make an alternate rudder stop solution.

So, my question is, what are your thoughts on just connecting to the radial drive, and skipping the separate tiller arm?

Thanks,

jv
 

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Old Fart
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It should work but it also puts the drive as the critical piece in the system overall. If you do it you should be sure to inspect it carefully first and if you drill a hole in it that may weaken it.

I had a separate tiller arm fabricated at a local shop for my autopilot and as I recall it wasn't too expensive. You might consider that first.
 

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Same here, I built a separated tiler below designed to support involved forces. When you push your quadrant using an autopilot, the tremendous force is, mostly times, aplied to where it was not designed to. In special at a distance from the rudder post where the force-arm is shorter, pushing it even harder. I had this arrangement before, and faced a problem just once, when the attachment post on quadrant got loose, enlargening the original hole I did.
 

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I had the same reaction to the 'single tiller is forbidden' language in the Simrad manual, reiterated by the Simrad tech I spoke to (frequently). I ended up putting a 2nd tiller arm in, but I did it without the hassle of dropping the runner. In my case, the key-way (for the original quadrant connection point to the rudder post) was cut with about 1.5" exposed just beneith the quadrant's fix point. This allowed me to install a Buck-Algonquin 2-part tiller arm - also keyed.

If your concern is the hassle/effort required in dropping your rudder (vs. just the expense of a 2nd tiller arm), carefully examine your rudder stock just below where your quadrant/tiller is attached. You may be pleasantly surprised by an exposed, usable, key-way.
 

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Discussion Starter · #10 ·
I had the same reaction to the 'single tiller is forbidden' language in the Simrad manual, reiterated by the Simrad tech I spoke to (frequently). I ended up putting a 2nd tiller arm in, but I did it without the hassle of dropping the runner. In my case, the key-way (for the original quadrant connection point to the rudder post) was cut with about 1.5" exposed just beneith the quadrant's fix point. This allowed me to install a Buck-Algonquin 2-part tiller arm - also keyed.

If your concern is the hassle/effort required in dropping your rudder (vs. just the expense of a 2nd tiller arm), carefully examine your rudder stock just below where your quadrant/tiller is attached. You may be pleasantly surprised by an exposed, usable, key-way.
Thanks for the reply. I would not have to drop the rudder in any case: the recommended Edson tiller arm opens on the big end so it can be installed with the rudder shaft in place. And, the rudder post is a stainless steel tube (it's a Catalina 36), so, no keyway. The radial drive wheel is clamped on, then "pinned" via a through hole and nut and bolt. Edson requires that the tiller arm be pinned as well.
 

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Old Fart
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Autopilot arm

Here is the arm I had made. It fits over the top of my rudder post and is clamped into place with the four bolts you see near the bottom. The hydraulic control arm in on the right and the rudder follower is on the left.

Sorry it took me so long to respond.
 

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It should work but it also puts the drive as the critical piece in the system overall. If you do it you should be sure to inspect it carefully first and if you drill a hole in it that may weaken it.

I had a separate tiller arm fabricated at a local shop for my autopilot and as I recall it wasn't too expensive. You might consider that first.
Hi Dwayne,

I would be interested in getting more information on the tiller arm you fabricated. I will pm you and send you my email address. Thanks!
 

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Special Delivery
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I had a new control head installed on my autopilot. The installer did not reset the turn limits after installing the head. The ram actually broke the Epson tiller arms in half when the quadrant hit the stop. If this had happened with the ram attached to the quadrant, I'm not sure what would have broken.
 
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