Brian, When affixing an autopilot tiller arm, the primary “attachment” of the arm to the rudder post is the clamping tolerance of the arm to the post, generally bored .002-.003” undersize to achieve a good grip on the post. There are three secondary attachment methods that can be utilized to prevent the arm from slipping on the post in the event of a hard grounding, loose clamping bolts, etc. The most commonly used secondary method is that of a keyway on the arm that would match up to the factory installed keyway on the post (which most C&Cs will have). This is a simple installation method that requires no drilling or machining by the installer. A square key is placed in the keyway on the post and when the tiller arm clamps in place, the key stock prevents the arm from slipping on the post.
The second most common is “pinning” or through bolting the arm to the post. Typically this method is used with a hollow stainless post with no keyway cut in the post (or if the keyway doesn’t extend far enough on the post to match the positioning of the arm on the post. The through bolt serves like an oversized cotter pin and when the tiller arm is supplied by the manufacturer (such as Edson), the arm has a hole drilled in the cap of the arm only. The installer positions the arm in place on the post and then uses the hole on the cap as a pilot hole to drill through the rudder post (all the way through) and then through the rest of the hub of the tiller arm. The through bolt is then installed and nutted to secure it in place. This through bolt is never tapped into the arm or rudder post itself. The final method used, mostly when the rudder post is made of solid steel as opposed to hollow pipe, is a set screw fastener. There are typically two 3/8” set screws drilled and tapped into the cap of the tiller arm. The rudder post must then be drilled and tapped so that the threads for the set screws extend into the post, thus creating a positive attachment. Simply dimpling the post and tightening the set screws against the dimples actually works against the attachment as the set screws will actually pull the cap away from the post if tightened down too hard. From the images I’m looking at with your boat, I would assume that the set screw method is what is on your boat. I can’t tell if the auto pilot tiller arm is made from bronze or aluminum, but if aluminum, stainless set screws have a nasty habit of galvanically seizing up if an anti seize compound isn’t utilized. In that case, the method of heating the arm to free the bolt as I described in the earlier email is what seems to work best. As Josh suggested, the front half of the tiller arm should remove easily if the 4 clamping bolts are removed. Typically, stainless bolts threaded into bronze don’t seize very easily and can be extracted without much drama, even if cross threaded. Best of luck, Chuck Gilchrest S/V Half Magic 25 Mk1 1975 Pandaram, MA Soon to be the owner (pending survey) of: S/V Orion 1983 LF 35 > On Dec 12, 2015, at 1:55 PM, Josh Muckley via CnC-List > <cnc-list@cnc-list.com> wrote: > > Brian I still can't understand what the bolt is for. Does the rudder shaft > have a groove or key way? Does it align with the threaded bolt? Did the > front/arm part come off when you removed the 4 bolts? > > To reply to postings or responses to your original post, simply hit reply and > leave the subject the same. Since the subject is the same many of our modern > day email clients will automatically compile the emails with the same subject > or RE: or FWD: as part of the same conversation. Try to keep the message > tails (quoted text) short to minimize the burden on the email server. > Normally if the original message came from cnc-list@cnc-list.com > <mailto:cnc-list@cnc-list.com> then a reply would automatically populate the > TO: section with cnc-list@cnc-list.com <mailto:cnc-list@cnc-list.com> which > will be subsequently and automatically forwarded to all list subscribers. If > you decide to respond to someone off list you can do that by looking at the > message details and extracting their email address. Then replace > cnc-list@cnc-list.com <mailto:cnc-list@cnc-list.com> with their address in > the TO: section of your new email. > > Let me know how things go, > > Josh Muckley > S/V Sea Hawk > 1989 C&C 37+ > Solomons, MD > > On Dec 12, 2015 11:44 AM, "Brian Fry via CnC-List" <cnc-list@cnc-list.com > <mailto:cnc-list@cnc-list.com>> wrote: > Thank you for your replies. I havent figured out how to reply to the posts, > so I will just reply here. > > The threaded rod appears to be threaded into the shaft, on one side only. > The 4 bolts holding the arm and clamp together came apart easily. > I tried first with vice grips. No dice. > Now trying to rethread to try the 2 nut idea. > > > _______________________________________________ > > Email address: > CnC-List@cnc-list.com <mailto:CnC-List@cnc-list.com> > To change your list preferences, including unsubscribing -- go to the bottom > of page at: > http://cnc-list.com/mailman/listinfo/cnc-list_cnc-list.com > <http://cnc-list.com/mailman/listinfo/cnc-list_cnc-list.com> > > > _______________________________________________ > > Email address: > CnC-List@cnc-list.com > To change your list preferences, including unsubscribing -- go to the bottom > of page at: > http://cnc-list.com/mailman/listinfo/cnc-list_cnc-list.com >
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