Tiller arm install for new AP?

[LouK]

Will be installing a split head tiller arm for an AP on a 2” dia. solid SS rudder shaft. The shaft does not have a keyway. Question is will it be easier to drill through the shaft for a bolt or grind a keyway? Seems like obtaining really close alignment will be difficult either way.

Thanks ya’ll.
LouK

[Rucksta]

Originally Posted by LouK

Will be installing a split head tiller arm for an AP on a 2” dia. solid SS rudder shaft. The shaft does not have a keyway. Question is will it be easier to drill through the shaft for a bolt or grind a keyway? Seems like obtaining really close alignment will be difficult either way.

Thanks ya’ll.
LouK

Keyway is preferred.
Removal of rudder would seem indicated.
Once the keyway is ground alignment is straight forward.

Install the tiller arm and AP
Adjust the geometry until satisfied
Mark the tiller arm for keyway location.
Remove tiller arm and cut keyway.
Reinstall tiller arm with key.

If you are out by a couple of degrees the AP software will adjust during commissioning.

Bolts are problematic as the clearance required for the shanks is enough to allow fretting of the holes
i.e. bolts don't secure the tiller arm to the shaft and prevent slippage
rather bolts attach the tiller arm to the shaft and stop it moving vertically when slippage does occur.

[Celestialsailor]

If you use a bolt, you weaken the shaft and assuming you use a SS bolt, it would bend and wear over time. Grinding on the shaft for a DIY key-way is flatly insane. The correct way of doing it is to mark the shaft where the arm will go, drop the rudder, take it to a machine shop (with the key) and get it machined.

[calmissile]

Originally Posted by LouK

Will be installing a split head tiller arm for an AP on a 2” dia. solid SS rudder shaft. The shaft does not have a keyway. Question is will it be easier to drill through the shaft for a bolt or grind a keyway? Seems like obtaining really close alignment will be difficult either way.

Thanks ya’ll.
LouK

I would suggest calling Edson and speak to their tech support if you have any questions. They were a great help to me and offered some advice that was beyond what they publish in their "Steering Arm Worksheet".

If your sure that your rudder post is solid they can also answer the question as to whether the bolt through the rudder post will significantly weaken it. They have made hundreds if not thousands of these arms and I respect their opinions.

I agree with other posters in the sense that if you are on the hard and can pull the rudder post, then using a keyway is clearly the best mechanical solution. Of course, you would have a machine shop machine the keyway rather than trying to do it yourself.

My rudder post actually turns out to be tube about 2 3/4" dia. and can't use a keyway. My quadrant is secured with a bolt through the rudder post as will be the steering arm when it arrives. It was Edson's recommendation to secure it in this manner.

Good luck.

[Celestialsailor]

I have been a Toolmaker/Machinist for 41 years as well as a Mechanical/Field Engineer. If you put a 1/2" bolt through the center of the 2 inch. rudder stock, it will be the most volume (mass) of material removed. Essentially 30% of the shaft material at that particular point. If it were a substantially less of a bolt, the effect might not be so bad. But we don't have that information here. Call Edson all you want, it will not change the physics.

[LouK]

Thanks for the advice, clearly a spring time operation when the boat is out of the water.

[goboatingnow]

I use the jefa tiller arm , my version has two m8 bolts that are locked until drilled dimples on the shaft , works well

[LouK]

You're suggestion regarding the Jeffa makes a lot of sense! Earlier this morning I looked at the photos of steering quadrants on the Edson site, wondering how these were attached to the rudder post. I was slightly surprised to see, guess what- no key or thru-bolts, simply friction.

It seems unlikely that the forces exerted on the rudder stock across the face of the steering quadrant cannot be more than that of a tiller arm, assuming the surface area bearing on the rudder post are approximately equivalent.

My thought was rather than extend a bolt through the post, drilling & tapping a tiller arm to receive an elongated set screw which could be easily received by a short dimple drilled into the shaft (which one could do in 4 quadrants as necessary to distribute the force) would likely provide a similar amount of frictional resistance that a shear key resistance would exert.

It would appear that Jeffa's method of attachment proves the hypothesis. Thank you.

BTW, what has been your experience with the Jeffa drive?

[Celestialsailor]

Originally Posted by goboatingnow

I use the jefa tiller arm , my version has two m8 bolts that are locked until drilled dimples on the shaft , works well

This would be a good alternative in keeping the integrity of the rudder shaft.

[calmissile]

Some additional data from Edson gathered from my experience in ordering a tiller arm from them.

First, a response from them about securing the tiller are to the rudder post.....

"Good Morning Doug,
Thank you for your inquiry. The bore of 2.845” for the tiller arm appears to be consistent with the information in our files for the Columbia 45. The clamping action is not sufficient to withstand the loads from the auto pilot so another method of securing to the rudder post is required.
I have attached our tiller arm data sheet to be completed plus a related bulletin indicating the methods of securing.
Once we have your input, we will be able to provide you with an accurate quote.
Let me know if you need further assistance. Thank you again.
Sincerely,

Ken Martin
Customer Service

Edson International
Tel 508-995-9711
Fax 508-995-5021
Email: ken@edsonintl.com"

The catalog data displaying the various tiller arms they supply...

https://edsonmarine.com/autopilot-tiller-arms/

The worksheet they have you fill out when ordering.....

https://edsonmarine.com/content/EB37...ta%20Sheet.pdf

The instruction sheet for doing the installation.......

https://edsonmarine.com/content/EB380QuadrantInstr.pdf

Note that Edson uses 3 different methods of attachment...
1. Keyway (for solid shafts)
2. Set screws (for solid and some hollow shafts)
3. Through hole bolts (for hollow shafts) Edson picks the appropriate size bolt for the shaft size.

Agree, that using a 1/2 inch bolt through a 2 inch shaft would probably not be the size chosen by Edson for the attachment due to the weakening of the shaft in that case.

I don't recall if the data was on the worksheet, but Edson told me on the phone that in the case of setscews, you need to drill and tap the rudder post for the screws. The steering arm will have the holes drilled and tapped for both screws. I found it odd that both the arm and the rudder post would both be threaded, but they confirmed that is what they recommend. They also specified the depth of the holes to be drilled and tapped in the rudder post.

Hope this add a little clarity to the subject.

[goboatingnow]

Originally Posted by LouK

You're suggestion regarding the Jeffa makes a lot of sense! Earlier this morning I looked at the photos of steering quadrants on the Edson site, wondering how these were attached to the rudder post. I was slightly surprised to see, guess what- no key or thru-bolts, simply friction.



It seems unlikely that the forces exerted on the rudder stock across the face of the steering quadrant cannot be more than that of a tiller arm, assuming the surface area bearing on the rudder post are approximately equivalent.



My thought was rather than extend a bolt through the post, drilling & tapping a tiller arm to receive an elongated set screw which could be easily received by a short dimple drilled into the shaft (which one could do in 4 quadrants as necessary to distribute the force) would likely provide a similar amount of frictional resistance that a shear key resistance would exert.



It would appear that Jeffa's method of attachment proves the hypothesis. Thank you.



BTW, what has been your experience with the Jeffa drive?

The linear arm is excellent , and can be ordered with an integrated rudder reference which is very handy. The integrated telescopic section means it really is a one size fits all

[Celestialsailor]

Originally Posted by calmissile

quote.

I found it odd that both the arm and the rudder post would both be threaded, but they confirmed that is what they recommend. They also specified the depth of the holes to be drilled and tapped in the rudder post.

Hope this add a little clarity to the subject.

Absolutely right Doug...makes no sense at all. There is no clamping effect unless one part has a though hole and the other, a thread. The opposed threads would only "jack" against one another at best and still not create much of a solid connection.

[LouK]

I wonder if it makes sense to have Edson tap their tiller in lieu of just having them drill it. Then you could use the holes on the tiller arm to align the holes into the shaft, then tap both. Will have to give them a call. Thanks to all for some really good insight!