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Old 25-03-2015, 01:00   #31
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Join Date: Oct 2007
Location: Cape Town
Posts: 69
Re: From tiller to wheel, the mechanics

I think that wheel steering is quite do-able, but the difficulty in fabricating a wheelstand and pedestal, as well as a wheel makes a store - bought unit very attractive!
I designed a system for a custom boat that had no underdeck access to the rudder shaft, and needed the wheel right over the rudder.
It came out beautifully, once we calculated the rudder torque. After we calculated the mechanical ratio of the lever system we could then find the rim load on the wheel, and now Moondance has a beeeeyoodiful mechanical steering, so light that moving the rudder when she's out of the water makes the wheel spin.

Eat that cold, all you nay-sayers and open-wire and transmission-steering enthusiasts!

But the real witch-doctoring came down below.
I took an Edson draglink pedestal and ran the linkage out to a bellcrank under a custom-fabricated footboard/arch with teak slats. This means that the helmsman can snug down on the low side, or ride the rail on the high side whilst still having a level floor underfoot.
You can just see the arch behind the mainsheet traveller in this photo.

The issue which I overcame was the misalignment of the rudder stock. You can see that the vertical axis of the draglink is rather skewed against the head of the stock below it: fine for a tiller but impossible for a pedestal.

There are many arguments in both cases, but wheels are comfortable to use, and they give a range of steering positions, but the real advantage of a mechanical system like this is the Ackerman effect which you won't get with straight transmission steering.
in dead-ahead position, the rudder does least work but has greatest effect, so with the levers set to maximum radius, the return for effort is max. As the rudder approaches max deflection, the force it transmits approaches max, but the levers are working at minimum radius at that point. Don't ask me- draw it! At max rudder angle any helm command produces minimum rudder change, but maximises the force.
Simple, but very effective!

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Old 25-03-2015, 09:22   #32
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Join Date: Jul 2013
Location: Annapolis, MD, USA
Boat: Menger 19' Catboat
Posts: 248
Re: From tiller to wheel, the mechanics

Wow! That is a very clever and elegant installation, Splash.

The athwartship linkage to the bellcrank is pure genius, and I do think the Ackerman effect would be advantageous.

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Old 26-03-2015, 12:32   #33
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Location: Gulf and Caribbean
Boat: Irwin 30
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Re: From tiller to wheel, the mechanics

Hi, my idea as well...I bought an aluminum 2:1 gear reduction box(new) and I will use the length of the arms attached to steering shaft and rudder post to change ratio as needed. I am copying the Edson adjustable rudder shaft arm except with stainless steel and 3/4" heims joints on each end. I am also toying with the idea of st. steel U joints on the down shaft in the pedestal itself so I can move it over to the right for ease of installation. I have pillow block bearings to attach the shaft wherever I want to put it...I don't want too many weak points in the proverbial chain though, what do you think?
If you wanna exchange any info etc. PM me. I can send ya pix of the box and the pivot arms I want to use.
What will you make the actual pedestal with...I am toying with stainless...but to weld it and grind/sand/polish it ...Galvanized painted white is coming into view more often than not. I want to have wood accents though in a high gloss finish, maybe Nyalic or something...
Don't think I am sooo smart, I have to give credit to this site for all the info to get my wheels turning...THNKS TO YOU ALL!

Be safe and happy...
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Old 26-03-2015, 17:53   #34
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Re: From tiller to wheel, the mechanics

Very nice Splash!

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mechanic, wheel

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