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#1 Wed 17th Dec 2014 13:30:08
- sackbut
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- Registered: Thu 20th Nov 2014
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Testing import of old forum
Peter Jagodzinski
Nov 30, 2013 - 5:23PM
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Linear drive autopilot
Has anybody fitted a linear autopilot drive to the rudder arm? I'm looking at the Raymarine Evolution system but the instructions say that the drive unit must be mounted in the same plane as the plane of rotation of the rudder arm. In a Seadog that would put it above the top of the bunks in the after cabin. Not very comfortable!.
Peter
SeaDog Name (if owner or crew) Dogmatic
Eric richardson
Dec 4, 2013 - 7:29PM
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Re: Linear drive autopilot
Hi Peter
I would have thought that a linear drive could be set to operate on the long link ( like a track rod) and fitted below that rod nearer to the steering box. The rod may need stiffeners fitting to allow for the bending moment introduced.
Eric
SeaDog Name (if owner or crew) Ex Taliesin
John Lansdell
Dec 9, 2013 - 9:18AM
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Re: Linear drive autopilot
If a linear drive autopilot were fitted it would have the effect of driving the wheel back through the linkage. The wheel would then tend to act as a flywheel and might thus cause increased wear to the pins in the vertical shaft and also within the gearbox behind the wheel as it stopped and started every time the actuator operates. This does not happen when the wheel is used manually.
SeaDog Name (if owner or crew) Twotails
Peter Jagodzinski
Dec 17, 2013 - 6:02PM
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Re: Linear drive autopilot
Thanks Eric and John for your comments.
I've been in touch with the Raymarine technical desk and with their Plymouth agents, Promarine. Their advice is to mount the linear drive under the port cockpit locker and attach the tiller pin to a new bracket on the steering rod, just aft of the arm that comes off the bottom of the steering column. in that position there is movement fore and aft (ie the steering movement) and from side to side (ie the lateral movement of the steering column arm) but there is no up and down movement. Two brackets will need to be made up. I'm going ahead with that plan and will post again when it's either working or has been consigned to the deep.
Peter
SeaDog Name (if owner or crew) Dogmatic
Peter Jagodzinski
Dec 17, 2013 - 6:05PM
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Re: Linear drive autopilot
PS I should also have said that the Raymarine advice is exactly the same as Eric's!
Peter
SeaDog Name (if owner or crew) Dogmatic
john king
Dec 18, 2013 - 8:16PM
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Re: Linear drive autopilot
the raymarine fitting looks good. I have always found it important to be able to disconnect the pilot and revert to hand steering quickly . would this be possible ? john king
SeaDog Name (if owner or crew) seafleur
Peter Jagodzinski
Dec 19, 2013 - 1:41PM
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Re: Linear drive autopilot
According to Raymarine the linear drive has "low backdrive force, to minimize the drive’s effect on the boat’s steering when the autopilot is in standby."
It looks like a spanner job to physically disconnect the drive so I'm hoping Raymarine are right. Hopefully I'll be able to answer this question, and any others, from my own experience in the Spring.
Peter
SeaDog Name (if owner or crew) Dogmatic
john king
Jan 13, 2014 - 9:54AM
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Re: Linear drive autopilot
Pl see Practical Boat Owner Feb 2014" Repairing an autopilot" in particular difficulty of disconnection I am v interested in this subj as my belt drive is getting near replacement time john
SeaDog Name (if owner or crew) seafleur
Peter Jagodzinski
Jan 13, 2014 - 11:56AM
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Re: Linear drive autopilot
The Raymarine Evolution kit has arrived now (thank you Santa) and it's possible to clarify some points.
First, disconnection of the linear drive is easy. Simply withdraw a sprung pin and drop the ram fitting away from the steering rod bracket.
Secondly, the back-resistance of the drive is quite light so I don't envisage a problem with leaving it connected when not in use.
Thirdly, there is not enough room in Dogmatic's engine room (Beta 1305 35 hp) to mount the linear drive unit there. A viable mounting position in Dogmatic is in the narrow inboard port side locker in the after cabin. The steering rod runs through this locker and the plan is to mount the motor end of the drive unit at the forward end of the locker just below the locker lid. The ram end, facing aft, should connect to a new bracket, yet to be designed and fabricated, on the steering rod.
Any suggestions for the design of this bracket would be gratefully received.
It looks as though there is enough articulation in the mounting of the drive unit and in the rose joint on the end of the ram to cope with the range of movements in the steering rod as the rudder is turned.
I'll keep you posted as the job proceeds, eventually with photographs.
Peter
SeaDog Name (if owner or crew) Dogmatic
Eric richardson
Jan 13, 2014 - 6:07PM
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Re: Linear drive autopilot
Hi peter
Just a thought, could you make an arm almost identical to the one that fits to the top of the rudder square but actually extends on to the existing arm retained by bolting it in place. Then fit the linear drive in a manner similar to the steering rod but on the Starboard side. The operating arc would be identical so it would not alter the loads. It would also remove all bending loads from the existing steering rod and could be used as a totally independent system in the event of a jammed steering box.
All you would need to do in an emergency would be to release the track rod end on the steering rod and be back in full control via your new system!
Eric
SeaDog Name (if owner or crew) Ex Taliesin
Peter Jagodzinski
Sep 5, 2014 - 9:22PM
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Re: Linear drive autopilot
As planned I fitted the Raymarine Evolution Autopilot linear drive in the small port locker in the after cabin.
The original steering rod runs through this locker. The linear drive ram is mounted with the its motor end at the forward end of the locker just below the locker lid. The motor end is attached by 4 x 10mm bolts to a new piece of 12mm marine ply. The ply is wood-screwed to battens glued and screwed to the locker sides. The ram end, facing aft, is connected to the steering rod by means of a stainless steel hinge clamp. The hinge clamp is a very beefy, off the shelf item modified to reduce its internal diameter to that of the steering rod by welding in short lengths of half section stainless tube. I've posted photos of the ram mounting.
This part of the fit is the trickiest, particularly planning the location. The method used has the advantages of requiring no welding or drilling of original Seadog components, it is adjustable for fine tuning of position, and it could be removed leaving no trace.
The fitting of the other components of the Evolution was relatively easy:
-the computer is mounted in the same locker as the drive, on the locker side;
-the sensor unit is mounted in the starboard locker in the forepeak
-the control unit is mounted on the forward side of the cockpit just to port of the steering console.
Connections are by Raymarine Seatalk network cables. These are simply plugged into the components so you are never faced with copper! Routing the cables is not easy but if anyone wants to know I can tell them what I did on Dogmatic.
So does it work?
Yes, its the most effective autopilot I've ever experienced. This summer it has steered a consistently straight course in quite heavy conditions (eg Force 5-6 on the beam with all plain sail up) on all points of sailing, motoring and motorsailing.
It's quiet, takes up no room in the cockpit and seems to have more than the power it needs.
It exerts no perceptible back pressure on manual steering in standby mode.
It brings a new level of reassurance and safety to short-handed and single-handed cruising. For example when you have to drop the main in strong wind and quite rough sea you can rely on it to hold you unswervingly head to wind, unlike the old Autohelm 3000 which simply couldn't cope with rough conditions when you need it most.
For once the hype is fully justified.
Peter J
SeaDog Name (if owner or crew) Dogmatic
I used to eat a lot of natural foods until I learnt that most people die of natural causes
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