Autohelm 4000 tiller failure

[dan104]

Sailing in a stiff breeze all of the autopilot ram went total slack. Needless to say it was a pain as I was single handing but we survive.



As I researched the web the problem, over and over the answer was replace it $800). Not my kind of answer, so down to the bench.. After separating the two main cylinders I found what looked to be a small sheer pin broken which held the screw section to the motor drive.


Removed the remains and measured and found it is a 3/32" by 3/8" dowel, looks to be stainless steel. Raymarine has no part # or even shows it on theirTiller shear pin failure.pdf breakout pages.


Any way a machine supply house had them in quantity of 100 for $7.

attached is the repair procedure I created for the job.

[nuku34]

dan104: I had almost the same thing happen to my 4000. The pin only sheared on one side so the ram was making a clunking sound when it reversed because of the play. The pin that sheared is not stainless. The original is a "roll pin", a hollow pin with a slot running lengthwise. They are completely common and as you discovered, any good engineering supply store can sell you one (my shop sells them individually) for a few $'s.
I didn't see any attachment to your post....I didn't have any trouble replacing the pin, but you have to be careful to get the planetary gears back in properly.

[Franziska]

We had the same happening and did an emergency repair with a piece of the backend of a drill which we press fitted with onboard means.

[bergius]

These guys sell the Chinese linear drive that Pelagic autopilot uses, adapted as a tiller drive for various popular autopilots. Way cheaper than the Raymarine part (you could get it even cheaper from China, but then you have to do the adapters yourself. And I think you can only order ten at a time):

https://pcnautic.nl/nl/autopilot/st4...ent-set-detail

I haven’t bought one yet, but I’m planning to get one as a spare for our tiller drive.

[Franziska]

Originally Posted by bergius

These guys sell the Chinese linear drive that Pelagic autopilot uses, adapted as a tiller drive for various popular autopilots. Way cheaper than the Raymarine part (you could get it even cheaper from China, but then you have to do the adapters yourself. And I think you can only order ten at a time):

https://pcnautic.nl/nl/autopilot/st4...ent-set-detail

I haven’t bought one yet, but I’m planning to get one as a spare for our tiller drive.

That's very good to know if we need to replace one day. Thanks.

[wingssail]

Originally Posted by bergius

These guys sell the Chinese linear drive that Pelagic autopilot uses, adapted as a tiller drive for various popular autopilots. Way cheaper than the Raymarine part (you could get it even cheaper from China, but then you have to do the adapters yourself. And I think you can only order ten at a time):

https://pcnautic.nl/nl/autopilot/st4...ent-set-detail

I haven’t bought one yet, but I’m planning to get one as a spare for our tiller drive.

I'm curious, what do they mean by "no free wheeling"?

[wingssail]

Originally Posted by dan104

Sailing in a stiff breeze all of the autopilot ram went total slack. Needless to say it was a pain as I was single handing but we survive.

As I researched the web the problem, over and over the answer was replace it $800). Not my kind of answer, so down to the bench.. After separating the two main cylinders I found what looked to be a small sheer pin broken which held the screw section to the motor drive.

Removed the remains and measured and found it is a 3/32" by 3/8" dowel, looks to be stainless steel. Raymarine has no part # or even shows it on theirAttachment 263121 breakout pages.

Any way a machine supply house had them in quantity of 100 for $7.

attached is the repair procedure I created for the job.

I have not had that failure.

I've been using the ST4000 for 25 years, always the "GP" version which has a slightly bigger motor. I've worn out or broken two of them so I'm on my third, and I have a spare (new) drive unit. Currently with a Raymarine X5 computer unit and control head. I've had them apart several times and I saved all the good pieces so I have some spares. The motors are expensive and that's what has killed mine in the end however this one I am using now is at least 10 years old and so faded that the drive unit has turned golden in color. It still works.

The thing is that these units have to work hard with a heavier boat, especially with a boat with a heavy tiller, and in a stiff wind it's pretty hard on them. But in all that, I have not had issues with the gears, mostly just wearing out the motors. My boat is tiller steered and weighs 18000lbs. I consider that about the limit and even then I don't use the ST4000 in tough conditions. If it is rough or a lot of weather helm exists I either hand steer or use the wind vane. Usually the wind vane. Of course it is best to reduce sail area.

We save the ST4000 for motoring or very light wind sailing. It does not handle the spinnaker very well but if the boat is balanced it can do that too.

[fourlyons]

Originally Posted by wingssail

I'm curious, what do they mean by "no free wheeling"?

Isn't freewheeling the ability of the ram to move freely when the pilot is disengaged, but still physically connected to the tiller? I think they are saying these units don't have an electromechanical clutch, hence the claim of lower electrical consumption and greater durability. But I'm not familiar with the st4000, perhaps it can't freewheel in the way I'm describing.

[bergius]

Originally Posted by fourlyons

Isn't freewheeling the ability of the ram to move freely when the pilot is disengaged, but still physically connected to the tiller? I think they are saying these units don't have an electromechanical clutch, hence the claim of lower electrical consumption and greater durability. But I'm not familiar with the st4000, perhaps it can't freewheel in the way I'm describing.

ST4000 tiller pilot doesn’t have a clutch. Not sure what they mean since I’m not a Dutch speaker, and haven’t yet bought their unit. But the same linear drive is (as far as I’ve heard) used by Pelagic and has a pretty good reputation.

[Franziska]

Originally Posted by wingssail

I'm curious, what do they mean by "no free wheeling"?

Built in "below deck" drive units have a sort of clutch.

These on deck units need to be mechanically disconnected as they don't have a clutch.

We have a little custom solution for this, as our rudders are transom hung, but we do not want to climb on the stern to disengage when it's rough.
So now we have a sort of mechanical clutch which we use instead.

Pull the red line tight and the pilot gets blocked on the slide. Then press auto to have it steer.
To quickly disengage release the red line and the ram can slide on the rail.
Press standby when doing this.

We plan to replace the current plain plastic bearing sliders with ball bearing Harken cars in the future.
We had an X style traveler track with ball bearing cars before to achieve this, but it turned out that this works only when pulling on the traveler not when pushing on it.
The flat bearings are already much better.

[nuku34]

Re "freewheeling":
my 4000 ram plunger, when in standby mode, can be moved in or out by hand (although it takes a heavy hand to do it), but I don't think it is good for the gears and the linier drive to do that. There has to be quite a lot of resistance to the ram plunger moving by pulling/pushing on it otherwise the ram would move when its not actively being moving via the motor.

[wingssail]

Originally Posted by nuku34

Re "freewheeling":
my 4000 ram plunger, when in standby mode, can be moved in or out by hand (although it takes a heavy hand to do it), but I don't think it is good for the gears and the linier drive to do that. There has to be quite a lot of resistance to the ram plunger moving by pulling/pushing on it otherwise the ram would move when its not actively being moving via the motor.

The reason I bring it up is because my ST4000 gets slammed by the tiller in any kind of seaway. The problem of course is that I have a heavy, powerful boat and the waves and wind tend to put forces on the tiller which exceed the resistance of the ST4000 drive unit. The tiller slews it off to one side or the other. Then, as the boat turns, the ST4000 gets input from the head unit and slews the tiller the other way. It's Whirrr whirrr whirrr back and forth. Usually I would avoid those situations and either put on the windvane, which, thankfully, has plenty of power to hold the tiller, even in heavy weather, or I steer. I too can handle the tiller.

But I wonder about a drive unit which cannot "free wheel". It seems to me that the forces trying to move the tiller might break the drive unit if it is unable to give a bit.

[nuku34]

Hello Wingssail:
I think you are right about a drive unit that can't move when subjected to really big forces, especially the violent ones you are talking about. Something will brealk either internally in the ram or its mounting hardware.

The 4000 has a helical-cut screw with a ball bearing follower and a planetary gear system to gear down the motor rpms. That gives quite a bit of resistance to being moved when the ram plunger is forced in and out by external force (your heavy tiller) as I mentioned above, but it will move. That's a good thing to prevent breakage, but in your case there is so much force that the ram cannot hold a steady position when its not being moved by the motor.

Its obvious to me that the 4000 tiller drive is way under-powered for the size and weight and heavy tiller forces of your boat.

Your rudder looks like a balanced spade, I'm surprised that its so heavy on the tiller. Maybe your sailplan is not balanced or too big for the conditions...Also, being an ex-racer IOR design, they do tend to be a bit heavy on the bit (like some horses).

[nuku34]

wingssail; A really beautiful boat BTW, and must go like a freight train upwind (and be a bit of a handful on a run).

[wingssail]

Originally Posted by nuku34

Hello Wingssail:
I think you are right about a drive unit that can't move when subjected to really big forces, especially the violent ones you are talking about. Something will brealk either internally in the ram or its mounting hardware.

The 4000 has a helical-cut screw with a ball bearing follower and a planetary gear system to gear down the motor rpms. That gives quite a bit of resistance to being moved when the ram plunger is forced in and out by external force (your heavy tiller) as I mentioned above, but it will move. That's a good thing to prevent breakage, but in your case there is so much force that the ram cannot hold a steady position when its not being moved by the motor.

Its obvious to me that the 4000 tiller drive is way under-powered for the size and weight and heavy tiller forces of your boat.

Absolutely, for this reason we don't usually try to use it an anything but mild conditions. We bought it for motoring.

Your rudder looks like a balanced spade, I'm surprised that its so heavy on the tiller. Maybe your sail plan is not balanced or too big for the conditions...Also, being an ex-racer IOR design, they do tend to be a bit heavy on the bit (like some horses).I think I overstated that a bit.

The tiller is not heavy, it's fairly easy to hold but that takes some force when we happen to be overpowered. The thing is, we hold the end of the tiller which is nearly 6 feet. The autopilot connects at 18", per Raymarine installation instructions. So the leverage is way different.

Where the ST4000 get really active is upwind in significant waves. It seems to work but I worry about how the waves and the tiller constantly knock it around.

I don't view this as a problem I need to solve. We just use the wind vane, which works perfectly, but I was wondering about the option of that other drive unit should I decide I needed to buy another spare. My current drive unit is really old.

And thanks for the complement.