What do I need to get this autopilot going again?

[Silhouetta]

First post here and sorry - it’s a bit of a dumbass question.

Basically I’m wondering what components I would need to make this ancient autopilot system go again.

My girlfriend and I bought the sailboat three years ago. 39 foot, 24,000 lb displacement. Much neglected. We have no regrets at all though and are having fun. Which is the point, right? Enjoying the learning curve of figuring it all out as we go, by fixing everything…

The AP was broken prior to purchase so we are somewhat used to not having one. I am finally getting to the point of looking in the bowels of the ship to consider the situation.

Hydraulic steering

The old AP is a Benmar Course Setter 21R.
I dissected things enough to figure out that the power unit (not shown) is quite rusted out. I doubt it’s worth repairing even if the other parts (fluxgate compass and the course control dial) work, which is doubtful. I did contact the Benmar rep Robert Edwards a few times but it was difficult to get much out of him, and my sense is it’s probably not worth throwing money at.


After the Benmar power unit is an electric motor as seen in the pics, which presumably powers a hydraulic pump. I jumped 12v power to it directly. It works and powers the hydraulic arm. Reverse polarity to bring the arm (and the rudder) back the other way. The electric motor didn’t sound very pleased to be woken up from years of sleep, but it does go.

As you can see everything is rusty and pitiful looking. I can’t make out any information at all on the electric motor. I do have the autopilot manual. The Benmar system seems to end at the power unit, so I’m assuming the electric motor and hydraulics shown are not specific to any AP setup.

It looks to me like the entire system must boil down to the signal to that electric motor. Three possible options. Go, reverse, and stop (no current).

This is where I run into a void of my own shameful ignorance, and come to the questions.

Could I put pretty much any old auto pilot system in here? What are the limiting factors? I mean -it looks like all it has to do, in simplest terms, is to run that 12v motor. (?). Am I missing something?

If so- What AP system might be a good choice?

Given that we are constantly low on boat money from all the refitting, quite used to having no AP at all, and don’t mind going primitive, the ideal fix for this might be some other ancient but reliable AP parts from ebay or wherever. We would be happy to just get it going on the cheap, get a better understanding of it and upgrade from there in future.

Or- we can save up and buy something decent and new. That’s OK too. Any insight is appreciated. Thanks!

 

[kappykaplan]

How is the hydraulic ram attached to the rudder? Any photos of that?

 

[DougM]

How is the hydraulic ram attached to the rudder? Any photos of that?

It looks from the photo as though the end of the hydraulic piston rod is attached to an arm on the rudder post. The cylinder end, not shown, is attached to a bulkhead somewhere.

In my personal opinion (worth about two cents), that hydraulic unit belongs in a museum or a scrap yard.
I’m thinking the electronics might be beyond all hope as well.

 

[mikeracca]

So the control unit is pretty much same same from AP to AP for the most part. What you are going to need to know is if the power unit is capable of powering the motor directly or through relays. Direct powering requires robust and expensive components in the power unit, whereas relay types are cheaper as the driver chips do not need to produce the high current a motor needs. The relay uses low current to switch a high current circuit on and off. There would be 2 relays one for left and one for right. Now you may ask why the different systems? Well the built in power units tend to use solid state transistors and are capable of finer control, relay type do not have the precision. There is always a trade off. So depending on your needs and wallet you could retrofit a new AP to your old pump… but get that pump serviced just to be safe…

 

[Silhouetta]

Thanks all.

I’m away from the boat this week but next time I’m down there I will investigate it more and see if I can get a clearer picture of it all, mentally as well as actually. It’s a mess back there alright.

 

[kloudie1]

Looks like the power unit is off its mounts (wood cleats to the left and under of the unit) and is fouling the rudder post arm. The drive looks to have a chain connection or belt connection between the motor and pump. If the hydraulic oil has been kept clean, the pump is probably fine even though it has a bit of surface corrosion. If the motor runs and the rudder moves, inspect/repair the connection between the motor and pump which is under the plate that the motor is mounted to. Note the slotted motor mounts on the plate to allow the chain or belt to be tensioned. The pump is probably a standard hydraulic component .. Good luck,
EDIT: The motor can be opened and cleaned and re-lubed (or bearings changed?) and the brushes checked/replaced.. while you are evaluating the chain/belt..

 

[RoyS]

I would not mix and match. Just because there is corrosion present on the hydraulic unit does not mean you need to toss the system. If it were my boat I would try to determine who manufactured the system and see if a replacement controller was available at a reasonable price. If so, then I would service the hydraulic unit as best I could and clean and paint it. It is, as you say, still functional. IMHO your two choices are repair the original with compatible components from the original manufacturer or replace the system with new throughout. Mixing and matching from different manufacturers seems risky to me. The original engineer would have determined how sensitive to make the system to respond to course changes. He probably would have had some options for the end user as well. Let us know how you make out.

 

[Silhouetta]

Good eye kloudie1. I detached that power unit to access it better, when I was tracing wires earlier in the year. That was the first time we finally got to looking at the dead AP situation at all.

FWIW i found a pic which shows the hydraulic setup a bit better

.

The situation as described by the previous owner -was a brief comment that it was an old and simple unit that worked really well for decades before it ‘quit working’. For health reasons he let a lot of things slide badly in the last few years of his ownership. It is what it is. We are working on fixing it.

We opened the power unit up and found enough corrosion in there that we pronounced officially dead for all practical purposes. No doubt it should have been mounted somewhere drier.

So the eyes and brains of the AP are toast. That leaves the remaining links in the chain which actually do work. Next - that electric motor which obviously doesn’t look very good. As for the hydraulics I think/hope that part might be fine after some TLC. I mean, it works now. If it breaks later that will only leave us where we already are now. I don’t foresee safety concerns with that, since we will not be completely relying on the AP in the foreseeable future.

So - for now, I can hook a 12v battery to that electric motor and make it all go. Technically a person could sit there reversing the wires or flipping a switch and steer the boat that way. Or if they had the skills, rig up some sort of Arduino type gizmo to a compass. All that is required is that simple signal to the electric motor. Right?

I’m not seriously planning to steer the boat that way, but that’s basically the thought behind this thread.

Let’s assume for simplicity that the electric motor and arm are completely fine (yes I totally realize they’re probably not). But I can figure that stuff out.

What I do not understand is- what are the limiting factors when it comes to attaching a new AP unit to this old gear?

Autopilot units are sold specified by boat size.

But surely that’s mainly down to the the electric motor and the hydraulic arm, which we already know is powerful enough.

The rest of the setup just exists to provide the signal to the motor, as far as I can see. ??

What you are going to need to know is if the power unit is capable of powering the motor directly or through relays.

So there is this. Which I will investigate. Thanks.

Obviously at the end of the day we just want to be able to find an auto pilot that will work, buy it, and install it.

I probably should’ve waited till I was back on the boat before posting this thread, but insomnia got me thinking about it in the night.

Thanks again for any and all comments! I appreciate it.

 

[DArcy]

If you have a working (for now) drive unit and are really tight for cash but good with electronics you could consider a PyPilot. The site is very thin on information but there are some YouTube videos out there describing it a bit more. For the cost of a Raspberry Pi and a couple of sensors and relays you could have a working AP.

 

[jssailem]

Ingenuity is an excellent skill. It sure sounds like you possess this. If it were so simple as to just flick switches there would be no complexity. Maybe we could rename it a Relay Pilot.

Regrettably is is not so simple. The modern and even aged AP systems made hundreds or more small adjustments to the rudder angle too accommodate the goal of keeping the boat on a set bearing (magnetic course) as the winds and waves attempt to constantly knock the boat of the course set by the skipper.

You can attenuate this by trimming the boat sails and rudder but winds, waves, currents are unrelenting.

From reading your account, a used fully functioning Fluxgate compass and a computer with the ability to drive the relays mentioned by @mikeracca, be able to react to the compass inputs; might get you there. There would be the ability to hold a compass bearing.

Todays modern AP's do this and much more. They interact with a chart plotter communicating and reacting to the inputs of a plotted course. Perhaps that is why they are so expensive.

Certainly giving the motor and hydraulic system the TLC you identify, will save you costs of that part of the system. Finding compatibility with the Computer will be dependent on your ability to get the voltage/current demands of the electric motor and the reaction times of the motor to affect change in the hydraulic system.

This is an interesting post. I look forward to your discoveries.

 

[Silhouetta]

Thanks again guys. I don’t want to go the route of inventing my own gadget. We will budget whatever we need for an AP. Having said that, I do like old stuff and would be perfectly happy with a reliable used simple auto pilot. No particular craving for bells and whistles at this stage.

So - we are just trying to determine where the old auto pilot setup ends and the new one begins.

I’ll do some more research and try to figure out the specs of that electric motor, which has zero legible information on it.
But after thinking about it for a little longer this morning.
It’s might be best to just cut to the chase and assume that rusty 12v motor will be replaced too.

So that would leave the hydraulics to figure out how to attach something new to. That seems like it should be a pretty simple thing to figure out, right…

 

[mikeracca]

One thing nice about hydraulics… they haven’t changed much in the last 50 years. Pump a fluid into a space to make a ram or motor move.

 

[kappykaplan]

You may be better off spending the boat bucks on a type 1 linear drive. You already have a tiller arm attached to the rudder post.

 

[dLj]

Perhaps more of a sidebar note - a few years ago I bought an old autopilot off ebay that was a perfect replacement for an old autopilot - same model and 20 + years old. It was originally purchased and not used - lived for many years in a guys garage before he decided to sell it. No idea if you could find a similar original autopilot to replace yours. I wouldn't hold my breath, but I would keep my eyes on that option...

dj

 

[Silhouetta]

Because I live pretty far out off the coast of North America here, I don’t get to many garage sales where I’m likely to find cool old things - but have been checking the net. I haven’t seen many parts of this particular AP come up at all so far, but then -it’s pretty damn ancient so numbers have probably thinned. I have got a couple worthwhile things off eBay - but it seems like with this old stuff people usually shoot for the moon with their prices.

My chances would be better if I could retrofit various options into there.

There is a fellow online selling a partial COMNAV 1001. Autopilot – ComNav

Shockingly, I think he doesn’t have a huge amount more time to answer my stupid longwinded questions about it sorry about that Peter...

In his words -

“This system would need a fluxgate compass, a pump, and a rudder feedback unit. ….the 'rotary unit' which is for the rudder-angle feedback to the A/P. You would need to confirm, but I believe these do not need to be Comnav branded products.“

In Comnav’s words re the unit -

“Suitable for mid-sized vessels, in the range of 30 to 60 feet / 10 to 20 meters

• Compatible with most standard types of steering systems
• Motor Drive Controller to interface with pumps or mechanical drives

I contacted the company to see if it is true what he said about compatability. It might just fit with what I have here. Also, I do have the old fluxgate compass though who knows if it works or not.

If it did - we’d just need to find the rudder sensor, and plug FrankenPilot in….right?

Somehow I don’t feel… bursting with confidence, writing that.

Any thoughts are very welcome of course -and thanks to all for the previous replies.