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Old 22-01-2017, 06:30   #1
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Problem with Sharp Autopilot

I have a problem with my autopilot and I hope that maybe someone can help me here.

It is a Sharp seapilot, which has a threaded rod (approx. M16, about 700mm long) with ball head accessing directly to the rudder quadrant. The installation is probably around 20 years old. The whole is controlled by a Raymarine unit.







In summer 2015 we once had a bit stronger wind (about 25kn) and a little bit more wave than usual (about 2.5-3m), where it could not hold the course anymore. It then did not work properly for the rest of the day. The next morning it seemed to have recovered and worked perfectly again.

This summer the pilot still worked well - except for the last day of our trip with again about 25kn of wind and 2-3m wave and swell. The pilot did not have enough power to luff over a certain point. I looked at the pilot more closely and noticed that the threaded rod still moved to a certain point, but then the motor just rattled. The pilot did not get particularly hot. After this, the pilot did not work anymore - even with less wind and wave. Unfortunately I cannot tell, if it has recovered and would work again now.

I have examined, cleaned and greased the thread. I could not see any defects in the thread and with the autopilot switched off the rod could smoothly slide over the entire length.

  • What could be the cause of the problem? Could the electric motor be done? Is there a clutch that could be worn?
  • How was it possible that the pilot could recover and work normally again?
  • As this installation is pretty old, would you recommend replacing the Sharp unit with a new mechanical linear drive (Raymarine ACU 200)?


Thanks for any help!
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Old 22-01-2017, 06:39   #2
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Re: Problem with Sharp Autopilot

FWIW:
You can download the SeaPilot Technical Manual
Here ➥ https://webcache.googleusercontent.c...&ct=clnk&gl=ca
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Old 22-01-2017, 08:37   #3
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Re: Problem with Sharp Autopilot

You might want to check if your hydraulic pump is a type 1 or 2 and if it is sufficient to handle the gross weight of your boat. Looking up the manufacturers specs should tell you what tonage the pump will handle.
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Old 22-01-2017, 08:44   #4
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Re: Problem with Sharp Autopilot

If I were you I would disassemble the unit and find out what the problem is instead of us trying to guess. From the looks of things in your pictures I really doubt that it is the hydraulic pump...
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Old 22-01-2017, 09:52   #5
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Re: Problem with Sharp Autopilot

If I understand what I am looking at in these pictures, this would appear to be an electric drive unit. If that is correct then surely there is a clutch, motor, and gearbox inside the case. Any one of these could have failed because of overload/ wear. If you are not comfortable in operating on the internals then might be time to start looking at a replacement.
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Old 22-01-2017, 22:31   #6
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Re: Problem with Sharp Autopilot

Quote:
Originally Posted by Frankly View Post
If I understand what I am looking at in these pictures, this would appear to be an electric drive unit. If that is correct then surely there is a clutch, motor, and gearbox inside the case. Any one of these could have failed because of overload/ wear. If you are not comfortable in operating on the internals then might be time to start looking at a replacement.

Ok, thanks! I am not uncomfortable in operating the internals, but I seriously doubt that I can find out what part is failing by looking at them. There was no particular heat or smell. Therefore I don't think that there will be any obvious damage, like burnt pieces. Even if I look at the pilot operating with opened casing, I don't think it will be visible what part is failing. Also the system might have recovered again and there won't even be failure until the next stronger wind. But maybe I am wrong there - so:

If I open the thing, what shall I look for?
If I figure out what part is failing, will a clutch, motor, gearbox be fixable? Are there spare parts for those old Sharps available?

Thanks again!
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Old 23-01-2017, 08:25   #7
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Re: Problem with Sharp Autopilot

I am not familiar with the Sharps unit but if you get it out then I would first connect it to a 12 Volt source and see if you can hear the motor running (do a reverse polarity test also). If the motor is running then apply 12V to the clutch circuit and see if the output shaft is turning. If the motor is not running then open the case up and take a look at the area of the motor commutator/ brushes. Brushes might be worn or carbon might just be fouling everything.

I am running a 30+ year Benmar drive unit on my IP (rotary drive). I have two spares I picked up from ebay but the original will probably outlast the yacht. Driving it with a Raymarine X-5 electronics set. Opened it up and cleaned relubed the gears once. 20 YO grease more like wax.
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Old 23-01-2017, 09:25   #8
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Re: Problem with Sharp Autopilot

Quote:
Originally Posted by alingher View Post
Ok, thanks! I am not uncomfortable in operating the internals, but I seriously doubt that I can find out what part is failing by looking at them. There was no particular heat or smell. Therefore I don't think that there will be any obvious damage, like burnt pieces. Even if I look at the pilot operating with opened casing, I don't think it will be visible what part is failing. Also the system might have recovered again and there won't even be failure until the next stronger wind. But maybe I am wrong there - so:

If I open the thing, what shall I look for?
If I figure out what part is failing, will a clutch, motor, gearbox be fixable? Are there spare parts for those old Sharps available?

Thanks again!
Since this is most likely a mechanical failure then burnt or overheated parts probably not involved.

Look at the motor, how the motor shaft attaches to the gear that drives the threaded rod, how the motor is secured in the housing, attachments/nuts/bolts etc. Basically anything with excess play, loose, moves where it shouldn't. Usually pretty obvious.
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Old 23-01-2017, 10:47   #9
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Re: Problem with Sharp Autopilot

Hi,
Most of the time the problem is with worn brushes.
Make some tests.
First ask someone to command the pilot to turn and measure if it have 12V at the output that feeds the electric motor in the pilot's processor. Also measure what feeds the clutch. If not, problem with the processor board. Disconnect the clutch and listen if the motor tries to spin free.
Turn on the pilot and try to move the weel by hand. If that is not possible, it means that the clutch works and probably mechanics as well.
If it is possible, it means that the clutch does not work or some mechanical break.
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Old 23-01-2017, 12:05   #10
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Re: Problem with Sharp Autopilot

I'm not an expert but it is probably a brushless stepper motor which has a finite stall torque. Once stalled the pulses trying to drive the motor would make it vibrate.

If it has always been like this then under these circumstances you are just asking more than it can provide. I think the good thing is that you can't really damage the motor in this way. It just tries its best and will set off again correctly when restarted.

Can you get the boat more balanced to reduce the driving loads?

Not an expert however....
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Old 23-01-2017, 12:58   #11
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Re: Problem with Sharp Autopilot

It looks like in the images that the drive pinion is designed to match the standard "All thread" that is unbelievable. Rack and pinion would have been better, I'd say the pinion is toast. Wonder what other bodgy stuff has been done.
Rotary drives are in my opinion more desirable than linear drive, but I never seen one or conceived it could be applied like this, usually they have a bike chain type drive then connected either to the quadrant or steering wheel shaft.
The pinion has to be pulled out to check for damage to the thread, if its that hard (heat treated) that it is not damaged, the "All thread" would be damaged in which case all you need do is rotate the "All thread" say 1/4 turn.
Could be wear of the bracket that holds the "All thread", tight to the pinion.

Getting a replacement Rack and pinion drive may be more trouble some than replacing with a Ray linear drive.
Same with more traditional chain drive.
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Old 23-01-2017, 15:54   #12
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Re: Problem with Sharp Autopilot

We have the same Sharp SDU1 electrical drive unit installed in our boat and have repaired it several times on our own (it's now 37 years old). I do NOT recomment to replace it with some modern equipment, since the Sharp unit is extremely robust (all metal, no plastic) and reliable, excellently engineered, easy to repair since the user manual contains all required information, all electronic components can be found in any DIY electronics shop, and most mechanical components can be rebuilt by any machine shop. I recommand to open it, see which is the problem, and to recalibrate it by following the instructions given in the user-manual, which can be found via google in the internet.
Instead, the poorly engineered rack & pinion configuration chosen by the shipyard provokes high friction losses, which might be at the origin of Your overload problem. Your Photo shows also that the system is by far too dry. To operate reasonably it needs to be lubricated by applying a lot of grease.
In any case, once You will have repaired the drive unit, I recommend to make photos and to ask a local machine shop to modify and improve the transmission to the rudder.
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Old 23-01-2017, 22:30   #13
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Re: Problem with Sharp Autopilot

Thank you all for all this input! That's a lot to consider: brushes, clutch, rack/pinion, etc... Another thing is the wiring. I am not sure if the right diameter of cables was used. A lot of the wiring on this boat was done by the previous owner - and he left a real mess.

I am about 600NM from the boat at the moment and it will take a few months till I get there, but I will post my progress.

Thanks again!
Mark
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Old 02-04-2017, 03:41   #14
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Re: Problem with Sharp Autopilot

Okay, I have now opened the thing and it looks pretty bad:



All this brass swarf that you see in the cover is a gearwheel from the transmission that has disintegrated. Can anyone give me a hint, where to find a replacement for the transmission? Does anyone know a Seapilot for sale?

Thanks again!
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Old 02-04-2017, 14:27   #15
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Re: Problem with Sharp Autopilot

Recommend to bring the unit to a lathe and milling workshop. They should be able to rebuild the ruined gear.
The rest of the unit seems fine. But first You need to find out, which was the reason for this failure. Lack of lubricant (grease)?
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