Autohelm Linear Drive - jams one way on Standby

Richard10002

Richard10002

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Hi,

Famous Last Words:

http://www.ybw.com/forums/showflat.php/Cat/0/Number/857083/an/0/page/5#857083

I know this has been covered, but I cant find an answer which could apply to my particular problem.

I've read Geoffs, (Hightec), 6 possible causes of jamming,

http://www.ybw.com/forums/showflat.php?C...rue#Post1126040

So here goes:

Autopilot linear drive started making a grinding noise in Biscay. Took it off to find the centre splined gear completely worn, ( the gear is driven by, or drives, the 4 brass gears situated around it, and it is at the middle of a piece which is driven by the motor), and fitted Heavy Duty Gears service kit, (Raymarine part no N026). Applied a 12v supply to both motor and clutch, and the arm moved in and out freely when powered, (polarity reverses to make it go in or out). Could also pull/push arm in and out with clutch not powered.... so all seems well.

Re-fitted drive to boat and rudder... tested autopilot alongside... seemed to work.... tested steering... a bit stiff but thought nothing of it. Set sail from Bayona to Leixios, steering very stiff, mainly to port .... disconnected arm from rudder..... steering very free... hand steered to leixios.

At this time I found i could push the rod in by hand, but could not pull it out.

Got the linear drive dissassembled to gearbox on saloon table.

with a 12v power supply, (clutch not powered), I can make the arm move in and out very freely with slight pressure on the clutch plate. I can also make the arm move both ways with no power, by rotating the belt, and pressure on the clutch plate.

So the arm seems to behave correctly, and moves freely under power.

However, with no power applied, (i.e. replicating STANDBY), I can push the arm in by hand, but cannot move it even a millimetre outwards... it's jammed.

The only one of Geoffs causes seems to be:

"2. The ball screw has a damaged ball(s) and is causing a lock up. Usually recurs regularly and easy to find. Not normal on a low usage unit unless it has been abused"

but as it moves freely one way by hand, and not the other, and as it moves both ways under power, it is difficult how to see a ball causing this specific problem?

One thing I did when refitting the drive, after fitting the new gears, was to grease the arm quite liberally... This was before i saw geoffs advice to grease it sparingly! But still cant see how this would cause a jam one way and not the other, also allowing it to move under power.

Anyway.... I think i've described everything.... so any help gratefully accepted.

We're probably going to hand steer the 25/30 hours to Cascais and revisit the problem there.

Cheers

Richard
 
What is the distance from the rudder shaft to the linear drive fixing?

Are you assuming that it is something you did wrong or are you wondering why it is giving you so much trouble?

You say that the gears were "completely worn" do you have an explanation. Has the rudder suffered any non-water caused forces.

Sorry we missed each other. Have fun.
 
[ QUOTE ]
What is the distance from the rudder shaft to the linear drive fixing?

Are you assuming that it is something you did wrong or are you wondering why it is giving you so much trouble?

You say that the gears were "completely worn" do you have an explanation. Has the rudder suffered any non-water caused forces.

Sorry we missed each other. Have fun.

[/ QUOTE ]

Distance about 1ft - it has worked fine for the last 3 years in my fathers ownership, and probably since fitting 10+ years ago.

I dont think I did anything wrong, but I might have done! - it comes apart and goes back together fairly easily, and the new parts just went where the old ones came off.

I am guessing that the 1 gear was worn as it has been in use for 10+ years, and I think it was plastic. The replacement is brass, (or brass coloured), as were/are the 4 gears which revolve around it.

In terms of fun, it's turning into a true shakedown cruise. Things keep breaking, and I keep fixing them! --- but its still fun, and beats the hell out of working!!

Cheers
 
Since posting, I've taken the new gears off to see if there is a point where the jam frees up.

It freed at the point where I took of the 4 gears which are attached to a brass plate which sits on a spindle which goes int where the arm is. the gears are at the corners of a right angle and rotate around the centre spline, (which caused the problem in the 1st place). A bit of teflon grease seems to have freed things up, so I can pull/push the arm out and in.

Having refitted it, the wheel, (helm) now turns freely both ways hard over. However, testing the autopilot, (alongside), it seems to move OK to starboard, but gives up easily, and goes to Standby, to port. This could be another jam, or merely that the boat wont turn anyway. We'll have to see what happens when we get to sea later, (if the fog lifts!)

I dont think it's going to work, but it may be that more grease will solve it.

Cheers

Richard
 
Hi Richard,

OK, First thing is to go back to basics. Remove the new gearbox bits and gears etc so that you only have the end of the drive shaft sticking through the backplate. Then try pulling the drive in and out, if it is sticking one way at that point then the drive balls are likely to be damaged.

Then check for any end float on the shaft as there is a bearing in the rear plate with a roll pin through it that can shear and cause the clutch to bind. if you find there is end float then you will need to open the arm up real carefully and replace the pin, making sure you keep your balls in place /forums/images/graemlins/wink.gif).
However if there is no end float and the drive goes both ways freely then you need to start rebuilding piece by piece until it sticks again. the big gear on the shaft should be very free running and may need easing on the shaft slightly, however it should not flop around as this will then twist and jam the shaft.

If you rebuild slowly and test each time you add a bit, eventually you will track the sticktion down.

Post again if still stuck.

Geoff (aka hightech) /forums/images/graemlins/cool.gif
 
[ QUOTE ]
Hi Richard,

OK, First thing is to go back to basics. Remove the new gearbox bits and gears etc so that you only have the end of the drive shaft sticking through the backplate. Then try pulling the drive in and out, if it is sticking one way at that point then the drive balls are likely to be damaged.

Post again if still stuck.



[/ QUOTE ]

"stuck" <g>

Many Thanks for the quick reply. Still fogbound, so may have a chance to do a bit more work on it:

OK... on the saloon table, took it back to taking the plate with the 4 brass gears off, and the stickiness went... replaced the brass gears and applied a bit of teflon grease... reassembled.. no stickiness.

Fitted to boat and tested... possible stickiness turning to port.

I am thinking of cutting the wires and powering it up with a 12v supply, to see if it is sticky, or if it is merely that, as the boat cant physically turn to port, the drive gives up and says "RELEASE".

Is it a good idea to power up like this? I cant see any other way of testing without going for a spin, and I seem to get rid of the stiction when it's on the saloon table.

Richard
 
It's possible that something has gone off centre or eccentric. A worn bearing say, such that one way it will turn the other it will lock.
 
[ QUOTE ]
It's possible that something has gone off centre or eccentric. A worn bearing say, such that one way it will turn the other it will lock.

[/ QUOTE ]

Thanks for the suggestion:

It's clearly possible, but everything seems to be as it was before I fitted the new gears, so it's hard to see what might have changed... but something might have... I cant see anything obvious.

I've narrowed down the stiction to to the brass plate with 4 gears on it "catching" on something, which can only be the large gear which is driven from the motor, and which drives the 4 gears, which spin the spindle, which moves the rod in and out, using the balls.. i guess.

This will mean little or nothing to those who havent opened one up..... but will do when you do <g>
 
Geoff,

Thought I'd found, and cured, the stiction where the 4 brass gears meet the large gear which is driven by the motor. This is definitely where it is sticking... with everything off to the spindle, the arm moves in and out fine, and the spindle appears to have no play.... put the large gear and belt on, all fine. put the brass plate with 4 gears on and fit the pin.... sporadic stiction, put the clutch on the 4 gears, sporadic stiction etc....


In practice, leaving Leixoies yesterday, the drive worked sporadically, mainly giving up when it tried to put the helm more than 5 degrees to port. however, the helm still spun freely when in Standby. After about an hourof this, the drive seemed to be able to cope with nup to 7 degrees to port, then it gave up and jammed so the helm was stiff in Standby.

I've had it apart again, and it seems to work freely and easily on the saloon table, so we'll see how it goes leaving Cascais tomorrow.

If it doesnt work, I am thinking of having a Raymarine Service, but wonder if it may be worth buying a new drive, given that a service to bare bits will probably cost a few hundred pounds, and may not solve the problem.

Any thoughts welcomed!

many Thanks

Richard
 
OK... fitted it yet again, behaves normally when connected to the rudder and my 12v power supply. Wheel moves freely. Turn on Autopilot, set it to Auto... anything to Starboard is fine, including hard over, (+1 & +10 simultaneously). Anything to port, it gives up, display says RELEASE and reverts to Standby.

I'm now fed up with it and will probably buy a new one rather than risk throwing good money after bad.


Thanks to all for the help.

Richard
 
Can't help at all Richard as have never had one apart. But regardless this thread has been a very useful introduction to what is inside them and the potential problems and approaches to them. So thanks for that as we have a similar drive.

I trust a solution is found.

John
 
The internal workings of this thing are really simple so, apart from Geoffs "DO NOT TAKE THE BALLS OUT!", if it fails there seems to be every reason to dismantle it and see what is happening.

However... be aware that by dismantling, something has happened to make mine jam, where it didnt jam before!

I could really do with an exploded view diagram of all the parts, to make sure that I havent lost anything, or put something back in the wrong order. I'm sure my answer is very simple... we shall see.

Cheers & thanks for the thoughts
 
[ QUOTE ]

I could really do with an exploded view diagram of all the parts, to make sure that I havent lost anything, or put something back in the wrong order. I'm sure my answer is very simple... we shall see.

[/ QUOTE ]

Like I said on a related thread - Raymarine support in Portsmouth were happy to send me a service manual for the beast, which included an exploded diagram. Try giving them a ring: +44 23 9271 4713 <UKProduct.Support at the domain name raymarine.com>
 
Hi Richard, glad you sound as though you are enjoying yourself despite the problems. A couple of thoughts. We have the same servo and it went once round the world with no probs (AFAIK) and before we left the UK I sent it to Raymarine for a check and overhaul if requ'd. The reported back that it was in 'as new condition' so either the PO had had it serviced just prior to selling (it is possible) or there is very little wear on this boat in this installation (seems unlikely).

BUT, these units have a very good reputation for reliability so the poster who queried the installation has a good point. Other long-distance cruisers have made the point to me that you should never cross an ocean without a wind-vane system as well as the electric autopilot. I met one couple (whose boat I nearly bought) who left with the ARC and had autopilot failure a day or three out and had to steer by hand between husband and wife (not a young couple, either) all the way for 20++ days. Best wishes, David
 
Hi David,

We're in Lagos.. the sun is cracking the flags... Janet flies in tonight... how bad can it get? <g>

When I spoke with Raymarine they said that older Linear Drives have a plastic gear at the centre of the sprocket, (which the belt goes around), and that wearing of this is a common fault. The new gear kit has a brass gear which should not wear.

Just spoken with a service engineer and he has given me a few ideas to try.

failing that, i may send it to Raymarine when i go home for a few weeks. i'm told it should only be an hours labour or so.

Cheers

Richard
 
[ QUOTE ]

Like I said on a related thread - Raymarine support in Portsmouth were happy to send me a service manual for the beast, which included an exploded diagram. Try giving them a ring: +44 23 9271 4713 <UKProduct.Support at the domain name raymarine.com>

[/ QUOTE ]

just called raymarine at your prompting. One of the service engineers has given me some things to try, (which I hadnt tried), which may resolve the problem.

Thanks for the gentle pressure.

Richard
 
[ QUOTE ]
Hi richard,

Stick with it, generally they are fixable!

Reply or PM if you need any more assistance.

Geoff.

[/ QUOTE ]

Geoff

Arrived Lagos last Tuesday and have had a lazy week. Fixed a sheared shear pin on the bowthruster yesterday, and took the linear drive apart again today.

Scott from Raymarine suggested 2 things:

1) use the 4 original brass gears rather than the new ones from the kit.

2) check for play in the spindle which the various gears slide onto, (as you had already suggested), remove it and check the bearing between it and the drive rod.

on 1) the 4 small gears have a raised centre on one side, and are completely flat on the other.. does the raised bit sit on the big brass gear with the 4 spindles, or does it face the big gear which the belt goes around? Hope that makes sense.

on 2) Imay have misunderstood you.... there is no play when I waggle the spindle from side to side, but there is a fair bit when I push/pull it in line with the arm.. i.e. in and out of its hole. I took it off and find a thick'ish washer underneath, which sits on a kind of roller bearing affair which also comes off... i darent go any further becaus I'm sure I'm getting close to the famous BALLS! <g>

I may as well replace the pin and roller bearing so do you know what the part number is/are? If not, I can call Scott at Raymarine.

having said that... having put it back together, with the old small brass gears, with the raised bit facing the belt gear, it seems much free'er than previously. Not sure whether I can be bothered with the hassle of fitting it back to the boat before getting the new bearing and a bit more advice.

Many Thanks for your help so far

Richard
 
Hi Richard,

If the end spindle goes in and out, then there is your problem. When the drive runs out, the spindle gets pushed in toward the rear plate and all will be well. when the drive runs in, the spindle will be pulled out of the plate and all the bits attached to it, the gear assembly, will jam against the plate and bingo sticking drive.

Take everyhing off the back end of the unit (the gears etc) Run the ram out a few inches from the fully in position. At the back of the main plate ther should be a top hat plate with four screws in it, if you undo these and thenpush the ram back in you should find two flat thrust bearings either side of a central plate. Thru the middle of this plate should be a roll pin, my guess is that has sheared and is where your probelm lies. New roll pin and you should be sorted.

If I remember correctly, the later units had either a double roll pin arrangement (small on inside a big one) or a solid pin, as these used to break under a sudden load on earlier units (with no other damage).

You may see some scuffing on the rear plate where the big wheel rubs it (the one the belt runs on).

Provided you only move the ram around the mid portion of it's travel then your balls will not get loose.

If you look carefully, the raised bit on the gears should be acting as a spacer washer and from memory I cannot remember if it faces in our out, however if you look at the whole thing there should be clearance both side of the gears when they are in place, if you have loads of space on side and none the other, then it is upside down.

If you need talking through this then call me on the land line number.

Fair winds and full sails,
Geoff.
 
Geoff,

Thanks for that.... I'll have a closer look to see if I can make head or tail of things behind the top hat plate.

I had the plate off the other day and I think I found, in order...

Spindle, thick flat washer type thing, thin washer shaped bearing with needle rollers across the diagonals... then something which, if removed, alows access to the balls, so I pushed this back in quickly <g>

As I said, I'll have a closer look with your description in front of me, and report back.

many Thanks again

Richard
 
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