What Next??? Autopilot cant pull steering system wires.. Grrr!

Richard10002

Richard10002

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Having fixed the autohelm linear drive unit, and the rudder reference transducer, I thought I had cracked it… but no… God has it in for me.

The steering system is Whitlock Constellation pedestal where the wheel turns a cogged wheel with a chain on it. The ends of the chain are connected to wires inside the pedestal, then the wires exit the pedestal through the cockpit floor into the engine room. At the cockpit floor, the wires enter a stiff tubing, (bit like a bicycle brake system), which continues all the way to the steering quadrant under the aft bunk.

At the quadrant the wires leave the tubing and proceed around the quadrant. One of the wires passes around a pulley type wheel to change its’ direction… so one wire pulls the quadrant one way, and the other wire pulls it the other way.

The autopilot linear drive unit arm is connected to a tiller arm which is fixed to the rudder stock under the quadrant,

Having fitted the drive and reference transducer, I tested the steering with the autopilot on standby. Everything fine…wheel spins freely, rudder quadrant turns freely, linear drive moves in and out freely, rudder reference shows correct readings.

Turn the autopilot to auto, and add 10 degrees… nothing moves. Try minus 10 degrees… nothing moves.

Test linear drive with independent 12 volt supply and, whilst it tries to, it cant move the rudder, and nor can I … the drive moves fine when disconnected from the rudder.

Disconnected the wires from the quadrant, rudder moves freely, both by hand and by powering the linear drive.

At all times, hand steering at the wheel works fine.

So… something is stopping the steering gear wires from being pulled from the quadrant end, at the same time allowing them to be pulled from the wheel end.

Any ideas?

Many Thanks

Richard
 
[ QUOTE ]
is the drive / A/H in the correct mode
IE port or stbd configuration
is the wheel mid-ships wnen you actuate the A/H & not against the stops @ the end of its travel

[/ QUOTE ]

The autopilot is fine. tested with wheel amidships in correct mode. I even disconnected the drive from the tiller and it works fine and smoothly.

It's definitely something to do with the system from the wheel to the quadrant, (inclusive), as I can turn the quadrant by hand with the steering wheel wires disconnected, but I cant move it at all with them connected.

Thanks for the thoughts

Richard
 
Only ideas. I'm getting to know the inside of your boat better than mine!

Have you tried pulling only one of the cables at a time. i.e disconnect one cable and try changing the tension on it while moving the quadrant. What about if you slacken off the tension on the cables so it has a lot of play.

Might explain your autopilot stripping gears!

Another difference is that at the sprocket. When the wheel is turned, the side of the sprocket pulling is "engaging" teeth. When the quadrant moves the side of the sprocket that is pulled is "disengaging" teeth.

Have you checked the sprocket wheel for worn teeth and the chain for stretch. It a long shot but you can catch chains in concave worn teeth so they don't disengage.

Any chance of full pictures? How difficult is the wheel and steering movement? With cables to quadrant disconnected and some one pulling lightly on them both how much force does the wheel need?
 
[ QUOTE ]
Only ideas. I'm getting to know the inside of your boat better than mine!

[/ QUOTE ]

MMM! I do seem to be hogging the limelight a bit dont I.... but I truly hope that the solutions to my problems will help others with similar ones, (as you have previously intimated).

[ QUOTE ]

Have you tried pulling only one of the cables at a time. i.e disconnect one cable and try changing the tension on it while moving the quadrant. What about if you slacken off the tension on the cables so it has a lot of play
Might explain your autopilot stripping gears!.

[/ QUOTE ]

Yes, I've tried several variations and every one results in the wheel moving freely, but being unable to pull the wires with the quadrant

[ QUOTE ]

Another difference is that at the sprocket. When the wheel is turned, the side of the sprocket pulling is "engaging" teeth. When the quadrant moves the side of the sprocket that is pulled is "disengaging" teeth.

Have you checked the sprocket wheel for worn teeth and the chain for stretch. It a long shot but you can catch chains in concave worn teeth so they don't disengage.

[/ QUOTE ]

Not considered this... I'll have a look tomorrow. Thinking about it, there cant be much chance of all of the teeth being worn, (at exactly the same time?), so if I try at varying degrees of wheel, port and starboard, it should be free at some point/s?

[ QUOTE ]

Any chance of full pictures? How difficult is the wheel and steering movement? With cables to quadrant disconnected and some one pulling lightly on them both how much force does the wheel need?

[/ QUOTE ]

I'll have a go at pictures. Wheel is a bit stiff if the wires are tight, but anything less than tight and it is as free as it's ever been. It wont frewheel, but it's not very stiff.

I dont think the wheel will move if the wires are disconnected, but I'll have a go tomorrow.

I can see me pulling the wires out, and causing all kinds of problems if I'm not careful. I'm guessing there might be something wrong with the wire inside the tubing... maybe a strand or two preventing movement in one direction, but not in the other.

Thanks for the thoughts... i'll let you know.

Richard
 
Is this not just a matter of gearing?

If the wheel has a, say, 6 to 1 gearing then the wheel will be 6 times easier to manipulate than the rudder stock. But . . . . the rudder stock will be 6 times harder to turn than the wheel. Does this make sense?

By the sound of it, the sprocket at the wheel is quite small and the wheel is probably quite big. The wheel has an awesome moment of leverage that the rudder stock probably doesn't. If my engineering thinking is correct (often isn't), then the larger the sprocket, the easier it will be to turn the system from the rudder end?

Just a thought. I know that I broke a cable on my steering once and had to steer with the emergency tiller connected directly to the top of the rudder stock and it was an absolute mission but my wheel was as light as a feather.
 
Hi Richard
I have an M376 with a similar setup (other than using a wheel driven pilot). When I have worked on the steering gear fitting the rudder ref unit etc. I don't think I could turn the stering quadrant by hand with the cables attached.
I would check the motor drive first as it does need a lot of grunt to move the rudder with so little leverage. The mechanical advantage at the wheel is considereable.

Cheers

Andy
 
try turning the rudder blade .. if that turns the wheel ok then your problem is the power of the autohelm.
 
[ QUOTE ]
Is this not just a matter of gearing?


[/ QUOTE ]

I dont think so. even when the autopilot was jamming, it easily turned the rudder and wheel when it actually moved...

What happens when I power the linear drive is that it takes up the slack in the system and keeps the pressure on. When I depower the clutch, it loosens with a bit of a bang/jerk.

I cant for the life of me see how the drive can be less powerful now than it was before all the problems.

I'm tempted to try and free the chain from the cog in thepedestal and see what happens... not sure how easy this is.

Thanks for the thoughts

Richard
 
[ QUOTE ]
Hi Richard
When I have worked on the steering gear fitting the rudder ref unit etc. I don't think I could turn the stering quadrant by hand with the cables attached.
I would check the motor drive first as it does need a lot of grunt to move the rudder with so little leverage. The mechanical advantage at the wheel is considereable.


[/ QUOTE ]

See my other reply, and I can add that the power of the drive seems such that it looks like it could break something... When I realised what was happening, I turned it off fast as I thought it was going to twist the rudder but not the quadrant, and possibly damage the rudder mounting thing.

I must admit that it seems a massive coincidence that just as I refit the drive and reference, a problem like this should occur..... but life is sometimes a bit like that.

I'm sure that, when I identify the cause, it will be something simple <g>
 
[ QUOTE ]
try turning the rudder blade .. if that turns the wheel ok then your problem is the power of the autohelm.

[/ QUOTE ]

Easy for you to say <g> We've actually got scuba gear so, if I dont solve it alongside, then next time we are here, I'll get an air tank and nip over.

Good idea by the way!
 
OK! with a bit of help from the wheel to get it started, the autopilot drive will keep the quadrant/rudder/wheel turning. As soon as it stops, it needs some help from the wheel to get it started again.

There must be some "stiction" somewhere. I've sprayed teflon grease down the pedestal, so hopefully some will have got onto the wires at the bottom, and I've sprayed as best as I can from the quadrant end.

We'll see what happens.
 
If you assume 70degree rudder and just less than 2 complete revolutions of the wheel for lock to lock that gives a factor of 10 ratio.

In the dock using the same leverage distance as the quadrant I can move the wheel with one finger I should only need 10 (give or take friction) to move the quadrant. However, any problems in the binnacle are 10 times worse on the quadrant.

Could you estimate the wheel forces? With and without the cables connected to the quadrant. Push on the wheel spokes at the same diameter as the quadrant.

You should also be able to move the wheel by pulling on the cables.

With my pilot ram (hydraulic) which is 500Kg force, I have to pull hard on the wheel to stop the pilot. Puts huge forces on the linkages but gives you an example of what it should be like. I forgot which version is yours but I thing it should have 450Kg of peak push. Does it?
 
[ QUOTE ]
....Whitlock Constellation pedestal where the wheel turns a cogged wheel with a chain on it. The ends of the chain are connected to wires inside the pedestal, then the wires exit the pedestal through the cockpit floor into the engine room. .....


[/ QUOTE ]

Just a thought. Is that everything there is?

About a year or so ago whilst moving a 1973 SWAN with this steering system I had to replace the wires. I discovered that the wheel was NOT directly connected to the 'chain cog'. Instead it drove a worm gear which in turn drove the axle with the chain cog. If you system is setup like this it would require a lot of force to make the chain drive the worm gear to move the wheel. This may not be the setup you have but worth checking out.

Also whitlock are still around. They are now part of LEWMAR and I have found both of these very helpfull whenever I've needed technical advice. Lewmar Website
 
Another thought...

How long is it since your steering system was properly greased? The cables do need greasing from time to time, if friction is to be kept low.
 
Re: Another thought...

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How long is it since your steering system was properly greased? The cables do need greasing from time to time, if friction is to be kept low.

[/ QUOTE ]

Probably not since new <g> I bought her in March.

I'm beginning to think that it is a friction kind of problem, so greasing would be appropriate and I'm trying to look at the bearings which the wheels axis sits in, (except that I have come across 3 frozen allen bolts... Stainless in Aluminium). About to try cutting a slot in the top of one to see if I can get it out with a normal screwdriver).

I need to take the pedestal off to grease the tube which the wires run in, and this could be a big job involving getting in the engine room, which I am too fat to do <g>

Anyway... as I think we are getting close to the cause, I feel better. It's the not knowing which is really frustrating.

Many Thanks

Richard
 
Re: Another thought...

MMM! cant get the allen keys on the bearing housing to turn. Sprayed all with release oil from both ends... wont budge. Ground a slot in the end of one... wont turn with an ordinary flathead driver. Drilled it out to about 3/4", but now the head has come off, the drill wants to slide into the plastic surrounding it.

Getting fed up now, but found this:

http://www.defender.com/product.jsp?path=-1|118|297677|311630&id=180792

just need to find the plastic thing which houses the bearing, then I can destroy it and fit a new one
 
Similar problem on my 41 earlier this year. Turned out to be the output transistors in the control unit (autohelm 300) had blown so not giving full voltage to drive unit. Check voltage to drive unit when in auto and if not 12V this may be your problem.
 
Agree, sounds more like brushes worn out/commutator dirty, not enough current getting through the motor so the thing has no power.
 
Thanks for the thought but I'm powering it from a 12v independent source, (Halfords Booster pack), and there is so much power that it threatens to separate the tiller arm from the quadrant. When I release the clutch it snaps bag with a bit of a clout, so I'm careful not to power it for too long once it's stuck.

There is definitely some stiction somewhere, so I'm going to replace the bearings at the wheel end when I get back in November, and see how it goes.
 
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