Re: {Disarmed} Re: [Amel] Autohelm ST 7000 linear unit drive


John and Anne Hollamby <annejohn@...>
 

The Autohelm linar drive unit has three parts which can wear and fail. The unit consists of an electric motor which is connected to the drive unit by a small toothed belt which turns the outer cage of an epicyclic gearbox when the unit is energised by the computer.The supply of power does two things,it starts the motor and it switches on an eletromagnet which locks the drive from the motor to the inner cage of the little gearbox which makes the drive move in or out. There are thus three parts that can wear out. The brushes of the motor which on my last boat lasted about 40,000 hours, The drive belt never seemed to wear but the gears were made of some sort of nylon or plastic and only lasted for about 10-15,000 hours.The plastic gears only cost about £12 in the mid nineties but could be replaced by a set of brass ones for £120. These should have a much longer service life.
Olivier assured me that the gears in my unit (2001) were brass and I have taken his word for it. However it seems quite probable that earlier installations may have had the plastic gears.
It is a very simple matter to remove the drive unit and open up the works to see if the gears need replacing and also to check the brushes.In my case the brushes were so worn that the carbon dust in the motor housing was shorting out .
Additionally spares for these parts should be carried after checking that you have been given the right ones because Autohelm changes suppliers from time to time and celebrates that fact by ceasing to stock parts for the old motor. In my case I was in Vanuatu when the brushes wore out and the Australian Agent sent me the wrong spares and Raymarine were very unhelpful.
I think that if I were to be going long distance again I would make sure I had spares for the linear drive and a spare course computer.

Good cruising, Anne and John, SM319

----- Original Message -----
From: dlm48@aol.com
To: amelyachtowners@yahoogroups.com
Sent: Monday, December 01, 2008 6:23 PM
Subject: {Disarmed} Re: [Amel] Autohelm ST 7000 linear unit drive




I dont think you read the post properly - the question was - should i replace the present linear drive with a new one - and keep the old one as a spare?

At least this is how i read the post - and i would say sounds like a good idea to me.

I am NOT convinced with your suggestion to mount the drive unit using a rubber mount though - that is going to introduce some free movement into what seems to me to be a big plus for the linear drive that is that it is directly coupled to the rudder stock and does not have the slop/free play of driving the rudder remotely using the steering mechanism - of course with the linear drive you have the additional advantage of in extremis being able to steer the boat should any part of the steering mechanism fail

previous post as below - bolding is mine

We plan to cross the atlantic next year. On our SM 227 we still run the

Autohelm ST 7000. I am thinking of buying a spare linear drive unit in

case of a problem during the passage. Since we are just the 2 of us on

the boat (my wife and myself)that might be worth to do.

One option I am thinking of, is to install a new lienar drive unit and

keep the old as spare part. Did anybody do this already and was it

difficult to install? According to Raymarine, the new unit should

perfectly work with the old Autohelm parts, e.g. the comptuer, compass

etc.?

Many thanks for your feedback

Paul

LunaBlu SM 227

re
gards

David

-----Original Message-----

From: Joel F. Potter <jfpottercys@att.net>

To: amelyachtowners@yahoogroups.com

Sent: Mon, 1 Dec 2008 4:17 pm

Subject: RE: [Amel] Autohelm ST 7000 linear unit drive

Keep both units and mount a switch near the rotary/chain drive drive

unit as Amel does. Run the one in the galley(the rotary)at night so

the noise will not be under your bed .Run the linear drive that will

be under the aft cabin berth during the day when the noise will not

disturb you. Running each drive unit for a twelve hour on/off duty

cycle will greatly increase their lifespan as they won’t get very

“hot”. Heat is the big problem with autopilot drives that are on for

days and days.

Be sure to mount the end not attached to the rudder Quadrant on some

medium soft rubber padding to make it much more quiet. Through bolt it

as normal, just don’t fully tighten the fasteners and use Nyloc nuts

or double nut with Loc-Tite.

As always , this is from me as an Amel owner and not as the Amel guy

for North America.

All the best,

Joel F. Potter

Joel F. Potter - Cruising Yacht Specialist, LLC

Amel's Sole Associate for the Americas

401 East Las Olas Boulevard, #130-126

Fort Lauderdale, Florida 33301

Phone: (954) 462-5869 Fax: (954) 462-3923

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