Lewmar/Whitlock Drive Unit - Electromagnetic Clutch Question

[MagicalArmchair]

My wheel drive Whitlock\Lewmar drive unit was making some strange grinding noises since I've owned the boat and for the first time came up with a "DRIVE STOPPED" error on our first shakedown sail last Friday. The DRIVE STOPPED error, I believe, roughly equates that for the requested course change, the drive unit is drawing too much current and it has stopped steering (read: I'm jammed):

I dropped the unit off and took it apart. The below is the plate attached to the electromagnet. Note, it should probably be free and makes a squeak similar to that heard in the cockpit when spun:

As I understand it, in the picture below, when the electromagic on the plate on the right is engaged, it "sucks" the plate on the left towards it, engaging the clutch. When I spun the plate on the right (this is the side that has the motor on it, not the side attached to the chain that drives the wheel) without the electromagnet engaged, it made a grinding noise. Could that be the noise from the cockpit? Would that cause the jam through that excessive additional friction?

Now I have this in its component parts, I'm not sure how to proceed. A couple of the awesome and helpful members of the Bavaria Owners Association have had a similar problem, one noted he freed the clutch plate (by sanding it) on the electromagnet side and the squeak and unit overload never returned. Below is a picture of the back of the right hand (drive) wear plate. Where should I sand it to stop that friction?

Electromagnet this sits on top of:

Has anyone had a similar issue and what do you suppose would fix my struggling drive unit? Could it have nothing to do with where I am looking?

Original Forum Post: Self Steering 'Grunting'

 

[penfold]

Now I have this in its component parts, I'm not sure how to proceed. A couple of the awesome and helpful members of the Bavaria Owners Association have had a similar problem, one noted he freed the clutch plate (by sanding it) on the electromagnet side and the squeak and unit overload never returned. Below is a picture of the back of the right hand (drive) wear plate. Where should I sand it to stop that friction?

Electromagnet this sits on top of:

Has anyone had a similar issue and what do you suppose would fix my struggling drive unit? Could it have nothing to do with where I am looking?

Original Forum Post: Self Steering 'Grunting'

The clutch drum does appear to have some rub marks, but I'm more interested in why it's now rubbing on the electromagnet than where to abrade it. What's going on at the end of the shaft it mounts on? It looks like it's been attacked with an angle grinder. The shaft must have moved axially to remove the clearance between the drum and the magnet; has a circlip come adrift, a clamp loosened? The axial displacement of the shaft which is causing the rubbing may be bearing wear, how old is the boat? From your thread on the bav forum; the sprocket should go back on with the aid of a mallet, heating it in an oven will help.

 

[MagicalArmchair]

want to use.

The clutch drum does appear to have some rub marks, but I'm more interested in why it's now rubbing on the electromagnet than where to abrade it. What's going on at the end of the shaft it mounts on? It looks like it's been attacked with an angle grinder. The shaft must have moved axially to remove the clearance between the drum and the magnet; has a circlip come adrift, a clamp loosened? The axial displacement of the shaft which is causing the rubbing may be bearing wear, how old is the boat? From your thread on the bav forum; the sprocket should go back on with the aid of a mallet, heating it in an oven will help.

It's quite surreal - clearly someone with little care has had at it. All the machine crews were loose (as in finger tight - the whole thing wobbled about before I took it apart). Half the screws holding it together are missing altogether when compared to other photos, and there is a strange gasket made out of cardboard behind one of the clutch wear plates. Heaven only knows why its been hacked at with a grinder! I did wonder re the bearing. I do have a new bearing I could press in here to the below, I think getting that key out of the keyway might be a mission though... Its wedged pretty good. Given that half of it is missing makes me think someone has already had a hack at it (probably the same monster with the grinder!).

Edit, ignore me talking about abrading the electromagnet - its the other face I need to do. The boat is 20 years old, a Bavaria 40.

 

[penfold]

I'm not keen on abrading the clutch drum to fix the rubbing; it will probably work but it offends my engineering sensibility and it doesn't address why the axial shift has occurred in the first place. Is the shaft likely to move some more? Unknown. The wavey thing next to the bearing in your last video is a split ring and it looks damaged, if that is for locating the shaft then it is a good suspect for why the shaft has moved. If you've got your lucky pants and brave trousers on I'd investigate the motor, get a new split ring and consider replacing the bearings.

 

[MagicalArmchair]

I too wanted answers to those questions, so I sent it off to Lewmar for them to take a look and their response was:

So the drive has been inspected by our drive team. I’m sorry to say that the conclusion is that the drive is beyond economic repair. They are advising a replacement drive of part number 89300016. You will be able to order this through your local Lewmar retailer.

A cool £2,500 for a new unit... I have sought more details from Lewmar. What exactly is wrong with the unit?

There is a mamba version on Ebay here - note, no shaft as Mamba units work without sprockets and chains. Lewmar Mamba Drive Unit 1/4HP 12v for self steering autopilot use | eBay

Could I use the shaft and gears from the Constellation version to fit to the Mamba unit? Giving me a spare pancake motor? Spare electromagnet? Or does madness lie that way, and I should abandon my PBO compulsions to limit waste and try to fix and make do, bin this unit and buy a new drive unit?

 

[PabloPicasso]

Not economic to repair for whom? Them, or you?

 

[penfold]

Not economic to repair for whom? Them, or you?

Code for "We don't keep bits on the shelf for 30 year old equipment and our workshop has enough on its plate fixing defective examples of our current paragons of engineering".

 

[penfold]

I too wanted answers to those questions, so I sent it off to Lewmar for them to take a look and their response was:



A cool £2,500 for a new unit... I have sought more details from Lewmar. What exactly is wrong with the unit?

There is a mamba version on Ebay here - note, no shaft as Mamba units work without sprockets and chains. Lewmar Mamba Drive Unit 1/4HP 12v for self steering autopilot use | eBay

Could I use the shaft and gears from the Constellation version to fit to the Mamba unit? Giving me a spare pancake motor? Spare electromagnet? Or does madness lie that way, and I should abandon my PBO compulsions to limit waste and try to fix and make do, bin this unit and buy a new drive unit?

I think the rubbing is eminently fixable, the rest of the system appears quite robust and has borne 20 years of bodgery and neglect quite well; whether it makes sense to do so is your decision.

 

[MagicalArmchair]

Lewmar have not responded to any calls, or emails. Fabulous. There is a 4 week lead time on buying a new unit, so says my local Lewmar unit. I'll try and get my unit back - I wish I had never sent it in the first place!

I will look at going to Jefa perhaps? Or Raymarine? Any suggestions for a replacement?

 

[MagicalArmchair]

After continued radio silence and no one returning my calls for a further day, I demanded they send the unit back on a next day delivery (after all, I had a fix for it I could try). They later contacted me and conceded they couldn’t send it as it was still in its constituent parts, and in trying to pull some of the bearings they had destroyed them, and they couldn’t put it back together into its original state in order to return it.

This rather bleak story takes a more positive turn at this point. The manager pointed out as it was so old, they could not do a normal service as they would then need to warranty it for a year (hence the “beyond economical repair” comment). He also said the clutch and all the gears were broken (look at the photos above, the gears are fine, which is curious), never mind.

He then offered to press new bearings into the unit, and put it back together for the £60 inspection fee. No guarantee, and he said I shouldn’t rely on it, but I’m confident I can get it working again with a shim to give the clutch clearance again. It’s worth a go for £60 vs £2,000, and these units are really not that complicated.

 

[penfold]

It's entirely feasible the bearings were well on their way to valhalla anyway and I would not normally reuse a bearing if I've had to use a puller to get it off as it's easy to cause damage. It will be interesting to see if they replace the knackered split ring and if it cures the rubbing.

 

[MagicalArmchair]

The bearings were quite rumbly, so for all my grumblings about Lewmar, they might yet be my saviour after all. If they manage to help me get up straight for this season, when I come to replace the drive unit I’ll be more minded to use another Lewmar one.

I would be curious to see if they manage to replace that bearing at the back of the clutch - the key was pretty wedged in the key way there.

 

[MagicalArmchair]

Lewmar have returned the drive and have said (after the engineers "took pity of me") its ready to be fitted after replacing the bearings and no further shimming is required. They will not put any warranty on the drive but they tell me they have bench tested the unit and it works fine.... however, now it has arrived the shaft does not spin freely, like the clutch is locked on. The service manager told me "Thats normal! You have far more leverage using your wheel! The clutch cone should have some friction when not engaged...".

For one, it doesn't have a clutch cone, it is has clutch plates, for two, that makes no sense. Any friction introduced to my steering system needlessly seems like poor design. Also, that would be additional wear on the clutch plates...

I want to believe Lewmar and go and fit the unit, but my common sense tells me, with the electromagnet disengaged, the shaft should spin freely. Should it? Or should it be solid and not able to be turned by hand with the electromagnet disengaged?

 

[penfold]

If it doesn't spin like in your 'clutch apart' video then I'd assume something is wrong. That said how much effort is involved in fitting it and testing?

 

[MagicalArmchair]

Well, that shows what I know! I fitted it to the boat over lunch today to "prove" that it would lock the steering and it was as good as Lewmars word. The wheel still spun perfectly well, with a little extra resistance, but not really perceptible. I didn't get a chance to wire it up to properly test it in the berth, however, I am feeling more confident now. If anyone does venture this way - the sprocket needn't spin freely by hand with the clutch disengaged.

I'll finish wiring it up (it is only four wires! I just ran out of time), and test it at the weekend...

 

[MagicalArmchair]

After wiring it up, I tested that the clutch engages and disengages in the berth, and it gripped really well. So I thought I had cracked it.

We set off on our first summer cruise yesterday, the weather had not been kind enough to give me a chance to shakedown sail with the "fixed" drive unit. On setting off, I pressed the auto button on the ST6001 and the autopilot steered hard to port, I tried again, and again, it steered hard to port. 10 hours on the helm later, we arrived ?, with aching feet.

Could I have wired it up the wrong way? Could it be the fluxgate compass? Seems a bit of a coincidence as that was working pre the drive unit.

Edit: I may have been overthinking this. Crammed with all our gear next to the fluxgate compass was the 12v dinghy pump, bristling with magnets... this may well explain in. En route to our next destination I'll see if it's works. Fingers crossed!

 

[MagicalArmchair]

There was our dinghy pump motor near the flux gate... plus I had wired the pancake motor up the wrong way.

Stupidly I had assumed I could only test the autopilot whilst underway and we had a heading over ground - but it’s not working off that of course, it’s working from the compass.