Bewildered by Lewmar windlass

[Plevier]

Dismantled this windlass (Pro 1000) expecting to find a stripped gear. Instead it's the spindle of a compound gear that has sheared. If you look at the pic from left to right, the pieces that stack on the spindle are:
first there is a plain hardened bush that runs in a needle roller bearing in the casing
then a hardened thrust washer
then the small gear is internally threaded and screws onto the spindle
then there is a needle roller thrust washer sandwiched between two washers
then the large gear, which is locked to the spindle by two dowels (used as keys not as pins)
then a nut (that goes inside a boss on the right of the large gear that runs in a needle roller bearing in the casing)

So why is it made like this? The small gear can only move on the spindle by however much slack there is in initial assembly. In the driving direction it screws down onto the plain thrust washer and locks solid; if torque was applied in the reverse direction it would screw up against the needle roller thrust washer to the large gear and lock solid.

I thought at first this was a slipping drive for if you are winding the windlass up with a ratchet spanner if the motor has failed but it isn't, it can't slip.

Can anyone see a purpose in this complex and vulnerable assembly? Why isn't it made as a one piece compound gear, like the other one in the drive train?

Now I have to try and get a spare - wonder if Lewmar will supply the spindle or only sell the whole assembled gear?

 

[cobolt]

Because it acts as a one-way clutch.

If you contact info@lewmar.com, stating the serial number of your unit, the team will be able to advise of the replacement part number.

 

[Plevier]

Because it acts as a one-way clutch.

If you contact info@lewmar.com, stating the serial number of your unit, the team will be able to advise of the replacement part number.

Please explain how it can act as a one way clutch.
Did you read the description of how it is assembled?
With the large gear keyed to the shaft and the small gear on a screw thread on the shaft, how can it slip? I'm sure it can't.

 

[West Coast]

If you look on youtube, some very useful info as to how this winch works, how to strip and rebuild it.

 

[Plevier]

If you look on youtube, some very useful info as to how this winch works, how to strip and rebuild it.

Thanks!
Understood now, it interacts with a locking needle roller bearing in the housing. I hadn't realised that was one way not a normal bearing.

 

[prv]

Please explain how it can act as a one way clutch.
Did you read the description of how it is assembled?
With the large gear keyed to the shaft and the small gear on a screw thread on the shaft, how can it slip? I'm sure it can't.

The two gears don't slip relative to each other.

What happens is that the small gear moves outwards on the thread, and the part you refer to as "plain hardened bush" gets clamped between the gear and the head of the spindle, thus becoming locked together with the gears. The "needle roller bearing in the casing" is in fact a special one-way bearing (no idea how that works) and so the whole assembly can now only turn one way (chain upwards). This prevents the chain running out when the power to the motor is turned off (all the gearing is reversible and a turned off electric motor will spin freely, so without this mechanism the chain would not be held.)

To lower, the motor turns the other way a little, the small gear moves back down the thread, and the spindle is unlocked from the "plain hardened bush". The latter is still unable to turn in a downwards direction due to the one-way bearing, but that's ok as the spindle now turns within the bush. I don't know whether the idea is that the chain now falls under gravity with the motor freewheeling (until you apply a pulse of wind-in to lock it up) or whether there's enough friction etc that it needs to be motored down.

Apparently the one-way bearing is prone to corrosion and losing its one-way properties.

Pete

 

[vyv_cox]

Thanks!
Understood now, it interacts with a locking needle roller bearing in the housing. I hadn't realised that was one way not a normal bearing.

My Seawolf is similar, what looks like a needle roller bearing is a sprag clutch. Simply Bearings stock them and the similar needle roller bearings, I've had excellent service from them.

 

[Plevier]

The one way bearing/clutch is fine.
The gear spindle has failed in torsion there is no other damage and no corrosion.
Just hope Lewmar will supply, it looks uneconomic to make a one off.

 

[KellysEye]

You will find the parts diagram here: http://www.lewmar.com/cms\assets\1\Literature/B10490 Iss2 Pro Series-Fish_English.pdf

 

[Plevier]

Thanks, unfortunately that only shows the fully assembled compound gear as an item and going by US websites it's about £100 - I hope I can get just the shaft as everything else is perfect.

 

[KellysEye]

>I hope I can get just the shaft as everything else is perfect.

I've never come across a marine that doesn't sell individual parts, just call Lewmar.