Stowe Dataline Wind Sensor

[Houleaux]

The cups on the above stopped rotating so I took the unit down from the masthead and applied a little gentle encouragement to them. They would move a little way and then meet some gentle resistance - a bit like they were being wound against an elastic band. Anyway, a little more encouragement and the "elastic band" snapped, after which the cups rotated freely. I re-fitted the sensor and had a working wind speed indicator again. Great.

But... Since then the wind direction can't be relied upon. I can reset the mast offset so that 12 o'clock is head to wind but, within a few minutes, it's wandered off again and head to wind might be, for example, 10 past.

Does anyone have any idea what might be wrong? I'll just ignore it rather than fork out for a new one (c. £395!) but it would be nice to have it working properly.

Also, the wind vane just lifts out of the unit. Is that right?

As always, any help would be much appreciated.

 

[Norman_E]

I have never seen the internals of the Stowe Dataline unit, but some time ago I posted a piece about repairing a VDO Siemens Mast Head Unit, and included the photo below. The works that deal with speed and direction are at opposite ends of the circuit board, and that is likely to be true for pretty much any make. It follows that unless your actions freeing up the anemometer cups have caused the circuit board to come loose inside the unit and move about by a few degrees it is fairly unlikely that you caused the problem. In the photo, the detached part to the right is the bearing holder for the windvane, with the rotating magnet and coil that work inside the coil fitted to the end of the circuit board to generate the direction signal. Either your problem is an electronic one, or what has happened is that when you handled the unit the wind vane became loose on its shaft. If the latter it will be an easy fix.

 

[donm]

If it's anything like mine (which is probably older) there is a small cap on top of the vane. Prise this off, and there should be a small nut holding the vane in place?

 

[Houleaux]

Ah!

So it seems that the vane itself is simply loose on its shaft.

In fact, I don't think it's attached to the shaft at all as I can simply lift it away from the unit (I'm surprised it hasn't blown away!). I'm probably only getting any readings at the display by virtue of friction between the vane and its shaft.

I'd better get up there and see if mine has the cap and nut that donm's referred to.

Thanks to you both for your help.

 

[pvb]

As donm has said, there should be a washer and a nut holding the windvane on. If that's missing, you need to replace it or you run the risk of losing it!

NormanE theory that the windvane is loose on its shaft isn't correct - the shaft is fixed to the body, the windvane should spin freely on the shaft and has a magnet inside it, and there are sealed sensors inside the body which determine the direction. Similarly, the circuit board is held in place by the small oiling nipple on the front of the body, and you can't have moved it by turning the wind cups, as there's no mechanical connection.

I suspect the bearings are worn/damaged, and that forcing the wind cups to turn has freed these up (but probably only temporarily).

As for the inaccurate wind direction, you need to check that the circular magnet in the wind vane is securely fixed in place, as if this turns the direction will drift. Originally, it would have been glued in.

 

[Houleaux]

As donm has said, there should be a washer and a nut holding the windvane on. If that's missing, you need to replace it or you run the risk of losing it!

NormanE theory that the windvane is loose on its shaft isn't correct - the shaft is fixed to the body, the windvane should spin freely on the shaft and has a magnet inside it, and there are sealed sensors inside the body which determine the direction. Similarly, the circuit board is held in place by the small oiling nipple on the front of the body, and you can't have moved it by turning the wind cups, as there's no mechanical connection.

I suspect the bearings are worn/damaged, and that forcing the wind cups to turn has freed these up (but probably only temporarily).

As for the inaccurate wind direction, you need to check that the circular magnet in the wind vane is securely fixed in place, as if this turns the direction will drift. Originally, it would have been glued in.

It sounds from what you've said that the Stowe is a different design to the VDO that Norman_E has pictured (he said that he'd not seen the internals of the Stowe unt), so thanks for the additional description / tips.

As for the bearings, I suspect that I've been lucky and that there was just something causing an obstruction that I managed to dislodge. What I didn't say in my original post was that I'd actually freed them up some months ago and they're still going well!

 

[Norman_E]

If the bearings are OK you are lucky. I did free up my VDO anemometer bearings once or twice, but they became sticky again. The fortunate thing is that they were just standard sized stainless ball races, replaced for £3.50 the pair!

 

[pvb]

The fortunate thing is that they were just standard sized stainless ball races, replaced for £3.50 the pair!

I think all these wind units use standard off-the-shelf bearings, it's not worth having unique sizes made for such low production runs.

 

[Houleaux]

Not being all that quick at getting around to things, I've just retrieved the sensor from the masthead.

I've prised off the cap as was suggested and the nut is in place on the shaft. The trouble is, the shaft just pulls out of the main body, allowing the wind direction vane to be lifted off.

The shaft is about 3/4 of an inch long and has what appear to be tiny splines on the end furthest from the vane. It can be turned when inserted in the main body of the sensor. There doesn't seem to be anything (or any way of) holding it securely in the body.

Does anyone know what these things look like inside or how to take them apart?

Cheers,

Rob

 

[alteredoutlook]

as pvb has said, you can get to the internals by undoing the oiling screw - I think you just use a small allen key - this allows the wind speed cups to be removed and potentiometer and circuit boards - you should then be able to get to the wind direction internals.

Be careful you don't pull any wires free - there isn't too much space in there!

The following voltages should exist at each wind angle ( if 12 volt is supplied to red, -ve to black)

Angle Green White Yellow
0 0 9.0 9.0
30 1.6 6.0 10.4
60 3.0 3.0 12
90 6.0 1.6 10.4
120 9.0 0 9.0
150 10.4 1.6 6.0
180 12 3.0 3.0
210 10.4 6.0 1.6
240 9.0 9.0 0
270 6.0 10.4 1.6
300 3.0 12 3.0
330 1.6 10.4 6.0

If I recall correctly the dataline wind instrument is no different from the older stowe wind instruments. occasionally these can be had at a boat jumble - (although they may be faulty themselves!).

 

[Boathook]

I've never taken mine apart, but on the old models the cups were held in place by a small nipple with a rubber cap on the front that was also the place to put oil once a season. The wind direction sounds like knackered electronics, though the fact that the splined shaft pulls out does not help either.

 

[Houleaux]

Thanks for the information. I think on reflection I'll call in the professionals rather than risk doing further damage!

 

[pvb]

The shaft is probably just glued in to the body.
.

 

[alteredoutlook]

Thanks for the information. I think on reflection I'll call in the professionals rather than risk doing further damage!

I've taken mine apart - its not that difficult - honest - but it is fiddly!

The is a complete unit going on fleabay in 4 hours time - http://www.ebay.co.uk/itm/Stowe-Mas...tEquipment_Accessories_SM&hash=item2329948cbb

you could cannibalise the best bits to make yours work again?

 

[Plevier]

If you look at https://picasaweb.google.com/113567095843010399028/Stowe you will see a very old Stowe MHU I took apart.
This is from a Navigator series but I believe the Dataline one is the same except for the direction transducer itself. In mine it's a potentiometer, in the later ones it's Hall effect sensors.
The wind vane shaft is fixed into a disc magnet which is very close to - but doesn't touch - the disc magnet you can see at the left side of the pictures on top of the direction transducer holder so it drives without contact. If your shaft comes out of the top of the MHU it must have come unstuck from the magnet, you might just need to epoxy it back in and re-insert from below.
The direction transducer holder is held in the MHU by a very small socket head grub screw through the front, just above the oil nipple that secures the speed transducer holder into the MHU.
Everything comes out downwards when those two screws are removed.

Edit - I made the assumption the two magnets shouldn't touch, on thinking about it now, maybe they are supposed to stick together? Seems an involved way of making a coupling. You'd have to experiment.

 

[pvb]

The wind vane shaft is fixed into a disc magnet which is very close to - but doesn't touch - the disc magnet you can see at the left side of the pictures on top of the direction transducer holder so it drives without contact. If your shaft comes out of the top of the MHU it must have come unstuck from the magnet, you might just need to epoxy it back in and re-insert from below.

The Dataline unit is different. The shaft around which the vane rotates is fixed. The vane has an insert with 2 small magnets in it, whose position is detected by hall effect sensors inside the body of the transducer. If the OP's shaft has come loose, it probably just needs aralditing into place, being careful obviously to avoid excessive glue which might prevent the vane spinning freely.
.

 

[Plevier]

The Dataline unit is different. The shaft around which the vane rotates is fixed. The vane has an insert with 2 small magnets in it, whose position is detected by hall effect sensors inside the body of the transducer. If the OP's shaft has come loose, it probably just needs aralditing into place, being careful obviously to avoid excessive glue which might prevent the vane spinning freely.

Sorry, misinformed then!
No way of telling which type is on ebay AFAICS.

 

[Houleaux]

So....

If I araldited the shaft back in place, is it likely that the original problem (the wandering wind direction) would be solved?

Nothing else appears loose at the wind vane end.

As you can probably tell, I'm struggling to get my head around this!

Thanks all.

 

[pvb]

If I araldited the shaft back in place, is it likely that the original problem (the wandering wind direction) would be solved?

No. The sensing of the wind direction is purely a matter of magnets rotating around the hall effect sensors. You might check that the magnets are in place and firmly fixed in the vane head.

 

[Houleaux]

No. The sensing of the wind direction is purely a matter of magnets rotating around the hall effect sensors. You might check that the magnets are in place and firmly fixed in the vane head.

Thanks pvb. I thought a quick fix with araldite was too good to be true!

The two magnets are present and securely fastened, so I think there must be an internal fault - perhaps linked in some way to the peculiar feel (as if something snapped) when freeing up the anenometer cups themselves (this was when the problem started).

Off to the repairers with it then.

Thanks once again for all the help.