Is it my paddlewheel?

[Miker]

My Autohelm ST50 Plus log showed a zero speed on the last sail of last season. During the winter I took the paddlewheel off and cleaned it. Since launching the speed shown is still zero. I've just checked the paddlewheel and it spins around freely. The paddlewheel has been in for eight years now so is due to be changed according to the handbook. Could this be the cause of the zero reading?

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[oldharry]

The paddlewheel has a small magnet embedded in it, if this falls out, then the log does not work. check to see if it is still present with a pin or similar

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[broadcaster]

Hi,

I think there is normally a magnet on the wheel which passes a sensor, could it have fallen out.

Andy

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[billmacfarlane]

It happened to mine when it was 10 years old and yes it was the paddlewheel. You'll probably find that a replacement isn't the same size and you'll need a new skin fitting as well.

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[Miker]

Thanks. I'll pop down to the boat tomorrow and have a close look. When I cleaned the paddlewheel, I don't remember seeing anything like a magnet.

I don't like the sound of a new skin fitting which will have to wait until the lift out next winter - if that's necessary, I'll make do with the GPS for speed/distance.

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[tcm]

um, apart from the magnet fing, it has to face forward in line with the lickle arrow and then screw down the ring thingy. You knew this of course.

Otherwise it may possibly be "knackered". So, soddit.

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[jerryat]

Hi Mike!

Yep, agree with the majority. Probably the magnet, a tiny little thing embedded in the end of one of the vanes. I don't see why you couldn't fit another bit of magnetic material back in if yours is missing, it's worth a try anyway. I assume you've checked the lead back to the instrument head and all is ok there.

Autohelm may be able to provide an exact replacement impeller, or at least the magnetic bit. Might be worth a bit of grovelling with their technical repair people!

Good luck anyway.

Good sailing!

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[jorinda]

Raytheon can supply new paddle wheel if it the magnet which has gone, or suggest you wait till you lift out again and fit (I think its an ST 60 transducer) with a new housing with the flap valve, stops a lot of water getting in when checking the paddle wheel.

Regards Bob.

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[webcraft]

My NASA Target log has two magnets in the paddlewheel . . . one was knackered last year, so we had to multiply the speed by two. Now we have a new paddlewheel - sheer luxury, no difficult sums to do.

- Nick



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[Miker]

Yes, it was my first thought that I had fitted the paddlewheel upside down, or something like that. But NO, I had fitted it correctly.

I have sent an Email to Airmar, a name on the leaflet which came with the thingy.

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[MainlySteam]

Be careful regarding expecting to find the magnet bits as is being advised.

Have never dismantled an Autohelm one to be sure, but assuming that it is the plastic version, in the bottom of the transducer above the paddle wheel there is an about 4 mm dia hole in the bottom of which is a metal component. I believe that this is the temperature sensor - I am not sure of that, but have just assumed so as I recall seeing in some of Autohelm's service material at some time that if the temperature function does not work (which it frequently doesn't) then if that metal component has changed to some colour then water leakage into the temperature sensor has occured. It would also seem sensible that the temperature sensor be in direct contact with the sea for fast response to temperature change. I would be careful about poking it with anything.

If that is correct, then the sensor(s) responding to the paddlewheel rotation is inside the body somewhere and I doubt that it can be physically checked and certainly will not have fallen out.

Seems to me you have a problem in the transducer, the cabling (including the connectors) or the Speed instrument. The transducer can be easily checked if you can find out the nature of and check the presence of the pulsed signal from it. Perhaps someone can advise what to specifically expect on the cable for such a check to be made.

{Edit: Just caught up with your Airmar leaflet comment - maybe you do not have the Autohelm transducer. Try Raymarine for help regarding Autohelm equipment}

John

<hr width=100% size=1><P ID="edit"><FONT SIZE=-1>Edited by MainlySteam on 06/05/2004 01:30 (server time).</FONT></P>

 

[Gordonmc]

Miker,

Can you let us know what Airmar have to say, please.
I bought an ST 50 specifically because it it compatible with the Airmar triducer which was with the boat when I bought it. Unfortunately the triducer cables had been cut at the instrument end, so I had to cobble up the connections to the instrument tails.
I don't want to change the impeller as it would mean cutting a new hole in the hull (wood). If you can get a replacement for an old impeller I might go the same route.


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[William_H]

I may be stating the obvious but if you remove the paddle wheel while still connected electrically you can spin it and should get several knots indicated. My experience has been with an old Smiths paddle wheel. The magnet is about 1/16 inch diameter like a nail right through the paddle wheel with the ends exposed. There was always a sign of rust on the ends. In that case the wheel is removed by loosening the screws which are the needle bearings. Possibly the Autohelm is nothing like that. Anyway the original design had a reed magnetic switch to sense the magnet passing. I replaced this with a Hall effect device and a transistor amplifier This worked well however the saltwater always found its way into the encapsulation of the Hall effect device. This coupled with the constant fouling problem ( I only fitted the transducer when sailing)( yes water everywhere) led me to throw the whole system away. A GPS is cheaper and better although not as quick on the speed update. regards will

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[Miker]

I'm getting a bit confused now, but no more than normal. The equipment came with the boat and I'm going with documentation I was given. The display certainly is an ST50 Tridata and the transducer looks exactly like the Airmar documentation, including the picture of the Airmar paddlewheel and part no. Airmar in US replied within 24 hours (pretty good from my usual experience) and said that the paddlewheel should be changed. They gave me an address of a supplier, Gem Electronics, also in US, and their telephone no. I have just found them on the WEB and Emailed them.

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[Miker]

I'm getting a bit confused now, but no more than normal. The equipment came with the boat and I'm going with documentation I was given. The display certainly is an ST50 Tridata and the transducer looks exactly like the Airmar documentation, including the picture of the Airmar paddlewheel and part no. Airmar in US replied within 24 hours (pretty good from my usual experience) and said that the paddlewheel should be changed. They gave me an address of a supplier, Gem Electronics, also in US, and their telephone no. I have just found them on the WEB and Emailed them.

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[Miker]

Been to the boat today and co-opted the crew of the boat next door to watch the display while I spun the paddlewheel. I was unable to do it before as it is difficult to be in two places at once. To my surprise they said that the display registered over 2 knots both backwards and forwards. So the paddlewheel is in again and I await the next sail tomorrow with interest. I'm wondering whether the sling around the boat when it was launched somehow disturbed the paddlewheel. Anyway fingers crossed!

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[Miker]

It was the paddlewheel

A belated thankyou for all the advice. Eventually I telephoned Gem Electronics in USA and got a replacement paddlewheel for the ST60 transducer. I went out yesterday for the first time with it fitted and it worked like a dream.

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[claymore]

Mike - in my experience the paddlewheel is the principal herald for a general downturn in boat technology so best cut to the quick and get a new boat.
How's things?

<hr width=100% size=1><font color=purple>regards
Claymore<font color=purple>
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[Miker]

John.

Good to read that you're still in form. My wife would be quite happy for me to sell the boat but not to buy another. I'm trying to get in some sailing but at the moment it is just Piel Island and back.

Mike

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