Sidepower Bowthruster Solenoid - repairing burnt contacts

[TonyS]

Over the last 10 years I have twice had to clean the burnt contacts in the solenoid when one direction stopped working. Should this be necessary or is there a way of preventing them burning. Also the burn was pretty severe on one set of contacts and there is now very little of the contact material left after filing it smooth. Does anyone know if next time I can build the contact up again with solder?

 

[David2452]

Perhaps after 10 years of faithful service it may be time to treat it to a new solenoid, or at least see if you can source some new contacts.

 

[Phoenix of Hamble]

It is possible to pair up solenoids to share the load (and reduce the risk of welding them shut!).... probably not worth it, but if you are interested, here's a link to just about every variant of solenoid combinations you could ever dream of!

http://www.wms1.com/wms1/InfoDrawings.html

 

[grumpy_o_g]

Does anyone know if next time I can build the contact up again with solder?

That's a definite no I'm afraid. Apart from being physically too soft the solder will literally vapourise and splatter everywhere as soon as you get the slightest arcing. David has given you the options I'm afraid - new contacts or even a new solenoid. If you do just replace the contacts make sure they are correctly aligned and the solenoid is moving freely.

 

[TonyS]

That's a definite no I'm afraid. Apart from being physically too soft the solder will literally vapourise and splatter everywhere as soon as you get the slightest arcing. David has given you the options I'm afraid - new contacts or even a new solenoid. If you do just replace the contacts make sure they are correctly aligned and the solenoid is moving freely.

Thanks for the replies. I am trying to avoid a new solenoid as they are about £300. What are the contacts made of then? It looks like solder and is very soft. Anyway after the work yesterday the bowthruster worked today to get out of Ile d'Yeu and into Les Sables.
Another point is the contacts are held in place by an undersized serrated washer that is pushed onto the terminal shaft and the barbs hold it there. They cannot be removed without breaking and I haven't any replacements. However it looks as if there are 2 sets of contacts of which only one set are used. Certainly there is no sign of contact on the one side. If I had some more serrated washers......

 

[lw395]

I suspect a starter motor solenoid might do the job.
Perhaps a motorbike one, as they are separate from the motor?
Or some serious MOSFETs?

I bodged one fairly successfully on a Moto Guzzi years ago by soldering a piece of copper on to rebuild the contacts.
It lasted some years of daily use.
(The Guzzi has a car type starter to avoid thread drift.)

 

[Phoenix of Hamble]

Starter motor solenoid is almost certainly not a good idea, as it won't be rated for continous current for the durations that a bow thruster can be used.

 

[TonyS]

Starter motor solenoid is almost certainly not a good idea, as it won't be rated for continous current for the durations that a bow thruster can be used.

Sorry that this thread is disjointed but I am on the boat and on the move. We have now arrived in La Rochelle. It is an interesting point as to how much time a bow thruster is used. I have the 55S which on 12V draws 350 Amps and is rated for 3 mins continuous use. I generally use it for less than 5 secs and at the most 10. Which does the most damage to the contacts several short 2 sec bursts or 10 secs continuous.

 

[TonyS]

I suspect a starter motor solenoid might do the job.
Perhaps a motorbike one, as they are separate from the motor?
Or some serious MOSFETs?

I bodged one fairly successfully on a Moto Guzzi years ago by soldering a piece of copper on to rebuild the contacts.
It lasted some years of daily use.
(The Guzzi has a car type starter to avoid thread drift.)

Can I ask if you used normal solder or a high melting point type when you rebuilt the contact. I think I will have to do the same but, in future, will refurbish before the start of each cruise to France.