Magnetic Coupling or shaft seals?

[froggyman]

The new MATE competition rules this year force us to inclose any exposed motors (i.e. a brushless motor), and as a result we need a way sealing our motor in an enclosure. Currently we are looking at something involving PVC to house the motor and ESC. Does anyone here have any experience with either magnetic coupling or shaft seals that might be able to point us in the right direction to go with this?

[martinw]

Both have their benefits and drawbacks, as in any engineering path/choice.

I personally went for a shaft seal.

http://www.martin-wareham.blogspot.co.uk/

But you'll probably need to do a bit of CNC machining (as I have had to do), whereas possibly with a magnetic coupling you might just get away with just a lathe ...... maybe

I'm no expert on the magnetic couplings.

Martin

[froggyman]

Where did you get your shaft seals from? I'm finding it hard to find a 5mm shaft seal.

[bikerbones1968]

Magnetic couplings and water tight enclosures for your motors are far superior by sheer design to any shaft seal. Or you can uses very inexpensive brushless motors run completley submerged and when or I should say if they fail just replace it.

[froggyman]

Magnetic couplings are also more difficult to work with...

Now, if we had an unlimited budget (or at least larger one...) and more time on our hands we would definitely go with magnetic couplings. However, we don't and we only need to go 19feet down for 10-15 minutes at a time.

[bikerbones1968]

Go with brushless and do not worry about water proofing. Take a look at the Open ROV web site.

http://openrov.com/

[martinw]

The new MATE competition rules this year force us to inclose any exposed motors

Have they given any reason why?

Martin

[sthone]

I believe they don't want any electrical connections (what so ever) exposed to the water because during the competitions they have divers in the pool. Even though it's only 12 volts and low amps it's still a safety concern.

As for small seals... I've had luck at my local power sports shop, there a variety of small oils seals that motorcycles use that will probably work for you.


-Steve

[bikerbones1968]

Steve didn't you have a DIY magnetic couplings thread posted somewhere? A person could actually butcher a few brushless motor for the neodyme magnets and make the couplings very easily and very cheap.

[sthone]

Yeah your probably talking about this monstrosity --- http://www.homebuiltrovs.com/magneticcoupler.html

It never got past the initial testing phase, it was started before Neodymium magnet were readily available (or even know to me) I do have a few other designs on paper (not online yet) that will be easier to make and should actually work I just haven't gotten around to trying them yet. (this might be the year though) I really want to combine a Brushless motor and magnetic coupler in one but that might be a ways down the road....

-Steve