Sorry still sending only half the message. Don't know why. Mountfleet Models once produced a Chariot kit. This is R & R Engineering's drive unit for it at £290. The picture of the unit might give you some ideas. Good luck .
Tim

Sorry Jacko, for some reason this website only sent half the message. Look at this website (it does exist ) http://www.rcsubs.co.uk/mountfleet-models-chariot-conversion-kit the unit costs£290 and was used to power a chariot kit produced by Mountfleet Models. I don't think the chariot kit is produced anymore. The pictures on the website might give you some ideas. You definitely need the contra rotating props otherwise the chariot might lean in the opposite direction to the prop.
Good luck,
Tim

Hi Jacko,
I've had a look at the Lego sub and the chariot MK1 diagram. Under normal circumstances a simple prop tube assembly glued into a sub would be sufficient as there isn't enough water pressure to force water into the body if it is surface running and the prop shaft is greased. However the chariot had contra rotating props. I can't imagine how to solve it. The Lego system is novel but I would worry that if it hit a submerged object in a pond the prop assembly could get dislodged. Don't let me discourage you as I'm sure there is an answer out there somewhere.
R & R engineering (http://www.rcsubs.co.uk/mountfleet-models-chariot-conversion-kit) did produce a unit at £290 to power the Mount fleet models (not in Production any more) Chariot kit. Maybe you could get some ides looking at the pictures.
Good luck, Tim

this will be to drive a chariot mk1 sub surface so none diving ??? if i can get time to do it with the other projects on the go, take a look at lego submarine's on youtube

Hi Jacko,
Can you expand a bit on why you need a magnetic drive? The reason I ask is that subs use a different method to keep water out of the waterproof cylinder whilst driving a propellor.
Best wishes Tim

Interesting project. Modern neodium magnets are much used to hold tops in place and are very powerful so may improve on Colins attempts some time ago.
You can buy magnetic clamps for lathes to hold work so I suspect a similar set up might work. You may have to set the magnet in place when the shaft was stationery but once attached these magnets are very difficult to separate.
Another project to consider should the present unfinished models allow.
Dave976

Hi Jacko, I have used a magnetic drive disc to propel a small model car experiment for Rolls Royce at college a few years back.
Main problem with this system is find strong enough magnets that are small enough.
Then there is the issue with the distance between the drive magnets and the driven disk, which didn't work well with any shielding between them.
We only managed about 20% efficiency. So the experiment was dropped.
Cheers Colin.