Magnetic Coupling or shaft seals?

[seantaylor]

Here are the couplings I've been working on.

Made these up with a mini-lathe, and a mill to drill the holes to hold the magnets.

The magnets used are 8mmx8mm arranged with the North/South polls in alternative directions. with a 3mm gap between the couplings there is more than enough holding force for the motors I've been testing with.

[rossrov]

Hi Folks.

Made a mag coupled unit a few months back. Decided against making another 2 or 3 thinking that oil-filled with a seal may be simpler to make, plus have some other benefits, so oil-filled is the current plan. Seeing I went to the trouble of making the one mag unit however, I thought I'd post some details.

The pressure bulkhead is a piece of FR4 circuit board with a thrust bushing stuck to the centre. The cable entry consists of solid copper wire potted in epoxy. Have to be quick soldering so epoxy doesn't melt. Motor is sub 800Kva, about 200 (claimed) watts max, though in practice would have been running a lot lower. Prop is low-pitch model aircraft type cut down a bit.

I am fortunate (?) enough to own a lathe, so was able to turn the other parts. The magnet wheels were drilled using a crude indexing head, made for the purpose from scrap PVC sheet, and a small drill press.

Tested in water in an Esky after hooking up to rest of gear. Power of the magnet/motor combination was easily as much as the project required required, then the magnets "slipping" when more power applied. Handy feature to prevent damage should anything get stuck in the prop.

Cheers,

Ross