I posted a thread a while ago about a new type of magnetic transmission. Since then I have been intrigued by the idea of non contact magnetic gears. I decided to make a test stand that I can use to try out some of these configurations.
In the first photo the pinion to driven gear spacing is set large to better show the parts. Normally it would run with the minimum possible gap for maximum torque. Several thing about this have surprised me. There is very little cogging action in the drive. The torque transmission capability is considerable. Below the slip torque the drive is positive, no slip and quite stiff.
The ratio is set by the number of poles, not the relative diameters of the pinion and driven gear. In this demo there are 2 poles (N-S) on the pinion and 14 on the driven gear. This gives a ratio of 7 to 1. The pinion makes one complete revolution as the driven gear moves the distance between magnets on it's perimeter.
While the best name for this sort of drive seems to be "magnetic gears" there is little real similarity to purely mechanical gears with meshing teeth other than the obvious visual aspect. Ratio is independent of diameter. Torque is independent of ratio.
This is a first effort and I am surprised at how well it works. There does seem to be something analogous to a pitch circle and it seems to be somewhere in space past the OD of each gear. This pair of gears operates much more smoothly with a large gap than it does with a very small gap. It may be important what the spacing is of the magnets on the driven gear, more experiment is called for. Also, these "gears" have no pole pieces to concentrate the fields. One thing is already obvious, the driven gear may be placed in any planar alignment up to and including a right angle drive. More experiments...
I used Lexan for the test stand to minimize unwanted magnetic interaction and because it makes it much easier to see what is going on.
To really appreciate how this works you need to watch the short video. It shows the gears operating at speed and at a very slow crawl so you can see the relationship between the pinion and driven gear rotation.