Introduction to the SFT

[Classic]

You may want to use some plywood instead of plastic or just wood. For sliding rods, find and chop saw or anything that use sliding rods and adapt it.

Also, I can see your iron disc is not slotted as it should to switch magnetic flux.

For some frictionless you can use some superglue and graphite ... look up for "Lidmotor" youtube channel.

[Ufopolitics]

Well, the SFT-Mk5 is all assembled but sadly it is not rigid enough. I'm hoping that if I beef up the supports for the bellcranks that might make it stiff enough to work. The problem at the moment is that the magnets stick to the rotor and the mechanism is supposed to limit their travel so that can't happen but there is too much movement in the bellcrank mounts and that lets the magnets get too close to the rotor. Oh well, iterative process.

Hello Prajna,

Sorry about that!

But you do NOT need to make a Rotor that is a fully steel plate constructed.
You can make a thicker rotor in plastic, that can have stiffer and wider bearings and bolt on the metal strips to it.
Actually, a full steel rotor will deviate the magnetic fields where they are not supposed to expand to.

For sure a thin metal plate rotor would wobble under the magnetic attraction.

Cheers 

Ufopolitics 

[Prajna]

Hello Prajna,

Sorry about that!

But you do NOT need to make a Rotor that is a fully steel plate constructed.
You can make a thicker rotor in plastic, that can have stiffer and wider bearings and bolt on the metal strips to it.
Actually, a full steel rotor will deviate the magnetic fields where they are not supposed to expand to.

For sure a thin metal plate rotor would wobble under the magnetic attraction.

Cheers

Ufopolitics

Yes. In fact my first design was like that but I wanted easy construction with this model. It is just for testing the principle and to try different configurations of rotor. I imagine the rotor will develop considerably but for now the first priority is just to prove the principle.

regards,
Prajna

[Prajna]

Just an update. I've just finished the design for Mk-7 (Mk-6 used gearing to sync the magnets and the 3D printer I have access to just isn't up to the accuracy required for printing gears that mesh well). I will be printing parts to test fit but the design requires bearings, which I have ordered but they won't arrive until the middle of August. I'll get this design up on my github soon in case anyone fancies to do a repo. Meanwhile I will be doing some calibrating on the printer to try to get it more accurate and I'll be working on Mk-8, which will be a combination of this principle and the Luling magnetic motor that @ufopolitics helpfully posted earlier in this thread.

[Prajna]

So, while I wait for bits to build Mk7 I've been pondering designing a rotary machine based on switching flux using a ferromagnetic sheet between opposed poles, i.e based on this same principle.

Take a look at the following (very rough) sketch:



Imagine two magnets with their poles opposed (the rectangles in the image), they are constrained to run in sinusoidal grooved tracks and in line with each other. When they are at point A they encounter a sheet of iron in the gap and will be attracted to it, imposing a vector force on the grooves, that are converging, making the track displace to the left (or the magnets will displace to the right.) When they get to point R there is no longer the iron sheet between them and they will repel, imposing an opposite vector force on the track, which is now diverging, and causing them to continue to displace the track to the left (or the  magnets will displace to the right - either we constrain the track and the magnets move to the right or we constrain the magnets and the track will move to the left).

If this idea works on a linear basis then we can wrap that linear arrangement around a cylinder, producing rotary motion.

Thoughts?