FEMM simulation showing COP 3 and 7

[broli]

In designing a practical version of this machine , much attention needs to be paid to the side bars . They need to be as light as possible consistant with performance .These bars need to move fast , and so heavy weight will cause problems with inertia and momentum . Either by calculation or experiment , their dimensions need to be minimised . A composite material , probably ferrite like in nature might serve . Is ferrite lighter than iron ? this would have the added benefit of eliminating eddy currents .

Yes this was on my mind, if we use cams there's a chance that the cores won't follow nicely at high speeds due to inertia. I thought of using springs to remedy this.

As for core material, I would use laminated iron, steel or even better silicon steel. These are easier to get or fabricate than large ferrite cores of the same dimensions. But indeed much heavier.

[lumen]

I would think a crankshaft would be best for both the magnets and the bars. Time them using elliptical gearing for the best overlap in operation. Something like a stirling engine but with magnets!
This way all parts are locked together for both push and pull operation and can recover all forces of every component.

[neptune]

Re core material .I have ofter thought that it would be possible to construct your own ferrite-like core . First you need a powder with magnetic properties , such as iron oxide , iron filings , or pulverised ferrite rods from old AM radios . Then you need a binding agent such as car body repair paste , epoxy resin , or possibly even plaster of Paris . Mix your materials , put it in a mould and allow to solidify . The resultant cores could be trimmed using glass paper if necessary . Going back to weight of cores , this is the same as using light weight valves of exotic materials in a fourstroke racing engine .

[broli]

Re core material .I have ofter thought that it would be possible to construct your own ferrite-like core . First you need a powder with magnetic properties , such as iron oxide , iron filings , or pulverised ferrite rods from old AM radios . Then you need a binding agent such as car body repair paste , epoxy resin , or possibly even plaster of Paris . Mix your materials , put it in a mould and allow to solidify . The resultant cores could be trimmed using glass paper if necessary . Going back to weight of cores , this is the same as using light weight valves of exotic materials in a fourstroke racing engine .

To be honest I think you'll find that process to be truly hell. You'll have to spend a lot of time and potentially find out it doesn't meet the needs. If possible I would buy it ready made and save a lot of effort, time and even money.

[phoneboy]

@ broli, thanks for the suggestion, I have to wrap my mind around it and I'll make some mods to the design. A suggestion for the core, form my design I intended to use three large c8 sheet magnets http://www.magnet4less.com/product_info.php?products_id=256 and heat them past their curie point.  In the course of reading about processing materials I came across microwave sintering, I don't know how well a microwave susceptor the magnets would be but if not you could surround them with magnetite powder (great susceptor) in a alumina brick surround, nuke them for while to demagnetize, and then grind them to shape.