Ron I agree about polyester, it is reasonable for jobs that are made from glass fibre in its own right and where adhesion to other things is not required.
It also works fairly well for stators considering the extreme temperature some are expecting it to stand. I have not had the slightest trouble with stators but as others have found, even if you cover the magnets completely the resin parts company from the steel plate and rust starts.
You may be right about epoxy but again the snag is finding the right ones,not all epoxies are good for this.
I have recently had to repair an epoxy potted bell hammer coil and expected major difficulty removing it from the cast iron housing, in fact it was brittle and was stuck little better than polyester and presented little trouble so obviously this type of potting epoxy would be useless.
I have used West system with great success on wood but I have only used it to stick windings on to an iron core, I have not used it in bulk as for a magnet rotor. It may be good for this.
It is definitely not capable of standing the temperatures of stators. Even 3M Scotch cast and similar electrical potting resins are only good for class B temperature rise.
They do stick extremely well but the cost would make one think twice about casting magnet rotors with it.
I think that gradually people will try different things and find what works and what doesn't. Data sheets don't always give a good idea, every product is perfect when you read the data sheet. If you use the material for a standard application this is no doubt true but when you use it for something odd then not always so.
For magnets, sticking them on is no problem, weather protection needs thought if you are in a damp climate.
For stators, if you want to push them to class H then vinyl ester is likely to be the best material, but I suspect that it's true rating is about class F.
Flux
