Does anyone know where to get or does anyone have a set of plans or schematics for a zapper ?these dont look difficult to build for anyone with half a brain !! yet people are charging hundreds if not thousnds of dollars for them .They only work on basic physics principles its just a question of getting the number of winds in the electro magnet right

There are things that you need to do to make the zapper actually work properly. The copper and machine work for the magnet cores and motor plug will be in the $200 range so some of the lower priced zappers are pretty reasonable.

If a zapper won't completely saturate a set of magnets it's not powerful enough. Buyer beware. Ask for measurements on the strength of zapped motors compared to new and used ones.