SWITCHING POLARITY USING ROLLER COMMUTATOR SWITCHING:
To switch polarity of current through a motor coil using roller-commutators (as an example of a swtiching system), you can use two timing discs on the shaft to do this, as shown here:
Note the inner three-roller timing disc and the outer three-roller timing disc...and note the single brush shown here contacts with the inner timing disc rollers only:
The outer sleeve and brush is shown installed here, so that now a 2nd brush can also contact the outer timing disc rollers...so now both the inner and outer timing disc sleeve's timing is independently adjustable:
Below are two photos of another roller-commutator set-up which can handle high voltages and high speeds.
The contacts now are of stainless steel wire against 3 rollers.
There are two contact-arms hitting against three rollers on a disc, for 6 pulses per revolution. This is one way way the polarity of the pulse can be alternated into motor-coils - if for example this triggered two relays sending current into the motor coils and there are two seperate power sources for each relay:
