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Armature timing and Aftermarket timing fixtures.


Armature Timing - For simplicity's sake, think of the commutator as the "switching system" for turning the poles of the armature on and off in their function as electromagnets. "Armature timing" is the term used to describe the relationship, in degrees, of the segments of the commutator to the stacks or poles of the arm. As you can see in Figure 1, below, armature timing is expressed in degrees of advance from a base of zero at the nominal centerline of each stack leg. Looking at the com end of an armature, one with 0° of timing would have the leading edge of its com segment - or the trailing edge of its com slot(s) - lined up with the center of each stack leg. A common misconception is that the edge of the armature stack is used to determine armature timing. This is wrong, the stack edge has no bearing on armature timing at all. True timing is figured from the center of the stack leg (which is not visible in a finished armature).



The differences between one level of timing and another may appear slight, but slight is all it takes to make a major timing change at the com. Consider it this way: given a com diameter of .202", one degree of timing at the comm is approximately .00178" of its circumference (diameter * pi / 360). Put another way, a .5 mm pencil line is more than 11 "com degrees" wide or a common piece of computer paper .005 thick is 2.8 "com degrees" wide at the same diameter. The slots used in ProSlot comms are .014" wide, in other words the slot itself is 7.8 "com degrees" wide.
(see figure 2)








Special Thanks to:

Dan De Bella

Frank Eubel