MPC brushes are different then postwar. Can they interchange?

[Fordiesel69]

On my postwar motors, the brush is one diameter all the way thru.  The MPC motor I have uses the same diameter up top, but the bottom that touches the commutator is smaller diameter.  Can I use the all one diameter brushes or is there a reason they reduced it at the end?

[lionelsoni]

I don't have any MPC locomotives; so I can't say absolutely that their brushes aren't shaped that way.  But I can't see any point (so to speak) to reducing the diameter at the commutator end, since the tip will wear off soon anyway.  The Lionel brushes I'm familiar with are of two types.  One is a right circular cylinder with a groove in one end for the straight brush spring.  The other resembles yours, but with the necked-down part on the other end, to mate with a coil brush spring.  Is it possible that someone replaced your brushes with the incorrect type, and put them in backwards as well?

[Fordiesel69]

Another hour or so will tell the tale.  They are almost worn to its bigger diameter.  I was going to buy some repro brushes off ebay and was just curious.  I will still try them and see what happens.   

[sir james I]

I/ve used those brushse for years and have just always put them in upside down. They are soft so you can cut a slot in the narrow end to hold the spring in place.

[cwburfle]

Fordiesel69

On my postwar motors, the brush is one diameter all the way thru.  The MPC motor I have uses the same diameter up top, but the bottom that touches the commutator is smaller diameter.  Can I use the all one diameter brushes or is there a reason they reduced it at the end?

I can confirm that those are original MPC brushes. Sometimes there is a slot cut into the wide end for the brush spring, sometimes not.
I don't know Lionel's reason for turning one end of the brush. I do know that the turned end will fit into a 2020M coiled brush spring, so these brushes can be used for that application (they are shorter than a 2020M brush, but that doesn't seem to matter).
So far, I haven't noticed any difference, or had any problems with using uniform diameter brushes in MPC motors that originally had these brushes.
When I use these brushes (the ones without any slots) in postwar locomotives, I cut my own slot in the narrow end, and put the wider end against the commutator.