replacing brushes

[irontooth]

I was looking at the brushes on my American Flyer and Lionel engines and am trying to decide when a brush is  pass time to replace. When do all of you decide what is to short for brush lenght??

Thanks

David

[David1005]

I have seen a reference that indicated that when a brush is 85% of the original length it should be replaced. 

[Nationwidelines]

You say Lionel and American Flyer engines....

Are you referring to pre WWII American Flyer O and Standard Gauge engines?  If so replace the brushes.  I say this because the Prewar American Flyer brushes are comprised of small copper wires that are pressed together to form a brush.  These brushes are inferior to the graphite brushes that are currently available and will cause excessive wear to the armature plates.  So whenever I get a prewar engine to tune up, I always replace the brushes, regardless of how worn they are. 

When replacing the brushes, you should also replace the springs, as over time they lose their compression strength.

[cwburfle]

When replacing the brushes, you should also replace the springs, as over time they lose their compression strength.

I don't replace brush springs unless absolutely necessary because I don't trust the reproduction springs that are available today. Often they seem to have the wrong tension.

When should brushes be replaced?

1 - if they are wet with oil or dirty with grease.

2 - Otherwise, I don't have a firm rule. If I am doing a repair for someone else, I always replace the brushes. (they are too inexpensive to risk the engine coming back over fouled brushes) If I am servicing a motor on my own equipment which was just acquired used, I almost always put in a fresh pair of brushes. Subsequent service rarely requires brush replacement. 

If the brush is too short to be held straight in its holder without wiggling, then replace it. Otherwise it should be fine.

I did a little Goggle search on "when should motor brushes be replaced". There were all sorts of answers and no agreement.

Be aware that some of the brushes available today are simply no good. Get your brushes from a reputable Lionel or American Flyer parts dealer.
I have a bunch of brushes purchased directly from Lionel that have too much resistance to use in Postwar or older modern era trains.

[irontooth]

What do you consider too much resistance in a brush for postwar and older modren era trains?

David

[cwburfle]

irontooth

What do you consider too much resistance in a brush for postwar and older modren era trains?

Everything I've written below is my own opinion, based on my years of tinkering and what I've read. I have no formal education on the subject, other than some college level general physics.

There is a discussion pertaining to this issue on the other train board. I just looked up the thread by searching for the term "defective Brushes"

The original Postwar Lionel brushes I have measured run about .2 (two tenths) ohm.
The reproductions tend to be higher .4 (four tenths) ohm and up.

I am comfortable using the .4 ohm ones. They don't seem to be a problem.

My plan is to hold off on using any brushes with higher resistance as long as I can.

It's been a few years since I've restocked, I don't know what is out there today.

 

[irontooth]

Thanks for the info.

 

David