I have an AF300 engine and tender I just repaired with several new
parts I got from a vendor at the last local show. I ran new wires
from the tender to the engine, thoroughly cleaned and polished the
tender wheels and axle contacts, disassembled the E unit and cleaned
and gently wire brushed the E drum, inspected the contacts on the drum
for holes and springiness, and lubricated all moving parts.

I had the engine running very well and the E unit was operating
surprisingly well too, even on very low voltage. Then the engine just
stopped working. The E unit still rotated and buzzed but the motor
wouldn't turn. I tried giving the armature little pushes with
different E unit settings (as I didn't know when or if I was in
neutral at any particular time), but the motor was dead.

I disassembled the rear of the motor and removed the armature. I had
noted on my initial repair that the armature commutator was slightly
scored and somewhat blackened in a circular pattern where the brushes
rotate. I cleaned this up a bit with the Dremel prior to reassembly
but never removed all the scoring. During this second dis assembly I
gently wire brushed the commutator again and used 600 emmery on it for
a smooth finish. It is now pretty smooth. I also cleaned up both ends
of each brush and slightly stretched each spring to afford better
contact with the commutator. In addition I re soldered the three
armature wires to the commutator segments, as the solder looked a
little sparse.

I set the chassis up on test blocks and ran it at slow speed.
Initially it ran very smooth, however I could see a very slight arc
coming from one of the brushes. I have noticed this on many motors in
the past, and since it was so minor I didn't give it much thought. My
goal was to run the engine for a period of time at slow speed in order
to "seat" the brushes. After a period of time you could tell that the
motor was not running as smoothly as it did at the beginning of the
test. A small spray of silicone contact cleaner on the commutator
while it was running at slow speed would momentarily pick the RPM's up
and then they would drop back down and you could tell that the motor
was "missing" very slightly.

Again I pulled the rear end of the motor and noted that there were
some slight black marks across the sector gaps, which was evidence of
slight arcing on the three commutator sections. I cleaned the sectors
and brush ends up again and reassembled the motor. I set it up on slow
speed test again and it was still running, although not perfectly but
not too badly either after an hour at slow speed.

I have two other engines from the same era with similar motors that
don't seem to do this and I have serviced those motors similarly. Has
anyone seen this before? Is there a way to "arrest" the spark at the
brushes perhaps with capacitors? Thanks for any assistance. Lenny

On Sun, 3 Jun 2012 09:17:36 -0700 (PDT), klem kedidelhopper
wrote:

I have an AF300 engine and tender I just repaired with several new
parts I got from a vendor at the last local show.

Oh-oh.
http://www.hobbysurplus.com/xviews/300s1pcHSS.asp

I disassembled the rear of the motor and removed the armature.

Remove the wires from the motor contacts, attach an ohmmeter to the
motor leads, and SLOWLY rotate the armature. Rotate one commutator
segment at a time. What you're looking for is momentary short
circuit, or an imblance in the winding resistance (shorted turn). If
you get a short, then someone stuffed in the wrong size brushes. If
the measurements are very erratic, the brushes might have low spring
tension. If you get different readings on one commutator segment, you
have a shorted turn. Also, try running the motor outside the engine
to see how it runs.

I had
noted on my initial repair that the armature commutator was slightly
scored and somewhat blackened in a circular pattern where the brushes
rotate.

That's fairly normal.

In addition I re soldered the three
armature wires to the commutator segments, as the solder looked a
little sparse.

Careful that you don't unbalance the armature with too much solder on
one terminal.

I set the chassis up on test blocks and ran it at slow speed.
Initially it ran very smooth, however I could see a very slight arc
coming from one of the brushes.

Only one brush? It should be sparking equally under both brushes. Are
the brushes curved to fit the commutator shape? Is one brush
different? Are the commutator sections pitted? Are the brush faces
pitted? Are they the correct size and tupe of brushes?

I have noticed this on many motors in
the past, and since it was so minor I didn't give it much thought. My
goal was to run the engine for a period of time at slow speed in order
to "seat" the brushes.

You're idea of seating the brushes is my idea of burning away the
carbon and spraying the debris all over the inside of the engine. Find
a round file with approximately the same diameter as the commutator
and file the brushes.

After a period of time you could tell that the
motor was not running as smoothly as it did at the beginning of the
test.

I'm not surprised that it was running rough with one brush burning,
the other not burning, and oily carbon debris everywhere.

Has anyone seen this before?

Not exactly the same but similar. I do Marklin trains. This should
give you a clue as to the Marklin motor issues, which might be similar
to yours.
http://stores.ebay.com/Eckerts-Marklin-Trains-and-Parts/Marklin-Motor-Repair-Parts.html

Is there a way to "arrest" the spark at the
brushes perhaps with capacitors?

Maybe. An RC series network would help. However, the values are
calculated for a specific rotation speed and would probably not work
well on a train motor with a wide speed range. I would concentrate on
finding out why this motor is different and why it's sparking. Save
the band-aids for later.


--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

On Sun, 03 Jun 2012 10:40:07 -0700, Jeff Liebermann
wrote:

Only one brush? It should be sparking equally under both brushes. Are
the brushes curved to fit the commutator shape? Is one brush
different? Are the commutator sections pitted? Are the brush faces
pitted? Are they the correct size and tupe of brushes?

Add to the above list, are the brush springs sufficiently strong?

Your idea of seating the brushes is my idea of burning away the
carbon and spraying the debris all over the inside of the engine. Find
a round file with approximately the same diameter as the commutator
and file the brushes.

2nd thought, a file might be a bit too aggressive for the small
brushes. Find a wooden dowel of approximately the same diameter as
the commutator, wrap a piece of very find sandpaper around the dowel,
and use that to pre-curve the brush faces.

--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

On Jun 3, 1:45*pm, Jeff Liebermann wrote:
On Sun, 03 Jun 2012 10:40:07 -0700, Jeff Liebermann
wrote:

Only one brush? *It should be sparking equally under both brushes. Are
the brushes curved to fit the commutator shape? *Is one brush
different? *Are the commutator sections pitted? *Are the brush faces
pitted? *Are they the correct size and tupe of brushes?

Add to the above list, are the brush springs sufficiently strong?

Your idea of seating the brushes is my idea of burning away the
carbon and spraying the debris all over the inside of the engine. Find
a round file with approximately the same diameter as the commutator
and file the brushes.

2nd thought, a file might be a bit too aggressive for the small
brushes. *Find a wooden dowel of approximately the same diameter as
the commutator, wrap a piece of very find sandpaper around the dowel,
and use that to pre-curve the brush faces.

--
Jeff Liebermann * *
150 Felker St #D * *http://www.LearnByDestroying.com
Santa Cruz CA 95060http://802.11junk.com
Skype: JeffLiebermann * * AE6KS * *831-336-2558

Well you see the commutator is not round in the conventional sense,
it's flat with three sort of "pie" shaped segments on the back of the
armature. So the brush surfaces are flat. Lenny

Well you see the commutator is not round in the conventional sense,
it's flat with three sort of "pie" shaped segments on the back of the
armature. So the brush surfaces are flat. Lenny




I've tried and tried but can't imagine how that actually works.


Gareth.

On Jun 3, 4:57*pm, "Gareth Magennis"
wrote:
Well you see the commutator is not round in the conventional sense,
it's flat with three sort of "pie" shaped segments on the back of the
armature. So the brush surfaces are flat. Lenny

I've tried and tried but can't imagine how that actually works.

Gareth.

Can we have a photo (or maybe two or three)?

"Gareth Magennis" wrote in message
...

Well you see the commutator is not round in the conventional sense,
it's flat with three sort of "pie" shaped segments on the back of the
armature. So the brush surfaces are flat. Lenny




I've tried and tried but can't imagine how that actually works.


Gareth.

If the commutator was a cotton reel, I guess he's saying that the contact
segments are where the label would be on the end, not where the cotton would
be as in a conventional motor. Thus there are three segments in a flat 'pie'
configuration, presumably with the motor shaft through the middle, and a
brush either side, parallel to the shaft. I'm sure that I have seen this
somewhere on a motor over here.

As to the arcing at the brush contact surface, I guess some C across the
brushgear would help - much like the 'condenser' across the points in an old
Kettering ignition system. Also, are the gaps between the commutator
segments clean ? When I used to 'service' model motors many years back, I
always used to 'rake out' the gaps with the tip of a dressmaker's pin, and
also smooth the edges of the segments so that they were slightly rounded,
rather than a sharp 90 degree knife edge. If the contact area has been
subjected to emery paper treatment, the segment edges might well be quite
sharp.

Arfa

On Jun 3, 9:18*pm, "Arfa Daily" wrote:
"Gareth Magennis" wrote in message

...



Well you see the commutator is not round in the conventional sense,
it's flat with three sort of "pie" shaped segments on the back of the
armature. So the brush surfaces are flat. Lenny

I've tried and tried but can't imagine how that actually works.

Gareth.

If the commutator was a cotton reel, I guess he's saying that the contact
segments are where the label would be on the end, not where the cotton would
be as in a conventional motor. Thus there are three segments in a flat 'pie'
configuration, presumably with the motor shaft through the middle, and a
brush either side, parallel to the shaft. I'm sure that I have seen this
somewhere on a motor over here.

As to the arcing at the brush contact surface, I guess some C across the
brushgear would help - much like the 'condenser' across the points in an old
Kettering ignition system. Also, are the gaps between the commutator
segments clean ? When I used to 'service' model motors many years back, I
always used to 'rake out' the gaps with the tip of a dressmaker's pin, and
also smooth the edges of the segments so that they were slightly rounded,
rather than a sharp 90 degree knife edge. If the contact area has been
subjected to emery paper treatment, the segment edges might well be quite
sharp.

Arfa

The engine is from the late 40's You can see a picture of the armature
at the site below. The commutator segments are not visible in the
picture but you can get the idea. They are on the end of the armature
with the shorter shaft. Lenny
http://www.rfgco.com/tips.html?catal...ture_help.html

On Sun, 3 Jun 2012 20:59:34 -0700 (PDT),
" wrote:

The engine is from the late 40's You can see a picture of the armature
at the site below. The commutator segments are not visible in the
picture but you can get the idea. They are on the end of the armature
with the shorter shaft. Lenny
http://www.rfgco.com/tips.html?catal...ture_help.html

Do you have sufficient spring pressure?
http://www.rfgco.com/tips.html?catalog/steambrush_help.html

--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

wrote in message
...
On Jun 3, 9:18 pm, "Arfa Daily" wrote:
"Gareth Magennis" wrote in message

...



Well you see the commutator is not round in the conventional sense,
it's flat with three sort of "pie" shaped segments on the back of the
armature. So the brush surfaces are flat. Lenny

I've tried and tried but can't imagine how that actually works.

Gareth.

If the commutator was a cotton reel, I guess he's saying that the contact
segments are where the label would be on the end, not where the cotton
would
be as in a conventional motor. Thus there are three segments in a flat
'pie'
configuration, presumably with the motor shaft through the middle, and a
brush either side, parallel to the shaft. I'm sure that I have seen this
somewhere on a motor over here.

As to the arcing at the brush contact surface, I guess some C across the
brushgear would help - much like the 'condenser' across the points in an
old
Kettering ignition system. Also, are the gaps between the commutator
segments clean ? When I used to 'service' model motors many years back, I
always used to 'rake out' the gaps with the tip of a dressmaker's pin,
and
also smooth the edges of the segments so that they were slightly rounded,
rather than a sharp 90 degree knife edge. If the contact area has been
subjected to emery paper treatment, the segment edges might well be quite
sharp.

Arfa

The engine is from the late 40's You can see a picture of the armature
at the site below. The commutator segments are not visible in the
picture but you can get the idea. They are on the end of the armature
with the shorter shaft. Lenny
http://www.rfgco.com/tips.html?catal...ture_help.html



Thanks Lenny and Arfa, all is now clear.



Gareth.

On Jun 4, 5:30*am, "Gareth Magennis"
wrote:
wrote in message

...









On Jun 3, 9:18 pm, "Arfa Daily" wrote:
"Gareth Magennis" wrote in message

...

Well you see the commutator is not round in the conventional sense,
it's flat with three sort of "pie" shaped segments on the back of the
armature. So the brush surfaces are flat. Lenny

I've tried and tried but can't imagine how that actually works.

Gareth.

If the commutator was a cotton reel, I guess he's saying that the contact
segments are where the label would be on the end, not where the cotton
would
be as in a conventional motor. Thus there are three segments in a flat
'pie'
configuration, presumably with the motor shaft through the middle, and a
brush either side, parallel to the shaft. I'm sure that I have seen this
somewhere on a motor over here.

As to the arcing at the brush contact surface, I guess some C across the
brushgear would help - much like the 'condenser' across the points in an
old
Kettering ignition system. Also, are the gaps between the commutator
segments clean ? When I used to 'service' model motors many years back, I
always used to 'rake out' the gaps with the tip of a dressmaker's pin,
and
also smooth the edges of the segments so that they were slightly rounded,
rather than a sharp 90 degree knife edge. If the contact area has been
subjected to emery paper treatment, the segment edges might well be quite
sharp.

Arfa

The engine is from the late 40's You can see a picture of the armature
at the site below. The commutator segments are not visible in the
picture but you can get the idea. They are on the end of the armature
with the shorter shaft. Lenny
http://www.rfgco.com/tips.html?catal...ture_help.html

Thanks Lenny and Arfa, *all is now clear.

Gareth.

Spring tension is good. I've gone over this motor several times in
fact. So far it's still running in spite of the small sparking so
we'll see. Lenny