Atlas Motor Problem

[davefoxx]

@mmagliaro,

I'll certainly reimburse you for the cost of shipping the motor back to me.  I want to thank you and @peteski again for taking time out of your busy day to look at these motors.  I'm not sure that I can tear down a motor and successfully put it back together again, like you did, but at least I now know two causes for the problems that I had.  PM me your PayPal address and the cost of postage, or, if you don't use PayPal, I can send you a check.

DFF

[mmagliaro]

Thanks, Dave.  I've sent you a PM with my paypal address.  Just enough to cover a flat-rate box is fine.

Tearing these motors down is not something you'd want to do with a motor you can't afford to lose.  It's best to practice on a few junkers first.  Getting the flywheels off is the hardest part.  On these motors, the flywheels won't even come loose with a wheel puller for me.   I usually have to do like I did with yours: suspend the motor in a jeweler's vise, hanging by the flywheel on a V plate, and then drive the motor shaft out from above with a hammer and a small punch.  Since the whole motor is hanging free by the flywheel, smacking the end of the armature shaft doesn't put any stresses on the motor itself.  And once the initial "whack" breaks the shaft free, it can be pressed out the rest of the way with a wheel puller.

Anyway, if you have the time to test it in an engine, I'd be curious to see if it does any better, or if it just ends up running the same as before.  It ran when it got here, except that the speed was erratic, so it might run better now, but still not up to snuff compared to a new motor.  I'd be curious to know.

[davefoxx]

Max,

Payment sent!  I'll reinstall it in the locomotive that I tested all three motors in, to eliminate any other variables from affecting the new results.  Since I have the speedometer, I can get pretty accurate results.

Thanks,
Dave

[narrowminded]

One thing that might explain the lower voltage performance on the Peteski motor, if all else was equal, would be if he was using a PWM controller.  That's the point of them and why they work.  I suspect he'd have identified that and mentioned it but thought I would bring it up for those eavesdroppers who might not be as familiar as it would be an opportunity for a practical example of the "magic" of PWM (that isn't).

[strummer]

This is a most fascinating thread...usually, this kind of stuff gets discussed on the O scale forums.

You guys who can do this in N scale are madmen!...and I mean that as a compliment...

Mark in Oregon

[Doug G.]

Max, you didn't happen to notice if the brushes in that motor seemed soft, did you? I know that can fill commutator slots up pretty quickly.

Back when I first got my Atlas/RoCo locos in the seventies, they wouldn't run very long before they would start sputtering and acting erratic.
In every case, when I disassembled the motor, the slots were filled and when I scratched the side of a brush with my fingernail, I could tell the material was soft.

Now, many years later, they run fine and I surmise that the binder has hardened through evaporation, making the brushes harder. The slots don't fill up at all now.

Doug

[mmagliaro]

Max, you didn't happen to notice if the brushes in that motor seemed soft, did you? I know that can fill commutator slots up pretty quickly.

Back when I first got my Atlas/RoCo locos in the seventies, they wouldn't run very long before they would start sputtering and acting irratic.
In every case, when I disassembled the motor, the slots were filled and when I scratched the side of a brush with my fingernail, I could tell the material was soft.

Now, many years later, they run fine and I surmise that the binder has hardened through evaporation, making the brushes harder. The slots don't fill up at all now.

Doug

I didn't really feel them to see if they felt odd or soft.  They dropped out of the brush holders, and had the usual rounded end where they ride on the commutator, but otherwise, I didn't see anything unusual about them.  They didn't look like they were all worn down to nothing, either.

[peteski]

One thing that might explain the lower voltage performance on the Peteski motor, if all else was equal, would be if he was using a PWM controller.  That's the point of them and why they work.  I suspect he'd have identified that and mentioned it but thought I would bring it up for those eavesdroppers who might not be as familiar as it would be an opportunity for a practical example of the "magic" of PWM (that isn't).

Nope - my supply is pure-analog filtered/regulated DC from a home-brew circuit based on LM317 voltage regulator.

I was also surprised with the motor's surprisingly good low-voltage performance. Of course at that voltage it has almost not torque. My tach is not working so I can't give the rpms, but it look s like about 3 revs/sec (or about 150-180 rpms).

[mmagliaro]

Creepy, Peteski.  We tested with more identical conditions than I realized!

My workbench test supply is also a home-brew thing based on an LM317T.  Filtered and no pulse.
(I like it that way, because engines always come off the bench and run better on the layout where I have a throttle that has a little half-wave pulse in it!)

[peteski]

Creepy, Peteski.  We tested with more identical conditions than I realized!

My workbench test supply is also a home-brew thing based on an LM317T.  Filtered and no pulse.
(I like it that way, because engines always come off the bench and run better on the layout where I have a throttle that has a little half-wave pulse in it!)

 

I agree.

[rrjim1]

It's very easy to destroy one of these motor by prying on a flywheel. If you pry from the commutator side you can move the commutator toward the stacks. This will loosen the wires and if you move it too much the wires will rub and wear threw very fast.  Look at the picture posted of an armature and you should be able to plainly see what I am referring to.   

[mmagliaro]

It's very easy to destroy one of these motor by prying on a flywheel. If you pry from the commutator side you can move the commutator toward the stacks. This will loosen the wires and if you move it too much the wires will rub and wear threw very fast.  Look at the picture posted of an armature and you should be able to plainly see what I am referring to.

Absolutely!  Prying in any way is a complete no-no.  A wheel puller braces a V-plate behind the flywheel and pushes the shaft out, so all the pushing stress is only on the flywheel itself.  Likewise, slipping a V plate in behind the flywheel and letting the motor hang on that plate, and then punching the shaft out from above, puts all striking force and stress only on the flywheel itself.   Doing this any other way is a sure fire way to destroy the motor.

[tehachapifan]

Absolutely!  Prying in any way is a complete no-no.  A wheel puller braces a V-plate behind the flywheel and pushes the shaft out, so all the pushing stress is only on the flywheel itself.  Likewise, slipping a V plate in behind the flywheel and letting the motor hang on that plate, and then punching the shaft out from above, puts all striking force and stress only on the flywheel itself.   Doing this any other way is a sure fire way to destroy the motor.

Be careful with the hanging the flywheel from a plate then punching out the shaft method. I had a real stubborn flywheel once and progressively started punching a little harder and harder until the motor below basically blew apart, presumably from all the vibration.

[mmagliaro]

Be careful with the hanging the flywheel from a plate then punching out the shaft method. I had a real stubborn flywheel once and progressively started punching a little harder and harder until the motor below basically blew apart, presumably from all the vibration.

Well, yeah.  True.  There is some shock and vibration that the motor is subjected to using this method.  I try the wheel puller first and only use this method if the flywheel won't budge.  I've bent more than one hardened steel push bolt in a wheel puller trying to get these out.  They can be pretty stubborn.  I guess the watch word is "carefully".  You can't smack it too hard with the punch.  And you don't need to keep hitting it once it budges even a little bit.  Once it breaks free, put it back in the wheel puller and try again.  It almost always pushes out after getting it to break free.

[peteski]

Max, we have a lot of advice here about removing the flywheel, but none on reinstalling it. I'm curious as to how you reinstalled both of those flywheels.  That to me is the harder part (especially with a double-flywheel motor).