"Useless" motor armature swap

[mmagliaro]

After working with the Life-Like open-frame motor again on Lee's Hudson project, I was taken with something as I looked at some motors on my work bench.  I had an old LL motor frame with no armature, and I had a Kato motor marked "bad", that still had the armature in it.  I marked that motor "bad" because it ran erratically, and no matter how I fussed with the brushes and brush springs, I could never find out what was wrong with it, so I relegated it to the parts bin.  It always started and stopped, and the current draw was never high.  But while it ran, the speed would take random jumps up and down and it would just not run consistently (I know, sounds just like a brush problem).

Anyway, I wondered if I could put the Kato armature into one of those old LL motor frames.  They don't APPEAR to be the same size, but guess what?  They ARE.  The only thing I had to do was trim a little off the end of the Kato commutator, because the LL frame is about 2mm shorter.  Other than that, the magnets, brushes, bearings etc all line up and it works perfectly!  I put the arm into the LL frame with a couple of the original thrust washers on each end.  You need to trim the comm until there is just a hair of lateral play in the armature.  Otherwise, it will bind, of course.  Instead of running at around 12,000 RPM like the LL, now it runs at 19,000, which is more typical of the Kato straight-wound armature I used (not a desirable property).

"Useless" because I don't know what I'll ever do with this knowledge.  But it might be handy so I posted it.  I would also bet you could go the other way: transplant a LL armature into a Kato motor.  That would bring down the RPMs and get you the LL performance in a slightly narrower, slightly longer frame.

The LL frame is about 2mm shorter, and 1mm taller than the Kato.  Both are exactly the same width.

Photos:


This next shot is NOT the actual motor, but it was the only thing I had handy that showed the end of the commutator so
I could explain the trimming.

[wm3798]

I would think the opposite transplant would be the more useful of the two.

Many kudos to the Railwire Research Department.

[peteski]

I have swapped aramtures between similar motor like Kato and Atlas, or Life Like (which are basically Kato clones). Not the Life-Like one you are using here, but the other Life-Like motor (used  in GP18 or SW1200).  Those are easy swaps.

Also, after our discussion about your dislike of Kato motors, I dug into my stash.  There are 2 different versions of the GM-5 motor.  They are easily identified by the plastic end which holds the brushes, and by different metal frames.  The one with flywheels is the newer (current) version, with the other  one  being the original version of the GM-5 motor.




Now before we talk about the starting voltage, in my experience  I noticed that unlike motors with precious metal commutator and metal finger brushes, motors with copper commutator and carbon brushes, when sitting unused for some time, will need higher than normal starting voltage. But once they are run, just for several seconds, the commutator or brushes get "cleaned", and the starting voltage is stabilizes and is lower than the initial  starting voltage.

The starting voltage of the original GM-5 motor (even after initial run) is still around 3-4V (like you mentioned, rather high).
But the new version of GM-5, after initial run, starts most of the time at 1.3V, and reliably around 1.6V.  When it was running at higher speed first, it will stay running down to 1.2V (which is the lowest voltage my variable DC power supply puts out).

[mmagliaro]

Pete, that sounds completely reasonable.   The only "GM-5" motors that I call by that name are the old ones I used to use for repowering projects back in the 90s.  High starting voltage and all,  they were WAY better than the junk they were replacing, and our choices were more limited then than they are now, so I was glad to have them.

Yes, I see the same behavior with having to run a motor a little bit after it's been sitting a while, especially the carbon brush "conventional" motors.  I just did a test of the handful of LL motors I have in my stash.  They all behaved that way.  Started around 3 or 4 volts.  But after they ran a little while, they would all get into the 2.5v range, and some below 2.

Incidentally, my LL motors came from a guy who had a bag of them at a Timonium, MD train show.  He was selling them for $2 a piece, and I didn't really know what they were.  But they were 5-pole motors in the 1990s for TWO DOLLARS, so what the heck!  I bought 5.  (I should have bought the whole bag... I always do that to myself).

[peteski]

Our experience is similar     I also have a bunch of those "generic" Atlas black and gray motors from eBay (for couple of bucks a piece).  And yes,  both types of the "new" Life-Like motors (the larger one and the Kato clone) are pretty good motors. 

The reason I posted the Kato motor info here is because you had some harsh words about them in the other thread, and me being a Kato fanboy, wanted to set the record straight. Current Kato motors are pretty good (both the GM-5 and the small coreless ones).

[narrowminded]

At a glance and from memory is there any interchangeability of the Atlas motors with the Life-Likes?   Not important at the moment but curious and if the knowledge is there I'd welcome it.  I have a fair number of both and that could come in handy some day.

[peteski]

They looks very similar in size and configuration, but I haven't compared their dimensions.  I would say that there is a good chance that they are interchangeable.

But I'm talking about the clones of Kato GM-5 motor, not the larger Life-Like motor. That larger motor looks similar to the older Kato FM-5 motor.