Rewinding armatures - questions

[mmagliaro]

Here's a quick and dirty video of just starts and stops with the rewound armature.
You'll have to trust me that the original engine's start/stop was awful compared to this, since I don't have an unmodified one
lying around now.

And remember, this is a vintage 1969 steam loco mechanism.   I think this is mighty darn good for an engine with a 3-pole motor,
mod 0.4 gears, NO axle bearings, and tender pickup wipers with only 1-side pickup.

[narrowminded]

Pretty cool, Max.

[peteski]

Thanks Max. Assuming that you are using pure DC, I suspect that a pulsed DC throttle could make this baby crawl at 0.5 Smiles/hr.   

[mmagliaro]

Thanks Max. Assuming that you are using pure DC, I suspect that a pulsed DC throttle could make this baby crawl at 0.5 Smiles/hr.   

This is with a half-wave DC throttle, so it's not smooth.  But it's nothing like you could get from a pulse throttle or a PWM throttle.
I agree.  It could be nudged to go slower with a power supply like that.

Other notes:
I replaced the tender truck wheelsets with Fox Valley.  They fit perfectly if you use the slightly longer-length ones marked for "Atlas".  The metal plating on them is SO much better than that old "gray"junk metal the original Atlas wheels and axles are made of.  It stays far cleaner, and the pickup is much more reliable.  It's still axle-wiper, and on one side only, but believe me, far less frustrating.

I think this grand experiment proves what we expected.  Lower friction (delrin gears) + stronger motor = better performance.

I wish there was a way to rewind these things without doing them by hand!
 

[wazzou]

Okay Max...so I'm sure I can't be the only person wondering what the end game is here.
Is this just a boredom, Covid driven proof of concept or is there a specific project in mind?

[mmagliaro]

Okay Max...so I'm sure I can't be the only person wondering what the end game is here.
Is this just a boredom, Covid driven proof of concept or is there a specific project in mind?

It is long and meandering story.
Yes, it is a project with a definite goal that spawned other investigations.

The project:
Retrofit dead Rivarossi motors with a new armature and magnet to provide people with a drop-in replacement.
This would be for all the people out there who have dead Rivarossi steam, but don't have the skill or the desire
to cut/grind the frame or otherwise fit some other motor in there to get their engine running again.  If you don't have
a crumbling Zamac frame, the number one thing that kills these engines is the motor.

I will offer rebuilt motors for sale when I'm ready to announce that.
But any rebuilt motors I sell will not have hand-rewound armatures.  That is just too much work.  They will have a new armature (3 pole skew-wound), new magnet ring, new brushes and springs.  They draw much less current and are very robust.  If somebody has a dead engine in the drawer, this is an easy way for them to get it going again.

So to make it 100% clear, there is:
1. the original Rivarossi motor, which burns/melts and otherwise is a nuisance that is doomed to fail sooner or later
2. my rebuilt RR motor: new armature (skew wound instead of straight like the original), new magnet, new brushes and springs
3. an experimental rebuilt RR motor, where I hand-rewound the armature.  This last one will NOT be offered for sale.

Also, I have prepared a very detailed article with full photographs and the exact measurements and steps to refitting the
new armature and magnet into the RR motor.  If a magazine, like RMC, is interested, I will publish it and happily give away
the exact details of how all this can be done at home if you want to do it yourself.

The "off shoot" investigations:
I thought my Neodymium magnet ring would achieve a big performance boost in the RR can.  It does help: as the video shows, a RR engine with my reworked motor does run better, but not all that much better.   So then I became curious about rewinding the armature. 

The custom Delrin idler gears.   Another curiosity.  I surmised that all those brass-on-brass gear interfaces, with all the driver and idler axles spinning in the Zamac frame with no bearings, must be a source of a LOT of friction.  Replacing just the idlers makes all the gear-to-gear contact become plastic-brass.  There are no brass-on-brass anymore.  It did lower the friction.  This test
0-8-0 could only scrape by at 15 mph at best, even with the new (but not rewound) motor.  Putting in the Delrin gears got it down to 11 mph, which is a significant improvement.

[Maletrain]

Max, it would be interesting to know what the 12 volt speed is with the new motor in that loco.

With all of those other mods to the magnet ring, gears, etc., comparing the load pulling capabilities to the old motor is probably not going to tell me much about the change in torque due to only changing the armature windings.  So, I'll quit asking for that.

Anyway, that is one great motor you created.  I wish the newly manufactured motors had those features.  Any idea how it compares to what is in the Atlas slow speed motors?

[mmagliaro]

Max, it would be interesting to know what the 12 volt speed is with the new motor in that loco.

With all of those other mods to the magnet ring, gears, etc., comparing the load pulling capabilities to the old motor is probably not going to tell me much about the change in torque due to only changing the armature windings.  So, I'll quit asking for that.

Anyway, that is one great motor you created.  I wish the newly manufactured motors had those features.  Any idea how it compares to what is in the Atlas slow speed motors?

Unfortunately, I have packed up the super-rewound engine to mail it back to its owner (I do not own that one).
But given that the RPMs of the motor were 47% that of the motor with just the new armature (3200 vs 6800), we can reasonably assume
that the top speed is going to be about half also.
Small-drivered (0-8-0 and 2-8-2) top speed with new armature = 85 mph at 12v
Large-drivered (4-6-2) top speed with new armature = 110 mph

So the rewound armature is probably running that 0-8-0 at a top speed of around 40-45 mph.
I think that's a really nice stop speed!

I have no idea how this compares to the Atlas "Scale Speed Motors".  Those are considerably larger, and are 5 pole motors, so one would think they have more torque than mine.  But on the other hand, mine has a Neodymium magnet in a CAN design so that the magnet is completely around the armature instead of having two magnets in an open frame like the Atlas/Kato motors.  With the rewound armature, I think I have, essentially, the features of a Mashima, but without being a 5-pole (unfortunately.  The Mashimas were wound to run slower than model train motors also, typically a top speed of around 12,000 instead of 15,000 to 18,000 like a Kato or Atlas motor.
And they also utilized a closed can.

Too bad nobody bought the armature winding machine that THEY had after they closed up!

[glakedylan]

Max...i am always intrigued with the work you do. no different with this rewind and super magnet installation.
i can't help but think that getting the magnets especially made for such was of considerable cost.
i am wondering in terms of the % of better performance (torque) with the new magnet v. the cost of such if
it is a worthwhile investment? i have some old locomotives that i need to change out the motors for them,
and while having a supply of replacement motors that should no take a whole lot of effort or skill to install,
i am thinking a magnet rebuild of stock motors might be a more significant upgrade.
any info you can share re: cost, source, and availability of them.
thanks much, and especially thanks for sharing this process.
your work is beyond anything i hope to accomplish but it is wonderful inspiration nonethess.


thanks!


sincerely
Gary

[mmagliaro]

Max...i am always intrigued with the work you do. no different with this rewind and super magnet installation.
i can't help but think that getting the magnets especially made for such was of considerable cost.
i am wondering in terms of the % of better performance (torque) with the new magnet v. the cost of such if
it is a worthwhile investment? i have some old locomotives that i need to change out the motors for them,
and while having a supply of replacement motors that should no take a whole lot of effort or skill to install,
i am thinking a magnet rebuild of stock motors might be a more significant upgrade.
any info you can share re: cost, source, and availability of them.
thanks much, and especially thanks for sharing this process.
your work is beyond anything i hope to accomplish but it is wonderful inspiration nonethess.


thanks!


sincerely
Gary

Sure thing.  I have no qualms about people knowing exactly how much this all cost me. 
I was surprised that I could even get a magnet manufacturer to do such a small quantity (100 magnets), but they were able to do it.
And of course, they have to be just precisely the correct size, and they have to be magnetized the correct way.
It cost me about $300 to get 100 magnets made.   On top of that, as a test, I went to a Chinese supplier for another 100 magnets.
Theirs were also correct and work great.  They were much less expensive.  However, by the time I paid the import duty and shipping charges to actually get them in my hand, they weren't all that much cheaper than the ones I bought from the US supplier.

Yeah, that's a considerable investment, but $3 per magnet wasn't a bad price at all for such a small order.  At least, I don't think so. 
My gut feel was that if sell 25 or so at $25 a piece,  I'd at least make back all my money.  Of course, that doesn't account for all my time rebuilding these WITH the magnet and the new armature, and the machining to make it fit, etc.   But I wasn't in this to make $$$.    As long as I recoup most of my money, that's fine with me.  I have learned so much by doing this, it was well worth it.

[mmagliaro]

Now I have a question about the plastic gears I replaced in the "super rewound armature" example.
As I noted, I had these made (by Micro Antriebe - https://shop.kkpmo.com/index.php )
One thing important thing happened.  When I put the FIRST plastic idler in, and left the others brass, I got a noticable
improvement in the low-speed running- particularly that it would start with less of a "jerk" and would run at a lower
minimum speed.  But replacing the rest of the idlers didn't really change things.

My theory is that changing the brass gear that mates with the worm is the critical one.  A metal-on-metal worm mesh has a lot of sliding friction, and doesn't hold lubrication well the way the spur gear meshes do in between the drivers.  So changing just the one idler gear that mates to the worm may be the key, and leave the rest alone.

Any gear experts out there who care to comment?

[nickelplate759]

Interesting theory.  I'm tempted to try that on my Rivarossi 2-8-4.  I already remotored it with an old Sagami, but it definitely runs rough at low speed and there's a good bit of gear noise.

[mmagliaro]

Interesting theory.  I'm tempted to try that on my Rivarossi 2-8-4.  I already remotored it with an old Sagami, but it definitely runs rough at low speed and there's a good bit of gear noise.

What sort of Sagami did you use?  What size? 
I have one of those, purchased in the late 1980s.  I note from Spookshow's review that when Rivarossi took over production from Rowa, they changed the internal gears from plastic to metal.  So mine would have the metal gears, and it's silky smooth.  It can't run particularly slow, because like all engines of that era, it is geared too high.  But it certainly isn't noisy or rough-running at its lower speeds.

If you used an open-frame Sagami, or one of their 10mm cans, I would suggest you try a different motor.  Some of the open-frame ones were okay, some were not.  And the 10mm size were very weak motors.  Nothing like the 12mm black can motors they made, which were quite good.

[peteski]

Now I have a question about the plastic gears I replaced in the "super rewound armature" example.
As I noted, I had these made (by Micro Antriebe - https://shop.kkpmo.com/index.php )
One thing important thing happened.  When I put the FIRST plastic idler in, and left the others brass, I got a noticable
improvement in the low-speed running- particularly that it would start with less of a "jerk" and would run at a lower
minimum speed.  But replacing the rest of the idlers didn't really change things.

My theory is that changing the brass gear that mates with the worm is the critical one.  A metal-on-metal worm mesh has a lot of sliding friction, and doesn't hold lubrication well the way the spur gear meshes do in between the drivers.  So changing just the one idler gear that mates to the worm may be the key, and leave the rest alone.

Any gear experts out there who care to comment?

So you not only changed the idler gears, but also the worm gear (or is it a compound gear in those locos)?  You were able to have a worm gear manufactured (with angled teeth)?

I think your theory is sound. POM (Delrin) is a slippery self-lubricating plastic, so I imagine that there is less friction any time it is used for gears.

[mmagliaro]

No, the worm is still brass.  But at least it is a brass motor worm running against a Delrin idler.  I would think that still has a much reduced friction with all the sliding pressure that goes on in a worm.