Motors, torque, windings Scale Speed

[mmagliaro]

Victor, are you going to wrap the double strand in parallel?   In other words, starting at one commutator pad, solder
the ends of the two wires to that pad, and then just start wrapping as though they were one big wire?
If so, while the results may be interesting, I don't see what this proves.  None of the Atlas or Kato motors
are wound that way.

If you are going to go through the arduous task of rewinding a 5-pole armature, why not just run a Kato motor
at a certain rpm, say, at 5 volts.   We need some way to measure the torque at that speed.
Perhaps just mount a flywheel on it with a piece of steel wire shoved into it so it sticks out about 2 inches,
with a loop in the end of it.
Now just a simple spring gauge hooked onto the wire, with the motor securely fastened down on the work bench.  See how hard you have to pull on the gauge to stop the motor.

Now rewind the motor with, say, twice as many turns of a thinner wire, and again, get it spinning at
the same rpm.  Presumably, it will require a higher voltage to run at that same rpm. 
Now repeat the spring gauge test.

In fact, any old spring you have lying around will do the trick. Just see how far you have to stretch
it to stop the motor.  That will give us a higher/lower measurement.

For all the work of rewinding an armature, it just seems to me it makes more sense to directly
see which motor has more torque at the same RPM.   You could even measure 5 different rpms.

[Mark.S+10]

What effect  would replacing the magnets with rare earth magnets have?

Have fun, Mark

[victor miranda]

while I am trying to think up a graceful reply to Max's post...

Hi Mark,
It is the B in the torque equation. 

it will increase the torque... for free!

this is the reason the gs-4 is so powerful
that motor has some seriously strong magnets in it.

I don't know why Kato does not use them in the older motors.
( they may have,  I just have not purchased one .... yet.)

victor

[mmagliaro]

What effect  would replacing the magnets with rare earth magnets have?

Have fun, Mark

Yes, it greatly increases the strength of the magnetic field.
One of the reasons that Maxon and Faulhaber coreless motors are so powerful is that they
use Samarium Cobalt or Neodymium magnets (both "rare earth").
Neodymium makes for the strongest magnets, so for certain sizes of motors, Maxon is beating
out Faulhaber for power because Faulhaber is still using Samarium Cobalt.

However, Samarium Cobalt is supposedly more stable and also can withstand higher temperatures.

(And believe me, a Faulhaber is no piece of crap!  It's hard to beat precision stainless steel gears
and ball bearings)

... more than you ever wanted to hear about this... I know...

[Bill H]

Victor, are you going to wrap the double strand in parallel?   In other words, starting at one commutator pad, solder
the ends of the two wires to that pad, and then just start wrapping as though they were one big wire?
If so, while the results may be interesting, I don't see what this proves.  None of the Atlas or Kato motors
are wound that way.

Max:
That is exactly how the big bucks slot car armatures were wound in the sixties and seventies, sometimes even as triples. From what I have read recently, the current hot thing (no pun intended) is to layer, i.e. with the first wire 90 turns, then wind the second 90 turns on top of what was the wrapping of the first wire. In other words, not as a double strand in parallel.

Best,
Bill

[victor miranda]

last night, I had decided I was cranky and didn't think I should post.
tonight... re-reading this and I am thinking ....
geez what has you twisted, ole victor?

I think I'll start with what I expected...

wow, victor, that sounds like a good idea.
you can create a motor with all the same electrical properties
and twice the number of wraps?
according to the theory, that should improve the torque.
lets see if it does.

instead what I got was:
Here is one impossible way to build it.
What happens if you take two wraps off the motor and test it again?
Build a test rig like this.

On to some constructive considerations.
In answering a few questions about how a Kato 5 pole motor is
constructed, I have an open armature.  I think I have some magnet wire
and I am pretty sure I can fit the wire as proposed.

We have some theory that says more wraps is more torque.
I was not planning on deconstructing it after I wrapped it.
To take a few wraps off each coil you have to take four coils completely off the arm.

I want to build the motor first because we have not tried or agreed to any kind of test rig.
I am assuming some one else in addition to me is going to run the testing.
I think a test rig is not that hard.
generate a known load... and motivate it.

with a motor as different as I propose to build,
we will know if the theory holds water.

after that,  we may know something
then... well, maybe y'all will decide to wrap your own super motors.

or...

after that,  we crash and burn
then....we will know the theory is bogus.

victor

[victor miranda]

ah  well the first coil did not go well...

I measured the old wire. and got 10 and a half feet.

so I made a measuring board from a cardboard box
and measured out two strands...
did lots of coiling and one ended and the other was a wee bit longer...
it seems I cut one 2 feet shorter than the other.

I think I like beating my head on the wall.
perhaps I'll find the time tomorrow ... 
it looks like there is a brick here with no blood on it.

victor

[victor miranda]

victor
gah how do I make these strange decisions?

build specifics of the "more torque" motor.
the coils are made of 43 gauge wire.
two strands and 10.5 feet

my com plate to com plate resistance is 13.2 ohms
I ran it a bit, open.
16v and 110ma
and rolling slowly
1.25v and 62ma

I am planning to install it in an atlas gp9 frame I have.
and we can try toe to toe comparisons...

victor

[mmagliaro]

I am already impressed that it runs at 1.25 volts!

You may be on to something there.

[Lemosteam]

Who now we gotta start rolling our own armatures to keep up?  I am curious about how you will be measuring the torque.

[loyalton]

There are already people doing this as a cottage industry in the slot car world. You just have to make them aware that there might be a demand in the train world.

[mmagliaro]

Who now we gotta start rolling our own armatures to keep up?  I am curious about how you will be measuring the torque.

Not me.... Faulhabers will run at 0.3 volt...   

But of course, they don't make any useful power at that speed... you have to get up to a full volt to do that! 

Seriously, a conventional motor that can start at 1.25 volt is a mighty interesting thing.  I will be
very interested to see how much power it can really product in a loco, Victor.

[rodsup9000]

I will be very interested to see how much power it can really produce in a loco, Victor.

 I agree Max.  Also to see if it has enough torque to start the loco at that low of voltage.

[victor miranda]

forumers,
I can't imagine anyone taking up 5 pole arm wrapping.

it is an interesting flavor of motor.
changing the gear ratio is more noticable.

well, I am going to present the data I collected
lets see what it looks like

here are static measurements of a few motors.
measured across the commutator probes on the comm plate.

a random motor that I think is life-like 7 ohms
l-l     31 ohm
sw1200  31
ll      30
atl gry 25
atl gry 29
atl blk 10
atl blk 10

I ran 4 locos:
atlas grey GP9, atlas black GP9, rewrap GP9, and a ll gp-20.


just the loco
--------slow speed  -- speed per lap
-------------------- ------at 12 volts ------- 30sec/lap

atl gry  - 52ma 1.3v    - 5.4sec 107ma   64ma 3.0v
atl blk  -  33ma 1.5v    10.0sec   70ma   46ma 4.6v
rewrap - 65ma 1.5v    12.4sec 135ma   95ma 3.8v   
ll       ---- 50ma 1.9v    11.3sec 100ma   59ma 4.9v 

towing 10 car

--------slow speed ---- 30sec/lap

atl gry - 41ma 1.7v  -    63ma 5.2v
atl blk - 68ma 1.5v  -    90ma 3.5v
rewrap  82ma 1.8v  -  116ma 4.5v
ll  ----     55ma 2.2v  -   75ma 6.0v

and added calculations in parens() for extra eye glazing...


just the loco
--------slow speed   -------------speed per lap
-------------------- -----------------at 12 volts ------------------- 30sec/lap

atl gry -- 52ma 1.3v(67mw)    5.4sec 107ma(1284mW)   64ma 3.0v(192mW)
atl blk  -- 33ma 1.5v(49mW)   10.0sec  70ma( 840mW)   46ma 4.6v(212mW)
rewrap -  65ma 1.5v(97mW)   12.4sec 135ma(1620mW)   95ma 3.8v(361mW)   
ll    ------   50ma 1.9v(95mW)   11.3sec 100ma(1200mW)   59ma 4.9v(289mW) 

towing 10 cars

--------slow speed ---------------- 30sec/lap

atl gry -- 41ma 1.7v( 70mW)      63ma 5.2v(328mW)
atl blk -- 68ma 1.5v(102mW)      90ma 3.5v(315mW)
rewrap   82ma 1.8v(148mW)     116ma 4.5v(522mW)
ll     -----  55ma 2.2v(121mW)      75ma 6.0v(450mW)

some notes and my opinions
the rewrap motor didn't get warm (none of them did...)
at the slowest speeds possible it was noticablely steadier.
it was like watching some one walking.
it may be generating more torque, how one tells seems a struggle.

the gray chassis seemed the loosest.
the blk chassis and the rewrap seemed similar

I am going to sleep on the rest of this.

[mmagliaro]

Well, here's the thing about starting speed.  Even if the motor cannot start a loco moving at 1.25 volts,
my experience is that motors that can start and run at voltages that low usually still deliver impressive
power at low RPMs.   Time will tell, I guess.

By the way, I bit the bullet and ordered one of those Atlas Scale Speed motors.  I'm going to
do some head-to-head torque measurements at different RPMS between that and the Kato motor that is
in my E8.   I don't have a dynamometer, but I ought to be able to rig up something with a spring and lever
that will let me make relative measurements.