New Kato motor

[u18b]

While I agree that the Mehano motors were junk, I found them to give decent low speed performance. Here is a video of a MRC RSD15 mechanism that I stretched out over 40 years for a C630 project (that I never finished):

Note that this has been sitting in my junk box for decades and the "idler" wheels are dragging. 

Mark

Having dealt with many old mechanisms....  that video is impressive to me.

[peteski]

@Mark5
I see you visited the forum couple of days ago. 

Throughout our 3-pole motors suck exchange in this thread I have asked you to provide some specific examples of 3-pole equipped locos you find inferior, and you pussyfooted around the subject.  Fine.  So, on Jan. 5th I asked you to maybe give me some examples of 5-pole equipped locos you find satisfactory (as far as slow speed goes), and that request was again met with silence.  I'm beginning to think that you are full of it (not disrespect meant, but what else should I think?).  It only takes couple of minutes of typing to provide some examples I asked for.

[woodone]

Wow, this is an interesting thread. I am guessing we (model railroaders) are looking for a motor that has a very smooth starting .
Are we attacking this from the right end (MOTOR)?
To get a motor running we must apply enough voltage to over come the static friction.
We keep on upping the volts until the moment to motor starts to turn- static friction no longer applies, it is now kinetic friction.
Once the static friction is gone we now need much lower volts to keep it running.
This is what PWM does-it apples spikes of volts to try to kick the motor to turn. Once that happens we really do not need PWM, do we?
Maybe we need to use a gear box reduction so the motor uses high rpm’s .
Just a thought?  Like 500 to 1 ?

[Chris333]

I think the problem with Kato is they have like no gear reduction in their locomotives. Just make it move and stop there. Add gear reduction and just about any motor will preform better. The motors will still be running fast, but the locomotives will be slow.

With Kato's excellent manufacturing abilities they should work on their own 4:1 (or 3:1, 2:1) gearhead to fit their motors and now worry about the motor.

[peteski]

Wow, this is an interesting thread. I am guessing we (model railroaders) are looking for a motor that has a very smooth starting .
Are we attacking this from the right end (MOTOR)?

Yes a very smooth start, smooth slow speed, and realistic (not extremely excessive) top speed are all highly desired features for model locomotives).  Motor is only one part of the equation.  The rest of the mechanism (including the gear ratio), including overall low-friction design all play important roles in how the model runs.

To get a motor running we must apply enough voltage to over come the static friction.
We keep on upping the volts until the moment to motor starts to turn- static friction no longer applies, it is now kinetic friction.
Once the static friction is gone we now need much lower volts to keep it running.

That's pretty close to what's going on.  But if done as you described, it would cause the model to lurch before the voltage can be lowered.  Plus, at very slow motor rpms, it produces very little torque (inherent to the motor's design), so unless the mechanism is very low friction, the model could easily stall again.

This is what PWM does-it apples spikes of volts to try to kick the motor to turn. Once that happens we really do not need PWM, do we?
Maybe we need to use a gear box reduction so the motor uses high rpm’s .

You are confusing PWM and "pulsed DC".   PWM is a method to produce a variable (zero-to-full) average voltage using variable width pulses of full voltage.  This method is universally used in the motor driver circuit of DCC decoders because it is very efficient, so the small surface-mount motor-driver transistors on the decoder do not have to dissipate much heat. They act like switches - either full on or full off (so they do not have to act like variable resistors dissipating whatever power is not delivered to the motor).

The frequency of those PWM pulses is too high to have a kick-like effect on the motor's armature. Those "kicks" have to lower frequency to have desired effect on the armature.  But conveniently, the same circuitry used for PWM motor power can also be utilized for the "kicks".  The microcontroller on the decoder (or electronics in a PWM throttle) can modify the PWM pulse duration to produce those "kicks".  The same motor-driver circuitry also measures the BEMF voltage generated by the motor using it as feedback indicating the motor's rpms, and adjusts the PWM signal appropriately to keep the motor running smoothly.

In a simple old-school pulse capable throttles, the normal variable DC voltage was actually 120Hz full-wave rectified voltage coming from the transformer inside the throttle.  If pulse feature was turned on, it changed the output voltage to half-wave rectified DC. That created the pulses needed for kicking the motor's armature.  It was fairly crude, but effective.  There was no BEMF feedback.

Just a thought?  Like 500 to 1 ?

Well, that kind of gearing would produce extremely smooth start and slow speed, but even with full throttle the model could only achieve probably 2 scale MPH. Kind of like if your car was stuck in first gear (well actually more like in a 0.1 gear - much slower than first gear).  But you are right, Numerically higher gear ratios trade rpms for torque, and the more torque is available, the smoother the model will run.

But many of the N scale locos are geared numerically too low. Basically they have excessive top speed, which also makes them poor performers when it comes to smooth starts and smooth low speed, as there is very little torque available at low speeds.  That would be like trying to gently start your car in 3rd gear and trying to maintain smooth slow-speed running. That's all without being able to use the variable friction clutch - the motor would be solidly connected to the gearbox, since we have no clutches in our models.  These are extreme examples, but demonstrate the idea.

The best solution IMO would be to have the models geared in a way which would result in a top speed similar to the prototype speed.  Well a bit higher, since many modelers would consider prototypical top speeds too slow for operating on a layout (especially NTRAK layout  ).  I know, I'm an NTRAK member.  That, plus a good quality motor (like a coreless motor with plenty of torque) would make our models run well on slow speeds,. Of course lets not forget the low-friction mechanism.  With all those things there would be very little need for "kicking" the motor's armature.

[woodone]

Wow, this is an interesting thread. I am guessing we (model railroaders) are looking for a motor that has a very smooth starting .
Are we attacking this from the right end (MOTOR)?
To get a motor running we must apply enough voltage to over come the static friction.
We keep on upping the volts until the moment to motor starts to turn- static friction no longer applies, it is now kinetic friction.
Once the static friction is gone we now need much lower volts to keep it running.
This is what PWM does-it apples spikes of volts to try to kick the motor to turn. Once that happens we really do not need PWM, do we?
Maybe we need to use a gear box reduction so the motor uses high rpm’s .
Just a thought?  Like 500 to 1 ?

[rrjim1]

I just remove the high speed Kato motor and install a scale speed Atlas motor. Problem solved! 

[woodone]

Opps, looks like I did a double post—SORRY. !
Pete, on the over coming of friction, is that not what is happening. We apply voltage until motor starts to turn, now there is no way that I can see that we can lower the volts before the motor is over speed and the loco takes off like a rocket.
So.what ever controler we are using it is try’s to keep the motor running while at the same time trying not to apply too many volts.
Back when I used DC I built several throttles that had a (what was called PWM) at least that Is what I recall, built into the throttle. You could change the pulse rate has you ran the loco. You could hear the sweet spot while running.
No BEMF for sure

[peteski]

Pete, on the over coming of friction, is that not what is happening. We apply voltage until motor starts to turn, now there is no way that I can see that we can lower the volts before the motor is over speed and the loco takes off like a rocket.
So.what ever controler we are using it is try’s to keep the motor running while at the same time trying not to apply too many volts.

Yes, that's basically it.  Main problem is the very low torque generated by the motor at low voltage, low rpms. Pulsing the DC voltage (using full 12V) gives the armature the "kick" needed to keep spinning and overcoming any hitches in the mechanism.

Back when I used DC I built several throttles that had a (what was called PWM) at least that Is what I recall, built into the throttle. You could change the pulse rate has you ran the loco. You could hear the sweet spot while running.
No BEMF for sure

Yes, I built a throttle like that too (TAT V throttle I housed in a modified old MRC throttle case), and I could control the pulse frequency, duration and few more parameters.  It can  make the loco run really smoothly.



While those pulses are a type of Pulse Width Modulation, like I explained earlier, it is different than the higher frequency PWM a DCC decoder uses to vary the motor voltage.  That type of PWM is described in https://en.wikipedia.org/wiki/Pulse-width_modulation. This type of PWM is not uses to "kick" the armature, but to provide a variable voltage to run the motor.

[woodone]

Wow, that is some deep reading!!
I do not think we can come up with a good gearing solution  action for are locomotives.
How about a fluid coupling. I read something about that some time ago. Do not recall where.
But that would let the motor ramp up and we would see a very slow output. Too fast or slow, change the viscosity of the fluid.

[peteski]

Wow, that is some deep reading!!
I do not think we can come up with a good gearing solution  action for are locomotives.
How about a fluid coupling. I read something about that some time ago. Do not recall where.
But that would let the motor ramp up and we would see a very slow output. Too fast or slow, change the viscosity of the fluid.

The thing is that there are combinations of low-friction mechanism design, gearing ratio, and motors with appropriately ample torque (even at low speed) that perfection can be achieved.  Just ask Mark - he is fussy about smooth low speed, and he seems to have found such combination (but he is keeping it a secret  for now  ).

Fluid coupling?  Yes, that is exactly what replaces the dry clutch in cars with automatic transmissions: Torque converter.  Interesting idea, but I think that just like mass, viscosity does not scale.  I could be wrong, but either way, that could get messy. 

[woodone]

Well yes & no. A fluid coupling has only three elements. Where a toque converter has three also but one being a stator.
The fluid coupling has a driven pump and a drive pump contained with a housing. No stator used.
There is no torque multiplying with the fluid coupling. With the torque converter the stator redirects the fluid to get more torque.

[peteski]

Well yes & no. A fluid coupling has only three elements. Where a toque converter has three also but one being a stator.
The fluid coupling has a driven pump and a drive pump contained with a housing. No stator used.
There is no torque multiplying with the fluid coupling. With the torque converter the stator redirects the fluid to get more torque.

Similar idea though. Likely not feasible for N scale, and how would it handle a loco pulling a long train (not running light)?  Anyway, I don't believe we'll see a fluid coupling in N scale locos in the immediate future.

[Mark5]

@Mark5
I see you visited the forum couple of days ago. 

OK, I have been VERY busy this month with real life stuff. It's been a few weeks since I've been on the forum - at last I have to time to sit down and do fun stuff and I come back to see this ... 

Throughout our 3-pole motors suck exchange in this thread I have asked you to provide some specific examples of 3-pole equipped locos you find inferior, and you pussyfooted around the subject.  Fine.  So, on Jan. 5th I asked you to maybe give me some examples of 5-pole equipped locos you find satisfactory (as far as slow speed goes), and that request was again met with silence. 

Pete, we've been around the block on this topic many times over the years - it gets tiresome repeating myself. A few examples:

I've seen the bmann and kato 3 polers cog.

I have not yet witnessed the wonder in the MP15.

Of the Bachmann locos I own I have four Bachmann locos with 3 pole motors: 2 N&W "J"s, 1 2-6-6-2, and one FM H16-44. The "modern" 3 pole motors perform well in slow speeds, but with that "stutter" that only I seem to have the "gift" to see.

I have one of the 4-6-2s. The tender pickup was stupid (1970s style). Not a biggie as the loco I plan to build needs a USRA long hand me down tender. The Bachmann USRA long with its excellent pickup solved that prob.

Test runs were pretty good - the gearing must be good as it was able to run smoothly at low speeds, even with the crappy 3 pole motor.

Mark

Subsequent to these posts I am quoting above, I took a sabbatical from my "real" career for a few years and worked full time in customer service at MBK - this afforded me ample time to test run all sorts of locos.

I'm beginning to think that you are full of it (not disrespect meant, but what else should I think?).  It only takes couple of minutes of typing to provide some examples I asked for.

"not disrespect meant" - in the the middle of what I can only take as thinly veiled insult.  Is this forum moderated? 

I don't understand your hostility to folks that don't care for these motors. I have come to the conclusion that you and I have different ideas about what we consider to be acceptable low speed performance.

I came into this thread because the prospect of a better motor from Kato that might fit the GS4 excited me ... alas now I think I might to need to take a break from the railwire.

Mark

[peteski]

I don't understand your hostility to folks that don't care for these motors.

I believe you are confusing hostility with curiosity.  If I held some positive or negative opinion about something, and I was asked to present more specific details about on what I base my opinions on, I would gladly provide those.

I am sorry if I offended you Mark, but your refusal to provide some specific examples of acceptable and unacceptable models (as far as slow speed is concerned) was really very surprising to me.  Looks ike the older posts you quoted give me some insight to your experiences. Thanks!