Large Scale Central

Aristocraft Dash 9

The E8/9 have the same drive as the Dash 9 and SD 45 and were all produced in similar versions in the same production runs and therefore with the same issues.

Version 2 still had 12 volt motors but isn’t noticeable without disassembly and testing. The drives for all these locomotives were built separately and all the locomotive truck assemblies were thereafter designed to fit that drive. A number of drives with different versions were installed in all locomotives and the other thing is that we really don’t know if protocols were followed exactly to the year of assembly and what locomotives had version 2 drives installed or more recent. We also don’t know the exact change over date (to 24 volt) and how many version 2 drives were left over and installed in newer locomotives, or vice versa.

Another thing is, how many drives in the change over actually had the required new 24 volt motors that were to be installed in versions 3 and on. I don’t even think Aristocraft actually knew if the Chinese factory was legitimately installing the 24 volt motors required in the change over into every unit, (at least immediately) even though they were supposed to.

How long did it go on, that’s anybody’s guess. I do know, of the 9, E8 models I’ve worked on, I have found 4 drives (2 locos) with 12 volt motors. The rest were 24. So I think it’s the same issue any way you go with these drives.

You literally have to tear them apart and test them before you really know, unless motor/s fail. Then, if the locomotive has been under heavy strain, the voltage of the motor might be the reason for the failure because most of the time these drives don’t fail.

Tonight, I tested 2 locomotives (First run BNSF 12 V & CP Rail 24 V drives) for speed and amperage and the 12 volt speed difference is so minut that it’s hardly noticeable and maybe that’s why Navin said you can run them together. The amperage draw was more on the 24 volt by only 1/16th of an amp but that didn’t seem to make much difference. The only difference that I noticed (barely) is the very tiny speed difference in each locomotive on the track. The one with the 12 volt motors took a measured 612.6 feet of track to catch up with the locomotive with the 24 volt motors after being started only 6 feet away from each other originally. I have run these 2 (version 2 and 4) together for 8 years or so in my program pulling 35 cars on average (sometimes more) without any gear damage, excessive wheel wear or motor failure so I don’t believe running the 2 together harms them in any way. If it does do any harm, it must take forever. Most people probably aren’t even aware of the version in their locomotive and probably will never have an issue.

Again, just my thoughts and observations.

Ken

There are no marking on my motors, i gonna put the two 12 volts motors from Clay in the same motor block and keep my good motor for spare. So if my CP dash 9 have 24 volts motors, the front motor block will be 24 volts and the back will be 12 volts.

Francois

Greg Elmassian said:

PWM… so if you have a motor driver I would submit you want the higher voltage motor for safety…

The speeds may be proportional but not linear.

Greg

Greg,

Why higher voltage combined with a PWM motor controller at our voltages/current utilizing DCM is safer is eluding me this morning?

Michael

Michel, I suspect a missing coma has befuddled the thinker…

“PWM… so if you have a motor driver I would submit you want the higher voltage motor(,) for safety…”(https://www.largescalecentral.com/externals/tinymce/plugins/emoticons/img/smiley-wink.gif)

Fancois,

I’m running an engine like that and have been for years with no problems. I think you’ll be fine. No worries!

Just make sure not to put a lot of downward force on the drive train when you reinstall it into the black plastic drive block, so as not to bend the motor shafts or get it misaligned. Make sure your leads (pos. & neg) are the correct direction on both motors and that the motors turn free and that your axles/wheels are turning the same direction as the other locomotive motor block before installation. It’s up to you if you want to resolder the leads to the contacts but if you do, everything has to be in perfect line to avoid binding, excessive amp draw, overheating and excessive noise.

On mine, I’ve just gently squeezed the forks a little closer or tighter and at a very light angle for a snug fit with some double stick tape underneath and slightly to the side. Just make sure there is no bind anywhere when the cover is put on.

It’s really up to you either way but the one thing that is most important is to continually check for excessive amperage draw to be sure the drive is not binding anywhere before you reinstall it.

One last thing, when you reinstall it in the locomotive, don’t apply too much power on your first test, just in case there is a short or motor installed backwards, etc. You don’t want to fry something so check to be sure there are no shorts before putting a lot of power to it.

Believe me, it’s easy to do, even if you think you’ve got it right.

I would turn the locomotive upside down for power testing to make sure both motor blocks and all wheels are turning the same direction, on both blocks because if they are not and you put on a track for testing, you will have a direct short which can damage, motors, circuit boards, electronics, etc. If you find something running backwards or opposite, unfortunately, you’ll have to go back in and remove the drive and motors and turn the backward running motor over and put it all back together and try it again.

Just a few helpful hints.

Good luck! Ken

John Caughey said:

Michel, I suspect a missing coma has befuddled the thinker…

“PWM… so if you have a motor driver I would submit you want the higher voltage motor(,) for safety…”(https://www.largescalecentral.com/externals/tinymce/plugins/emoticons/img/smiley-wink.gif)

John,

As you note, I understood same. It’s simply a quandary for me as to why a 24V motor is safer with PWM verses 12V motor, even @ 24V.

What are your thoughts herein Greg?

Michael

Umm… Michael

You said “How often do you run at 24V?” That prompted my response “PWM”, figured that was enough explanation.

So, I ALWAYS run at 24V because I run DCC and the motor driver boards are PWM, so my motors are getting nice 24v pulses, and we also know that PWM does indeed heat motors more than DC.

Not sure of what you mean by “DCM” …

Now, how much a particular 12v motor heats at the same load as a 24v motor does, I would guess more… but who knows what the real specs are? Most motor failures that are not brush contamination or bearing problems are caused by heat. But one thing for sure, PWM puts full voltages pulses to the motor no matter what the speed and load.

Greg

Michael Glavin said:

Greg Elmassian said:

PWM… so if you have a motor driver I would submit you want the higher voltage motor for safety…

The speeds may be proportional but not linear.

Greg

Greg,

Why higher voltage combined with a PWM motor controller at our voltages/current utilizing DCM is safer is eluding me this morning?

Michael

Greg Elmassian said:

Umm… Michael

You said “How often do you run at 24V?” That prompted my response “PWM”, figured that was enough explanation.

So, I ALWAYS run at 24V because I run DCC and the motor driver boards are PWM, so my motors are getting nice 24v pulses, and we also know that PWM does indeed heat motors more than DC.

Not sure of what you mean by “DCM” …

Now, how much a particular 12v motor heats at the same load as a 24v motor does, I would guess more… but who knows what the real specs are? Most motor failures that are not brush contamination or bearing problems are caused by heat. But one thing for sure, PWM puts full voltages pulses to the motor no matter what the speed and load.

Greg

Well I haven’t pondered this stuff much of late… But the PWM duty cycle together with the actual load results in an average voltage as I recall. So, unless you run at 100% duty cycle and or throttle, the motor doesn’t see 24V… So how often do you run at 24V?

DCM = Discontinuous conduction mode; common with small DC motors and or RC/Hobby stuff. DCM is the norm verses CCM with our PWM controllers.

In reality, operating motors at higher than nominal VOLTAGE ratings does no harm them. Motor DAMAGE is atypical of brush arcing, bearing over-speed/loading and overheating. Voltage is an obtuse method for controlling our DC motors, on the other hand CURRENT is king!

Michael

Actually the motor always “sees” the 24v (or the full voltage pulses) and the inductance of the motor affects what happens in terms of resultant torque/hp, but the square waves make much more heat since that energy has to go somewhere, clearly the motor does not run 0 rpm and then full speed and then zero.

This heat has been known to overheat some motors, and the damage ranges from melted plastic structures supporting the windings, to overheating poor solder joints between the winding and the commutator segments but the most common thing damaged is overheated windings and insufficient heat resistance of the enamel insulation on the windings which results in short circuits.

The most common example are the ill-fated Aristo GP-40’s where most of the motors go up in smoke… (the insulation fails from the heat, which shorts some windings, which increases the current flow, which makes more heat, and away we go.

But I agree, as long as there’s no insulation breakdown, voltage means very little. There’s a recent test on track sweepers, and the motor supplied is rated for 6-12 volts and I have run it continuously for hours on 20v with no damage.

It does appear that with the normal PWM we use, where the only modulation is on time, and the size and inductive ranges of our motors we are most likely always in DCM… Have you seen any hobby stuff with FM modulation or more sophisticated schemes? (not counting the old style constant frequency and width pulse stuff with the rising DC background… which actually did not work too bad).

Greg

Greg,

While I concur with your premise with regard to the motor seeing 24V pulses and or FULL rail voltage (less electrical losses), for microsecond intervals together with microsecond OFF intervals. The result of same is known as the “DUTY CYCLE”. When its all said and done the Duty Cycle is the average voltage the motor sees at a given pulse width. A 24V Rail @ 50% Duty Cycle nets a 12V average.

PWM Switching Regulators are analogous with PWM Motor Controls, at they not?

Inertia carries the motors armature through the OFF cycles.

THE GP40 motors were defective, ill specified or did not meet requested specifications.

No knowledge of FM hobby stuff. Kinda recall someone playing with PFM though.

Michael

Maybe we are arguing over what “sees” means… what voltage is applied to the motor is the square wave pulse. The current is no longer a square wave due to the inductance. Yes, average, etc.

The heating that you get though for an average 12 volts from PWM at a 50% duty cycle is much higher than running 12 volts DC into the motor.

Switching regulators are another story, the inductors are chosen to work with the frequencies used, and are much more complex in how they modulate the signal. They also use toroidal inductors, not windings on an armature, and of course they are in continuous mode not discontinuous mode.

I can talk about PDM and other things that are part of modern switching regulators, but really not directly analogous.

Yes indeed the mechanical inertia forces the motor to keep turning, so far the basic laws of kinematics are still valid ha ha! Not sure what brought that comment, because we can get into BEMF and everywhere…

The GP40 motors had defective enamel insulation, proven by disassembly. This is a common cost cutting, using cheap enamel (or whatever) insulation that broke down under heat.

The FM was in terms of modulation of the power to the loco, where most PWM systems use a fixed frequency, there are some systems (not hobby AFAIK) that use FM modulation of the PWM system, can give more efficiency, etc. Usually used in larger motors from what I can glean.

Fun stuff…

Greg