SOLVED 9/02/2022: PS 3 powered locomotive abruptly stops and restarts after 3 minutes running

I’ve never been inside a Koh’s & Company anything, …..too rich for my blood, ….but nonetheless, how is this engine powered by Kohs?…..I see in your write up that this engine was converted in 2019, but that don’t really mean a hill of beans if it’s been a ticking time bomb waiting for 2022 to go off……I’d check mechanicals first, then disconnect the motor(s) from the board set and test them individually. Find out the max amp draw testing the motors on a straight power source,…..somebody might be able to note on here the max draw that board set can handle before it goes wonky……if your locomotive creeps up on or exceeds the allowable amperage being run on straight power, , then it’s game, set, match, time for plan B ……

Pat

Pat

Thanks for your input!  And I am glad you recalled my article!

The "roller test" I did (as cited in my original post) tells me there is nothing funky with the motors, the wiring, or the mechanicals.  I should have also mentionned in my original post that nothing felt warm during the roller test.

But your comment about "somebody might be able to note on here the max draw that board set can handle before it goes wonky" is why I asked the question if the PS 3 board can handle a motor drive of 1.4 Amps. If I am indeed exceeding the limits of the board, than that's the time bomb you have referred to. But if the board capability is more than that, then it would suggest something else is going on

@John Sethian posted:

Pat

Thanks for your input!  And I am glad you recalled my article!

The "roller test" I did (as cited in my original post) tells me there is nothing funky with the motors, the wiring, or the mechanicals.  I should have also mentionned in my original post that nothing felt warm during the roller test.

But your comment about "somebody might be able to note on here the max draw that board set can handle before it goes wonky" is why I asked the question if the PS 3 board can handle a motor drive of 1.4 Amps. If I am indeed exceeding the limits of the board, than that's the time bomb you have referred to. But if the board capability is more than that, then it would suggest something else is going on

How is that chassis powered/driven?…..what motor(s)?….what’s the drivetrain makeup?

Pat

@harmonyards posted:

How is that chassis powered/driven?…..what motor(s)?….what’s the drivetrain makeup?

Pat

Chassis powered by two Pitmann Series 9000 motors one at each end.  Each motor drives a gearbox that powers three axles through worm gears.   There are ball bearings everywhere. The photos below show the arrangement

Here are the specs on the motors, third column over for 12 volt

Since I was not running anywhere near maxium torque in any of my tests, the current I measured for two motors is consistent with the above

I just ran a similar running test with an MTH FM Train Master with PS 3.  Using the same protocols, the motor current draw was only .80 Amps. So I may indeed be up against a PS 3 current limit. But I'd like confirmation of that before changing to more efficient motors.

Thanks again

Ain’t gonna be the motors that are the problem, ….doubt you’ll get any more efficient than the Pittmans it came with……what I see is just ALOT happening under the hood of that GG1!…..don’t get me wrong, it’s a work of art,…even though they’re smaller Pittmans, I’d be willing to bet the 2 are kinda amp hungry given all the machinery that shaft has to go through to transmit power to the wheel sets…..correct me if I’m wrong, but all PS2 or 3 diesels and or electrics that are double motored, are powered by two small Mubachis …..not two honking Pittmans driven through an entire planetary gear arrangement…..😁

Pat

WOW!  I never saw that kind of complexity, that sucker should be a real stump puller!  The PS/3 board should be able to deliver more than 1.4 amps, but then we don't know what's happening with it's on the rails and running.  Pat is right, the MTH GG1 has two 3xx series Mabuchi motors, and they don't have that tortuous path to get to the wheels!

“Since I was not running anywhere near maxium torque in any of my tests, the current I measured for two motors is consistent with the above”

the motors aren’t running out of their intended specs, but I do believe the board set can’t deliver what the motors want via what the tach sensor is telling the board set to do …..the tach sensor doesn’t care if the board set eats itself alive trying to feed two grown adults vs. two small children…..all it knows is more, more, more….meanwhile, the board set is just like Scotty on Star Trek, …..” I’ve given er all she’s got Captain!” …”She’s gonna shake herself to pieces!” ….

Pat

You could very well be correct about the planetary gear arrangement, so I need to look into that.  Incidentally, these are not the motors it came with...those were even longer 9000 series motors.    I also think they are overkill for this (to give Kohs bragging rights, no doubt).   I am sure there are mor efficient motors out there

And you are correct about the MTH set ups.

Again though, I'd like to know the current spec on that PS3 motor drive. Anyone else know?  My tests show 0.64 Amps should be good.

And for that matter, I'd like to know what is actually happening!

@John Sethian posted:

You could very well be correct about the planetary gear arrangement, so I need to look into that.  Incidentally, these are not the motors it came with...those were even longer 9000 series motors.    I also think they are overkill for this (to give Kohs bragging rights, no doubt).   I am sure there are mor efficient motors out there

And you are correct about the MTH set ups.

Again though, I'd like to know the current spec on that PS3 motor drive. Anyone else know?  My tests show 0.64 Amps should be good.

How exactly are you concluding actual motor consumption being delivered via the driver portion of the board set?……and can you conclude consumption (amps) when the locomotive is on your layout at the point of failure?……you’d have to correct me if I’m wrong, but if you’re pulling your amp readings from the AC output, ie; reading it from the rails, that’s a different deal than what’s happening between the driver and the DC motors….in other words, the board set might be consuming what’s considered tolerable, but what’s happening between the driver and the motors might not be,……

Pat

@harmonyards posted:

How exactly are you concluding actual motor consumption being delivered via the driver portion of the board set?……and can you conclude consumption (amps) when the locomotive is on your layout at the point of failure?……you’d have to correct me if I’m wrong, but if you’re pulling your amp readings from the AC output, ie; reading it from the rails, that’s a different deal than what’s happening between the driver and the DC motors….in other words, the board set might be consuming what’s considered tolerable, but what’s happening between the driver and the motors might not be,……

Pat

Measuring the current input into the TIU with the motors running and not running, then subtracting the difference.  Unless there are current  multipliers or transformers in the PS 3 board, the RMS current should be continuous. As a check,  the current I got with the roller test where the meter was in one of the leads to the rollers, matched the current input to the TIU.

@John Sethian posted:

Assuming current is continuous.  Are there current  multipliers or transformers in the PS 3 board?   The current I got with the roller test where the meter was in one of the leads to the rollers, mactched the current input to the TIU.

Wellllllllllllll,……it’s not 100% conclusive of what’s actually happening between the driver and the motors, …yes, it’s continuous, but reading the amps on the outside doesn’t really tell us what’s happening on the inside ….( per say )  …..we know the motors are hungry, ….they have to be with all that motion happening….and we know you’re going into fault. So rather than trying to figure out a mathematical ah-ha ….can you perform a couple tests?…is there any way to uncouple one motor, and make that truck in sense a dummy with out having a baby??…or is that gear train just so complex you’d need a degree in Astro Physics to pull it off?….also, I see what looks like two huge weights??…are they super heavy?…does that engine weigh as much as a real GG1 ( I mean we are talking Kohs here) so can we take things away and perform another running test to determine if we’re on the right path??…..it might be too late for the board set, but nothing beats a try but a fail,….If you can run on one motor, and it’s successful, maybe an option ( If space is available) is to add a second board and treat the one engine like a lash up, or maybe John or George could suggest some sort of slave option??…I don’t know 100% but my mind says those two motors just have alot to do and the board set finally said enough is enough…..😉

Pat

@gunrunnerjohn posted:

WOW!  I never saw that kind of complexity, that sucker should be a real stump puller!  The PS/3 board should be able to deliver more than 1.4 amps, but then we don't know what's happening with it's on the rails and running.  Pat is right, the MTH GG1 has two 3xx series Mabuchi motors, and they don't have that tortuous path to get to the wheels!

Thanks John! That current limit is exactly what I need! 

I am not sure this is as tortuous a path as you two think it is. I am not sure there are planetry gears in that tower.  The overall ratio between motor and drive  shaft is 0.875:1.  So I think there are probably just spur gears.  In which case it's a common O scale drive system to have a tower drive from motor shaft to drive shaft, and then a worm gear boxes to transmit the power to each axle.   Think Sunset with spur gears replacing the belt drive.

I have other more efficient motors on hand, which can provide the same torque at 2/3 the current. But if John's limit (and my mesaurement technique)  is correct, I should not be having problems with what I have  So, I can measure the current directly to one of the motors with the roller test. That should answer Pat's concerns. I will report back. Probably won't happen until tomorrow.

@John Sethian posted:

You could very well be correct about the planetary gear arrangement, so I need to look into that.  Incidentally, these are not the motors it came with...those were even longer 9000 series motors.    I also think they are overkill for this (to give Kohs bragging rights, no doubt).   I am sure there are mor efficient motors out there

And you are correct about the MTH set ups.

Again though, I'd like to know the current spec on that PS3 motor drive. Anyone else know?  My tests show 0.64 Amps should be good.

And for that matter, I'd like to know what is actually happening!

How did they fit longer 9000’s in there?…..the stubby motors already look like they’re at the space limits now, ……what’s the full Pittman model number of the OE motors?…do you have that handy?….and why go to the stubby motors in the first place?…what was the criteria for going backwards in motor size?….

Pat

I'm only adding one cent here and I only glanced over your issue.

Obviously there are factors that change what the board can do. If you ran at lower track voltage for example, or if something isn't providing full power to the board, I'd guess that would seem like the board would handle less.

I believe these PS3 boards handle good loads. I have them in other brand one gauge engines that are power hogs without issue.

I had a one gauge engine that had a power path burn out. It was a printed circuit board that carried power from wheel pickups and the actual printed path was burned so that was one less point of power. That engine did not run right until I fixed it.

Of course none of this may apply, I'm only throwing something at you to consider looking at everything.

I've seen MTH board equipped engines stall because the tach didn't get the expected response from the motors. I've had chaffed wires rubbing the frames. Even a missing insulator inside a truck power point causing havoc. An old PS1 Allegheny I upgraded, had an intermittent short from a protrusion touching a smoke unit power pad. Took me near a year to finally find that one. It only occurred on certain turns or shell twists.

I will watch this thread and try to stay out of the way. Good luck and I will try and help with the little I can add.

In response to Pat’s concern that I may not be measuring the motor current properly, I added a current meter to the leads to one of the motors:

The meter on the right (set at AC) measures the current to the TIU, the meter on the left (set at DC) measures the current to the front motor. To keep things unambiguous, the rear motor is out of the circuit.  The meter on the right stabilizes at 0.620 Amps

Note this is a roller test

This is what I got

SMPH   One Motor         TIU          TIU (adjusted)

0            0                    .620                    0       

15          0.57             .844                  ,224

20          0.60             .902                  .280

25          0.64             .954                  .334

30         0.68             .975                  .350

35          0.70             1.02                  .400

It appears that measuring the current through the TIU is not an accurate way to measure the current through the motor (Thanks Pat) AND at 35 SMPH on rollers I am right at the limit that GRG cited (0.70 x 2 = 1.4 A), so that explains why I had the drop outs when running on the layout.

As I said in a previous post, I have other motors I can try.

@harmonyards posted:

How did they fit longer 9000’s in there?…..the stubby motors already look like they’re at the space limits now, ……what’s the full Pittman model number of the OE motors?…do you have that handy?….and why go to the stubby motors in the first place?…what was the criteria for going backwards in motor size?….

Pat

Yes.  In order to fit the longer OEM 9434 motors, Kohs had to resort to a "Unique soft universal joint"  which was two discs which engaged each other via nylon pegs. A conventional U joint would not have fit

As you can see above, these pegs break easily.  (Which by the way, is how I got this thing so inexpensively).  Going to a 9232 Pittman allowed me to use a more conventional universal joint:

Given the fact that the motors are driven using PWM, you may not be getting an accurate reading as well.

@John Sethian posted:

Going to a 9232 Pittman allowed me to use a more conventional universal joint:

Have you seen the drive shafts that Pat uses on his Pittman upgrades?  They come in all lengths, and are really a major upgrade from the cheesy dogbone U-Joints.

@gunrunnerjohn posted:

Given the fact that the motors are driven using PWM, you may not be getting an accurate reading as well.

It’d be nice to know the amp draw of the two combined motors without the PS3 board set in play,  …..maybe via a simple rectifier set up, or straight DC track power, and then determine consumption requirements under load on his layout, ….no??

Pat