PS2 engine "jerky" at low speed

Depending on what engine it is MTH usually supplies them in parts section or if your good at those tiny measurements you could make your own. Another thing is the motors arent broken in whch that may be the case. What locomotive is it and how long have you had it?

I just got it on a forum purchase, so I've had it for one day.

I have never had to "break in" a can motor, is that really a factor?  I'm willin' to learn, anything's possible.

How exactly would you make your own tach tape?  The one on there looks fine with my "fixes", but I'm wondering if the real tape has some special reflective properties that my fixes don't provide.

I just ran into a similar situation with my 5V PS2 GP9, turned out to be a dying motor (not the tach motor). This engine was an eBay purchase, used, and had been fine for about 4 or 5 operating hours over a two year period.

A couple of weeks ago it started running jerkily at slow speeds, but seemed ok over about 15 SMPH. I took the body off and checked that the motors turned freely by hand - ok. I then put it up on a block of wood under the fuel tank, and connected to track power with clip leads. At slow speeds, the front motor was definitely jerky. I checked the voltage on the motor leads and both motors were getting the same voltage. At 2 or 3V, the front motor was stalled, while the rear motor ran fine. Up around 4 or 5V, the front motor ran slower than the rear.

There did not seem to be any noticeable difference in mechanical friction on either motor.

I ordered a new motor assembly from MTH.

Good Luck with your engine!

Gary F.

I guess it's time to put it on my track blocks and see what it looks like.  Hopefully, it's not the rear motor, then I'd need a new tach tape and I'd have to mount the sensor again.

Check the gears for small grains of ballast or other debris such as carpet fibers.  At slow speeds a speck of dirt can make an engine jerk. (hey that rhymed)!

I had a grain of ballast get into my Atlas GP9 (with PS2) a while back and it actually made the rear motor/gearing stop turning and drag down the track, while the front truck was pulling fine.

I think you're a genius Gary, it appears that the front motor has a problem.  I had it up to 3-4 scale MPH before that even started moving on blocks, and when it gets to 6-7, it gets much smoother, which is about where the engine smooths out. 

Bummer, I hoped it was something cheap.

I checked the gears, and even did some cleaning and relubing.  The motors turn fine by hand, and the front one actually felt even smoother than the back one to me, even if by a small margin.  However, on blocks, the front one doesn't run until I get up to 5-6MPH, and you can see it jerking until you get faster.  The rear motor appears to run much smoother at anything above 1MPH.  Since the motors are wired in parallel, I'd expect them to run pretty much the same with no load.  They do the same thing in reverse as well.  I also tried Gary's trick of suspending it above a block and connecting it to the track, same result.

John,

Is it that one motor is faulty or is it that the manufacturers don't use "matched" motors?

Maybe the "faulty" motor should be saved or even swapped and paired with another "faulty" one.

I'm sure they don't go into a lot of matching on these mass-produced motors, is the electronics suppose to account for mis-matched motors?

Motors can fail, such as if overheated, which makes brushes lose tension.  Or a bearing could be worn.  Or complain to seller.

I have noticed that MTH locos with 2 motors, that have PS2, that the motor without the tach stripe starts after the one with the tach stripe, as that is what the board reads when it powers up the motors; I don't know why they work that way, but it is especially notable when running the loco upside down in a cradle. For all practical purposes it shouldn't matter, but in this case it does. I don't know if a new motor would help much, but they are around $15 or so. LMK what loco you have, I might have a used one you could try out, and LMK if you want a tach stripe, I have several. The catch is, you have to measure the flywheel diameter to get the correct stripe for it. I do have a couple stripe sets that have four different length stripes, would send you a sheet of those for you to try. Be sure to clean the flywheel before putting the stripe on it, for best adhesion. You could try this, before buying a new motor for the loco. Email me, my address is in my profile.

hi all...try reloading the sound file...sometimes they become corrupt..i had a steam engine do the same thing....i replaced the tach reader and strip and still had the problem....i reloaded the sound file and the engine runs like a top...   vinny

Clint,  That should not matter.  Both motors get power in parallel from the 5 pin motor connector.  The tach reader just sits there measuring speed.  Both motors get the same signal.

The only difference are the length of the motor lead wire depending on where the PS-2 board is located, and the fact one turns gears in the fwd direction and the other in reverse since the truck is reversed.

Just as the old Lionel PW twin motor units required a check to ensure both were operated together, the DC motors should also.

Some items that I have seen is grease packing into the motor vents, smoke fluid overflow on to the motor, mechanical binding.  These motors can go bad.

John, one thing to try is cleaning the interior of the motor with a CRC electric type cleaner.  See if the that helps clean the communtator and brush area.

I also test the motors out of the unit and in the unit with an amp meter in series and read current flow.  Ensure the motor is unplugged from the PS-2 board if you don't desolder the leads.  If it is significantly different and if cleaning with a CRC spray doesn't help, time to replace the motor/motors depending on how many hours this unit was run.  G

I did shoot CRC cleaner/lube in, and that actually "slightly" improved the operation, though it's still pretty bad.  I also measured the connection between the motors, it's a dead short, both motors are in parallel, so obviously receiving the same voltage.  I also took apart both trucks and did a cleaning and lube, also checked to see if there was any gear damage, all looked fine.

At this point, I have to believe it's the motor, although the tach strip still has me wondering since I "repaired" it.  Totally free and dangling in space, the rear motor starts as expected at a scale 1MPH, the front motor starts it's jerky movement at 3 or 4.  Around 6-7, they smooth out, or at least go fast enough not to be able to see the problem. When the front motor starts running at slow speed, it is very jumpy, the rear motor runs a lot smoother at slow speed.

The engine has 25:36 hours and 244.8 miles, so it shouldn't be at it's end of life just yet!

John & G,

I also measured the connection between the motors, it's a dead short, both motors are in parallel, so obviously receiving the same voltage

Are you certain?

The way the motors maintain speed is that the master (tach strip) motor counts revolutions to match the speed set by the DCS Remote (or track voltage if operating conventionally) and then tells the slave (other) motor how fast to turn. You'll also note that the two motors have completely separate connections to the PS2 board.

Heres two MTH motors with tach tape and tach reader and connector to board on ebay http://www.ebay.com/itm/MTH-Motors-proto-two-w-reader-/130702078527?pt=Model_RR_Trains&hash=item1e6e73723f You can replace two motors instead of one eventually dying

Barry, re number of motor leads:  Cf the steam loco upgrade kit manual, pp 14 & 25, where it shows only 2 motor leads, even for 2-motored steamers (like Challenger).  On the other hand, p16 of the diesel manual does show separate leads to each motor. Interesting difference.

I did use a diesel kit when I converted a Weaver 0-6-0 brass to PS2, to get 2 couplers, but I didn't use the standard tender connection

I actually looked at the circuit board and measured the resistance directly at the motor connector.  While there are two connections, the motors are directly connected together, the pins on the board are wired in parallel.  This is on a 3V board in the MTH 30-2659-1 Catepillar SD-45.

Also, unless the folks at MTH have done something like the ERR Cruise Commander back-EMF sensing, they'd have no idea how fast the other motor is running.  I am pretty sure they just depend on the motors and trucks having similar characteristics.

I'd like to find the parts list for the MTH 30-2659-1, but it's not on the MTH site. 

Liam, I'm not sure I want to buy used motors off eBay, if they have the wrong gear, I'm stuck.  Apparently, there are several worm gear sizes for MTH motors.  Also, there's no certainty that "tested" means they run truly properly.  I could sell this pair of motors as "tested", after all they both rotate.

Hi all,

Apparently, there are several worm gear sizes for MTH motors.

Only in steam engines John.  All factory PS2 diesels (Railking and Premier) have used the same motors and worm gears.

That's good to know Dave.  I was aware that the steamers used different gears, I wasn't sure about the diesels.  Since I don't have one of each to compare, it's hard to know.

Where might I find a parts list for my MTH 30-2659-1 Catepillar SD-45, it's not on-line at MTH.

That's my feeling as well.  By the time I pay shipping, they're over $50, I want to know they're new for that.

Call Midge at MTH, 410-381-2580, x516. She knows all the parts! (and she's pretty busy, so bear with her...).

Or you can email her at midge@mth-railking.com

John,

Before buying anything, how about disconnecting the motors from the electronics and trying them each on straight DC. That way you can compare starting voltages of each one individually without any uncertainty about the effect of the PS2 board. That should tell you if there is really a difference in starting voltages for the two.

Jim

Since they're wired directly in parallel, it's hard for me to imagine they're not getting the same starting voltage, how could they?

I know that I can call her, I was hoping to find the exploded parts list for the locomotive.  I'd like to have that around anyway.

I agree, John - but I meant to also say test the motors separately while they are detached from the truck assembly. That would remove any frictional differences from the equation.

But, in my experience, such exact matching of the motors isn't really necessary for smooth slow speed operation. The motors we use aren't really high precision types, but most engines manage just fine. Slight differences manage to smooth themselves out.

I think something else is going on.

Jim

I did remove them from the trucks, so that they were running free with no load.  I got the same behavior there, which is why I'm about 95% convinced it's primarily the front motor that is just not carrying it's load.  Funny thing, I suspect if it was the rear motor, it would probably work fine, since the speed control would just keep pouring on the coals until it was at the right speed.

John, you have a knack for getting the long topics going:-)

If you had a direct short, not sure the motor would spin at all, and the amps would go pretty high.  I assume you took some amp readings during the test.  You may have a bad pole.

You have done everything possible.  Time to order a new motor. It happens, they go bad. 

Barry, Slave is probably not a good term for the second motor.   There is no independent motor FETs and Relays, so there is no independent control of motors.  They both get the same voltage. 

Even on a Slave power unit, there is not a feed back signal.  The expectation is the slave board and motor will perform like the Lead unit.  That is why when there is a wiring problem or motor problem in the Slave unit, the Slave board blows one or both of the motor directional FETs.  G

Gosh, I have a ways to go to get this one into the loooooong category.

I'm pretty sure it's the motor, I'm a little annoyed that wasn't disclosed by the forum seller.  I guess it really is caveat emptor nowadays.  I will have to get the motor.  I also want to replace the tach strip that was all rubbed off, though that seem to work pretty well with my "fixes".

I'm 100% sure they both get the same voltage, because the board has a direct connection between the two motor connections.  I suspect the individual wires are strictly a concession to wiring convenience, easier than having a splice somewhere to route the power to the motors.

They are connected.  You can see it on the trace at the pins.  G

I didn't even try to see that, just put a meter on it.  I figure that zero ohms means it's a pretty hard connection.

Don't know how badly you want to keep this engine, but my feeling is I'd ask seller to pay for new motor, or accept return for full refund.

Yes, but some one could say maybe a FET shorted, but the solid trace connection means it is meant to be that way.  :-)  G

Don't know how badly you want to keep this engine, but my feeling is I'd ask seller to pay for new motor, or accept return for full refund.

Well, since he didn't even respond to my email, I'm guessing he's just walking away.  Clearly, not everyone that sells here is 100% honest about the condition of the items.

I had a similar problem with my mth rk ny&atlantic switcher,the wiring was rubbing against the can motor/flywheel.There is very little room under that shell.I had added marker lights to the unit and had re tie all the wiring.  Lou

Not sure what was rubbing on this one, when I took it apart there were no wires or connectors that appears to be close, and I didn't find any evidence that anything rubbed, just a chewed up tach strip.

Gee Ted, thanks for the very useful post.   Perhaps now you can crawl back into the hole you crawled out of?

Jon,

I respectfully suggest that you read Ted's post again, carefully.

While you may not like what he has to say, what he says is, to a varying degree, what several of us have been hinting to you for a while.

You just got here as regards DCS and PS2, yet you have an annoying tendency to ccme across as "too smart, too soon".

You can profit from what Ted wrote.

One's best friend is the person who will tell them that they need a bath, or that the suit of clothes of which they are so proud doesn't fit well.  Ted's comment makes him a "best friend."

Ted, I support you, and suggest you don't dignify the author & his comment by responding.  Personally, I think any requests for aid from this poster should be ignored unless he apologizes to you for his comment.

Had he limited his response to more constructive tone, I'd have probably received it a lot better.  It appears the intent was simply to incite such an exchange.  In truth, I probably shouldn't have responded at all.