PS2 ABA Second A Unit Dragging Rear Truck at Slow Speed

The slave doesn't have a tach reader on either motor.  If it's dragging the one truck, my guess is there's excessive friction in either the motor or the truck gears.

Agree with John, the slave isn’t selective. If there’s power being applied to the motors, it’s equal. You need to be looking at obstructions, or foreign objects like ballast crunched up in the gears that can cause a drag. The motor itself could also be suspect. Pretty easy to swap that out. Although I’d rule out all other environmental factors, such as truck binding, etc. Check fasteners for tightness. A loose mounting screw can cause the motor to lean a touch, & that’s enough to make a slight load on any one motor.

Pat

Thanks for the info, I'll pull it apart more tonight and look for something that might be binding the drive up. I'm assuming since the set is older probably needs fresh grease.

You could also try a spritz of electronics cleaner INTO the lazy motor.  If it was stored in a damp environment, perhaps the brushes/commutator are oxidized and will burnish with regular use?

@Ted S posted:

You could also try a spritz of electronics cleaner INTO the lazy motor.  If it was stored in a damp environment, perhaps the brushes/commutator are oxidized and will burnish with regular use?

My only fear with telling folks to spritz contact cleaner into a sealed can motor such as a Mabuchi 385, etc, is the potential for fire ball if the solvents are not fully evacuated from the can, …..I understand a “spritz”, and I’m sure you understand a “spritz” but what about the rest of the railroading public?  ……..I’m always hesitant to suggest such a procedure, because I don’t know the end user’s capabilities or understanding. Just a PSA for those that don’t know about this,……

Pat

We use CRC Lectra-motive cleaner at MTH. Non flammable, we spray into the motor while it’s running.  If testing a motor with DC, the current usually drops in half.

I took the truck and motor out tonight, cleaned them good and added new grease and oiled the trucks well.  Everything is moving freely and there were no blockages.  BUT the issue is still there, I ran it again for a while to work the grease in and still below 6 Scale MPH it drags the truck or stutters a lot while running.  Just seems like that rear motor isn't getting the same power or moving as well.

Tomorrow I'm going to try to check the voltage at the motor while it is running and I might also explore getting a new motor from MTH, just not sure how much they are, have to look it up on the parts site.

For the record, I also have a set of FT ABA (20-2345-1) which I purchased brand-new circa 2004.  Mine did the same thing the OP describes up to about 5 scale MPH as indicated by the DCS remote.  I tried hard to resolve this "chuckle and surge" in the first few months of ownership through careful inspection and break-in running.  There was no binding or obvious mechanical issue with the problem truck(s).  My FTs in particular had thin flywheels that, in conjunction with a tall 10.5:1 gear ratio, don't store much momentum at those RPMs.  And the gears are self-locking, so if ANY motor stops turning it will momentarily act like a brake.  This can "trick" the speed control into feeding more power, which contributes to surging.

After a month or two I got disgusted and called MTH tech support for ideas.  Whoever I spoke to  said that it was too much to expect smooth operation at such slow speeds.  His last suggestion was to buy a couple of replacement motors in hopes of obtaining a set of four that had similar low voltage characteristics.  I didn't.

After Lionel's well-documented struggles with the Odyssey "lurch," Lionel solved this problem by fitting their dual-motored Legacy diesels with back-drivable gears.  If any motor stops briefly, the other one(s) can help it along through the rails until it starts turning again.  Also, the whole mass of the train contributes to momentum.  True story and food for thought.

@ArtsModelTrains posted:

I took the truck and motor out tonight, cleaned them good and added new grease and oiled the trucks well.  Everything is moving freely and there were no blockages.  BUT the issue is still there, I ran it again for a while to work the grease in and still below 6 Scale MPH it drags the truck or stutters a lot while running.  Just seems like that rear motor isn't getting the same power or moving as well.

Tomorrow I'm going to try to check the voltage at the motor while it is running and I might also explore getting a new motor from MTH, just not sure how much they are, have to look it up on the parts site.

I would Try Jon G.’s trick and spray CRC’s Lectra Motive cleaner in that motor. If there’s any improvement, at least then you’ve found your smoking gun.

Pat

I put a drop of Deoxit-D5 into the brushes of any can motor I have on the bench, it's amazing what it does for many of them.

When I'm trying to determine if a motor is bad, I run it free running on the bench and check the lowest voltage it'll start up on and also it's running current at a constant voltage of say 5V.  I find most of the Mabuchi RS385 motors commonly used will be running before the voltages reaches 2VDC, and at 5VDC, if they draw more than 150-160ma, I consider them marginal.  If the running current is more than 200ma, I consider them likely bad.  This is after I give them the drop of Deoxit-D5 on the brushes.

For slave units if one motor starts late the gear will grab and then it will take more speed (current to that motor) to start turning.

The PS-2 ABA slave can be problematic.  The Early 5V system had too much delay in the slave board applying power to the motors.  MTH modified the slave boards to remove delay.

Gear lash, binding etc... really needs to be check and removed.  Also some early units like E-8 the axle gear would crack and bind with worm.  Not your issue, but symptom for others.   G