MTH P5a electric loco problems

The MTH P5a drive design is not the best, as it uses one motor to drive two axles, and another motor to drive a single axle.  So the power is not balanced.  Since all the drivers are mounted to a rigid frame, all it takes is a little imbalance in weight distribution to lift one wheel, and hence start it slipping.  Imagine a teeter-totter with the blind center driver as the fulcrum.  If slipping starts on the motor with the tach reader, the DCS system will think the loco is moving, and won't apply more voltage to the stalled motor.  

Here are some things you can try; going from easiest to hardest

1) Remove the springs from the four wheel trucks.  That prevents weight from being taken off the drivers.  In other words,  maximizes the weight on the drivers, and hence minimizes slipping.  The four wheel trucks should track fine,  but if they  derail, add some weight on top of them

2) Pull off the shell, and spray contact cleaner into the motors.  Test with the shell off to make sure both motors start turning at the same time.  If that doesn't happen, start lubricating the drive train

3) Make sure the Tach reader is on the motor that turns two axles, and not just one.    This is not as much a help as you would like, as the pair of axles can slip as well, but your chances are better that the pair won't start slipping

4) Remove the motor that drives the single axle.  Add weight where the motor was.  This helps prevent the powered pair of axles from slipping.   And they should be powerful enough to pull a reasonable train

I have done the above, and that usually solves the problem

5) Remove the motor that drives the single axle, and power the single axle via sidewinder gears from the middle axle,  this is complicated, and not for the faint of heart. I have never done it, but have contemplated it from time to time, as I am sure it will solve the problem

John,

this should get it working.

thank you very much for the suggestions!

Jeff

Interesting; I have contemplated one of these when I see them at OK prices. Electrics are cool, even those of dumb 'ol Pennsy....good to know if I do and try to run it on my, ah, "less than perfect" track. 

3rd Rail did these, also, I think - but that is probably a whole 'nuther can of problem worms.

Thanks for the info. I wonder if you can get another powered truck that powers both axels and would it work properly.

Several years ago forum member PA posted a fix that follows John's #3 recommendation:

"The first MTH P5a had the tach tape on the motor that drove the wheels without traction tires. The wheels without the tires would spin without the P5a moving. By switching the motors so the motor with the tach tape powered the wheels with the tires, the P5a ran much better. Adding a little weight to the end with the traction tires also helped the P5a run better.

The later P5a had the tach tape on the motor that powered the wheels with the tires so MTH corrected that problem."

Sounds like switching the motors so that the motor with the tach tape is driving the wheels with the traction tires helps.

I wonder if the later versions were the ones with electrical operating pantographs?

This problem sounds like the issues with the Lionel Legacy Lionmaster T1-Duplex.  It has the same kind of traction issues.  I have the later P5a, and it's never had any traction issues.

I have a couple of earlier versions and the 3 volt versions. I was wondering if I could put a smoke unit in the 5 volt and have the smoke to come out by the wheels and have it look like steam coming from the bottom of loco.