Kato N scale SD45

[carmelmodelrr]

I have a pair of Kato SD45's--the older versions, not the fairly new "revisions".  I run DC.  I run the pair together and one of the two has been somewhat inconsistent--sometimes it pulls really well, other times it's erratically poor pulling.  After running the locos for about 45 minutes, I took off the shell of the inconsistent loco to see if I could solve the mystery and discovered that the main frame was hot--really, really hot--too hot to touch until it cooled down for about 10 minutes or so.  I was surprised that given the temperature of the frame it didn't harm the shell.  (The other SD45 frame was warm, but nothing to be concerned about.)  Any ideas as to what might be causing this heat buildup?

Thanks for your help.

carmelmodelrr
Richard Wroblewski

[ryan_wilkerson]

Seems like it shouldn't be friction with that much heat? Maybe there is an electrical short between the frame halves?
When uncoupled, do they both run at the same speed?
Does the hot one make a different noise?
Do you have a way to check the power draw of each locomotive when on the tracks and running?

I haven't experienced something like this...just some ideas.

[Bob Horn]

Richard,  I would start with lube on both locos, if they are old style dual light board locos that would help greatly. I use Conductalube on the gear train as well as the motor and chassis bushings. This has worked for me, the conductalube is light enough to loosen up bearings and not leave a mess. Bob.

[peteski]

Richard,
The chassis frames are just big slabs of die-cast metal and I don't see how they could heat up themselves.  So something else must be heating them up.  Most likely suspect is the motor. Did you by chance touch the armature of the motor (through the openings in the frame) while the loco was hot?  Was the armature also hot?

Can something be binding in the mechanism causing the motor to run harder? Does this loco run slower than the other one which doesn't get very hot  (if you put them on the same track but keep them separated)?

[nkalanaga]

I'm with Peteski.  A bind in the drive, or a bad motor, seems to be the likely cause.

Any electrical short between the two halves might heat the offending material, but if it's drawing enough current to heat two large blocks of metal it should have blown the breaker long ago.  If the breaker didn't work, the power pack would have overloaded, and either burned out, or had such a voltage drop neither unit would run.

[jagged ben]

If something binds the motor hard enough then it will draw more energy in an attempt to get up to speed.    If it fails to speed up because of the binding, that energy will dissipate from the motor as heat.  And since the motor is right up inside those frames they will heat up. 

So the source of the heat is probably electrical but the underlying problem is likely mechanical, like something in the truck gears that's stopping them from spinning. 

If it were me, I would overhaul the trucks and gears, not just count on lube to solve the problem.   These Kato trucks are well made.  If you take them out of the mechanism they should be free rolling for several inches across a flat surface.  If one (or both) of them is not, take that one apart and clean all dirt out of the gears real carefully.  When you put it back together and it's free rolling again, reassemble the mech.

[randgust]

Loosen the two screws, remove the trucks, and tighten back up.  Do a 'hot lead' test to the frame halves.    While the trucks are off, lubricate the worm shafts into the plastic bearing bushings.

Roll-test the trucks, they should pretty much roll freely.   Doubt it is the trucks.   I'm guessing either the worm shaft bearings are almost seized up/worn/misaligned, or the motor is gummed up/bound up/something.

If it still is running tight and hot after the bearings are lubed, disssassemble the frame halves, pull the motor out, and hot-lead test directly to the motor.  Spin the armature with your fingers to feel for binding, rubbing, etc.  LIGHTLY lubricate the motor bearings with a plastic-compatible oil like LaBelle 108.   If that doesn't cure it, it's time to think about a motor or mechanism swap.

There's no way it should be running that hot without something significant wrong.

As a last resort, always remember you can find the old ones on the auction site at pretty good prices.   I bought a total of seven of them, all used to a degree, and averaged about $25 a unit without shipping.   I regularly run five and keep two as parts spares.    For used units, they hold up far better than most locomotives, but I have had to lubricate motor bearings when I got the 'kato screech' a while back.

[rrjim1]

Everything Rand suggested plus, check the commutator and brushes, if there gummed up, clean with some kind of motor cleaner. Something else I have seen with the older Kato motors is a broken winding, replace motor! 

[ns737]

HI it is a good chance it is the motor. I had one kato sd40 that would get hot no mater what i did to try to fix it. the motor just never was right. this engine was new out of the box bad. i checked all parts,swapped trucks,worms,bearings, all where good, then i changed the motor. and the engine has been running great now to this day. no more hot running.

[peteski]

HI it is a good chance it is the motor. I had one kato sd40 that would get hot no mater what i did to try to fix it. the motor just never was right. this engine was new out of the box bad. i checked all parts,swapped trucks,worms,bearings, all where good, then i changed the motor. and the engine has been running great now to this day. no more hot running.

That sounds like (unless there were shorted windings) the commutator was clogged up with a mixture of carbon powder from the brushes mixed with oil. This can often happen on over-oiled motors).  The oil from the bearing oozes onto the commutator attracting the carbon dust from the brushes. Eventually that creates a low resistance path through the commutator segments which increases the current draw and heats up the motor.

You might have been able to save that motor simply by giving it (and its commutator) a thorough cleaning.

[ns737]

I did do a complete cleaning. that motor just was bad. it happens from time to time.

[peteski]

I did do a complete cleaning. that motor just was bad. it happens from time to time.

You didn't specifically mention cleaning the motor (just replacing it) - that is why I chimed in.

 But if you actually either dunked the motor in a ultrasonic cleaner filled with a solvent like naphtha or took a toothpick and picked the carbon dust from all the slots in the commutator (which is pretty much impossible on Kato motors since the commutator is not accessible without taking the motor apart), then I would say that yes, you did a thorough cleaning of the motor and it most likely had shorted rotor windings.  It does happen from time to time.

[strummer]

Just had to do the same thing with the MT Z scale F7 I picked up. Was running hot as blazes (I bet that's why the shell came to me warped and distorted); a complete tear-down, cleaning and new brushes and it runs fine, and MUCH cooler as well.

Mark in Oregon

[ns737]

no prob. sorry about that. but yes it was cleaned in a bath. I am the club repair guy only because i like to tinker and get things running again. what was nice is the club bought me the cleaning unit.

[carmelmodelrr]

Thank you for all of the replies.  For what it's worth, I had performed most of the suggested fixes before I started this thread.  I was leaning to replacing the motor as the best method to restore the locomotive to its original condition, but I wanted to hear what this group thought as a possible solution.  It looks like a small consensus feels that a new motor might be the answer--and I agree, so I'm ordering one this evening.  I'll let you know how this plays out.

Thanks again for your input.  It's appreciated.

carmelmodelrr
Richard Wroblewski