Growling Kato Motor

[BCR751]

Wanting to make sure there were no issues prior to installing a decoder, I took my new (to me) Kato SD40-2 apart, cleaned the old grease off the drive train parts, and re-assembled it with just the motor and the drive train installed in the frame, no trucks or body parts.  I installed the stock DC board and put the frame directly on the rails to test just the motor and drive train.  As I advanced the voltage, the motor started a gawd-awful growl.  It kept this up as I slowly advanced the voltage and didn't stop until the throttle was about half open.  When it reached that point, the growling stopped but there was a slight vibration.  I took the unit all apart again but I can't see what could be causing the growling unless I have a bad motor.  Anyone else had this issue with a Kato motor?

Doug

[peteski]

Did you test run the loco before taking it apart.  That would tell you if the problem existed before, or only occurred after reassembly.

Take the motor out of the chassis and power it directly with your DCC throttle.  Use jumper wires with alligator clips (if you have a pair available, or other means) to get the power to the motor. Does the motor growl by itself?

[mmagliaro]

Is this the newer "screwless" frame, or the type with the screws holding the frame halves together?

[BCR751]

Mine is the one with screws holding the frame halves together.   And no, I didn't run it prior to disassembly.   I probably should have, dammit.  I'll take the motor out and run it by itself tomorrow.

Doug

[Steveruger45]

Yep, I had a bad motor on the similar Kato sd45.  In my case the noise was above half throttle.  Tried everything including lube  the bearings sparingly and repeatedly, cleaning and drying the motor etc etc..  Testing the motor on its own it had a lot of vibration so figured it was out of balance some how.  New motor fixed it.

[tpwillie]

When you reassembled the frame you may have over-tightened the frame screws causing stress on the bearing blocks that results in the motor stressing to turn the shafts and worm gears.  With the trucks off there will be slop in the worms that can cause more noise and a possible growling sound.  Try loosening the screws(about a quarter turn) on the frame to see if the motor moves more freely and reduces the noise level.  Make sure all the bearing blocks are squarely seated also.  That can cause binding and excess noise.   Testing the motor outside the frame will let you know how freely the motor spins and at what voltage it begins moving.  Check to see if it spins freely in your hand without any voltage and then apply voltage gradually and notice the rate of rotation.  Also look at the armature to see if something (metal flakes, small screws, etc) is inside to cause binding.  Kato motors are hard to destroy, but I did have one that had a dead spot on it.  That results in the motor not starting when power is applied and the brushes are on the dead spot.  I'm sure you probably lightly oiled the motor bearings and bearing blocks to reduce friction after you cleaned everything.

[narrowminded]

With the description of vibration I would be highly suspicious that the flywheel was not made true or they managed to bend the motor shaft during assembly.  Do you have a way to rig the motor stationary and check for runout at the flywheel?  A dial indicator would be ideal but even just a piece of wire held close and stable will probably show a problem this severe.  If it's bad enough to be the cause of the problem you describe it won't be a half thousandth and so I suspect you'll see it even with a crude rig. 

If you should decide to just replace the motor I would be happy to receive the old one and see what I can see.  If it's of the nature I just described I could likely fix it.

[BCR751]

I took the whole thing apart again and re-assembled it making sure to install all parts correctly.  I think when I put it back together the first time, I put the motor in upside down and had a protruding portion of the plastic cradle butting up against the frame causing the motor to be a bit skewed.  With the motor installed correctly, it reduced the growl by quite a bit but it's still there.  The unit seems to run ok without any noticeable binding anywhere.

I did check the flywheels and neither showed any sign of being out of round so the minor vibration isn't being caused by those. 

It is interesting that, when the motor receives the correct voltage, the growling completely goes away.  Maybe it just need to be run a while.

Doug

[peteski]

I did check the flywheels and neither showed any sign of being out of round so the minor vibration isn't being caused by those. 

It is interesting that, when the motor receives the correct voltage, the growling completely goes away.  Maybe it just need to be run a while.

What is a "correct" voltage for a model train motor?  It should be operating correctly from 0-12V (which are the voltages the model was designed to operate on).

As far as balancing the motor/flywheel goes, they can be out of balance, even though you can't easily see it.  Kato doesn't seem to do any fine balancing of their motors (maybe because the production tolerances are tight enough for the motor to have acceptable balance, without any additional fine tuning needed), but many other manufacturers (like Atlas or FVM), have their motors/flywheels dynamically balanced.  They add "balancing weights" to the armature and to the flywheel. It is usually some sort of blue (epoxy?) putty stuck in the groove on the flywheel, or to the armature windings.  Also, the armature poles are often hand-numbered 1-5 (probably for the balancing process).

[mmagliaro]

Soooo... back to the frame screws.   As has been suggested, try loosening them a little and see if all the remaining growl goes away.  That's why I asked about what kind of frame you had.

[BCR751]

What is a "correct" voltage for a model train motor?  It should be operating correctly from 0-12V (which are the voltages the model was designed to operate on).

Semantics, semantics.  The 'correct' voltage in this case is 5.25 volts.  That's where the growling stops.  I think that's also where the centrifugal force overcomes the out-of-balance issue, if that's what the problem is. 

Loosening the frame screws didn't reduce the growl.

Doug

[mmagliaro]

I may have lost track here, but does the motor, by itself and out of the frame, make any bad noises when you apply voltage to it?
If you hold it against the bench or a block of wood, that will make bad vibrations obvious that you might not
notice if you just hold it in your hand.

If it doesn't, you might try putting it into the frame, by itself, without an other gears, so the motor doesn't engage anything, and see if just being in the frame causes the growl.   After that, put one tower gear back in so only one worm engages - and then try the opposite worm by itself.

[BCR751]

I may have lost track here, but does the motor, by itself and out of the frame, make any bad noises when you apply voltage to it?
If you hold it against the bench or a block of wood, that will make bad vibrations obvious that you might not
notice if you just hold it in your hand.

If it doesn't, you might try putting it into the frame, by itself, without an other gears, so the motor doesn't engage anything, and see if just being in the frame causes the growl.   After that, put one tower gear back in so only one worm engages - and then try the opposite worm by itself.

The motor shows no obvious signs of vibration when out on its own.  I did what you suggest i.e putting the parts back into the frame one at a time and the noise is almost unnoticeable until both drive lines are in place.  I even swapped them end for end and the same thing occurs.  I'm going to play around with it some more today.

Doug

[tpwillie]

Put the trucks on and see what the results are.  The worm and shafts without a load can be the wobble and binding sounds.  Try the trucks on the frame and see what results you get.

John (tpwillie)

[ncbqguy]

There was a time when the Kato motors were not what we expected.   
The problem was traced to worn out of spec fixtures which were bending the motor shaft during assembly. 
The factory built new fixtures and the problem was fixed.   
This was during my tenure at Kato but I don’t know if your unit dates back to early 2000-ish production.
Charlie Vlk