Q: Track conductivity at extremely low voltages

[mmagliaro]

Cody, I won't doubt that MR ran such an article.   I'll just say that I highly doubt that Samhongsa's claim
is really accurate.  First, I doubt they really test every single engine, but assuming they do,
what does "test" mean?   Attach some clip leads and make sure the motor spins?   Run it around a loop
of track a few times?   That is hardly a test, and in fact, your engine would probably pass such a test.

Now that you have described how you put the decoder in, and that the whole motor is pushed some
10 degrees to one side, I'd say that's the problem.   There is a universal joint coupling
in that engine between the motor and the worm, so theoretically, it can run with the motor and worm
shaft out of alignment.  But it's still a bad idea to introduce that much angle in the driveline.
But more likely, notice how that motor mount is designed to float in a spring-loaded bracket.
By wedging the motor/decoder against the shell, you have locked it in place, preventing it from being able
to spring or move anywhere.  So unless the motor is in a perfect spot for smooth rotation of the u-joint,
it now cannot move to GET into the right spot.   That is probably more of a problem than the
misalignment

I would wager that if the decoder were out of there and the motor were centered where it belongs,
the problem would go away.   You could confirm this by running it with the shell off for a while.  The motor
ought to be able to sit on-center and be able to feely bob up and down that way. 

Here's a thought.   If the motor were in a good spot, firmly mounted so it could not bob up and down,
but did not bind on start-up, it wouldn't be as ideal as the floating motor, but it should be okay enough
to always start up.  With the shell off, you could try placing some styrene shims under the back of the motor
and tightening down that screw back there, so the motor can't move around.  Fiddle with it
until it runs good and always starts up (you are trying to find a "spot").
Maybe that way, when you put the shell back on and it pushes against the motor, it won't be able to
MOVE the motor to a bad spot, and it will still start reliably.

[VonRyan]

Took a good look at the motor, and my estimate of 10 degrees was a huge overestimate.
I'd say it is maybe 3 degrees. 

The motor has plenty of play as I can tell from prodding it with my fingernail. It has some up/down spring and a good bit of side to side play.
If it weren't such a bugger to take the shell off of, I would take a look at the mech and shell to see if the tilt can be solved as I think it is caused by the way the brass of the shell is compressing three of the 4 decoder wires against the motor and the wire is resisting being cut by the shell which is forcing the motor to tilt ever so slightly.

I don't think that there is any way to solve it, so I'll duly apologize for hijacking your thread.


-Cody F.

[mmagliaro]

Took a good look at the motor, and my estimate of 10 degrees was a huge overestimate.
I'd say it is maybe 3 degrees. 

The motor has plenty of play as I can tell from prodding it with my fingernail. It has some up/down spring and a good bit of side to side play.
If it weren't such a bugger to take the shell off of, I would take a look at the mech and shell to see if the tilt can be solved as I think it is caused by the way the brass of the shell is compressing three of the 4 decoder wires against the motor and the wire is resisting being cut by the shell which is forcing the motor to tilt ever so slightly.

I don't think that there is any way to solve it, so I'll duly apologize for hijacking your thread.


-Cody F.

No apology necessary.   Your problem is interesting to me.

The alignment probably isn't the issue anyway.  Having something pressed against the motor is.
Why is the shell hard to get off?   There should be a couple of screws in the lower edge of the back of
the cab, then you loosen the pilot wheel truck screw to swivel it out of the way, and then
there is a screw up into the front of the boiler to be removed.  After that, it should just lift off.
 
If the shell is wedged tight because of the decoder and wires, that is interfering with the motor.

Are you sure one of the wires isn't ever so slightly rubbing on the armature?

[VonRyan]

No apology necessary.   Your problem is interesting to me.

The alignment probably isn't the issue anyway.  Having something pressed against the motor is.
Why is the shell hard to get off?   There should be a couple of screws in the lower edge of the back of
the cab, then you loosen the pilot wheel truck screw to swivel it out of the way, and then
there is a screw up into the front of the boiler to be removed.  After that, it should just lift off.
 
If the shell is wedged tight because of the decoder and wires, that is interfering with the motor.

Are you sure one of the wires isn't ever so slightly rubbing on the armature?

All the wires are clear of the armature.
The decoder is on the right hand side of the boiler beside the grey metal gear-tower.

The shell is less hard to remove that it is to put back on.
Putting the shell back on requires a fine screwdriver to keep the decoder pressed against the boiler wall so that the shell can actually be put back on.

From what I can see, there isn't anything directly pressing against the motor.
However, one of the wires may be pinched between the forward most part of the motor and the brass shell.
I didn't modify any of the shell as I don't want to risk it falling apart.

I'll be running it at a show this weekend so I'll be sure to take a count on how many fresh starts require a nudge and I'll also take notes on it's running quality.



-Cody F.