Drive Train Noise - Kato F7

[u18b]

Max, maybe I mis-read your post myself.

Do you mean with BOTH bearings installed.

Doug described the issue at the heart of this procedure that I recommend.

The typical design is fine IF everything is lined up absolutely perfectly.

But as soon as there is the tiniest change in a perfect alignment, noise happens-- all because the worm shaft is fixed.

But by removing the inner bearing block, any slight mis-alignment allows the worm to actually move (wobble slightly).  We are probably talking microns.  The end result is no bind at all.  And MUCH quieter.

In a long 6-axle Kato or Atlas loco, the worm is fixed with two bearings, but there is also almost always a true u-joint.
In a 6 axle loco, the u-joint absorbs any mis-alignment.    So in this inner bearing block removal, we are simply emulating a true u-joint.

In the case of the early F units, I think the culprit is those awful doughnut rings that hold the motor.   There is just no way that those things can hold the motor perfectly straight.   In fact- they have little shock absorbing braces on the inner rim that ALLOW the motor to wiggle slightly.

It was poor design.

[mmagliaro]

So Max, are you saying you leave both bearing blocks installed and just fiddle with the u-joint to get the required "slop" in the worm gear?

Doug

Yes.  When I have disassembled and reassembled F units, I always make sure there is a wee bit of lateral play in that worm between the bearings.  In fact, even on a steam loco like a Kato Mikado, where the worm rides in its own carrier between two bearings, I check for this.  I have found more than one where the worm is tight against one or the other bearing, and even one Mikado where the worm itself was just a hair too long, making it impossible to get any play in there, so I carefully sanded the inner face of one of the bearings to open up some room.  It makes a huge difference in current draw and noise compared to a worm that is tight between the bearings.

[mmagliaro]

Max, maybe I mis-read your post myself.

Do you mean with BOTH bearings installed.

...

Yes, I was talking about when you leave both bearings in there.  Although, even in the case of removing one, you wouldn't want the worm to push hard against the inside of the one remaining bearing.

[BCR751]

Yes.  When I have disassembled and reassembled F units, I always make sure there is a wee bit of lateral play in that worm between the bearings.  In fact, even on a steam loco like a Kato Mikado, where the worm rides in its own carrier between two bearings, I check for this.  I have found more than one where the worm is tight against one or the other bearing, and even one Mikado where the worm itself was just a hair too long, making it impossible to get any play in there, so I carefully sanded the inner face of one of the bearings to open up some room.  It makes a huge difference in current draw and noise compared to a worm that is tight between the bearings.

I would like to play around with that and see if it could make as much of a difference as removing that inner bearing.  It definitely sounds intriguing.  The removal of the inner bearing does have me a bit concerned due to the possibility of wear on the so-called u-joint inside the flywheel.  After all, it isn't  a true 'u-joint' in the strictest sense of the word.  Like Ron has pointed out,  the whole arrangement is designed to run with both blocks AND a straight connection to the motor, unlike the six-axle trucks that have a true universal joint.  So, I'm kinda wondering if this mod is going to cause problems down the road.  Maybe I'm over thinking the whole thing and I should just be happy my F-unit now runs "quieter". 

Doug

[peteski]

So, I'm kinda wondering if this mod is going to cause problems down the road.  Maybe I'm over thinking the whole thing and I should just be happy my F-unit now runs "quieter". 

If it was model I would keep on experimenting. But that's me - that is where the fun is for me in model railroading. 
If you continue experimenting, just make absolutely sure to properly line up the motro and worms inside the chassis. Those dougnut shaped motor mounts are a pain to line up properly (and they might even have slightly different top and bottom shape.  I don't remember the specifics - I might be thinking of another loco with similar motor mounts.
But I agree with you and Max: the model was designed with a pair of bearings for each worm.  Ron's solution works, but I also feel that with proper alignment the factory design can be made quiet.

[peteski]

In the case of the early F units, I think the culprit is those awful doughnut rings that hold the motor.   There is just no way that those things can hold the motor perfectly straight.   In fact- they have little shock absorbing braces on the inner rim that ALLOW the motor to wiggle slightly.

It was poor design.

Well, while I agree that those doughnut shaped motor mounts weren't the best design (difficult to assemble into the chassis), what you call "shock absorbing braces" are actually a desired feature which is present even in the current Kato motor mounts.  This is the motor mount cage from a P42 loco (the narrow hood units also use a similar mount).



Not only the thin flexible ring softly suspends the motor, the entire cage assembly slightly floats in the metal chassis (it doesn't fit tightly).  That IMO actually reduces the mechanical noise from the motor. The problem in the F units is that funky universal coupling. But since the distance between the motor and the worms is so short they couldn't fit the better double-ended ball-and-socket drive shaft and universals. So we are stuck with those oddball universal couplings.