Best Of *Science* of solving N scale diesel mechanism drivetrain vibration noise?

[Point353]

As we speak, I'm watching the milliamp meter to monitor pickup vs: added friction in my newest, smallest to date, N or Nn3 power truck (8.9mm off the rails with 24" wheels on a 44" wheelbase with a 130:1 gear reduction affording 15 scale MPH top speed).  I'm using a 100mA meter (.1 amp) and I'm working with friction added in a 1-1.5mA range from no pickups (not reliable contact) to pickups on four axles and VERY reliable.  Reliable pickup is very much there evidenced by the meter needle sitting fixed as though glued in place while creeping around at just above 0 and up to 5 scale MPH continuously without a hitch (but it's only been 6 hours or so).  So while it's running I'm jumping ahead to how to  fixture this to reliably and simply produce these parts if they continue to function well over the next week or so.  I think they will. 

And this is why I sing the praises of this tool when working on these small engines.  It's a no BS test that gives honest answers, no wishful thinking allowed.   It would prove the "too tight chassis halves" too.

Would this be a suitable test meter? http://www.tenma.com/products/product/72-8170
Below that unit in cost seem to be mostly compact "pocket-size" meters, with limited choice of measuring ranges, while above that are the "professional" type meters, such as those by Simpson, at ten times the price.

[mu26aeh]

Do they get quieter with the shell on after these modifications ?

[BCR751]

Today, I figured I'd tackle the worst offender in the growling/binding department, an Atlas C-630.  I took it all apart, making sure to mark and identify each part and where it came from and cleaned off all of the sticky grease with some naphtha.  As I was getting ready to re-assemble it, I noticed some gunk jammed into a portion of the little groove on the bearing block side of the fly wheel.  I picked at it lightly but it won't budge.  It looks like some sort of epoxy. Before I get more aggressive, I should ask....is this stuff supposed to be there?  Could it be put in there to balance the flywheel ?  Has anyone else seen this on their Atlas motors?

Doug

[peteski]

Today, I figured I'd tackle the worst offender in the growling/binding department, an Atlas C-630.  I took it all apart, making sure to mark and identify each part and where it came from and cleaned off all of the sticky grease with some naphtha.  As I was getting ready to re-assemble it, I noticed some gunk jammed into a portion of the little groove on the bearing block side of the fly wheel.  I picked at it lightly but it won't budge.  It looks like some sort of epoxy. Before I get more aggressive, I should ask....is this stuff supposed to be there?  Could it be put in there to balance the flywheel ?  Has anyone else seen this on their Atlas motors?

Doug

It is to balance the flywheel (to reduce vibrations).  :Just like you car's wheels.

I actually take everything apart (even remove gears from the truck's gear case) and then clean them in naphtha.  That way I'm positive all the nasty stuff is washed away, You can leave the slippery plastic parts in it overnight to soften the gunk  - they are not affected by solvents.

[mecgp7]

I've tried just about everything mentioned here. One gets better at solving the problem the more they do it. One thing that I do is isolate the trucks that cause noise. As many have said, the motor and drive shafts run quiet until the trucks are added.
I have a dummy truck consisting of an Atlas GP truck minus the double gear. I install it on one end and keep the original in the other. This not only tells you if and which truck is noisy, but it will give you an idea which end of the chassis may be causing the noise. Sometimes it has been as simple as swapping the trucks back to front.
I have found some bad trucks that cause a lot of noise yet look fine. Finally, I have accepted that there are just bad motors out there that will never be quiet.

[peteski]

I have found some bad trucks that cause a lot of noise yet look fine. Finally, I have accepted that there are just bad motors out there that will never be quiet.

That seems to imply that you think that a motor itself is a source of majority of the noise.  The way I see it, the motor itself is very seldom the source of noise/vibrations. I find that much more often that the vibrations are generated by mechanical components other than the motor.

[atsf_arizona]

I've tried just about everything mentioned here. One gets better at solving the problem the more they do it. One thing that I do is isolate the trucks that cause noise. As many have said, the motor and drive shafts run quiet until the trucks are added.
I have a dummy truck consisting of an Atlas GP truck minus the double gear. I install it on one end and keep the original in the other. This not only tells you if and which truck is noisy, but it will give you an idea which end of the chassis may be causing the noise. Sometimes it has been as simple as swapping the trucks back to front.
I have found some bad trucks that cause a lot of noise yet look fine. Finally, I have accepted that there are just bad motors out there that will never be quiet.

That's a great idea.  Add one more to our bag of tricks!

[atsf_arizona]

Do they get quieter with the shell on after these modifications ?

I will try putting the shells on my mechanisms later tonight and report back here.

[atsf_arizona]

It is to balance the flywheel (to reduce vibrations).  :Just like your car's wheels.

Peteski, this "balancing the flywheel" is another question that I have always had. 

How does one go about :

a)  finding if the rotating mechanism is out of balance
b)  finding where the out of balance point is
c)  what do you do to put it back into balance?   Add epoxy?  Drill a small hole in the flywheel to remove mass?   And how do you know how much?

Inquiring minds..... and a very useful question/answer, I think.   Thx.   

[PeyRil]

Boy this has been an interesting read! Tons of great info being brought together. I too have a couple of these sd50/60's that don't get used much for exactly these reasons. @randgust , You mentioned replacing the Atlas mechs with Kato sd40-2's. How did those go? Much modifications or shimming for fit? Is there much difference noticed for the truck centers being a little shorter?

[randgust]

What you have to realize is what I was REALLY doing is repowering an ancient Lima FP45 shell with an Atlas SD50 mechanism - I did a pair of them several years ago including significant body and paint work.   

I run this unit with two Kato SD45's  (see 

) and it was always fast under DC, and even with some diode-drops in series with the motor to drop voltage, tended to slip and spin on the point.  So it was kinda dragging the SD45's most of the time.   And, that accelerated gear wear....click, click, click, click.  Finally wore out the Atlas truck gears.

Checked the chassis against an 'original' Kato SD40-2 of my friends and it was really, really, close, so I bought one off of a friend minus the shell.  I've also pulled the same stunt with an Intermountain SD45-2 chassis - same Kato chassis - so it MU's flawlessly with my much larger fleet of Kato six-axle units.  So I've now done this twice.  Both times I get a much better performing unit.

The 'new' Katolima FP45 is a beast, loaded it up with lead, and it's now scaling in 130 grams with 28 grams of tractive effort - basically 20 grams heavier and 10 grams more of tractive effort than I got out of the Atlas chassis.  It's my six-axle pulling champ now, and by the way, deadly silent.  There's no sound added in that audio, you can hear my air horn and the wheels clicking across the joints.   Until the Atlas started clicking, it was quiet.

[peteski]

Peteski, this "balancing the flywheel" is another question that I have always had. 

How does one go about :

a)  finding if the rotating mechanism is out of balance
b)  finding where the out of balance point is
c)  what do you do to put it back into balance?   Add epoxy?  Drill a small hole in the flywheel to remove mass?   And how do you know how much?

Inquiring minds..... and a very useful question/answer, I think.   Thx.

LOL, I won't be much help here.  While I know some manufacturers balance the flywheels I don't know how.  I suspect that just like balancing the wheels on our cars, they use some sort of machine to do it.  I have seen blobs of some sort of putty (probably epoxy) added to the flywheel, and as far as removing material I have seen holes drilled or even some flywheel material ground away.

Flywheels are usually precision-machined from pieces of brass rod, so they are inherently well balanced to begin with. I'm not sure why some manufacturers take the extra step to fine-tune the balance.  maybe they are balancing the entire flywheel/motor-armature/flywheel assembly (not just the flywheels). But one thing is for certain - properly balanced wheel will greatly reduce any vibrations coming from the motor/flywheels.

[peteski]

There's certainly a ton of info here on hardware troubleshooting.  Has anyone experimented with different lubrication?  Could different lube affect noise? 

I'd be curious to know whether stuff like Lebelle 102 oil vs 106 grease makes a difference.  Or what about graphite?

Long ago, there was the "Toothpaste Method" for silencing growlers, since toothpaste has a mild abrasive to wear down tight mesh.  Does that still have any merit with today's equipment?

Yes, lubrication can affect the noise generated by the mechanism.  I recommend some good reading in the NWSL (the gear people) gear catalog: http://www.nwsl.com/uploads/chap4a_web_09-15.pdf

Here is a an excerpt about wearing-in gears:
YOU CAN’T WEAR A GEAR IN -YOU CAN ONLY WEAR IT OUT!
Over the years models and mechanical components have often been of second quality or less in order to keep
your costs (prices) as low as possible. As a result, modelers have become used to “wear-in” procedure in an
attempt to remove binds and other problems caused by the non-precision components and/or inadequately
engineered and built mechanical components. Proper procedure is to determine the bind cause (ie. eccentric
gear; improper gear mesh whether too tight or too loose; foreign object in gear teeth; gear wobble; gear warpage
such as often found in molded plastic gears; tight or misaligned bearings; etc.) and eliminate it.
. . .
Virtually all of the confirmed instances of premature/excessive wormgear wear of NWSL products
has been from inadequate lubrication and/or overload. Often due to the user purposely not lubricating while
they “break it in” or “wear it in” or whatever (which translated means “wear it out”!). Would you drain the
oil from your new automobile to break it in?

[peteski]

I've sometimes found packing the entire truck/bogie assembly with heavy grease helps a long with ample amount in the gear tower. But that means we're no better than some manufacturers that do the same thing during production.

That is not a fix - it only masks the problem and it will also attract dirt to the gears (which can eventually jam them).

About the bearing blocks themselves. Should they have a little play when seated in the frame? Do they need to be looser to allow some play or
tighter to eliminate play altogether? And the bronze bearing block tensioner: Fingers too loose or too tight against the bearing blocks, Or remove them altogether?

Loose parts will vibrate or oscillate creating noise.   In the perfect world the entire drive-train (motor and worms) would all be perfectly aligned and riding in permanently mounted bearings. But because our toys are not made to that type of tight tolerances, some play in the bearing block cradles has to be incorporated. It is not ideal solution, but a compromise.  The phosphor/bronze bearing block springs are one such compromise. Properly adjusted they allow the bearing to move but it they keep it from loosely flopping around in the bearing cradle.

[peteski]

Would this be a suitable test meter? http://www.tenma.com/products/product/72-8170
Below that unit in cost seem to be mostly compact "pocket-size" meters, with limited choice of measuring ranges, while above that are the "professional" type meters, such as those by Simpson, at ten times the price.

The meter you mentioned has a 300mA DC ammeter range - that should be perfectly suited for monitoring N scale locos. Any meter with a 200-500mA DC current measurement capability will work with an average N scale loco.