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

[Scottl]

If assembly precision is a factor, the Kato SD70ACe mechanism is smooth before and after customer assembly.  It is my best mechanism hands down in terms of smoothness and noise.

[atsf_arizona]

My conjecture is that Kato just has built much more play between the gear teeth.

Agreed, Kato trucks are very free rolling.

Conversely, perhaps Kato's manufacturing tolerances are much more exact.  That was postulated in the Atlas thread "SD50/SD60 truck fix thread" above.  From that thread as well as my humble, unscientific experience, the entire Kato mechanism appears to have finer tolerances.   

Regardless, this all leads to the same questions -  what are the engineering principles used by Kato in manufacturing and quality control in mass-producing their whisper-quiet Kato miniature mechanism designs?  More importantly, how does Kato assure consistent quality assembly of precision parts, resulting in whisper-quiet, coasting locos?   Alignment jigs?   Quality control tools?   

What diagnostic tools does Kato or Atlas use to identify a problem, if they get a batch of mechanisms that don't run the way they should? 

Surely it's not "trial and error" at the factory, for either Kato or Atlas.

Thx for the continuing conversation here.   Excellent input.

[tehachapifan]

Being doubtful that the manufacturers are using a super sophisticated method of installing and calibrating the drive components, wouldn't the orientation of the bearing blocks be the easiest explanation for a change in performance upon reassembly? Forgive me if I'm I making a overly simple and obvious point here.

[atsf_arizona]

Being doubtful that the manufacturers are using a super sophisticated method of installing and calibrating the drive components, wouldn't the orientation of the bearing blocks be the easiest explanation for a change in performance upon reassembly? Am I making a overly simple and obvious point here?

I do and did take great care to replace the worm bearing blocks in the proper orientation, exactly as they were before, when the loco was running quietly.  I paint little dots of red paint on the top of the bearing to make sure it's in the proper orientation, and the bearings go back in the same slot on the same end that it came out of.

So the mystery to me is, "what's changed?  Why does it growl now"?   That's what I've been trying to determine, for all the locos I've done over the years, which "acquired" the growl after re-assembly.

But, I do appreciate the feedback and it's important that we don't overlook something - thx Otto. (I still remember fondly, our visit back several years ago).   I welcome further comments or anything else I may have overlooked. 

[tehachapifan]

If not the bearing block orientation, perhaps we sometimes alter the shape of the plastic motor clips on even a minute level when we disassemble a loco....either by kind of forcing the frame halves apart or by attempting to pry where they hook into the frame halves. Or, maybe this happens during reassembly.

[peteski]

Agreed, Kato trucks are very free rolling.

Conversely, perhaps Kato's manufacturing tolerances are much more exact.  That was postulated in the Atlas thread "SD50/SD60 truck fix thread" above.  From that thread as well as my humble, unscientific experience, the entire Kato mechanism appears to have finer tolerances.   

Yes, I agree 200%!  That is why Kato models are much higher quality (and better running than the cloned designs).  No need to scientific measurements when the difference is clearly observable under magnigication and visible during usage.    But if you examine Kato and a brand "B" model parts and assembly under magnification, the tolerances are clearly much closer on Kato models.  Even parts like the electric pickup strips, or sideframe pickup plates on Kato seem to be manufactured to higher standard. The overall parts finish is better on Katos.

Regardless, this all leads to the same questions -  what are the engineering principles used by Kato in manufacturing and quality control in mass-producing their whisper-quiet Kato miniature mechanism designs?  More importantly, how does Kato assure consistent quality assembly of precision parts, resulting in whisper-quiet, coasting locos?   Alignment jigs?   Quality control tools?   

I think that when the parts are designed with closer tolerances, and the molds or dies are also designed to high standards then there is no special prcedure needed during assembly for the parts to have tight fit and operate smoothly. They just fall into place during assembly. 

What diagnostic tools does Kato or Atlas use to identify a problem, if they get a batch of mechanisms that don't run the way they should? 

I have no idea (assuming that they ever run into this type of a problem with a well-designed and manufactured mechanisms and shells)..  Kato is not perfect and they do sometimes need to offer fixes or retrofits for their models.

Things like redesigned power pickup from the drivers on their Mikado locos, GS-4 drive axle cracking, faulty electrical chassis design on the GS-4 and some other problems I don,t easily recall are usually acknowledged and addressed.

Kato also is sometimes a victim of their quest for perfection. The screw-less chassis for example doesn't seem to me like an improvement and the finer pitch gearing (which implies more precision) does result in the sweetest-running (yes, that is a technical term  ) locos, but that makes them very delicate and susceptible to jamming up with even a small pieces of debris (which will happen on layouts with ballasted track).  Ham-fisted handling will also easily rip off the traction tires or bend the sprung suspension on the 6-axle truck's center driver.

So sometimes a precision design can be taken too far.

[atsf_arizona]

If not the bearing block orientation, perhaps we sometimes alter the shape of the plastic motor clips on even a minute level when we disassemble a loco....either by kind of forcing the frame halves apart or by attempting to pry where they hook into the frame halves. Or, maybe this happens during reassembly.

1) Agreed.  I am going to do the side-by-side while-the-mechanism-is-running comparison that Randgust suggested, including using a long pin or needle to prod inside a mechanism to feel for vibration, and also to gently move the worm bearings while mechanism is running, to see if I can ID what difference it makes.  Perhaps I will find exactly what you pointed out.  Will keep you posted what I find.

2) I also have to try Randgust's suggestions to running the mechanism with successively more pieces removed, to be able to locate exactly what is making the noise.


3) I also found this tip by kiwi_bnsf at this Railwire thread about quieting an Atlas B40-8:  https://www.therailwire.net/forum/index.php?topic=28535.0

> kiwi_bnsf:  The trick of running the frame and drive train sans-trucks (i.e. *directly on the track*) does make it much quicker to verify whether
> your motor and drive train is quiet, and everything is true.

> You can hear issues more easily, and if your motor isn't running perfectly across all
> the speeds ranges, then don't progress until the issue is fixed (in my experience things will only get worse when you fit the trucks).


4)  By Victor Miranda in May 2011: 

the hex-joint alignment and/or drivetrain alignment can be a likely cause of the problem
when a loco goes from quiet to noisy when reassembled.

it is not easy to correct,
because it is both hard to see and the loco does run.

playing with the motor alignment is the best
way to get a quiet loco.

the first thing I do is wiggle the motor
to get the mount latched on the frame.
after that....I use slices of business cards
to wedge the motor up and down

and it does not always work...


5)  Finally, from Chad way back in Oct 2004:   http://forum.atlasrr.com/forum/topic.asp?ARCHIVE=true&TOPIC_ID=8922

Chad
 Posted - 2004 October 03 :  10:58:13 AM   
I had the same problem with several N scale engines, three GP-30's and a GP-9, and ask about it here a week or so ago and received some great help. They were much, much nosier then any other unit. The solution I used that worked great is as follows.

Basically my problem seems to be motor cradle / saddle mis-alignment.

I took the engines apart and found that between installing the decoder motor leads and running the wires a bit of pressure was being applied to the saddle. This seemed to throw the alignment off, so I milled out the inside of the frame half's where the wires attached to the motor brushes and any place the wires run so the cradle was the only thing touching the frame.

Next, a member of this board mentioned that the bearing blocks are not square. One way they fit tight, the other they fit loose and "float". I found the "float" position and installed that way. He also mentioned that the brass bearing holders on the one frame half should be pushed against the frame half as much as possible. If they stick out too far they can prevent the bearings from "floating".

With the motor, shafts and bearing block installed in one frame half I checked to see that the flywheels were dead center in the cutouts and everything turned smooth. Then I applied a very small bit of high temp lube to the worm and bearing blocks.

I installed the second frame half making sure that 1. the motor cradle clips fully engaged the frames and snapped in place, 2. the frame half's were perfectly aligned and lastly 3. the gap between the frame half's were equal end to end and top to bottom. If not, I took them back apart and reshaped the frames so they would be and re-assembled. Fortunately I only had to do this to one unit.

With everything installed except the shell I put the units on the track for a test. The difference was HUGE. They ran whisper quiet. I installed the shells and re-tested. These engines now run as quite as any of my new atlas units that have never been apart.

It's a lot of work but it does pay off. Hope this helps.

-------------------

Basically, all the above are saying that "drivetrain mis-alignment is what causes excess noise upon dis-assemble and re-assembling N scale locos". 

I have to try these as well.

[rrjim1]

It seems the noise problem still exist, even with the higher quality Kato brand locos. Two brand new Kato SDP40F locos, right out of the box, one runs quiet the other sounds like a coffee grinder. 

[atsf_arizona]

It seems the noise problem still exist, even with the higher quality Kato brand locos. Two brand new Kato SDP40F locos, right out of the box, one runs quiet the other sounds like a coffee grinder.

Hmmmm, rrjim1, sorry to hear that about one of your SDP40Fs is growling........  If you're up for it, the side-by-side while-the-mechanism-is-running comparison that Randgust suggested early in this thread, including using a long pin or needle to prod inside a mechanism to feel for vibration, might also help you ID what the difference might be.   This YouTube review of the Kato SDP40F points out how to remove the shell, go to 3:56: 

/>
All, I trust this conversation is useful and we're all learning a lot in a short period of time, all collected in one place, one thread.

I continue to seek:   How does one 'instrument' this growl, this vibration-caused sound?   What would a professional mechanical engineer, whose expertise is designing and building miniature electric rotating mechanisms, do to identify / isolate this problem?  What tools would he/she use?

[u18b]

Besides exacting tolerances on truck parts, Kato uses a different plastic than about anyone else.
The Delryn plastic they use is both tough and slippery.

The plastic that others use for gears is just not the same.  I fact I wonder if some problems are caused by shrinkage.

[Big Train]

Interesting discussion. One I've been having a while and glad to see there is so much intent to finally solve this vexing problem.

Some of the things I've thought of contributing to a noisy mechanism after assembly include the bronze bearing tensioners (too little pressure exerted by the fingers, or too much?).

How much torque is actually required when tightening the two bolts and two nuts on the frame? Is too much pressure forcing the bearing blocks hard against the bronze bearing tensioner?

Has the frame been previously distorted due to over-zealous tightening during the assembly in an effort to eliminate noise? The ends of the frame are closer together than at the centre where the motor is located.

How much distortion has occurred in the motor saddle or cradle at some point due to removal and installation?

How much distortion has occurred to the shell while removing and replacing?

There are others I'm sure. As much as we think plastic is rigid, that may only be true before it's been stressed by flexing, depending on the kind of plastic used. Sometimes I think my locomotives are quieter after I let them sit overnight: some still remain noisy.

I've even though of putting them in the freezer overnight to allow the plastic to contract somewhat over the frame for reduce that source of vibration. Drastic? I don't know and I will  let you know.

What is it they do at the factory that could be different than what I do here when I need to work on the mechanism and keep noise to an acceptable level? Nothing any different I think.

Like any assembly line, the parts are probably in plastic bins and the mechanisms are assembled according to the procedure. Based on some of the experience in using SPC (Statistical Process Control), the operator of the previous stage (the bearing blocks, frames. etc), would have check the component for conformance to the specification. The assembler, logically, does not have a need to measure them again prior to final assembly.

During assembly a sample, say 1 out of 100, may be test run on a track for a quality check (whatever that may include). If that unit fails, the other 99 might be assessed individually to determine where the problem first appeared. Or not. Some places I've worked at set the failure rate at 5 per cent, others 3 per cent.

Could explain why so many of us are complaining about excessive lubricant. Heavy grease can hide a multitude of sins. So much lubricant in some cases, I now store my locomotives vertically (trucks, bogies down) when in the jewel boxes to prevent the lubricant from oozing all over the downward side of the body shell.

What I am trying to say is, these aren't Omega watches, so don't expect a lot of precision, but just enough to meet customer specification.  And that specification is determined by the customer (Atlas, Fox Valley, KATO, Intermountain, Rapido, etc). If that customer wants to check every unit for quality, you as the end-user pays for that with higher per unit cost.

These are initially assembled in China, shipped (including an ocean voyage!) stored, shipped again, shelved how many times before we get them, and are mostly quiet (I did say mostly).

I look forward to all the opinions. It's too bad Cory from Atlas is no longer in the business, I'm sure his insight into the manufacturing of N Scale locomotives could shed some light here.

[atsf_arizona]

Big Train, thx for the good input.

I am very happy many are pitching here to constructively try to address this problem for everyone's benefit and knowledge.

As the locomotives in my YouTubes are the "long wheelbase, universal joint" mechanisms (thus are *not* candidates
for the "Beardenize remove inner bearing block" fix....)

--------

I came across Ron Bearden's post from January 2008 on "excess noise in a Atlas SD50/60, unrelated to the trucks":

http://forum.atlasrr.com/forum/topic.asp?ARCHIVE=true&TOPIC_ID=43690

In particular, Ron's idea to place a small portion of a Rapido coupler spring in the flywheel, to put a slight, slight
amount of pressure on the worm gear to prevent "rattling".    Some useful info to add to this thread in that post. 

NOTE HOWEVER:  I *did* try Ron's tip from that post, to try to immobilize the worm bearings, I tried it in the Intermountain SD45-2 mechanism in the YouTube.    But that did *not* work, by itself.   However, armed with the newer knowledge gleaned from this thread .....

-------------

I am going upstairs now and going to try to see if I can reduce the noise factor in my two locos in the  YouTubes, by playing around with the => alignment of the drivetrain <= via the motor saddle, via slightly moving the worm bearing blocks, etc., as per my previous posts.   I have to try kiwi_bnsf's tip to do this with the trucks off and the mechanism just sitting on the (DC) track, thus mimicking the layout environment as a "sounding board", and improving ability to hear where the noise sound may be coming from.

-------------

• I continue to ask:  "at the factory, what tools/diag's would a Kato or Atlas/Kader engineer use, to debug a bad batch of noisy N scale locomotives?"
  (i.e. is it really possible they never try to do this, or don't have any scientific tools to do that??)

also

• I also hear that "DCC Decoder installation experts have a lot of experience in locos becoming more noisy after decoder installation, and thus know a lot about how to solve that noisiness".   Decoder installation experts, any advice?

Thx in advance, for continuing to post your experiences and sharing. 

[peteski]

I continue to ask:  "at the factory, what tools/diag's would a Kato or Atlas/Kader engineer use, to debug a bad batch of noisy N scale locomotives?"
(i.e. is it really possible they never try to do this, or don't have any scientific tools to do that??)

I don't think that happens at the factory at all. They assemble the model and maybe give it a very quick test run (but even if that is done, I don't think that this is being done at all manufacturers).  If they do a test run I suspect that as long as it runs ok they don't worry about any noises. I suspect that you are overthinking the whole quality control thing.

[atsf_arizona]

I don't think that happens at the factory at all. They assemble the model and maybe give it a very quick test run (but even if that is done, I don't think that this is being done at all manufacturers).  If they do a test run I suspect that as long as it runs ok they don't worry about any noises. I suspect that you are overthinking the whole quality control thing.

Peteski, makes sense what you are suggesting about quality control testing (or lack thereof) in model railroad loco mass-production.

So that then begs the question:

• What do the Kato or Atlas/Kader *design engineers* do, when they are designing or specifying a new or improved silent running mechanism for a new loco  (such as the Kato UP 4-8-4 or new Kato SDP40F.... or Atlas when they were designing the Alco S-2 mechanism)?
• I would hope they build physical manufacturing prototypes to test out their theoretical designs for silent running, prior to committing capital dollars to production?  And thus, I would hope they have tools to locate and debug in their manufacturing prototypes, any vibration or excessively noisy  issues they find?

[atsf_arizona]

OK, I ran this test  (thx to kiwi_bnsf for this testing methodology)

(be *careful* or *avoid* if your loco has a plug n play DCC decoder - you could easily short the decoder!  Use at your own risk.   
This test is really aimed for proper testing of a DC mechanism's drivetrain alignment, prior to DCC install) :

/>
By inverting this  noisy-in-the-track Atlas B40-8 / C628 truck mechanism in this way, I can test for it's drivetrain alignment.

As we can see, the mechanism is relatively silent when running at full speed in this position.   

Therefore, it would appear that the noise we see in this other YouTube of same mechanism #2:

/>We could hypothesize that noise in mechanism #2 is coming from *the interaction of the worm gear and the trucks*, and not the mechanism itself.

(at least, that is the working theory of the moment).

This test, perhaps,  appears to be a helpful to identifying / isolating the problem away from the motor cradle and drivetrain.   We will see as further experiments proceed.

Regarding noise problem debugging in the worm gear/truck interaction area, we can reference Ron Bearden's thread about the SD50/SD60 mechanism noise (previously referred to in reply #26 above), here:   http://forum.atlasrr.com/forum/topic.asp?ARCHIVE=true&TOPIC_ID=43690

I am going to try the "Rapido coupler spring in the flywheel" technique that Ron describes.

Comments welcome.  Are my conclusions reasonable or not? (I am not sure yet).   More to come.