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

[u18b]

Guys,
On the topic of armatures etc.....

I have not had great success- no doubt to my inexperience.

For example, I once had a motor in a brass Kumata B&O E set start smoking.   I figured the windings were melting.

Instead of replacing the motor, I went through my stash and looked to GUT another motor and replace only the armature.

And I found one!  The small but wonderful skewed armature 5 pole motor Bachmann used in their Spectrum DASH-8s.

But here is what I found any time I have disassembled a motor.

There aren't any latches or convenient things that allow us to removed the plastic commutator end.  More often than not, there are metal tabs that are bent down into plastic slots locking it all down.

So you must bend the tabs up......
and then SPREAD the motor frame apart sometimes)..
to pull the armature out.

Not too bad getting it out.... but the problem is getting it back together.
I have found that my motors just seem to run 100% after this process.

My guess is that the bending of either metal frame or metal tabs (or both) are placing a slight bind on the shaft at the point of the bearing.
Hard way of saying that I think the bearing is no longer 100% true to the shaft--- thus performance is diminished.

(sorry no photos)

So I envy you guys that get good results.

[rrjim1]

The bearings in a Kato or Atlas motor are round, they can be moved around in there housing. When I have a motor disassembled I take a shaft and move them around to loosen them up. After the motor is assembled I apply a little side pressure to the shaft, not to much, but just enough to help line up the bearings.
 
When I disassemble a motor I am very careful not to bend the frame, I spring it just enough to remove the end bell.

I can usually tell just by bench testing a motor if it is good or need some work, I only disassemble a motor if I feel I can repair it.
 
One doesn't need to blue print a Model railroad loco motor but is sure helps the performance if the armature is very well balanced. It takes me about 15-20 minutes to disassemble, check and balance a motor, then I know for sure if the motor is good or bad.     

[peteski]

Ron,
When I take that type of a motor apart I try not to deform the metal frame and I'm usually successful by doing one side of the plastic back end of the motor (the commutator side) at a time.  The metal frame us usually springy enough not to deform.

Kato motors (and also some other brands) use spherical-shape bearings sitting in a plastic socket.  That allows for them to be moved in any direction. Very helpful in disassembly.

After reassembly the bearings are usually not aligned well and cause extra friction on the motor shaft.  My way of realigning them is to bang (or drop) the motor flat on my workbench (on all 4 sides).   Fairly vigorously. That stress causes the bearings to line up perfectly. I usually do this before installing the brushes so I can check how freely the armature spins before and after the alignment. 

I have also done this procedure with the brushes still installed. Sometimes I do this "shock method" bearing realignment even on factory fresh motors.

[BCR751]

No, that is not normal.  Suspect it's because the Android is trying to upload the raw footage, and that file is too big for the phone's main memory / connection / mobile web browser interface to YouTube,  to handle.  Remember that compared to your PC, a mobile phone may have much smaller main memory, much less network buffering, and less CPU processing power (in general, mobile CPUs are optimized for low power consumption and low cost first, and processing power only after that).

I suggest you transfer the video file to your PC/laptop first.  Then go and upload it to YouTube from the PC.   Normally, that works better because the PC has much more main memory, more CPU processing power, and often a faster WiFi card than your mobile phone.     After you upload it to the PC, let me know how big the video file is.   

Once you get it loaded via PC to YouTube, YouTube will then process + compress the file, and you can publish it and then share it here.   Let me know if further help needed, if I can help I will.

I uploaded the video (49 seconds long) to my PC and then went to YouTube to upload it.  This time, the total time was a bit shorter, 62 minutes, but I still think that is ridiculous for such a short video.  Any other suggestions are most welcome.

Doug

[peteski]

I uploaded the video (49 seconds long) to my PC and then went to YouTube to upload it.  This time, the total time was a bit shorter, 62 minutes, but I still think that is ridiculous for such a short video.  Any other suggestions are most welcome.

Doug

What video format does your smart device use to record videos? Can you view the size of the video file while on your device?  Maybe you are filming it in 4k HD format or some other high-res and low-compression format which generates huge video files?

I would expect a 1 minute video of an average quality to be less than 100MB in size.

[BCR751]

What video format does your smart device use to record videos? Can you view the size of the video file while on your device?  Maybe you are filming it in 4k HD format or some other high-res and low-compression format which generates huge video files?

I would expect a 1 minute video of an average quality to be less than 100MB in size.

I can't see the size on the phone but on the PC the video format is MP4 and the file size is 166MB.

Doug

[kiwi_bnsf]

Hi All,

This is a great thread - nice to see all so much info and experience distilled and linked into one discussion.


For me, loco tuning is neither science nor art — it's an exercise in practical engineering. Tuning a noisy or misbehaving loco is really about fault isolation — the process of pinpointing the type of fault and its location.

As has already been extensively listed in this thread, there are numerous sources of potential problems in the loco drive train — making for quite a complex system to troubleshoot. For me, the key to success is rule out as many of the issues as possible in the shortest time (because I'm impatient, and easily frustrated).

I don't think that it's any coincidence that much of this thread is dedicated to Atlas/Intermountain locos. In my experience they suffer a combination of issues that make life very difficult. On the bright side, once you've worked through fixing a particularly bad Tunnel Motor, SD60, or Dash 8-40B, all other loco maintenance tasks start to look easy (unless maybe you are fixing brass)!


A couple of things I would add to the collective experience pool:


Chassis vs Trucks

As a first step (as John has already kindly mentioned), I always remove the trucks and run the drive train sitting on the rails to isolate noise and vibration to the trucks or the motor-universal-worm chain. This is a great split-half search to save a lot of time isolating the cause of problems. One detail: I never do this with the loco upside down. Instead I do it with the fuel tank halves resting on the track. This minimises the chance of shorting/frying a light board or decoder, and is also the same orientation that the loco will be running once it has its trucks back on.


Drive Train

If the chassis is noisy sans trucks, then I focus my attention on the big four: Motor, Universals, Worms, Bearings
   - lube motor bearings, and check the motor is seated correctly in the plastic cradle
   - degrease and clean universals, worms, and bearings
   - reassemble everything and reduce the slack in the universal-to-flywheel joint - I gently move the ball joints on the shaft by hand - it sounds much dirtier than it is 

This process can take quite some effort. I’ve encountered bent universal shafts, ball joints missing one nub, flywheels loose on the motor shaft, bent motor shafts, worms with burrs, deformed bearing blocks, and noisy motors. In most cases these issues were only discovered because of methodically swapping out components until the noise was cured (and then inspecting the last component closely). In severe cases I’ve had to swap/replace the motor to remove vibration, and I’ve cracked one universal.



Frame Geometry

I would say the 80% of the time, the above process of working on the drive train has reduced noise to the point that it’s acceptable. However, 20% of the time it seems that nothing I do fixes the noise and vibration. I’ve found through experience of servicing ~100 locos, that the geometry of the frame and drive train is often the problem if noise persists.

It is worth experimenting with the tightness of the screws holding the frame halves together (as has been already discussed in this thread). It is also very important to check that the plastic motor cradle is sitting snug in the frame halves. I have had success in replacing plastic motor cradles (it seems the old ones are easily bent/deformed, or no long have enough “spring” to resist the motor torque). They can easily be damaged when disassembling the frame halves

One thing I have learned is that frame geometry can be easily be distorted by installation of a decoder. DCC decoders are almost always thicker than the light boards that they replace. This causes the top of the frame halves to be spread further apart, and can apply additional “crushing” pressure the trucks. It is a mistake to physically force a decoder in the space of thin light board slot — it needs to fit snugly, but easily. I’ve had good success widening the gaps in the frame halves using a diamond shaped hand file and in more extreme cases using a Dremel. If you go too far, and the decoder becomes too loose, it is easy to add some thickness to the pickup pads by tinning them with solder. Intermountain Tunnel Motors are particularly badly affected with their extremely narrow light board gaps.

Finally, on the subject of frame geometry, one of the most frustrating issues I regularly encounter is where the chassis is running perfectly without the shell, but then immediately develops noise once the shell is re-installed.  For me this boils down to two common cases:

1. Flywheels rubbing on the shell: the tolerances on the Atlas shells and the flywheels can be very tight. I quickly add a couple of layers of insulation tape to the exterior of the frames either side of the gaps for the flywheels. This adds additional some clearance space between the shell and the flywheels (the shell just flexes slightly). The Fox Valley GP60s suffer this issue very badly, and ship with little metal spacers to keep the flywheels from fouling the shell - I find these detach and stick to the motor or drivetrain. A couple of layers of insulation tape is much better way to snug down a shell and create some air-gap, while still allowing the shell to be easily removed.

2. Compression of the frame: occasionally the problem can be because the shell itself is compressing the frame halves. This can be fixed with some styrene shims. Often re-installing the plastic fuel tank has compressed the lower frame halves together too much, causing the motor to be too loose and this can also be fixed with a styrene shim. (Early Kato Dash 9s suffer from this problem - Kato later added a built-in shim as part of the fuel tank).

Occasionally I have encountered frames that are just bent (usually Tunnel motors and SD50/60/60M). This issue was terminal and I just cannibalised all the parts for other models.



Trucks

Once the drive train is quiet, I grab some trucks from a known-good loco (i.e. one that is quiet, and able to creep). If the chassis works with the known-good trucks, a good next move is to swap the troublesome ones onto the known-good chassis. This should reproduce the issue and 100% confirm the trucks are an issue. Unfortunately this only works if you have several locos of the same type.

I personally didn’t find running with one dummy truck, and one geared truck to be of much help because the slack in the entire drive train behaves very differently when both worms are engaged.

If the trucks are confirmed as troublesome, then it’s time to focus attention on dissembling and cleaning the original trucks, checking wheelset gauge, and making sure they run smooth when pushed along the track by hand (requires some gentle downward pressure to give enough traction to feel the gears moving). Trucks are one component where I think it is essential to purchase some spares to allow swapping of gears, wheels, pickup strips, and truck frames. In my experience, there is considerable difference between the original trucks and new replacement parts. There can also be variation between spares. It can be a case of mass-cleaning and reassembling half a dozen trucks, and then swapping them in to find the best match to a chassis.

Occasionally I find that known-good trucks mated with a quiet drive train are still noisy because the issue is caused by an interaction of the trucks and the worms (as already discussed by Ron). This can be a pain to fix, and is when you need to check for damaged truck nubs/pins, or loose pinion gears.

I replace all Atlas-style wheel sets with Kato 932090 wheel sets. I do this for appearance, and to avoid issues with the tight frog tolerances on my handled turnouts. I would consider Kato wheel sets mandatory for any Atlas HT-C equipped locos (SD45-2/SD50/SD60/Tunnel Motors ).



Loco maintenance and tuning can certainly consume a lot of time, but the reward of a loco that creeps silently at one-tie-per minute can be very satisfying. I’m quite time-poor, and I’ve found having a good stash of spares for my Atlas and Intermountain locos to be well worth the investment.

I personally would never engage in component-level repair of a motor - I just replace/swap things until it works.

If you are a runner and have a sizeable fleet, you are going to eventually end up with your own “dead line” of out-of-service locos due to melted trucks, worn components, or other accidents. Just like the prototype, these can become a useful source of spares. In extreme cases, I’ve simply resorted to buying another new loco with an identical chassis from eBay, and swapping components until I’m 100% happy.

Hope some of this info helps.

Cheers

Tim Benson

[Edited for typos]

[atsf_arizona]

Tim, thx, I learned a lot just by reading your excellent summary. 

[atsf_arizona]

I uploaded the video (49 seconds long) to my PC and then went to YouTube to upload it.  This time, the total time was a bit shorter, 62 minutes, but I still think that is ridiculous for such a short video. 

I can't see the size on the phone but after uploading to the on the PC, the video format is MP4 and the file size is 166MB.

Doug

Hmm, how fast is your broadband xfer rate to YouTube?    You can go to www.speedtest.net and find out (that's a safe website).

I have 5MB/sec (i.e. approx 50 Mbits/sec) upload and download  (B = bytes, by convention, capital B = bytes (typical of file sizes) and lowercase b = bits (typical of communication lines).
 
(full disclosure:  for ease of conversion, although there's 8 bits per bytes, often times we IT types do a 'close-enough divide bits/sec by 10 to get bytes/sec', as that also factors in some reasonable amount of overhead to account for the fact that the theoretical transfer rate will always come down to some lower effective transfer rate)

Thus at 5MB/sec, we'd expect 166MB/5MB/sec = 33 seconds. 

Thus, 62 minutes = something's wrong with the file transfer.  Can you upload the video to Google Drive and then send me a link to your file?   Maybe I can then cross-load it to YouTube for you.   

[u18b]

The somewhat disappointing thing for me is that I submitted a trouble shooting article to N-Scale Mag a couple of years ago that covers some of the info in this thread.

Who knows when or if they will publish it.
Probably appears to boring.

[BCR751]

Hmm, how fast is your broadband xfer rate to YouTube?    You can go to www.speedtest.net and find out (that's a safe website).

I just get a "page error" when I go to that link.

Belay that last report.  I just ran a test, two actually, and my upload speed is 1.04 Mbps.  Don't think I have to look any further.  That's atrocious.  I'll be talking to my provider in just a minute

Doug

[atsf_arizona]

I replace all Atlas-style wheel sets with Kato 932090 wheel sets. I do this for appearance, and to avoid issues with the tight frog tolerances on my handled turnouts. I would consider Kato wheel sets mandatory for any Atlas HT-C equipped locos (SD45-2/SD50/SD60/Tunnel Motors ).

Tim Benson

Tim, have you ever run into situation where the Kato 932090 wheelsets swapped into the Atlas/Intermountain HT-C trucks, caused the resulting truck to derail upon entering / curves? (12.75" radius)

I had exactly that problem with one of my Atlas/Intermountain HT-C trucks with Kato 932090 wheelsets (but no problems with the other one with Kato wheelsets).  I don't know what caused this truck to consistently derail (albeit, I didn't chase too much trying to debug it).  Because, just to test, I put the old IM wheelsets back in.... and the truck no longer derails.   Then found out that the noise problem was not in this particular set of trucks, via this thread.

That truck that used to derail with Kato wheelsets, but doesn't with IM wheelsets, is the right-hand truck in this previously seen video  (i.e. the one that is dull-ish silver):

/>
For what it's worth, the left hand very silver truck in the above video, is an IM truck that has Kato 932090 wheelsets, and it has no derailment problems. 

I am guessing it had something to do with fact that Kato wheelsets have longer axles, and some tolerance somewhere is just enough to cause that one truck to "lift the front wheel off the rails when entering curve sharper than a certain radius" when using the Kato wheels.   Maybe it's because the Kato wheelsets have smaller flanges than the IM wheels.  Curious.   

 (or maybe it's because my  track has a flaw in couple of places    )

[atsf_arizona]

  I just ran a test, two actually, and my upload speed is 1.04 Mbps.  Don't think I have to look any further.  That's atrocious.  I'll be talking to my provider in just a minute

Doug

Yep.  1.04 Mbit/sec = approx 104KBytes/sec.  For a 166 MB file, that equates to 27.7 minutes transfer time.  Keep us posted if you make progress on that with your service provider.

[atsf_arizona]

The somewhat disappointing thing for me is that I submitted a trouble shooting article to N-Scale Mag a couple of years ago that covers some of the info in this thread.

Who knows when or if they will publish it.
Probably appears too boring.

I certainly find your input here, Ron, words of golden wisdom.   Far from boring.   Would love to have seen, or see, your trouble-shooting article someday.

[kiwi_bnsf]

Tim, have you ever run into situation where the Kato 932090 wheelsets swapped into the Atlas/Intermountain HT-C trucks, caused the resulting truck to derail upon entering / curves? (12.75" radius)

I am guessing it had something to do with fact that Kato wheelsets have longer axles, and some tolerance somewhere is just enough to cause the one truck to "lift the front wheel off the rails when entering curve sharper than a certain radius" when using the Kato wheels.   Just curious.

I have not had my Kato upgraded HT-C trucks derail on curves or turnouts, but I don't have anything tighter than an 18" radius.

My best guess would be that the reason the truck is okay once you re-install the Atlas wheelsets is because the shorter axle points allow more side-to-side play inside the truck frame (essentially creating a poor-man's steerable truck). This is the reason for the annoying hopping middle axles in these trucks.

I would try narrowing the gauge of you Kato wheel sets ever so slightly, and see if the problem goes away (this essentially shortens the axle, and increases side-to-side play). Depending on the tolerances of your turnouts, you may be able to get away with quite a bit of gauge narrowing (most Atlas axles ship too narrow in the first place).

This is really just a workaround. If this cures the issue, you could look at using a wheel puller to move the Kato wheels slightly outwards on their half axles — thereby allowing you to have a slightly shorter axle while maintaining perfect NMRA gauge (this is what I've had to do when replacing Atlas B truck wheels with Kato wheel sets).

Hope this makes sense.

Cheers

Tim Benson