GP30 S4 Shell Noise with Quiet Motor

[Geeper]

I have NIB Bachman HO S4 and GP30 with nasty LOUD motor noise when they run. With shells removed... bare chassis they run like a finely tuned sewing machine with almost silent running. Without their shells I just hear very low motor hummmmm, and metal wheels on rails and a lovely (to me) 'click-click' when crossing rail joints. Put shells back on and that LOUD nasty motor noise returns.
Obviously the shell itself is becoming a sounding board, which then amplifies the motor noise (by a factor of 10 or 20). I'm not the first to have this situation... Has anyone found the primary source of the problem and what was your solution?

Bach-Man what say you??? [Is it a design or mfr issue I can fix?] Never had this issue with Walthers Mainline or Proto, Athearn Genesis or Kato. I have one Atlas with similar "noise by shell" problem, but it's volume is 10x less than inherent Bachmann noise...
I've posted this question on other forums and gotten weird answers from 'turn UP the X-mas music' to 'wear ear plugs'. Nobody knows the source or reason why Bachmann shells increase motor noise by 10-20 times. And nobody has any idea how to quiet them down. Bachmann designers might know the solution and should share it with Bachmann purchasers. 
I only run yard speed and double yard speed on my layout... so any LOUD motor noise is very unpleasant... and unnecessary.

[Quentin]

I don't know the cause, but what about soundproofing the shell on the inside? Have you considered that?

[Len]

Sometimes body shells get a slight warp when they come out of the mold, which can leave gaps that vibrate when installed on a loco. You can check for this by looking through the cab window while shining a bright flashlight along the bottom of the shell where it meets the chassis. If you see light inside the body, there's a gap.

The simple fix is to just build up the area on the shell where light came through with a few layers of electrical tape.

Len

[Geeper]

Hi Quentin; yep tried it with light foam and heavy foam cut to fit tight inside the shell, hoping to deaden the shell harmonics. Some suggested using caulking inside the shell to deaden harmonics.

Hi Len; Shells are good fits, no warping, I tried 1,2,3 layers of that Blue EZ removable painters tape on corners and edge of elec. mother board in case they touched the shell. No wires touching. Funny part is these locos run beautiful without the shell (a low motor hummmmmm)... only with the shell on... do they make any noise, more of a growl.
Other mfr have figured out 'low sound' smooth hummmmmmm... running locos. About half my Bachmann locos are too noisy and that one old Atlas... but it's much quieter than these two Bachmanns. I've read many other forums about engine noise... but those are mechanical and electrical issues needing repair. These Bachmanns run perfect w/o the shell... meaning it is not the motor, running gear, etc.

[Quentin]

I'll do some research.

[Len]

In that case check the play of the drive shafts. I've had some Bachmann locos where the universal piece on the motor shaft with the flywheel was pushed to far onto the shaft. This gave the ball end of the connecting shaft too much room to move around in, creating vibrations in the trucks and frame. Shell off you would not really hear it, shell on the noise was obvious.

Len

[Geeper]

Hi Len... OK you might have found the issue, thanks. Let me see if I understand your description of the problem...
From the motor, the shaft leaves the motor and goes into the flywheel. The problem is NOT with that shaft or the flywheel location on it.
The shaft exits the flywheel and goes to the universal connector (usually plastic) which slides onto the motor shaft... and this plastic piece might be too close to the flywheel. That would mean I need to increase distance between the flywheel and that universal shaft.
Is that the correct picture???
If I have it backwards... then that universal piece is too close to the flywheel and must be farther from the flywheel (further out the shaft towards the truck). So I would increase distance between flywheel and universal piece (on the shaft).
I'll take a look tomorrow... that means one OR both universals (front and rear) might be out of spec for proper functioning.

[Len]

From the motor, the shaft leaves the motor and goes into the flywheel. The problem is NOT with that shaft or the flywheel location on it.
The shaft exits the flywheel and goes to the universal connector (usually plastic) which slides onto the motor shaft... and this plastic piece might be too close to the flywheel. That would mean I need to increase distance between the flywheel and that universal shaft.
Is that the correct picture???

That's it exactly

Len

[Geeper]

Thanks Len, I got it and will check when I get a chance. Next two days I'm busy with other family stuff. Your idea and drive train solution, might just be (mfr oops) reality, for many strange Bachmann diesel loco shell harmonic noises.

I noticed Bachmann trucks are designed to "touch the chassis" on a single point (both left and right side). The drive train universal on motor shaft would "transmit sound" through (one or both) trucks and into the chassis.
W/O the shell on = "no noise". But with the shell on the chassis, it could very easily transmit noise into the side of the shell, making a harmonic sounding-board. Interesting concept to explore. Thanks again...

[Desert Rose]

We just finished upgrading 25 SD40-2 to DCC and about half of them had the same problem you're having right out of the box. The first thing we did was to brake in the motor brushes and gearboxes. Running the engines forward for twenty minutes at three different settings, then backwards for twenty minutes at three different settings this would quiet down a lot of them. Some of the motors were out of tolerances, transferring the noise to the shell making it an amplifier. Replacing it corrected the problem. On some gearboxes were making the noise, replacing them corrected the problem. On some the drive shaft universal joint was cracked allowing it to spin on the worm gear shaft causing the nose, one truck moving, and the other truck was being dragged. For us, the noise was the same but generated from different sources, the three leading sources for us was trucks, motors and universal joints. The nose and corrective actions were the same but different on each engine. 

[Geeper]

Hi Benjamen; Wow NIB with [1]motors out of tolerance, [2]noisy gear boxes, and [3]cracked drive shaft universal joints. That points to a much larger issue... total lack of quality control on the production line. When you buy brand NIB locomotives needing immediate replacement of motors, gear boxes and universal joints that is nasty and unacceptable. The production last inspection and test run, should be catching 99% of those parts and workmanship failures.
Thanks for the heads-up, I'll be looking for your 3 issues when I get to checking Len's idea on proper positioning of universal on the motor shaft (could be cracked too).

I also usually spend the first 1-2 hours of any new loco in a break-in fast/slow/fast/slow forward/reverse/forward/reverse mode. To date (not counting multiple harmonic noise issues) out of 30+ new locos, only one is still has an operational problem. At low RMP, slow jerky movement for first 20-30 feet, then it goes smooth and doubles the speed (without me increasing controller voltage).

I don't mind routine maintenance issues, and I've done Oops myself, needing repair. But having NIB part failures needing repair on 20% of brand new locomotives is unacceptable and costly.  Keep smiling...

[Quentin]

I've run only Bachmann locos, and none have had these issues. I don't have any input! But I do say that I will always stay with Bachmann.

[Geeper]

Hi Quentin; I really like Bachmann EZ-Track, EZ-Command, Silver series railcars and their selection of EZ-Mate knuckle couplers... Like Benjamen, I've had NIB loco issues (mostly minor) with their diesels about 50% of the time. The major issue for my slow yard-speed use is the LOUD harmonic noise.

As to other mfr locos I stick with their top-line products Proto, Genesis, Master Gold, etc... I also search for older NIB sales... Getting a NIB $300. DCC loco for $125. or a NIB $200. DCC-Ready for $90. I just might 'bite' and reel it into my loco fleet (CB&Q, GN, NP). I'm always in the market for NIB switcher, road-switchers and GPs. I have 18R curves, so I keep length of rolling stock and locos to a minimum. I model freight and avoid Pax cars. My wife runs mostly "wine" boxcars and "wine" tankers. It's a great hobby for nasty weather days to stay indoors... like today we have freezing FOG. Good wx I'm on the tractor in the wood lot, or using disc or brush hog.
Happiness is a way of living life daily... so keep smiling...

[jward]

One question I've not seen asked here: are these DC or DCC locos? Bachmann DCC OnBoard series locos I've bought tend to have alot of motor noise that comes from the decoder.  Switch decoders to an aftermarket brand and the noise goes away. This obviously doesn't affect the sound value series. I am not sure why this affects those particular locomotives, but I suspect they have a stripped down, low cost decoder that isn't fully filtering the way it should. I observed the same affect years ago in pre-DCC times on locomotives running with the old MRC power packs with a pulse control switch. Turn on pulse power and they made a grinding noise, turn it off and they sounded normal.

[Desert Rose]

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