Running noise of trucks

[faraway]

Preface:
My layout is mainly build of a large board of plywood screwed on battens at the wall and metal stands at the front. The tracks are glued to a layer of cork. The glue/water mix for ballasting soaks through the cork (at least after some reworks). The entire construction is sub standard from point of noise isolation. You may call is a drumhead. You should know that my ears are very sensitive and I define "noise" much more sensitive than most of you.

Observations:
1. Running a high quality engine e.g. Atlas GP40 on straight track produces minimal noise. It sounds like the wheels have rubber tire.
2. An Athearn RTR CF7 with a new high quality motor (Kato) but original trucks produces noticeable more noise. The drumhead is activated. There are a lot of resonance frequencies.
3. An Athearn Genesis GP15 with removed power train running as dummy with an Atlas TM GP38-2 produces the same kind of resonance as the CF7 with a high quality motor
4. Other brands of trucks are somewhere between Atlas and Athearn
5. I use old ROCO tracks in my staging yard. They have a simulated ballast made of soft plastic like rubber. Those tracks are very silent and Athearn trucks are close Atlas trucks.
6. The Athearn trucks do not emit so much noise into the air. They vibrate and activate the drumhead.
7. May be it does not fit into the test scenario but an Atlas engines runs like on rubber tire over Atlas switches while Athearn trucks have a tough fight metal to metal (all wheel and axis measure according to NEM) .

I did a little test:
An Athearn CF7 has been stripped down to the bare minimum. Only trucks without any gear wheels and the metal chassis is left.
That unit runs considerable more noisy than any of my cars.
I did than swap the Athearn wheel sets with P2K wheels sets (bought for the split wheel problem). The bare minimum unit ran one notch more soften but still much more noisy than a standard boxcar.
Looks like the wheels are part of the noisy production engine.

Question:
What does Atlas do to it's trucks other can not do and Athearn fails so very much? I do not think about he gear wheels due to observation 5 and 6. Something makes the wheels drum on the rails. How and why?

[Sumpter250]

I do not have any Athearn Genesis diesels, so I can't be sure about this, but.....
I know that the Atlas trucks, have the metal ( for electrical pick-up ) pieces mounted on the side frames, where the older Athearns, have them mounted on the gear case. These pick-ups bear on the metal axles, so the Athearn trucks with the gear case bearing the engine weight would transmit sound far better than trucks where there is some flexibility in the engineering plastic support between the weight bearing contact with the axles, and the gear box on which the loco's weight rests.

Just a thought, logical, but not proved.

[faraway]

....I know that the Atlas trucks, have the metal ( for electrical pick-up ) pieces mounted on the side frames, where the older Athearns, have them mounted on the gear case. These pick-ups bear on the metal axles, so the Athearn trucks with the gear case bearing the engine weight would transmit sound far better than trucks where there is some flexibility in the engineering plastic support between the weight bearing contact with the axles, and the gear box on which the loco's weight rests...

I did check the Genesis GP15 trucks and. They have a similar design as Atlas has. Another point are P2K trucks. They have the same basis design as Athearn RTR but they are significant less noisy.

ps. Might be my Genesis GP15 is an exception. I had a look at the Genesis MP15AC. It has the same Atlas like design and is a very soft runner.
pps. The Kato GP35 trucks (soft runner) are similar to Atlas design too.

[Gary S]

Great topic, Reinhard. I have gotten to the point that the only locos I will buy is Atlas precisely because of the noise issues. All my Atlas locos run smooth and quiet. My Proto2Ks are hit and miss, some are close to the Atlas models, others are quite bad. As an example, I have two P2K GP60s, both bought from the same store at the same time. One of them runs like a champ, the other is noisy like an Athearn. The 2 Kato SDs I have run good, with only slightly more noise than the Atlas models. The Athearn RTRs, while running fine, make alot of noise.

I had always attributed the noise to the gear boxes, hadn't considered the wheel issue. S2-fiddie's thoughts could be right on the money. The way the loco weight is supported from chassis to truck to bearing to wheel just may be the culprit.

My layout is 1/4" plywood with 2" foam, and cork roadbed on that. It does seem that the layout materials contribute to the noise problem, but again, the Atlas locos are beautifully quite, Kato is okay, and Athearn RTR is pretty much unacceptable.

I hope others will chime in on this thread with ideas.

[Sumpter250]

My layout is 1/4" plywood with 2" foam, and cork roadbed on that. It does seem that the layout materials contribute to the noise problem.

That's interesting, as the narrow gauge line on my old modules, crosses three steel arch bridges. The old MDC kit locos, grind and rattle all the way around the loop, but are almost silent, when they cross the bridges. :o

[faraway]

I forgot to mention the reason of this discussion. The standard procedure to make an engine run smooth is the installation of a high quality motor. That is certainly a move in the right direction but I learned the hard way that there are other components that play an important role. I was really surprised when I ran a bare naked chassis/trucks device and it made significant more noise than any of my cars. That is my motivation to discuss the role of the trucks in that game.

There are currently the trucks of a Kato GP35 on my table. They have the Atlas design and a similar king pin like RTR CF7. Is is just far to low. I would need some kind of an adapter.
As there some kind of "adapters" on the market to be used to mount X trucks under Y engines?

[Gary S]

I remotored two of my Athearn CF7s, and there was very little noise reduction, just as you found.

The P2K trucks use the same bearing arrangement as Athearn RTR, yet some of my P2K locos run almost as quiet as Atlas. Others are noisy. ????

[faraway]

...The P2K trucks use the same bearing arrangement as Athearn RTR, yet some of my P2K locos run almost as quiet as Atlas. Others are noisy. ????

That is a good point. I have an older P2K Geep that can spend the trucks at least for a test.

Next day:
Did a short test, they do not fit. I will keep on searching casual for alternate RTR trucks.

[videobruce]

Would acoustical sound panels help, either on the wall, or under the layout?

[faraway]

Would acoustical sound panels help, either on the wall, or under the layout?

Oh yes, for sure. But I did start this discussion some time ago about the different aspects of the engine design. But you are welcome to use it to discuss the effect of different roadbeds etc.

[doctorwayne]

While changing motors can mitigate some of the sound issues, drivelines, including shafts and couplings, flywheels, and the gears within the trucks all contribute somewhat to excess noise. The old Model Power E-units were very smooth-running and otherwise quiet locos, but slop in the U-joint driveshaft couplings made them quite noisy. Shimming the couplings solved the problem.



Cleaning-up the older Athearn gears, using a knife and/or file, often help dampen some of the racket, but I can't comment on a solution for the newer locos.

Imbalanced flywheels were once a common issue, and while I would think that it's no longer an issue, may be something which merits investigation. Much of the sound present is, of course, amplified not only by the track and layout, but also by the loco itself, especially the body shell. The older Atlas locos with which I was familiar were very solidly-built, with little unused space within the loco and they were very quiet-running. I've noticed that Athearn locos which I've re-built (usually including installation of a can motor and removal of the flywheels) were noticeably quieter, and if I added interior weight to the loco, quieter still. My guess is that solid weights, solidly mounted (screwed in place or affixed with silicone sealant) lessened vibrations and therefore noise. If you don't wish to add more weight or don't have room for it, some soft foam packed into appropriate spaces within the shell may absorb some of the noise.
Most of my locos seem quiet enough, with only those with older open gears (steam locos) noticeably noisy. I find, for the most part, rolling stock with metal wheels the biggest noise factor, and I don't have a great many such cars.
Layout construction obviously plays a part in the noise, and the more solid the construction, the more the sound seems to be absorbed, even though sound is more easily transmitted through solid objects. :? Foam or plywood supported every 2' makes more noise than the same materials supported every 16", and the materials which we use to fasten our track and ballast in place transmit the initial noise to that "drumhead". The myth about matte medium being quieter than white glue as a ballast fixative is, in my experience, exactly that: I have used both on my layout and can detect no difference. Mind you, spending almost 40 years in the din of a steel mill may have something to do with that perception (or lack thereof).

Wayne

[jwb]

Foam is very noisy. I was a member of a club in the 1970s that made extensive use of the old PFM sound system, and they had a technique of making a spline-style roadbed that had acoustic plaster applied between the splines. This was very quiet. For my current layout, I was strongly influenced by my experience in that club, but instead of the special spline-and-acoustic-plaster, I use Celotex (which is called "sound board" at lumberyards, too) laminated to 3/4 inch plywood. I've heard this is a better choice than Homasote, because it's more readily available, is cheaper, and doesn't expand when it's wet; the only downside is that it doesn't hold spikes as well, but I use flex track and cork roadbed anyhow. In addition, I followed an RMC article from the 1980s that suggested spacing the L-girder joists at a "phi" proportion interval, rather than a regular 24-inch (or whatever) interval, to minimize any tendency to develop resonant vibrations in the benchwork.

Meanwhile, sound went from PFM and similar analog systems to DCC, and I'm still not on DCC, so I don't have many sound locos, but operation is very quiet -- I've had open house visitors come into the layout room when a train is running, and they act all disappointed right away because they don't hear anything and thus don't think anything's running. People are used to visiting layouts and hearing a lot of racket from thin plywood or foam, irrespective of any sound system. Once I assure visitors that a train is in fact running, they're happy, and I suppose I should see it as confirmation that my benchwork is quiet.

Given my efforts at building quiet benchwork, I don't hear much difference in volume between Athearn RTR, P2K, or Atlas, they're all acceptable.

[videobruce]

I was referring to wall mounted panels, not foam roadbed.

[Squidbait]

I believe the material of the actual wheelsets will have a bearing on noise as well. Those with plated/polished nickle-silver wheels (like Kato and Atlas) will have less or at least different noise from those with steel/sintered iron wheels (Athearn, early Proto 2000).

Replacing steel wheels with n/s ones from JayBee or NWSL has improved the sound of many of my older Athearn diesels, which otherwise had a quiet drive line.

[doctorwayne]

I believe the material of the actual wheelsets will have a bearing on noise as well. Those with plated/polished nickle-silver wheels (like Kato and Atlas) will have less or at least different noise from those with steel/sintered iron wheels (Athearn, early Proto 2000).

Replacing steel wheels with n/s ones from JayBee or NWSL has improved the sound of many of my older Athearn diesels, which otherwise had a quiet drive line.

That's one of the reasons that plastic wheels were so popular when they were first introduced. I addition to being quieter than brass wheels on round-ended steel axles, the needle-point axle ends often rolled within plastic sideframes. This allowed them to roll much better than most of the older metal-on-metal offerings.
While I have metal wheels on some of my rolling stock, most have plastic wheels, which helps to keep the noise levels acceptable.

Wayne