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Author Topic: Engine room noise level  (Read 3411 times)
Seaman Apprentice

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« on: January 26, 2014, 01:23:35 AM »

Hello All, I know I can ask some of the craziest questions some times, and this could easley be one of them times. But if nothing else, it might give the old brain matter a little stretch……  uglystupid2

I am trying to do a little research on engine room noise on a Fleet Boat of WW2 vintage, namely a Balao class boat with the Fairbanks-Morse Model 38D8-1?8 9-cylinder opposed-piston diesel engines.

To say the least, I know it was LOUD, but what I am looking for is technical data to quantify it.

 I am looking for any information that would tell me:

1. The sound level (DB) inside the engine room, at different engine speeds (RPM)?

2. What would the engine speed be at varying different loads on the main battery bus?

3. What would be the frequency of the sound that would be heard at different RPMs of the drive motors?

4. Along similar lines, when one of the engines are running, are they always running at a approximantly fixed speed, to keep the generators in-sync with each other or the line frequency of the boat (~60hz)? If so, what approximant speed (RPM) was that? Then does anyone know what the firing sequence was on one of the engines? Were they sequential (in any order) or where there parallel cylinders firing at any time?

Well let’s see what comes of this posting, I hope it’s interesting.

Jay Boggess
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« Reply #1 on: January 30, 2014, 10:19:33 AM »

I've only heard submarine diesels running once - on Silversides back in 1986 or 7 for a Memorial Day event.  They had two of their F-M's idling unloaded at about 400 rpm.  BUT I've heard many, many locomotive diesels at all sorts of horsepowers and engine rpm's from inside and outside the locomotive body.  The Silversides were strangely not nearly as obnoxious and loud as a locomotive diesel.

Because submarine diesels are spinning DC generators, there is no syncing as such.  Enclosed is the engine load graph for the Cleveland Diesel 16-248 engines on Bowfin.  You can see there is a desired "sweet-spot" loading band from low engine rpm to high rpm.   At a particular rpm, the engine room noise will have a certain pitch, but (from my locomotive experience) the tone at the same engine rpm will likely change and probably grow louder as the engine load increases.

You can find the firing order of an F-M diesel  on page 80 of  Rich Pekelney's Fleetsub manuals ( but for the 9-cylinder, it is 1-9-2-7-4-5-6-3-8 for left hand rotation and 1-8-3-6-5-4-7-2-9 for right had rotation.

Except for maybe Rich Pekelney on his foreign sub field trips, I suspect no one has heard one of these engines at full speed / full power for a long, long time, if ever...

jay b.

* 248 Load Graph.JPG (160.67 KB, 480x640 - viewed 344 times.)

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« Reply #2 on: November 07, 2014, 03:18:50 PM »

I'm currently taking care of the engines on the Silversides and have been for the past five years. We start them up about every three weeks during the summer to keep them alive. Currently we are only running # 3 & 4. I am a retired senior chief engineman and like most now just a little hard of hearing but spent a lot of years on watch. Because the boats are DC power 60 cycles does not apply. As for sounds all different manufactures engine had there own sound. Fairbanks are in my opinion the best built and sweatest sounding. When it came to snorkeling they couldnot be beat. A rule of thumb was run main engines at a 80 / 90 combination. Eighty percent speed, ninety percent load, they would run forever. I don't think the railroads have run fairbanks for many many year. there using 645's mostly. This could account for the sound you are referring to. Contact me if i can answer any of your guestions.

Frank Lydell
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