Whistle setting

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SteveM
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Whistle setting

Post by SteveM »

I have a couple of small whistles with Jenkins valves (I used to work near the Jenkins Brothers factory).
20190525_153018.jpg
The bell of the whistle (if that's the correct term) is adjustable up and down to a limited extent.

The bell is about 2" diameter and 4" long, and the air inlet is 3/8' NPT.

Right now, at 100psi, I can get 101db measured about a foot away (with my phone, which is not an analytic instrument, but probably close enough).

Is that decibel level about what I should be hearing from this at that pressure?

is there anything I can do to improve the sound?

I understand that I'm running it on air and not on steam, but I don't have a steam source that can generate the pressure.

While I realize that I might need to play around with it, is there a "starting" distance I should use from the base to the bottom edge of the bell?

On one of them, the bell doesn't quite line up, and it appears that it's the threads at the top of the bell that are crooked.

I thought of using the lathe and running a tap into it straight to correct it. That would straighten it, but possibly make it a bit loose. I could use a nut on the inside to support it so that the top nut locks it into position.

Any suggestions greatly appreciated.

Steve
Soot n' Cinders
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Re: Whistle setting

Post by Soot n' Cinders »

Unless you really want it as loud as possible, I think youre over complicating it. The distance from the bell to the languid plate is really only adjusted if the whistle overblows, thus hitting a higher overtone that usually is more of a screech. If it sounds good, Id leave it alone. It will sound different on steam rather than air, itll be higher since sound travels faster through steam. So if you plan on blowing it on steam, I would adjust it on steam. Otherwise air will be fine
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Glenn Brooks
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Re: Whistle setting

Post by Glenn Brooks »

Steve,

I’ve had and have a couple of whistles in the size range you describe. I would say your dB rating is about right for 100 psi of air. Although I am no sound expert and haven’t rated whistles by Decibel - but mine have been in your dB range. As I remember from my flying days, 85 dB is about the max exposure before a human starts to suffer hearing loss. Certainly these smaller 4” three chime whistles exceed that level by a good margin.

I’ve heard these whistles often were used atop factory smokestacks to announce end of shift, etc. So they were meant to be loud and shrill so the sound would carry down to the factory floor and throughout the grounds. Which makes them LOUDer AND SHRILL-ER close up, such as, on miniature locos.

Now, certainly you can adjust the tone a bit by screwing in or out the whistle shell, as you describe. I don’t know what the part is actually called... this alters the harmonics and can deepen or raise the tone a certain limited extent.

If you want to lower the whistle volume, for example, to make it more pleasant sounding indoors, or close up - just add a small, globe valve to the bottom and adjust the amount of air pressure flowing into thenvalve. Also you could machine a small bushing with a small hole drilled in the middle, and insert this bush8ng into the ID of the valve stem. This effects reduces PSI and lowers the tone of the whistle, even if operating at steam pressure on a loco. I know a couple of live steamers that do this routinely to mitigate excessive whistle noise.

I don’t know about re cutting the threads. My guess is this would degrade the existing thread pattern and maybe ruin the whistle, if you didn’t hit it spot on...

Only way I know of, to get a much deeper tone would be to make a new, longer, sound chamber - maybe something in the range of 12” long and replace the existing one.

Glenn
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Fred_V
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Re: Whistle setting

Post by Fred_V »

If you are using this on a livesteam loco it would be better to lower the sound level for the benefit of those around you.

It could be the center rod is bent rather than the threads being off. Just straighten the rod.
Fred V
Pensacola, Fl.
SteveM
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Re: Whistle setting

Post by SteveM »

Fred_V wrote: Fri May 31, 2019 6:57 am It could be the center rod is bent rather than the threads being off. Just straighten the rod.
The center rod is 1/2" threaded stainless steel and is near dead straight.

When I thread the bell on, you can see it wobbling as it goes around.

That's why I was considering straightening the threads.

Maybe the solution is to drill it out and have nuts top and bottom to lock it in place.

Steve
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kenrinc
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Re: Whistle setting

Post by kenrinc »

Might be better to make a "spider" that either threads on or is a close fit to the major diameter of the threaded rod. This assumes the rest of the whistle is reasonably in line with said threaded rod. $.02

http://patentimages.storage.googleapis. ... 1171-0.png

Ken-
SteveM
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Re: Whistle setting

Post by SteveM »

kenrinc wrote: Fri May 31, 2019 12:27 pm Might be better to make a "spider" that either threads on or is a close fit to the major diameter of the threaded rod. This assumes the rest of the whistle is reasonably in line with said threaded rod. $.02

http://patentimages.storage.googleapis. ... 1171-0.png

Ken-
Interesting. That might work.

Steve
SteveM
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Re: Whistle setting

Post by SteveM »

I pulled the second whistle apart.

I knew that the valve was sticking, so I cleaned, polished and lubed all the parts so it would work smoothly and quickly.

Tried and and... nothing. No air coming thru.

I had blown thru the valve when I cleaned it so I checked it again and it was OK.

The disk that creates the ring of air had been installed upside down, and it seated against a ring in the bottom casting, blocking the air flow.

When I flipped that around and reassembled it, even with the bell slightly off, it generated exactly the same 101 db that the first one did, so I think these are good to go.

Steve
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Fender
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Re: Whistle setting

Post by Fender »

In principle, the bell should be a distance above the languid plate equal to 1/4 the diameter of the bell, in your case 1/2”. You may want to experiment by making a new languid plate to reduce the opening size. This will reduce the dB of sound produced by the whistle.
Dan Watson
Chattanooga, TN
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Fred_V
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Re: Whistle setting

Post by Fred_V »

Thanks Dan. I always wondered about the slit and what difference it made.
Fred V
Pensacola, Fl.
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Fender
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Re: Whistle setting

Post by Fender »

It’s a bit more complicated than what I said. Again in principle, the size of the opening should be a function of the steam pressure, with higher pressures needing a smaller opening, to avoid “overblowing”. But with a lower pressure, the smaller slit will reduce the pitch and the dB output.
Dan Watson
Chattanooga, TN
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