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Piping for chime whistle

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Paul Sherriff04/03/2022 18:06:24
12 forum posts

I’ve got a large chime whistle which I want to install on the Romulus I am building

The fitting on it is 1/2” BSP (big). What is the minimum pipe I should consider piping it up with? Was hoping tp use 1/4” OD copper, making a suitable fitting Would that be enough?


Edited By Paul Sherriff on 04/03/2022 18:07:32

Edited By Paul Sherriff on 04/03/2022 18:08:20

bernard towers05/03/2022 09:23:05
693 forum posts
141 photos

Could you not test performance with a compressor and variable regulator?

Clive Brown 105/03/2022 10:13:54
871 forum posts
47 photos

In "Shop Shed & Road" LBSC seems to use nothing bigger than 1/8" dia. for his whistles so 1/4" should be plenty.

Incidentally, he tells that he used his 5-pint blow-lamp as a compressed-air source for testing the notes.

Paul Lousick05/03/2022 10:18:06
2079 forum posts
728 photos

Chime whistles are multiple whistles combined into the one structure and as you have said, the 1/2" BSP fitting is big and probably used 1/2" NB pipe.

Standard 1/2" NB pipe has an OD of 21.3mm and an ID of 15.7mm. So is 1/4" OD (6.35mm) tube with a bore of approx. 5mm going to work. (Note. The size stated for pipe refers to its nominal inside diameter, not its OD. Unlike tube which refers to its OD)

It is going to require a lot of air/steam to make a decent sound. I would use a minimum of 12mm tube, preferably 16mm OD


roy entwistle05/03/2022 10:20:32
1552 forum posts

You will not get the same results on air as on steam


Paul Sherriff05/03/2022 13:29:11
12 forum posts

Thanks guys. Your input is much appreciated

SillyOldDuffer05/03/2022 13:57:36
8912 forum posts
2000 photos

Posted by Paul Lousick on 05/03/2022 10:18:06:


It is going to require a lot of air/steam to make a decent sound...

I read somewhere that unnecessary whistling was strongly discouraged during the steam-age because it's so wasteful. How much steam does a whistle use? Does anyone have any figures for full-size or model locomotives?

More usefully perhaps, the diameter needed to achieve a given flow depends on length too - 10 metres of ⌀3mm pipe offers much more resistance than 0.1m of ⌀3mm, and heat loss from long pipes makes them even worse. In practice, driving a big whistle calls for largest shortest pipe that can be managed: a long small diameter pipe is likely to throttle the whistle. I vote for the biggest diameter that looks OK on the engine.


noel shelley05/03/2022 14:31:21
1451 forum posts
23 photos

I'm with sod and Paul, I would use 12 or 15mm copper pipe, in part as I have it ! It should look OK and work well. Noel.

Edited By noel shelley on 05/03/2022 14:32:36

Paul Lousick05/03/2022 22:43:37
2079 forum posts
728 photos

Whistles sound muck better on steam than on air.

SOD. " Does anyone have any figures for full-size or model locomotives? ". This is data from the Lunkenheimer catalogue published in 1912

lunkenheimer steam volume.jpg

From the table, for a 2" whistle with a 1/2" pipe fitting it requires 0.24 cu.ft of air per second at 40 psi to blow it. (An air compressor that can deliver 14 cfm. )


Paul Lousick05/03/2022 23:48:40
2079 forum posts
728 photos

Whistles sound muck much better on steam than on air. (although muck on air could be appropriate)

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