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  #1  
Old 29th March 2019, 12:56
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YM-Mundrabilla Australia YM-Mundrabilla is offline
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Landlubber questions.

As an old Railwayman Landlubber can I ask a couple of (perhaps stupid) questions, of some of the engineers on SH, please?

Assuming a reciprocating steam engineroom:

How are the various speeds 'full', 'half' and 'slow' etc defined? Is it by RPM which presumably (?) gives a more or less set speed?

Am I correct in understanding that marine reciprocating steam engines do not have 'cut off' on the valve gear (as in a locomotive) but only ahead/astern? On this assumption is engine speed controlled only by the boiler steam throttle/regulator valve?

Again assuming, on the basis that there is no valve cut off, the lost efficiency is more or less made up by compounding?

I have some steam locomotive knowledge but know little (nothing actually!) about marine steam.

Any comments will be appreciated, please.

Regards
Geoff (YM)
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Old 29th March 2019, 17:01
Engine Serang Europe Engine Serang is offline
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YM, its 40 years since I did my Chiefs and things are a bit hazy, will check.
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  #3  
Old 30th March 2019, 07:27
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Tom Alexander Canada Tom Alexander is offline
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Quote:
Originally Posted by YM-Mundrabilla View Post
As an old Railwayman Landlubber can I ask a couple of (perhaps stupid) questions, of some of the engineers on SH, please?

Assuming a reciprocating steam engineroom:

How are the various speeds 'full', 'half' and 'slow' etc defined? Is it by RPM which presumably (?) gives a more or less set speed?

Am I correct in understanding that marine reciprocating steam engines do not have 'cut off' on the valve gear (as in a locomotive) but only ahead/astern? On this assumption is engine speed controlled only by the boiler steam throttle/regulator valve?

Again assuming, on the basis that there is no valve cut off, the lost efficiency is more or less made up by compounding?

I have some steam locomotive knowledge but know little (nothing actually!) about marine steam.

Any comments will be appreciated, please.

Regards
Geoff (YM)
Being a "deckie" who never sailed with reciprocating steam (only turbines & Doxfods) could any one answering the thread also elucidate on what happened to the steam/engine when stopped or in astern ?????
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Old 30th March 2019, 13:45
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Chief ES and Deckie Tom.
To elaborate a little, my questions arose from a demonstration last Thursday 28/3 of a museum based two cylinder vertical steam engine, allegedly from a Murray River paddle steamer of the late 19th century, when the restorer repeatedly threw the valve gear (instantly) from 'full ahead to full astern'. I have to admit that the engine looked nothing like a PS engine to me but then I have no knowledge beyond the few Murray River paddlers having steam roller/traction engine machinery.
I always previously thought (still wonder) that this would not be good for the machinery and it was at this point when I asked about cutoff on marine reciprocating that the conversation became confused.
Regards and thanks.
Geoff (YM)

Last edited by YM-Mundrabilla; 30th March 2019 at 13:49.
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Old 20th October 2019, 22:45
Murchison65 Australia Murchison65 is offline
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Don't know these questions have been answered elsewhere but this might be of interest.



https://www.youtube.com/watch?v=XIzwF0fnRHg


Cheers
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  #6  
Old 20th October 2019, 23:33
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Varley Isle of Man Varley is offline
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YM, its 40 years since I did my Chiefs and things are a bit hazy, will check.
Entirely OK old man. We do understand that in those days the feathered headdress was a requirement of part A Chieftans.
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Old 21st October 2019, 05:23
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Took a look at the cast of that film. Some familiar names further down the list.

https://www.imdb.com/title/tt0051816...=tt_cl_sm#cast
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  #8  
Old 25th October 2019, 11:52
daveybm daveybm is offline
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Full Ahead to Full Astern immediately on a T3 Expansion engine is accomplished by throwing over the Stephenson Reversing Link, no big issue as can be seen in the film clip posted by Murchison65, I sailed on one Steam Recip job, CS Edward Wilshaw 2495 Gross Tonnage, 2 x triple expansion 3 cylinder engines total IHP 2100, great for manoeuvrability not so good for top end (about 10 Knots), it was a bit of a change from 484,000 dwt and 45000 shp Globtik Tokyo.
Full, Half, Slow, Dead Slow and Stop are controlled by the throttle valve.

Last edited by daveybm; 25th October 2019 at 12:20.
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Old 25th October 2019, 12:23
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Thanks All.
As one of the totally uninformed it just seemed 'a bit hard on the machinery' the way it was demonstrated to me back in March on what was a relatively tiny engine.
I will pay a bit more attention if I ever go back to the museum in country Victoria again.
Geoff (YM)
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  #10  
Old 25th October 2019, 19:00
Howard Howard is offline
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Quote:
Originally Posted by YM-Mundrabilla View Post
Thanks All.
As one of the totally uninformed it just seemed 'a bit hard on the machinery' the way it was demonstrated to me back in March on what was a relatively tiny engine.
I will pay a bit more attention if I ever go back to the museum in country Victoria again.
Geoff (YM)
When you think about it the pistons and associated gubbins are reversing direction twice a revolution. Itís only really the crankshaft that is doing much different when the engine is thrown astern.
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  #11  
Old 6th November 2019, 20:29
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Originally Posted by YM-Mundrabilla View Post
Thanks All.
As one of the totally uninformed it just seemed 'a bit hard on the machinery' the way it was demonstrated to me back in March on what was a relatively tiny engine.
I will pay a bit more attention if I ever go back to the museum in country Victoria again.
Geoff (YM)
It is not the normal practice YM but can be done in an emergency. It is, as you say, hard on the machinery. It is handy if the engine continues to turn slowly after the throttle is at stop. Astern movement can be made without waiting for complete stop. Doing it from full ahead is a whole different thing.
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