Landlubber questions.

[YM-Mundrabilla]

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)

[Engine Serang]

YM, its 40 years since I did my Chiefs and things are a bit hazy, will check.

[Tom Alexander]

Originally Posted by YM-Mundrabilla

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 ?????

[YM-Mundrabilla]

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)

[Murchison65]

Don't know these questions have been answered elsewhere but this might be of interest.



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


Cheers

[Varley]

Originally Posted by Engine Serang

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.

[BobClay]

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

[daveybm]

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.

[YM-Mundrabilla]

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)

[Howard]

Originally Posted by YM-Mundrabilla

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. It’s only really the crankshaft that is doing much different when the engine is thrown astern.

[Apple82]

Originally Posted by YM-Mundrabilla

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.

[Tim Gibbs]

Originally Posted by YM-Mundrabilla

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.
Geoff (YM)

My one & only short steam triple expansion recip experience was v nearly 60 years ago but my memory is running with stop valve full open and controlling speed with boiler pressure and shut-off on the reversing gear. Did I dream that and fail my Chief's ticket?!

[wazeyes]

Been a very long time since worked on triples but with Stephenson gear on the wiper shaft was a link the allowed small adjustment to the position of the link motion so adjusting the cut off and hence power and steam consumption
If no tacho fitted speed was adjusted by looking at the Medium pressure cylinder steam chest pressure and the throttle v/v used to obtain the required pressure. Boiler pressure remained for all intense and purpose as constant as possible
stand to be corrected on the above.

[Chillytoes]

If you ever had any doubt about the ability of steam engines to instantly go from Full Ahead to Full Astern, take a look at the River Don engine at Kelham Island Museum. It's a 12,000 HP unit, 3 cylinder, each cylinder working at boiler pressure, i.e. no compounding. It was employed rolling armour plate.
In the Mark Williams series "Industrial Revelations" (can't remember which episode) you can see the engine going full ahead to full reverse in rapid succession, as was necessary for rolling the plate.

[lakercapt]

Being a deckie who sailed with two triple-expansion steam engines and having spent a little time in the E/R my memory when maneuvering was the speed was controlled by the valve to the engine from the boilers. Full speed was about 60 rpm and half 30 rpm slow about 15 and dead slow about ticking over. There was a small steam engine that changed cams. I may be wrong but it was 67 years ago