Help with Stuart Triple Steam Engine

[Andy Munns]

Sorry for reply length, but a complex subject...

Yes - Condenser vacuum is created ONLY by the collapsing volume of exhaust steam and air harms this vacuum because at these low pressures, air occupies a huge volume.

A condensate or extraction pump (termed by my steam turbine friends) removes condensate only and a separate air extraction pump removes entrained air.

Air enters the exhaust system via rod gland leaks plus air dissolves in open boiler feed water and enters the system. Sometimes larger steam plants have a feed deaerator to remove some of this air - Smaller plants, say <1000 IHP mostly did not.

Most smaller steam recip plants (say < 1200 IHP) tended to have an engine-driven extraction pump, which recip engine engineers called the "air pump" because its largest duty was removing air - The condensate was also removed by the air pump - Condensate was also necessary to lubricate the air pump plus the design of the pump at the head valves form a water seal weir that helped seal against air leaking back. The air was discharged into the engine room while the condensate flows back to the feed pumps via the hotwell or a float tank.

The Stuart triple resembles the smaller high-speed engines that had balanced cranks and shorter strokes commonly fitted to fast launches and naval craft. Search Bolton triple on the other hand - This is based on a Sydney (Au) double-ended ferry engine and resembles more the sort of double column triple fitted to tugs and ferries. Double column engines often did a lot of astern running.

 

[Richard Hed]

The March 8, 1923 issue of Model Engineer and Electrician has a double expansion engine. I have seen only one triple expansion plan--the French one. does anybody know others? I ordered that book, not from amzon but from Abe books, much cheaper!

 

[Steamchick]

K.N.Harris: Model stationery and Marine steam engines: Does a twin Pinnace engine -n with alternative details to make a compound twin. Stuart make a triple compound casting kit and plans, and I think possibly Bassett Lowke did a triple compound casting kit and plans? I am a curator of the Sunderland Model Engineers' twin compound engine. It has a plate stating 1923 - or something - but I understand it was made by some apprentices - when they used to do that sort of thing... possibly 1930s, or 50s? When I run it (at annual shows) it runs for maybe 5 mins after pre-warming the HP cylinder, for maybe a further 5 mins until the LP cylinder is heated sufficiently to avoid large quantities of condensate. Then suddenly it will increase speed when the LP cylinder starts to do some real work.
K2

 

[oldengineguy]

Thank you all for your knowledge and patience in explaining the "why" to my question re eccentrics in compound steam engines . It makes sense to me now.(sort of). There is a long way to go on this engine still before it's ready to run. I have the crank and eccentrics made and fitted ,now will get on with the straps and con rods before the top end. I like to make the "go round bits " before the "up and down stuff". Mechanicboy Is that a Stuart Double 1 0 with reverse gear in your avatar? Thanks again Colin

 

[Mechanicboy]

Mechanicboy Is that a Stuart Double 1 0 with reverse gear in your avatar? Thanks again Colin

Yes, it's my D10 with own made reverse gear. See at my movies..

 

[grahamgollar]

Re an earlier comment from Richard Hed - Q: do you require complete construction drawings for a triple expansion engine or just the valve gear?
Regards

 

[Steamchick]

Yes, it's my D10 with own made reverse gear. See at my movies..

Nice to see the twin running.
Just "my preference" but I should prefer to see a lagged boiler and steam pipework. Not a problem when you are proving it all works, but if models are meant to represent the full sized works I can't imagine why any hot stuff would be un-lagged. Also, I'm Not sure why the safety valve is horizontal in the boiler, but if/when it blows it will send a jet of steam across the kitchen at anyone there. Not just a whiff of water vapour as per your fingers dabbling in the exhaust (unsafe practice, but your fingers!), but a jet of full pressure invisible steam releasing maximum power from the boiler. The sort of thing that will de-flesh a hand in seconds. So please arrange the safety to exhaust vertically away from unsuspecting people.
Sorry to sound like Grandma, but steam in the wrong place can be extremely dangerous.
Cheers,
K2

 

[Richard Hed]

Re an earlier comment from Richard Hed - Q: do you require complete construction drawings for a triple expansion engine or just the valve gear?
Regards

Eventually, I expect to make a triple expansion, but first a double expansion. I have a French set of drawings, but am always looking for alternatives. The French are in metric which I can work with but prefer imperial. Also the dwgs I have either have different rules for drafting or are done improperly which is a terrific pain but since I always redraw them anyway, I can fix them to my own standards. Anyway, if you have a complete set, I would like to at least compare them to the French set I already have, then I will have a choice between two triple expansions when I get around to making one. I expect to make changes in any and all drawings when I thimk there can be improvements.

 

[Charles Lamont]

You may get better results if you search for 'compound' engines, as this is what double expansion engines are usually called.

 

[grahamgollar]

Eventually, I expect to make a triple expansion, but first a double expansion. I have a French set of drawings, but am always looking for alternatives. The French are in metric which I can work with but prefer imperial. Also the dwgs I have either have different rules for drafting or are done improperly which is a terrific pain but since I always redraw them anyway, I can fix them to my own standards. Anyway, if you have a complete set, I would like to at least compare them to the French set I already have, then I will have a choice between two triple expansions when I get around to making one. I expect to make changes in any and all drawings when I thimk there can be improvements.

Stuart Turner supply castings for a triple as do A J Reeves, both with drawings in proper (Imperial!) units. The Reeves engine is based on O B Bolton,s design from the 1950's updated by J P Bertinat in 1985. The Bolton design is more akin to a large ship propulsion engine compared to the Stuart Turner which is more typical of a launch engine. I've attached a GA of the Bolton design.
I agree with Charles Lamont that the usual terminology used this side of the pond is compound engines for two cylinder arrangements - who said that we are two nations divided by a common language?!

 

[Richard Hed]

Stuart Turner supply castings for a triple as do A J Reeves, both with drawings in proper (Imperial!) units. The Reeves engine is based on O B Bolton,s design from the 1950's updated by J P Bertinat in 1985. The Bolton design is more akin to a large ship propulsion engine compared to the Stuart Turner which is more typical of a launch engine. I've attached a GA of the Bolton design.
I agree with Charles Lamont that the usual terminology used this side of the pond is compound engines for two cylinder arrangements - who said that we are two nations divided by a common language?!

Thank you for all that. No, even in USA, I thimk, it is called a compound engine, I just forget what to call it. I can visualize things but cannot put a name to them quite often. However, I thimk, that double and triple expansion are also proper. Maybe triple expansion compound engine would be the perfect name explaining all one needs to know.

 

[oldengineguy]

Over a year since the last post on this thread. In that time I have decided against trying to run this engine on steam as boiler construction is beyond my tools and capabilities. So on to compressed air. With eccentrics made for steam with 30 & 15 degree offsets( as per drawings) the engine will run on air on HP & IP but will not reverse. With LP connected, engine would run in forward only, but needed 60+ PSI. I made new eccentrics for IP &LP with 30 offset , same as HP and could get engine to run for.& rev. on HP, IP or both but when LP connected would run in forward but not reverse or reverse but not forward depending on timing of eccentric. I made 2 separate eccentrics for the LP cyl so the timing could be set independently and now have a smooth running engine. I know it's not a triple expansion but I now have an engine that works for show and tell. Will run as slow as 275 RPM @ 20 psi and run above the2000 max of my tach @50 psi. Not the way Stuart designed it ,but it works for me. Colin

 

[Richard Hed]

Stuart Turner supply castings for a triple as do A J Reeves, both with drawings in proper (Imperial!) units. The Reeves engine is based on O B Bolton,s design from the 1950's updated by J P Bertinat in 1985. The Bolton design is more akin to a large ship propulsion engine compared to the Stuart Turner which is more typical of a launch engine. I've attached a GA of the Bolton design.
I agree with Charles Lamont that the usual terminology used this side of the pond is compound engines for two cylinder arrangements - who said that we are two nations divided by a common language?!

Graham,
Do you have anything more to this Bolton Triple expansion engine? Do yo know where to get plans?

 

[Richard Hed]

Re an earlier comment from Richard Hed - Q: do you require complete construction drawings for a triple expansion engine or just the valve gear?
Regards

Geez louize, I don't know if I ever answered this. Yes, I would like a set. do you know where to get one?

 

[PeterDRG]

Hi
Does anyone have copies of Tom Walshaw´s articles in the SIMEC magazine for July, September and November 1979 please ? Some correspondence with Tom suggests that I have them, but they must have been misfiled :-(

 

[PeterDRG]

Hi
I do now have copies. Thank you.