[jamesgpobog]

I have no experience with them at all. I found this very simplified animation on the John W. Brown website...

http://www.liberty-ship.com/html/vto...eanimation.gif

I hadn't realized that the pistons were acted on in each direction. Now, my question is because what my brain is telling me doesn't match what I see in the diagram, but it's probably because of lack of detail.

Am I correct in assuming that the exhaust from each cylinder, from each direction, is valved into a manifold that then becomes the intake (for both directions) for the next cylinder?

[Mikepg]

The exhaust from the high pressure cylinder exhausted into the steam chest of the medium pressure cylinder and that from there exhausted into the steam chest of the low pressure cylinder. Each cylinder had it's own valve gear to distribute the total steam from the previous source, normally. Apart from toys like 'Mamods', most steam reciprocating engines were 'double acting', and there were even some double acting marine diesels. A double expansion steam engine is normally refered to as a 'compound'.
Regards, Mike

[Long gone]

Looking at that diagram, were all the valves slide valves or did the h.p. cylinder have a piston valve?

Another thing that intrigues me. What would happen if the h.p. cylinder stopped on 'dead centre', or the h.p. valve was 'blind'?

[chadburn]

Act on an impulse.

[Ron Dean]

Originally Posted by Long gone

Another thing that intrigues me. What would happen if the h.p. cylinder stopped on 'dead centre', or the h.p. valve was 'blind'?

I'm not sure there will ever be a "dead centre". I suspect there will be a small degree of overlap on the various ports, in which case the highest pressure will always take over in the direction of rotation. Just my thoughts - I don't know for sure.

Ron.

[jamesgpobog]

Originally Posted by Ron Dean

I'm not sure there will ever be a "dead centre". I suspect there will be a small degree of overlap on the various ports, in which case the highest pressure will always take over in the direction of rotation. Just my thoughts - I don't know for sure.

Ron.

That makes sense to me. I know that in automotive gasoline engines there is always some valve overlap that can be played with to give different performance qualities...

[John Paul]

Manually operated valves could be used to admit live steam to the IP or LP cylinders to give the required impulse to get the HP off a dead centre,from memory these could act on the top or bottom of the cylinders depending if going astern or ahead.

[jamesgpobog]

Originally Posted by John Paul

Manually operated valves could be used to admit live steam to the IP or LP cylinders to give the required impulse to get the HP off a dead centre,from memory these could act on the top or bottom of the cylinders depending if going astern or ahead.

Damn, that makes sense too. Sure would give a solid 'baseline' for any kind of valve timing 'tuning' to be done...

[John Paul]

I recall setting valves on a triple expansion when serving my time,Piston valves were done with sticks and flat v/vs with feelers to measure port opening top and bottom Revering gear was placed at full over ahead so eccentric rod was inline with v/v rod. and the engine bared over to TDC or BDC. Once FAOP indicator cards would be taken and horsepower calulated, to balance up power the links were adjusted in or out..Impulse valves also known as starting valves

[Varley]

Father (as 'Plump Plumber' of 13th, I think, ML flottila) visited a merchantman in (again 'think') Gibraltar. Chief had brass template for the indicator cards he returned to HO - actuality of this detail was not HO's business! Never heard a hint of this in my time.

[david freeman]

Some where in my distant past Auxilary steam pumps and fans etc, had no lap or lead, and therefore steam was admitted for the whole stroke-Unless you had a weirs pump wiyth the shuttle valve, then there was a small lap and lead, and one had a spaneer if the steam valvle become stuck or the steam pressure reduced being insufficient to power the piston stroke.
On a main Triple expansion engine main engine or a Bellis and Morcom Steam deriven genny engine the piston of 'D' valves had lap and lead and so live steam was not admiitted for 100% of the stroke, it expanded as the stroke progessed and did work. On a main Recip Marine engine one had some short of valve gear where one could adjust the position of the valve movement, so making the steam wok harder and more efficiently.

[Long gone]

Originally Posted by John Paul

Manually operated valves could be used to admit live steam to the IP or LP cylinders to give the required impulse to get the HP off a dead centre,from memory these could act on the top or bottom of the cylinders depending if going astern or ahead.

That confirms my thinking; it sounds a similar system to that used by the Smith-Johnson Midland Compounds, where a valve admitted steam at 85% of boiler pressure to the l.p. receiver, to aid starting. They had 1 h.p. and 2 l.p. cylinders

[chadburn]

Originally Posted by John Paul

Manually operated valves could be used to admit live steam to the IP or LP cylinders to give the required impulse to get the HP off a dead centre,from memory these could act on the top or bottom of the cylinders depending if going astern or ahead.

As I indicated John, "act on an Impulse", just for further information for those who may not know, impulse steam is usually at reduced main steam pressure and is injected straight into the desired cylinder bypassing the valves and as indicted by John depending on direction. It can also be used to give the engine a bit of a "boost" if done correctly. Long leggers are a double acting gas engine's.

[Ron Dean]

Originally Posted by chadburn

As I indicated John, "act on an Impulse", just for further information for those who may not know, impulse steam is usually at reduced main steam pressure and is injected straight into the desired cylinder bypassing the valves and as indicted by John depending on direction. It can also be used to give the engine a bit of a "boost" if done correctly. Long leggers are a double acting gas engine's.

Somewhat akin to getting a compression ignition engine started with compressed air, to get the beast turning.

[jim garnett]

My memory may not be too good as it is 60 years since I served on

a triple expansion engine.I believe if it was stuck on tdc we only had to give the reversing gear engine a bit of a nudge and thus alter the valve position.As regards lap and lead the steam steering gear did not have any for obvious reasons.
Many triple expansion engines were fitted with exhaust turbines.
As I found out you never routed the steam winch exhaust steam to the main condenser while underway.It makes a VERY large knocking noise in the L p cylinder.
JIM GARNETT

[murrayis]

On a triple expansion steam tug I used to crew, we had the occasional stop on TDC. It always seemed to happen just when those pesky wharfs jump out in front of you (or some other solid object) and you’re trying to go from full ahead to full astern. You could hear the engine stop, then a lot of technical words coming up from the fiddley as the engineer rocked the reversing gear back and forth until finally she would kick. In reality it was probably a matter of seconds but it seemed like an eternity.

[teop]

Hi,
yes a special lever/handle for impulse steam to kick the stuburrn hp crank.
Near by, facinating with linkage set, a triple, cranks bouncing from one side to another without rotating during warming up.
regards
teop

[chadburn]

Absolutely right Teop, most Engineer's would not only use this method for warming up but also between telegraph order's, when stop was requested they would bounce the crank's to prevent a possible jam up until the next "request" from the Bridge when approaching or going alongside.

[jim garnett]

When was the last commercial triple expansion vessel built.I went on board a brand new triple expansion vessel with an exhaust turbine.after the lp cylinder.It was on it's maiden voyage in 1953 when I visited it in San Pedro de Macoris WI.It was one of Hogarths and had three oil fired scotch boilers.The chief was very proud of her.I'm not sure why.
Jim Garnett

[Basil]

When you think about it, a triple has the same number of power strokes per revolution that a 12 cyl car engine would have. Smooth!

[chadburn]

When I started at Smiths the last triple with LP Turbine was being built there in 1955 my initial's were/are popped on the bedplate, she was called the "Tynemouth". My first MN vessel was Hogarth's "Baron Ardrossan" she was also a Triple with an LP turbine and built in 1954. VTE's of all size's were a joy to operate and work on it's just the Boiler's that were a bally nightmare on occasion's.. They appear to have stopped building VTE's about the mid 1950's---------unless someone knows different of course!!!!!!

[Duncan112]

The Bosporus ferries were built at Fairfields with Triple Expansion Engines in 1961, and remained in service until the late 1990s/early 2000s.

[gordy]

http://pspsscotland.blogspot.com/201...viewshipa.html


Above site states not all the Turkish Ferries had Clyde built engines.
I started my time in June 1961 and the fitting out basin with the 9 ferries in there was spectacular.

[Duncan112]

Thanks for the link Gordy, film clip is spectacular!!

Have you any photos of the fitting out basin?

[chadburn]

Good posting Gordy, they must be the last of the engine build, I wonder how many Engineer's on this Site were on VTE's, I thought that they were a great engine and it's little wonder that Shipowner's stuck with them for so long. It was the Doxford engine that brought about their demise. Although the initial build cost for a Diesel engined vessel was high the fuel usage was around 11tns per day at sea whereas the old steam job was around 34tns per day.