To get a triple

A special section just for steam engines and boilers, as without these you may as well fit a sail.
Ralph B
Just Starting Out
Just Starting Out
Posts: 11
Joined: Wed Nov 18, 2009 6:20 am

To get a triple

Post by Ralph B » Wed Nov 18, 2009 7:04 am

From what I have seen available there are only 2 sources for launch sized triples, Elliot and Reliable. For a while I thought about taking a V-6 or I-6 and sleeving the cylinders to make what would be in effect 2 single acting triples. What turned me off about that idea is the wet crank as it has the potential to make a lot of work into a lot more work.

We can see through our gracious host the trials and tribulations of putting together the Elliot. I must say I like the "long legged" attributes of that engine. The Reliable has a much shorter stroke and bore and I wonder if it will generate the full 7hp listed. Is there any experience out there with this engine? I wrote Peter but never received a reply.
User avatar
csonics
Anne from Little Britan
Anne from Little Britan
Posts: 232
Joined: Tue Nov 17, 2009 11:17 pm
Boat Name: No Boat Yet
Location: Roseville, MN
Contact:

Re: To get a triple

Post by csonics » Thu Nov 19, 2009 2:35 pm

I am also curious to hear about options/experiences with the Reliable Triple since I considering building one.

-Mike
User avatar
Maltelec
Master of the Forum
Master of the Forum
Posts: 268
Joined: Sat Nov 14, 2009 7:01 pm
Boat Name: No Boat Yet
Location: Cumbria, UK
Contact:

Re: To get a triple

Post by Maltelec » Thu Nov 19, 2009 10:14 pm

When we did a brake test on the Elliot Bay under non-ideal conditions we got 6.4 BHP. That was with no vacuum, no superheat, no lagging on the very long steam pipe and not full pressure on the boiler.

I am pretty certain that 15 IHP would be obtainable, maybe 12 SHP if everything is right.
I've got the vehicle, just need the boat.
Edward
Full Steam Ahead
Full Steam Ahead
Posts: 138
Joined: Tue Nov 17, 2009 9:25 pm
Boat Name: No Boat Yet
Location: Ambleside , Cumbria , UK.

Re: To get a triple

Post by Edward » Fri Nov 20, 2009 12:49 am

"Your observations are correct concerning the lack of vacuum on the LP exhaust since no condenser or air pump has yet been fitted . In fact it was in some ways even worse as the LP cylinder drain was partly open and the steam supply was through a 6' uninsulated steel pipe with only 150psi at the boiler ! So we are not a little pleased with the result so far .
Ken Hall has a similar engine in his boat Oesa based in British Columbia as has Peter Cowie in Witch of Endor in Australia . Both run at 185 psi and at 375 rpm Ken reckons he is getting about 9 hp , Peter thinks he is getting about the same though I don't know if they have tested their engines on brakes .
When fitted with an insulated steam pipe , condenser and air pump and running at the boilers full pressure of 200 psi this engine could well be producing something like 10 hp .
It is a real credit to SteamboatJacks' engineering and machining skills . "

The above is what I posted on the " Old Forum " about the Eliott Bay Triple built by Steamboat jack , I think Maltelec is being rather optimstic with his estimate.
Having said that Simpson Strickland produced a triple with very similar dimensions about 100 years ago ; they claimed an output of 35 horsepower !! BUT this was at 750 rpm and a pressure of 350 psi , I also imagine that this was an indicated output rather than proved on a brake .

The output claimed by Reliable is also at high rpm , even so I am a little sceptical about the claim and I'm not sure how long the engine life would be if these rpm were used frequently .
At 600 rpm everything is just a blur and to my mind you lose most of the pleasure of having a steam engine.
steamboatjack
Full Steam Ahead
Full Steam Ahead
Posts: 275
Joined: Fri Nov 20, 2009 8:02 am
Boat Name: grayling
Location: Cumbria U.K.

Re: To get a triple

Post by steamboatjack » Fri Nov 20, 2009 9:23 am

Just a few basics here, the triple expansion engine was designed for one reason only, to reduce the fuel consumption of marine engines. It does this by expanding the steam further and in stages to reduce condensation losses in the cylinders. There is no other reason to have one (other than they look nice). As an engine designer primarily and builder of engines (including two elliott bays in hand) I would not choose a triple for sizes under about 12 inch L.P. bore, I just do not think its worth the extra hassle over a compound or simple expansion engine. The heat losses on small engines and the friction losses with three cylinders probably negate any advantages.
Triples should run at about 200PSI which is not always practical.
Ok turbine smooth running is a good feature but if you must have three cylinders build a compound (two L.P.) this would have cylinder ratios of 1: 1.414 diameters to get a volume ratio of 1:4 which is normal for condensing compounds. Put the H.P. in the middle to reduce heat losses. A somewhat lower initial pressure would then be acceptable.
Better still build a three cylinder uniflow with poppet valves (inlet only) and a good condenser.
An approximate power of any multi stage engine can be obtained by considering it as a single cylinder engine of the L.P.'s dimensions, this is know as the "referred IHP" .
The initial steam pressure is that of the H.P. which then has to be reduced to a calculated M.E.P. by a fudge factor and used in the familiar I.H.P. equation.
It is a pity that as far as I can see none of the available sets of castings (at least in the UK) are of engines which are complete with tried and tested designs which have been designed by a person competent in the theory and drawn using drawings acceptable to a professional machine shop. I was going mention scaled up models but though better of it! I have no axe to grind with model engineers but I cannot think of a UK engine which does not have these traits (thats why I design my own!)

regards Jack
mcandrew1894
Full Steam Ahead
Full Steam Ahead
Posts: 193
Joined: Fri Nov 20, 2009 10:12 am

Re: To get a triple

Post by mcandrew1894 » Fri Nov 20, 2009 10:32 am

Hi, :)
Reliable has a good reputation in my neck of the woods, but I have not run one of their engines.....they spin fast. The Stuart 6A spins fast also but it has a low expansion ratio, so though you could run it on higher pressure, your not really gaining anything

I believe Peter Cowie did run his triple on a brake, though perhaps he would like to comment on that ?

If designed correctly, 600 rpm in a small engine is not at all intimidateing and they run well. Lubrication or should I say application of lubricant can be a problem.
Piston speed, sufficient bearing area and proper balance are really the key there to long life.

Cheers!

Dave
Ralph B
Just Starting Out
Just Starting Out
Posts: 11
Joined: Wed Nov 18, 2009 6:20 am

Re: To get a triple

Post by Ralph B » Fri Nov 20, 2009 12:46 pm

Jack,

I haven't seen any designs like you mention. Do you have any on paper? Probably the biggest reason I am interested in a triple is because...well, its a triple. If something similar was available that would be more practical in this size range I am all for it. Low RPM, 150PSI, and long legs.

Ralph
87gn@tahoe

Re: To get a triple

Post by 87gn@tahoe » Sat Nov 21, 2009 4:06 am

When "long legs" are mentined, the "York" compound always comes to mind.
User avatar
barts
Full Steam Ahead
Full Steam Ahead
Posts: 898
Joined: Wed Nov 18, 2009 6:08 am
Boat Name: Otter, Rainbow
Location: Menlo Park, CA
Contact:

Re: To get a triple

Post by barts » Sat Nov 21, 2009 8:21 am

Triple expansion engines were basically only ever used commercially in ships and pumping/compressor stations, as it is not particularly efficient when operating outside a fairly narrow power envelope. Uniflow and Corliss engines were preferred when dealing with varying loads.

A large steeple compound is a good traditional choice; you can build such an engine nice and tall and they'll make effective use of 150 psi steam - much more so than a triple.

- Bart
-------
Bart Smaalders http://smaalders.net/barts Menlo Park, CA
Ralph B
Just Starting Out
Just Starting Out
Posts: 11
Joined: Wed Nov 18, 2009 6:20 am

Re: To get a triple

Post by Ralph B » Sat Nov 21, 2009 11:16 am

It's not so much tradition that interests me as the look...steeples don't grab my eye. From my limited understanding of uniflow engines they usually operate at a higher RPM than a counterflow engine. Granted I have not seen one in operation and only read a little about skinner engines in WW2 Liberty ships. I would enjoy looking over how one works...but I haven't seen any designs available for purchase.
Post Reply