Experience of A.A. Leak's compounds

A special section just for steam engines and boilers, as without these you may as well fit a sail.
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malcolmd
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Experience of A.A. Leak's compounds

Post by malcolmd » Sun May 08, 2011 9:41 pm

I think I have decided to build the A A Leak compound 3"&5"x3" 11 IHP as the first step in building a steam boat.

Before I write Camden some large cheques for the castings, I have two questions:

1 - there do not seem to be a lot of these around (about 5 in the SteamBoat Association's register), what is the forum's experience of them - are they a good engine?

2 - the construction manual says that it (and the 290lb/hr boiler) will not fit in anything under 25-feet... but most of the boats I can find listed using this engine are under 25-ft.... why is this? will it really fit in and drive something like the Selway Fisher Golden Bay 25-ft comfortablly in tidal waters?

Mal
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Re: Experience of A.A. Leak's compounds

Post by malcolmd » Mon May 09, 2011 9:40 pm

this is omminous! a complete silence - are these engines the albatros of the steam boating world, and no one is prepared to speak of their awfulness?
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Re: Experience of A.A. Leak's compounds

Post by Aheadslow » Mon May 09, 2011 11:04 pm

I have no personal experience with the Leak Compound , I do share your curiosity about them tho. I am quite sure however that someone here will have the information you a looking for. Or at least some good leads. You might try checking the steamboat register for email addresses for owners of boats powered by one of these engines.
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Re: Experience of A.A. Leak's compounds

Post by DetroiTug » Mon May 09, 2011 11:05 pm

I have no experience with them, other than reading stats on many engines over the years. Judging by the cylinder and stroke size. The HP rating seems a bit high?? 3+5X3 and 120 psi, producing 11.2 ihp? Of course that was at considerably fast RPM, 450. Not that it really matters. Looks like a very nice engine though. It says up to 35 foot hull length, unless they are talking about a narrow canal boat, that is also not following average expectations or claims.

From all that I've read, it seems the horsepower of a compound can be figured this way, and this is my own summation. Take the high pressure bore and stroke and compare it to other offerings, the Tiny power M is 3 X 4 (longer stroke) and creates 5hp @ 150 psi. The low pressure cylinder of a compound usually in specs tend to offer 50% additional power output. So, I would guess that engine to be around 8hp at 150 psi. I may be wrong about that, maybe someone else can chime in.

I wouldn't mind having that engine in my boat. looks well designed and aesthetically pleasing.

-Ron
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Re: Experience of A.A. Leak's compounds

Post by Midship » Tue May 10, 2011 6:06 am

Hello

A friend of mine owns a set of castings for this engine and could sell them to you
If you are interested please contact him by mail or phone
Bruno Martin-Neuville
bmartin.neuville@noos.fr
+33145864033 mobile +33682416034
(he speaks english ;) )

Kind regards

Thierry
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Re: Experience of A.A. Leak's compounds

Post by steamboatjack » Tue May 10, 2011 12:15 pm

I too have no direct experience of these but I do know three boats with them in, From conversations with the owners I would say check the drawings carefully as some of the dimensions do not tally, I am afraid to say an all too frequent problem with engine designs around at the moment on both sides of the atlantic.
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Re: Experience of A.A. Leak's compounds

Post by steamboatjack » Tue May 10, 2011 12:29 pm

Regarding the power of a compound, the best rule of thumb is what was known as "referred IHP" simply ignore the HP and calculate the IHP of the L.P. as though it was a single cylinder engine but operating at the full available boiler pressure using the time honored PLAN/33000 formula. With the mean effective pressure taken at 60% of the boiler pressure you get a fair idea of the power.
at 120PSI boiler pressure and 450 RPM we get 9.6 IHP. (72PSI MEP)
To get 11.2 you would need a MEP of 84PSI rather high for 120PSI supply. I am sure there are none that run at 450RPM anyway.

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Re: Experience of A.A. Leak's compounds

Post by the severn bore » Tue May 10, 2011 12:31 pm

Hi Mal,

I am building one of these engines currently. I have 'graduated' from a model engineering background - sold my steam lorry and got stuck in.

I don't know where you are based, but I am in the UK, so became a member of the SBA. They're a nice group of guys who are really knowledgeable, friendly and encouraging.

As always, there are positives and negatives to any design. The book states 390 lb/hr (not 290), giving a water rate of around 35 lb/hp/hr. To achieve 11hp, I have calculated that I would need a BMEP of 114psi in the HP cylinder! Can someone verify this for me? With the mother of all boilers at 200psi WP this might be possible???? I am looking at using a published design for a 3 drum water tube (Roberts type?) boiler, but I'm way off worrying about that just yet! The advice I got was to open up the back of the balanced LP valve, as the movement will throttle the passage to exhast at the as drawn dia, and also fit a strongish spring. Also fit a spring in the valve on the Edwards air pump (none shown) to help things. I was also told that there may be wiredrawing on the HP valve, so I set out the geometry to check it in line with one of my textbooks, and I think the eccentric rods may be too short. Can anyone advise?

From what I have seen on the water, the boats have smaller boilers and live with the fact that they are only getting maybe 7-9 hp out of it (anyone?), which is obviously adequate for the hull sizes, as they seem to go alright.

I am also looking at Selway Fisher's designs around the 25' mark.

C.
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Re: Experience of A.A. Leak's compounds

Post by malcolmd » Tue May 10, 2011 3:13 pm

Well thankyou all!

A flurry of information.
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Re: Experience of A.A. Leak's compounds

Post by malcolmd » Tue May 10, 2011 8:48 pm

DetroiTug wrote: I wouldn't mind having that engine in my boat. looks well designed and aesthetically pleasing.

-Ron
I agree Ron, it looks nice and well designed, there was one on display at the model engineer's exhibition in London last xmas. It was an outstanding job with so many bells and whistles and a fabulous standard of finish that I actually did not recognise it as being a Leak one, it was only later reading the reports I realised. - I think it won one of the prizes... but I don't thik it had ever seen any steam at that point - here ar3 some pictures i found...

http://modelengineeringwebsite.com/compound_marine.html
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