Henry Greenlys' paddle engine.

[malcolmbeak]

Ray
May I suggest that you mock up some simple psddles from say 3mm ply before you start cutting metal then you can try out the engine to see if there is enough power to drive that size. So is it the stroke or crank throw that's 59mm - twice (or half) the power available.
Nice piece of copper tube, but about twice as thick as you need, but if the boat will take the weight theres no problem except that boiling the water will take longer. How much steam it will produce will depend on what type of boiler you use. I believe you have a copy of Harris "Model Boilers and Boilermaking" which should give you a few ideas. It also has information on how much steam any type should produce so knowing the swept volume of your engine and the speed it must run at it should be possible to come up with a design. Of course, to know how fast the engine must run you need to know how fast the boat is intended to go and the effective diameter of the paddles. Remember to allow for the slippage of the paddles - about 66% efficiency seems to be about right.
Having worked out the required engine speed, you can check if you get that driving the mock up paddles.
Hope this is of use  Malcolm 

[Bierjunge]

Based paddles on 'Neuchatel' with simplifications. I've drawn them up at 227mm outside diameter, floats are 35mm deep, 75mm wide.

Bore is 9mm, crank throw (stroke?) is 59mm.

Am I being too optimistic?

Maybe. You are planning direct drive without reduction gear?
I don't know the exact geometry of you wheels or mechanical efficiency of your engine. But a very rough calculation I just made resulted in a speed of only some 50 rpm at 3 bar steam pressure.

Moritz

[rayspan]

Thank you both, gentlemen, quite a lot there to assimilate which will take a while. I quite expect poor performance, but accept that it's probably a good way to learn.

I should have said Malcolm, crank throw is 29mm, so piston moves 58mm from tdc to bdc. BUT steam is only introduced around the half-way point, so I assume the power-producing 'stroke' will be 28mm. Am I right?

Yes Moritz, I plan direct drive. Total simplicity because I'm very much a newbie. I'm quite prepared to build Mk III if required, it would be very easy to increase length of valve shaft to accomodate bigger bore cylinders, with a new crankshaft to fit. I quite like the idea, actually, confidence takes a quantum jump every time a new engine works!

Meanwhile, I'll press on with loading tests. I'll measure RPM as well when it's up and running, and post results here.

[kno3]

Nice engine, runs very well.

[rayspan]

As expected, under load performance is somewhat reduced. You can see it running here:

http://www.youtube.com/watch?v=PdcW8hDsCCs

You were a tad optimistic Moritz!

Results as follows:

28 p.s.i   -  22 r.p.m.

40 p.s.i.  -  28 r.p.m.

60 p.s.i.  -  36 r.p.m.

It was running so slowly I didn't need the Tachometer, I timed it by counting revolutions against my watch.

I had great fun making the paddles Malcolm, having drawn 'em up, as usual I had an insatiable itch to 'see them in the round.'

And round and round they go . . . slowly!

Now I'm going to go back to my P.C. and make some improvements. Bigger cylinders, & increase crank throw.

Meanwhile I think I'll have a go at the boiler, (I have my Sievert torch) so should be busy for next few weeks.

Please feel free to comment, make suggestions et.c. I will be glad of any advice.

[steam up]

Great to see it running well done on a great build

[rayspan]

Thanks for that steamup. Boiler construction well under way now. Been hammering copper sheet around a former for a few days to make the ends. They've turned out really well.

[rayspan]

Boiler completed, together with electronic level sensing. Literally completed only a couple of hours ago. Still to complete testing, I read Megatrons level sensing post.

I've posted details in reply to that.  Will follow up with results on that posting if anyone's interested.

[grayone]

Hi great looking build, can you post a pic or two of the bolier ?

[rayspan]

Hi Grayone - (guess I should call myself 'pink & shiny') thanks for compliment. Yes I can do that this evening.  It isn't pretty, as you will see, but I think I've sealed all the leaks! Hope to do a final pressure test today.

[rayspan]

Here you go grayone, sorry I couldn't manage it yesterday.

Made a bit of a mess with brazing, and the bends in the water pipes, but hey, next one will be better.

I tested it on the compressor this morning, immersed in water, at 100p.s.i. Only significant leak is from the teflon washer on the filler plug. One very minor one from a water pipe joint.

I calibrated the safety valve to about 60 p.s.i.

Now I have to mount it, and make a burner.

[deverett]

I know this is an old subject, but after building Malcolm Beak's 3 cylinder paddle engine, I came across this thread during a Google search and joined the forum.

Do any plans actually exist for the original Henry Greenly design of the 3 cylinder engine?  I've seen the model on www.modelengines.com and that has prompted the question.

Dave
The Emerald Isle

[malcolmbeak]

Dave
The original Henry Greenly design appeared in a series of articles published in the Model Engineer in 1944. They are in the Magazines portion of the downloads section. You will need to have made several posts (can't remember how many) in order to make the download. If I've done it correctly you should see the drawing here. When I built my version, I decided that his was a bit complicated and came up with the design I guess you have built.
Malcolm

[deverett]

Many thanks for that drawing, Malcolm.

Yes, it was your design that appeared in Model Engine Builder that I made - not for a boat, but just as a demonstration engine.  It has always drawn lots of interest where I have shown it.

Dave
The Emerald Isle