Henry Greenlys' paddle engine.

[rayspan]

Browsing through 'model marine steam' by Stan Bray, I came across his three cylinder single-acting design.

Fascinated, I've begun drawing it up accurately from the 'not to scale' drawing in the book. Further research led to the construction photo-sequence on the 'http://modelengines.info/' website, (and the link to
paddleducks, which is how I found it.)

A couple of points have had me scratching my head, so I'd be glad of comment.

First thing, the exhaust steam channels shown in the drawings from 'Model Engineer 1944' seem to be omitted in the photo-sequence. Could be they are to come later I suppose, but they seem to be essential, so that seems a bit odd.

Second thing, using the dimensions given in the drawing, leads to considerable difficulty in siting those channels on the steam distributor shaft. If you develop the drawing to include the piston-rods and crankshaft it places those channels so close to the steam input holes in the shaft that leakage from inlet to outlet looks very likely. Attempting to increase the crankshaft throw to increase their separation is defeated by the geometry. Not only does it become necessary to monkey about with con-rod lengths, but the reciprocation angle stays the same.

If the channels are separated arbitrarily, the piston inlet/outlet holes never line up with the steam outlet channel.

Thirdly, I am puzzled by the operation, it seems to me that steam will be injected, not only at the top of the stroke, but also at t'other end - which will surely detract from efficiency.

Lastly, I'm not sure I understand how the reversing mechanism works. It looks as if the steam inlet holes will be permanently blocked by rotating the distributor shaft with the lever.

Could be I'm just too thick to read the drawings properly, I would be glad of assistance.

[kiwimodeller]

Hi Rayman, not sure that it applies to this engine but there have been posts in the past pointing out errors in the Stan Bray book and publishing the corrections. I suggest you do a search of previous postings looking for "Stan Bray" or "Model Marine Steam" and see what comes up. Hope this helps, Cheers, Ian

[rayspan]

Thanks Ian. Useful input.

 I've spent the last couple of days drawing it up. I found at least one dimension mistake.

More to the point, I've increased the stroke significantly to accommodate increased crankshaft throw. It does yield a couple of degrees extra reciprocation angle. Still a bit iffy but I'm working on it.

When I've sucked it dry I'll post results on the forum.

[rayspan]

Herewith (if attachment works) fruit of my labours hitherto.

The most effective method for separating steam inlets from outlet channels is to increase the distributor shaft diameter.

Increasing stroke also permits greater crankshaft throw.

Drawing shows shaft diameter increased from nominal 1/2" to 3/4".

Stroke has been increased to 82mm. This requires cylinder tube length of 98 mm, so I should be able to cut
three from a 12" length of tube.

These dimensions open up the reciprocation angle to 29 degrees.

That allows 1.5mm diameter steam inlet holes in the shaft, together with 2mm wide outlet channels
on the surface of the shaft.

Original drawing in Stans book shows 3/64" for inlet & 5/64" for outlet channel width.

It looks sufficiently OK to start construction. Now the fun really starts.

[rayspan]

Please excuse me a moment . . . while I wipe a thick layer of egg off my face . . .

Idly looking over my drawing five minutes ago . . . the light came on.  Now I know how the reversing mechanism works, and how my misunderstanding of it led me astray regarding everything I've posted previously.

I've meticulously drawn up a system where the cylinders oscillate between outlet channels.  They should oscillate between inlet port and one or the other outlet channel.

Turning the distributor shaft will then swap outlet from one to the other and thus reverse rotation.

Thus - at a stroke(pun) - I can double the gap between inlet port and outlet channel.

I'll revisit the drawing later today and repost it.

Must say I'm glad I spotted it before anyone else did!

[rayspan]

Here is drawing using original (approximate) dimensions.

You can see Henry got it right.

[rayspan]

Malcolm, attached my idea for freeing up Henry's Steam joint.

Looks like a nice simple turning job.

[Eddy Matthews]

An image of the engine from Malcolm Beak.

Regards
Eddy

[malcolmbeak]

Ray
Looks OK although I would be inclined to incorporate an O ring to prevent leakage.

Eddy
Thanks Eddy
I guess an explanation of why this picture is here is needed.
I attempted to post a comment and the photo, but it didn't work. So here's the comment.
Some years ago I had a look at Greenly's design and wasn't at all happy with his valving arrangements so came up with my own ideas. This culminated in the design that is shown in the photo that Eddy has so kindly posted above.
Drawings and comments on the design and construction have been added to the downloads section. (I see that several people have already downloaded - hope it's understandable). Although shown as a vertical engine, a redesign of the frames is all thats needed to convert to diagonal.

Malcolm

[rayspan]

Well Malcolm - I did it! I expect you thought I'd fallen off the perch! Months have passed since I started, most of it remaking parts I messed up at least, 1, 2, 3 times. It was a brilliant project for learning the lathe. Not to mention brazing, and milling with the vertical slide attachments et.c.

I also blew a lot of cash on tools and attachments. Here is the result. It isn't pretty but it works.

I expect I'll start over to apply what I've learned about this engine, hopefully with better results. Most sensitive feature is positioning the reverse lever,
it's extremely critical. I started it up after much fiddling, then walked away for a cuppa and came back 40 minutes later. It was still running and has loosened up nicely.

As you said . . . it's quite a buzz!

Ray Spanner.

[steam up]

I would love to see this engine running,any chance of a video?
Interesting posts thanks

[malcolmbeak]

Great stuff Ray. So now you know how to turn, mill and silver solder and you have plenty of tools you can build (and design) your own engines. No need to splash  out vast sums on commercial plant.
I bet you were tickled pink when it ran, and when one of your own designs runs it's an even better feeling.
But I still prefer my idea for the valve shaft - it's easier to make and works nicely. If readers of this post wonder what I'm talking about, you can find my version in the downloads section.
Malcolm

[rayspan]

Hi Malcolm & Steamup - ref video. I did try to post a video clip, but Paddleducks rejected it. File was 8MB, and we are limited to 500KB. It looks really good in the clip. I'll check with my ISP to see if they will let me email it direct. If so I'll post on here and we can arrange to do that.

Ref. your suggestion Malcolm. I did try to do it that way. Trouble is, I made the valve shaft out of 3/4" diameter, and it only just fits the hole in the drive on my lathe. If I try to offset it, it won't fit. I gave up at that point. Subsequently after a bit more experience of the lathe, I think maybe I could use a centre bit as a 'steady'  in the tail stock and set it up like that. I have a 4 jaw independent chuck now so will have a go.

Henry's grooves would have caused me to lose some hair if I had any, but truth to tell, I learned quite a lot about the milling attachment, using a 2mm slot drill. Had three goes at it before I got it right.

I now appreciate much better your reason for doing it this way. It would remove the sensitivity problem. I need to make a regulator anyway, and Stan Bray's book has a neat little design for a reversing one which I'll have a crack at. Also your remark about an 'o' ring in the feed nipple is bang on. Without it, it leaks badly. So much so, the compressor was running continuously, when I tried to restart it I think it has seized. I'll dismantle it today and try to sort it.

[Tugwilson]

Hi malcolmbeak,
                        if you have a youtube account you could load it to that and set a link on this thread that way we can see it but not take up download space on Paddleducks which cost money because we are hosted not server owned.
regards Tug

[rayspan]

Try this:

http://www.youtube.com/watch?v=U88uXGG1ez4

Works for me.

Ray.