Paddleducks
Other Marine Models => Live steam => Topic started by: rayspan on March 26, 2012, 12:08:33 AM
-
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.
-
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
-
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.
-
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.
-
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!
-
Here is drawing using original (approximate) dimensions.
You can see Henry got it right.
-
Malcolm, attached my idea for freeing up Henry's Steam joint.
Looks like a nice simple turning job.
-
An image of the engine from Malcolm Beak.
Regards
Eddy
-
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
-
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.
-
I would love to see this engine running,any chance of a video?
Interesting posts thanks
-
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
-
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.
-
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
-
Try this:
http://www.youtube.com/watch?v=U88uXGG1ez4
Works for me.
Ray.
-
Very nice Ray.
I've been trying to post a design for an alternative regulator that should be easier to make (and I think more effective than Stan Bray's), but it doesn't seem to work. It is the one on the drawing set for the 3 cylinder paddle engine. I've made several of these in different sized and they all work fine.
Malcolm
-
Woops! Just checked the download and the regulator is NOT there.
It seems that I can't post attachments - can you help Eddy?
I'll try again in a few minutes.
Malcolm
-
It's not working, and I get the following message
This error (HTTP 500 Internal Server Error) means that the website you are visiting had a server problem which prevented the webpage from displaying.
Malcolm
-
Woops! Just checked the download and the regulator is NOT there.
It seems that I can't post attachments - can you help Eddy?
I'll try again in a few minutes.
Malcolm
Send the file to me via email and I'll sort it for you Malcolm - eddy.matthews@paddleducks.co.uk
Regards
Eddy
-
spot on Ray, nice little runner.
Tug
-
Worth the wait thanks Ray. I can just imagine that this engine would run slowly under load.
-
Malcolm - many thanks for regulator drawings. Is this the one in the image you posted of your version of the Greenly engine?
-
Ray
Yes - I had forgotten that I had sent it to you. Old age; brain fade; you name it!
Please feel free to phone me if there any questions 01923 672341
Malcolm
-
Malcolm, I know the feeling . . . but actually you didn't, I found the file you uploaded yesterday! So you see, your memory ain't so bad as you thought!
I've been browsing your drawing for an hour or two. Seems pretty clear. Probably make a start on it tomorrow, it's a good 'fill in' while I'm waiting for a start capacitor to arrive, (from Hong Kong of course) to fix my compressor.
Will let you know how it goes.
Ray
-
Hello from Austria!
Maybe a bit off-topic, but I remember - in the good old days of Windermere - there was a local guy named Ken Gamble, who was famous for his 'out of the normal' model boats.....
He once (must have been in the very early 90ies of the last century) showed a catamaran pontoon boat with one or two nice English ladies on board, the captain an English gentleman and the steam engine was a smaller version of this 3-cylinder you are talking about. It all looked a bit like a converted 'water bicycle'.
I also had a hard time figuring out the reversing mechanism, but then I saw that he had made a finely hidden flexible tube (covered with a blackened cord, so it first looked solid), thus turning the reversing mechanism into the right position.
It was the star of that years steam event and rightfully received a price!
I am very happy that you and the owner of 'modelengines.info' are now building and reviving this cutie!
Kind regards, Edward
-
Hi Edward, nice to hear from you.
I've now got 'Mk II' up & running. This one is very much thanks to you Malcolm.
First, I built your regulator, using a bit of round bar. I used a spring to press the selector disc against the bottom half. As you will see from the 'youtube' clip, it works well.
Then, I finally got around to your suggestion, that packing one jaw of the chuck enabled off-centre drilling, and successfully produced a two-gallery valve shaft. Went ahead and completed this one, avoiding most of the mistakes I made first time around.
Here is the result:
http://www.youtube.com/watch?v=7V1q1agXwuY
The shot of the pressure gauge is blurred, but it's reading 30 p.s.i.
I've drawn up a paddle wheel and plan on rigging up a couple of water baths so that I can test it under load, before proceeding to build the ship!
Watch this space!
-
I like it a lot. :bravo :clap On my to do list. :thinking :thinking
When I finally finish the Duke. Geoff
-
Thanks Geoff. I'm very new to this, but who doesn't like compliments anyway ;D!
If it wasn't for Malcolm's input, I don't think it would have happened.
Ray.
-
Really nice Ray. Beautiful slow running. It will be interesting to see how it goes under load. What size paddles are you intending to use?
Malcolm
-
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?
I haven't actually cut any metal yet, plan to start tomorrow, so I'd be glad of expert opinion.
For steam plant, I've acquired a 12" length of 3" diameter 1/8" thick copper tube, and am hoping my lady wife is going buy me (my birthday at end of month) a Propane gun & hose for a biggish propane cylinder. If I make the boiler 6" long will that produce enough steam do you think?
It really is all guess work, plus on-line reading. I've downloaded the two boiler making files from Paddleducks and am looking forward to that.
Ray.
-
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
-
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
-
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.
-
Nice engine, runs very well.
-
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.
-
Great to see it running well done on a great build :)
-
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.
-
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.
-
Hi great looking build, can you post a pic or two of the bolier 8)?
-
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.
-
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.
-
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
-
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
-
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