Paddleducks
Other Marine Models => Live steam => Topic started by: malcolmbeak on January 29, 2008, 09:14:53 AM
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Hello Steamers
Over the last 30 years I've built a number of steam engine, mostly intended for use in model boats. Before that, in the mid 1950's whilst still at school I had made one steam engine which wouldn't work, and amazingly enough three petrol engines that did! During the intervening years I played at motor sport until the expense got too much and I reverted to model making.
In the late 70's radio gear had become affordable compared with the 50's, and a friend persuaded me to make a steam boat. This turned out to be the Victorian yacht "Greta". Plans from MAP, 44" long and about 10lbs to play with. The engine chosen was Westbury's Trojan, a 5/8" bore and stroke slide valve single. Castings were bought and the engine made. It worked very nicely – on the air line at work at 70psi it did over 6000rpm and sounded like a small IC engine. The next question was what boiler to use. I had no idea what power I needed or what pressure I should run at. I thought 30psi seemed a reasonable figure, so using the design data in the K.N.Harris book on boilers I designed and made a centre flue one. With the hull completed, the engine, boiler, burner and radio gear on board I floated it in the bath. Oh dear! only ¼" freeboard! So another smaller and lighter boiler was made. Finally when ready to run there was all of ¾" freeboard.
Down to the lake, fire it up, wait for full pressure and set the engine turning over gently and off she goes. Now open the throttle. YE GODS!!! She shot off like a scalded cat with around 30 degrees list. Of course with the small boiler, the pressure very soon dropped and settled down to just below 10psi. Performance was still quite adequate, but I already realised that with no reverse capability things could get a bit boring. So a ½" bore and stroke V twin oscillator was designed and built. A feed pump was incorporated and we were in business.
So the two engines shown here are the Trojan and the V twin.
The Trojan has an oil tank mounted at the back. It feeds into one of the main bearings through the drilled crankshaft to the other main, the big end and the eccentric.
The V twin no longer has the water pump fitted, but the gear to drive it is still in place.
Malcolm
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Not too impressed with those two hey. Lets try a couple more. I guess the main trouble with these is that you can't see anything happening except the flywheel going round.
The flat twin is Westbury's Cygnet. Flat twin with a 1/2" bore and 3/8" stroke. If you want to know how the valving works, I'll dig out the drawing and copy that bit off. Works well on air – I can blow it over at about 150 rpm, but on steam it needs plenty of lubrication in the steam.
The little triple was just made to see if I could make something that size work. It does. Three cylinder single acting, ¼" bore and stroke with a rotary valve in the head. The block is made of nine pieces silver soldered together. (the oil filler and breather are soft soldered later) All the bolts you can see are 12BA. The crank is loctited together, but after reaching 8000 rpm it broke, and the repair isn't too good - must re-make it some time.
Malcolm
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I love that little triple Malcolm, absolutely gorgeous!
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Sorry about that Malcolm,
When I go to show unread posts, sometimes it doesn't pick them up.
All wonderful engines, and as Eddy says, that triple is rather tasty.
I built Westbury's Cygnet Royal a few years back now, before it was made famous by the write up in the model mags. It of course was a triple, and so smooth running.
http://www.floridaame.org/GalleryPages/g1Ex0124.htm
You can see the same pedigree in your twin.
John
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John
My Cygnet was made many years ago. Interesting to see that John Moores Cygnet Royal runs in reverse when swapping the inlet and exhaust. I've just looked up the relevant articles in the Model Engineers and see that the porting is slightly different for the twin compared to the triple. I seem to remember trying to do the same with my twin and having no luck - Ill try again tomorrow. I do have a set of castings for the Royal, but those along with several others have lain idle as I have found that I prefer making my own designs. A bit more of a sense of achievement I suppose.
While looking for the articles, I came across a simple little engine with only two moving parts. I have seen one powering an open launch. Knowing that you like unusual designs, I thought you might be interested.
Malcolm
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Malcolm,
The Cygnet Royal that you see in the pictures is in fact the one I built. As mentioned in the text, it does run well enough in reverse. But it is a gas guzzler, even though it does run on a very low pressure.
It just so happens, I have, only last month, received a set of plans from a friend in the States. It is for a Cretors Popcorn Engine, and it works on exactly the same type of valving layout as the one you have shown here, but not the same sort of output. I will be building it full sized, with a 7" flywheel. They were used in early steam fairgrounds for turning the heated 'popping' drums on popcorn stalls.
But that one you have shown looks a very viable quickie to build, have you any other dimensions?
John
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Sorry John, that is all there is. The article is just a lot of chat with some ideas of mounting two together to get self starting. It was obviously intended that one should scale from the drawing as there is a scale includes. Bad practice I know, needs must. At least the important valve dimensions are there. Do you want me to scan in the rest of the article?
Malcolm
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Hi John
I've just tried the Cygnet for reverse running. It does work, but not well. The pressure blows the valve off it's seating. There's only a thou or so for it to go, but it ruins the performance. Another couple of engines in a day or so.
Malcolm
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Hello again.
Only one engine this time but definitely different. It is also much larger than the others I've shown.
It started when a steam boating friend showed me an idea on the proverbial back of an envelope with the comment "Do you think this would work?" Well, as drawn it wouldn't, but with a few mods it would.
This is the result. A flat four single acting engine with the bore and stroke equal at 7/8" (because I had a piece of hard brass tube that size and just long enough). Steam distribution is through cut outs in the crankshaft. Timed for 70% cut off, reverse is obtained by swapping the steam and exhaust ports. This does make reverse somewhat lumpy, but never mind, it's not often used.
Hopefully the pictures show how it all works. The pistons drive on their outward travel and are pushed back as the engine continues to rotate. The back and forth motion of the yokes is converted to rotary using scotch cranks. The pistons aren’t actually joined onto the "con rods" as there is no need.
The drawing shows how some parts were changed as other ideas came up. Even the bore and stroke was changed, also note that the pistons are still connected here. I finally realised that with the pistons free, the "con rods" didn't have to be positioned so accurately.
At one time it was fitted in the friend's six foot long battleship - can't remember what it was – geared up 1:2 and driving four 3" props through a chain drive. With no attempt at balancing the thing, and working at around 100psi, progress was pretty good, but with a pronounced shimmy _ well ships are regarded as female!
Hope this is different enough for you John.
Malcolm
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Malcolm,
Very unusual design there, I bet it is a real 'thumper' when running at speed.
I made a twin cylinder scotch crank engine many years ago, but as usual, I gave it away.
I am only now realising how much these prototype engines are worth to collectors. I must have given away many thousands of pounds worth of engines.
I am just concentrating on getting my collection built up at the moment. I am just building some egg cup stirlings from Jan Ridders designs, but modifying them as I go along to attempt to get even more out of them. PTFE bearings and pure graphite pistons.
http://www.youtube.com/watch?v=TAhTyHSMVUw
John
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Malcolm a very impressive design. Thanks for sharing your ingenuity, the skill level shown is beyond what ever I could hope to achieve. John the link you posted shows a beautifully balanced hot air machine. Does the eg cup contain a flame ?
cheers
Jim
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Jim,
No flame, just warm water.
The engine runs on the temperature differential between the top and bottom plates. If you put it on an ice cube, it runs in the opposite direction.
If you can get the friction really low, you can get them to run on the heat from your hand.
John
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Thanks very much Jim, but not up to John's standard. That little hot air engine is lovely, and to get a low temp one that small to run so well is brilliant. I have one made from a kit. The displacer is about 4" diameter, it uses ball bearings and an aluminium piston in a groung glass cylinder. It usually gets turned out for our society exhibition, but I found running it on a cup of coffee a bit frustrating - having to replenish several times during the day. So I now have a container that takes around a pint of water, freeze it over night, and with 1/2" of expanded polystyrene round and under it, it will run for over 24 hours!
Then there is always the tin can engine shown here running on a night light.
Malcolm
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Wonderful engine Malcolm. I love those type of prototypes. :clap
They reckon that this is the way to the future in the third world. Using a parabolic reflector instead of the night light to generate power. The only problem is that the sun sets just as you need the light bulb on. But joking aside, they are using this technology to charge batteries, and the space shuttle has a sterling engine on board for its refrigeration plants, so this is definitely the power of the future. :goodnews
John
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I have been reading about this chap for some years now , Dean Kamen . ever since he desigened the "I bot" chair. He has apparently had a fascination with Sterling engines for some years and apparently his home has a large one in the entrance hall http://money.cnn.com/2006/02/16/technology/business2_futureboy0216/index.htm
Has anybody seen the trial going on in the UK , where central heating boilers have a sterling engine on the exhaust side and it runs a small generator and pumps it back in to the grid, I don't think it's that new because I read that in New Zealand they have had a system for boats for some years but there is supposed to be something like 50,000 homes on the trial over hear.
Peter
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I thought you guys might be intetrested in a couple of models that I have added to my collection over the years.
The first one is a three cylinder oscillator, mounted on the same crank on a circular plate. The supply and exhaust is arranged on the rear of the plate in a manifold style of arrangement and all three cylinders drive the same shaft. Very simple and neat and very interesting to watch. This was an Ebay purchase a couple of years ago and I have run the engine on compressed air but never flashed up the boiler. It has obviously been reconditioned, perhaps without paying the required degree of attention to being sympathetic to it's age but I have no idea of it's origins or age.
The second one is probably my favourite engine and I can just sit there and watch it turning over on air. It was also an Ebay find but I did get to discover that the engine was made from a set of plans published in a Model Engineering Magazine in about 1964. I actually contacted the magazine and was able to obtain back copies of all six issues that contained the plans. The model is made exactly according to the published plans and has been very nicely made and put together. I connect this up to a small air brush compressor and thoroughly enjoy watching it all turning. It might one day treat it to a bit of a clean but I wouldn't want to spoil it's original "patina" by over polishing or painting so it's not going to look a great deal differrent from as it does now.
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Colin
The article was published in the Model Engineer on November 26th 1953. Are you going to make one?
Malcolm
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Since my retirement my goal in life has been to design and build an oscillating steam engine (without) the obligatory spaghetti junction of copper tubes on top.
I have three designs, these pictures are of my V-Twin part built and loosely assembled.
(http://img80.imageshack.us/img80/3748/vtwin.jpg)
(http://img836.imageshack.us/img836/627/vtwin1.jpg)
(http://img716.imageshack.us/img716/8408/vtwin2.jpg)
(http://img339.imageshack.us/img339/7228/vtwin3.jpg)
Enjoy.
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Melcom
Many thanks for the information,and yes I will build the engine.
I am a retired engineer,and have managed to put together a small workshop
over the years.My interest in steam started many years ago with a U.S.E unit,
over the last few years i have collected plans and pictures of more unusual steam engine piston arrangements.
I am allways amazed at how many variations engine designers have found of extracting power from steam.
Since retiring i have designed three oscillating steam engines,the objective in designing
these engines,is to remove the usual spaghetti junction of copper pipe routing
the steam.I achieved this by moving all steam routing inside the engine including
forward stop and reverse,in two I managed to incorporate a displacement lubricator
not easy lots of hours on computer only a few Eureka moments.
These Engines are well advanced now,wont no weather i have succeeded until first run.
Engines originally intended for small batch production,unfortunately with price of metal plus
the credit crunch this has been put on hold. Would like to upload pictures when I find out how
(have uploaded with help from my grandson)
Regards Colin
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Very impressive Colin
Several years ago I built a V twin double acting oscillator with no external pipework. All the passages are drilled inside the main frame with the regulator/reversed mounted on top.
More recently a single acting triple paddle engine. There are a couple of short lengths of pipe connecting the r/r to the engine. Following on from the triple, a single using the same valving method.
Malcolm
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Woops missed a couple of shots
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Malcolm
Great engines especially the triple,must be a treat to watch at low revolutions.Still trying to work out the valve in the small single acting engine.Perhaps if you have time,a video post of some of your engines running if that's aloud. Referring back to the information you posted on the simplest steam engine.I have secured a copy of model engineer November 26th 1953 from e-bay member (cromersimpson),if anybody is interested he can be found by typing in model engineer magazine on e-bay.He appears to have quite a large stock.
Regards Colin