Oscillating Paddle Wheel Engine

[Tony Bird]

Hi,

Ok it makes sense now. It's always nice to see the sternwheelers puffing out steam alternatively from the two exhausts. This effect might be visible in model size too if the cylinders run slow enough.

The UK has been left for a couple of weeks to get a bit of warmth.  I have brought my pencil case and A.J.Goddard drawings to play with.  On studying the drawings AJG has a condenser so the double valve won't be needed but what to do with the exhaust?  A condenser could be fitted but it would be a shame to have no exhaust.

Regards Tony.

[Harold H. Duncan]

didn't a lot of the horizontal engines have a small blowdown line from the cylinder, exiting overboard to drain water that condensed in the cylinder  and help prevent hydraulic lock.
I have some photos of psManuwai with steam exiting at the stern from this line in the early 1900's.
Just a thought
cheers
kiwi

[Tony Bird]

Hi Kiwi,

A good idea. But a bit of a problem the exhaust will have to go through an oil separator first.  I'm still working on some ideas.

Regards Tony.

[Tony Bird]

Hi,

While away on a warm winter break, some drawings were done of an engine to be used on a model stern wheel paddle boat.  The model was to be less than a metre long and possibly of the A.J.Goddard used in the Klondyke gold rush.  This would mean at 1/20th. scale a 10 blade paddle wheel 110mm wide with a diameter of 120mm.

The engine to be made would still be experimetal first to find out what size it would need to be to power a paddle wheel of the above diameter.  For the engine to be near scale it would have a stroke of 26mm and a bore of 5/16" the mixed measurements will be explained later.  It will be possible to increase the power of the engine by fitting cylinders with a larger bore i.e. 3/8".

After deciding on the size of the engine the distance between the axle of the paddle wheel and the trunnion of the cylinder needs to be worked out.  To scale this measurement would be 145mm however this measurement would have a very small angle of oscillation.  The shortest distance between axle and trunnion could be 85mm which gives quite a lot larger angle of oscillation.  What difference does the angle of oscilation make?  The larger the angle the bigger the steam/exhaust ports can be made, the larger the ports the faster steam can enter and exit the cylinders and gives more power. Not so much for the steam entering the cylinder but allowing less resistance for the exhaust steam being pushed from the cylinder by the piston.  The drawing below shows the maximum and minimum centre distances possible along with the one to be used which is about half way between the two.  The increase from 1.25mm ports to 1.75mm is quite a lot in area 



Having decided on the size of engine and its angle of oscillation the cylinder and its piston can be drawn up.  With a long stroke engine it is desirable to keep the cylinder as short as possible.  This means that the steam and exhaust passageways in the port block will also be shorter and less metal in cylinder and port block to heat up.  The drawing below shows and engine with a conventional type of piston and the engine above it using a stepped piston which shortens the cylinder by 6mm.



With the cylinder sizes decided on the port block can be drawn up, this also shows the width that the port face of the cylinder needs to be so the ports in the port block aren't exposed by the cylinders oscillation.



This drawing is of the relative sizes of the engine to paddle wheel.



Before constructing the engine a test paddle wheel of the correct size has been made out of plastic sheet.



It is hoped of the next few days that a start will be made on the engine.

Regards Tony.

[Tony Bird]

Hi,

I have made a start on the cylinders following are some photographs showing their construction so far.  I have a some problems with Photobucket so will add some text about it in the next post.  Next jobs are paddle axle bearings and the steam port block.

K&S Tube with a 5/16" ID for the cylinder bore and bored hexagonal rod to make 2 cylinder port blocks.


Cylinder port faces machined.


Machining last face.


Tapping trunnion hole.


Trunnion holes taped K&S tube with '0' ring inside it.


Maching relief on cylinder port block face.


Sawing the 2 cylinde port blocks apart


Maching separated cylinder port blocks.


One of the K&S tubes soldered to its port block.


Cylinders lagged.


Regards Tony.

[Tony Bird]

Hi,

Some text for the photographs previously posted.  The reason for the imperial 5/16"bore is that a quick and easy way of making cylinders using K&S brass tube which is very accurately made with a well finished bore.  K&S being American have a larger range of imperial size tubes than metric also being in the UK though nominally metic it is easier to get small quanities of high temperature '0' rings in imperial sizes rather than metric.  The cylinders made this way are quite light which is an advantage in oscillating engines,  The cylinder covers will be secured in place using Loctite which is also quick and light.

Photograph 1.   Shows the tube and hexagonal rod cut and machined to length.  The ron is just drilled to accomodate the rod.

Photograph 2.  Shows two sides of the rod machined to the width of the port face of the cylinder.

Photograph 3.  Shows the sides of the rod being machined to the edge of the port face.

Photograph 4.  Shows the hole drilled for the trunnion hole of the cylinder being tapped it is important that this thread is a right angles to the port block face.

Photograph 5.  Shows the port block ready for its last machining job.

Photograph 6.  Shows the port block mounted on a wax chuck to machine the relief.

Photographs 7.  A piercing saw was used to cut the port blocks apart.

Photograph 8.  The two separated port blocks mounted on a wax chuck having been machined.

Photograph 9.  One cylinder bore has been soft soldered to its port block.

Photograph 10.  Wooden lagging secured with an epoxie glue to the cylinders.

The cylinders could have been made light had their sides been milled away to form a step for the port block face but the lagging makes the cylinders larger and more atractive?  Not sure that the lagging makes a lot of differnce to the engines performance.

Regards Tony.

[R.G.Y.]

Tony I can see why your engines work so well now.  Very informative thread, much better than my method which is suck it and see. Geoff.

[Tony Bird]

Hi,

Did some more on the engine today.  The bearings for the paddle wheel were made from some aluminium angle fitted with a bronze shouldered bush.

As this is still an experimental engine balanced crank discs were made which hopefully will allow the engine to run without the paddle wheel.
Using a drilling jig to locate the crank pin hole.



Using the cylinder port jig to position the paddle wheel bearings at their correct centre distance.



Using jig to drill undersize steam/exhaust holes in port block.



Port block with the steam/exhaust holes enlarged until they are the same diameter as the space between them and the steam/exhaust hole in the cylinder port block.



Using the jig to check the cyinder does not expose steam/exhaust port while oscillating.



Position of cylinder at its maximum angles.



Drawing of steam/exhaust passageways in port block and the means to be tried to purge the pipes and cylinders of condesation/ old oil and heating the system before starting the engine.



Work to date, well an hour or so ago. Shows the balanced disc cranks and one of the port blocks drilled and plugged.



Do check any of my drawings before using them as they are very much ideas before constuction and might have been modified while making the engine

Regards Tony.

[Tony Bird]

Hi,

The engine has been cleaned up a bit and one of the valves that hopefully will relieve any hydraulic locks in the engine and the long steam pipes that will supply it, has been made.

A shoulder was turned on some square brass stock, then the steam ports followed by the steam passageways were drilled in it.  Before the valve was turned to shape screwed plugs were soldered in the ends of the passageways.  One valve with its operating lever have been completed.  With the lever vertical steam will pass from the steam to the exhaust passageway and hopefully clear the system of water and old oil.  If the lever is moved either backwards or forward the valve will close and the engine start?

A tunnion and its spring has been fotted to one of the cylinders.










Engine to date.

[kiwimodeller]

Tony, going back to the exhaust question, I can see no reason why you cannot have an oil collector (not really a condenser)  and not have steam coming out the funnels. I have two boats with an oil trap in the exhaust line and the exit pipe from there goes to the funnel. Both give a healthy plume of steam out the funnel, especially as the throttle is opened. My other two boats have the exhaust straight to the side of the hull and I do not think they blow much more steam. They certainly do leave oily circles on the water so I guess I should add oil traps. Cheers, Ian.

[Tony Bird]

Hi Ian,

Tony, going back to the exhaust question, I can see no reason why you cannot have an oil collector (not really a condenser)  and not have steam coming out the funnels. I have two boats with an oil trap in the exhaust line and the exit pipe from there goes to the funnel. Both give a healthy plume of steam out the funnel, especially as the throttle is opened. My other two boats have the exhaust straight to the side of the hull and I do not think they blow much more steam. They certainly do leave oily circles on the water so I guess I should add oil traps. Cheers, Ian.

The few boats that I have built have either not had lubricators relying on wet steam to lubricate or if they had lubricators have oil separators fitted as well.  My thoughts were that most steam boats have condensers so no steam exhaust just smoke and may be fit a condcer to emulate this, but I do enjoy a plume of steam showing.  We shall see!

Video of one engine running.


Regards Tony.

[Tony Bird]

Hi,

I had a bit of a push and finished the engine.  She certainly has enough power under steam for the paddle wheel!  One wonders what size of paddle the larger engine would manage?

Video.


Relative sizes.


Engine with new cranks and regulator/reversing valve.


So it seems probable that a direct drive oscillating engine will easily power a model stern wheel river boat.  The hydraulic relief valves fitted to the cylinders work well allowing the engine to start without fuss.  It is getting to the train playing season so further experiments will have to wait until later in the year.  I think that a direct drive oscillating engine driving side paddle wheels would work well and not have the condensation problems that the long steam pipes of a stern wheel engine gives.

Some of the bits that will have to be made before starting on a hull.  These are used for testing engines.









Hope the group enjoyed the thread.

Regards Tony.

[Eddy Matthews]

Thats certainly impressive Tony, many thanks for sharing your design with us. I'm sure it will have more power than you'll ever need!

Regards
Eddy

[derekwarner_decoy]

Hi PD's.......yes an excellent build Tony......Derek