Orbital - Not Your Usual Oscillator

[Jasonb]

For some time I have fancied making an engine with a horizontal flywheel but never found anything that took my fancy. There is an old design for a marine engine that was tempting but not the nicest looking thing. Anthony Mount did the Whitmoore & Binyon but you can't really see the flywheel on that. Howeve while looking through some old copies of Dampf Modell magazine for something else, this photo caught my eye and that was all it took.



A bit of time spent with Alibre and I came up with this design. It is 11mm bore x 13mm stroke. Flywheel is 115mm dia x 6.75mm wide (to suit the offcut of thick wall tube I had) Alibre has the option to show the ctr of mass and by looking at this while trying a few different ball bearing diameters I got the design almost perfectly balanced, it does change as the engine rotates and the piston moves in & out.



The "spokes" were cut on the CNC from a disc of 4mm thick steel and then the various steam passages added on the manual mill. Here I am using a long series drill to get air from the hub to the cylinder.



Some further milling diverted the air around the cylinder pivot which had a bronze insert fitted. The hub was made up of two pieces of brass and the rim from the above mentioned offcut of thick wall tube. All assembled with JBWeld and then finish machined.



A 2mm drill shank was ground to make a cutter to form an annular groove in the bottom face of the flywheel which allowed air to flow from a hole in the base during the full rotation of the flywheel.



The cylinder was much the same as the other small oscillators I have been making recently which start a sa rectangular block that is bored & turned



Then the holes added and port face milled to width



I also milled some decorative flutes with a 2mm ball nose cutter.



The last job was a quick lap with 600g silicon carbide powder and oil mix



The base boss like the cylinder end cover and crank pin cap were turned with a mix of conventional turning tools, form tools for the balls and some freehand graver work for the concave parts.

[Jasonb]

I used some VHT wrinkle finish paint for the "cast" surfaces altough it did not wrinkle as well as it has done in the past. The Cylinder was done with Fial "orange red" and the rest left bare.

An offcut of Paranna pine provided the base which was finished off with three ebony bun feet.








Alibre seems to have got it right as there is very little tendency for the engine to want to start dancing around the bench. However it is very much a "stationary" engine as once running all that work becomes a bit of a blur, even the slowmo at the end of the video does not capture it very well.

<a href="https://www.youtube.com/watch?v=6sGIH-jBQ-k" target="_blank">http://www.youtube.com/watch?v=6sGIH-jBQ-k</a>

[crueby]

Unique!  Very cool.

[Sanjay F]

Wow - that's so different and quite a marvel to watch. It reminds me of the helicopter toy where you pull the cord and the circular disc takes off! 

I remember we spoke about the Whitmore & Binyon engine some time ago and you mentioned it was a shame the flywheel was covered. Now that I have seen your wonderful creation I couldn't agree more!

[Jasonb]

Now there's an idea. Alter the spokes to be more like fan blades, join four engines together and I'd have a steam powered drone

But that will have to wait, I've a couple of poor castings to work my magic on to get them looking like a half decent model. Where ehave we heard that before    But at least at the end of this major rework I will have the full set of three

[Michael S.]

That is an extraordinary engine! You’ve done a great job designing it for a new model.
I briefly wondered whether a handwheel from an old Singer sewing machine might have worked as a flywheel, too.
In which issue of the magazine *Dampf Modell* can the article be found?

Regards, Michael

[Jasonb]

Thanks

It is is Nr.3 1993. The one with a table engine on the cover. Though there is no real mention of it let alone any detail of how it worked.

[Michael S.]

Thanks for the heads-up.
I couldn't find any further information in the article either. It seems to be some kind of art object. I like your version much better. 

[Vixen]

Jason,

Add eight more cylinders and you will have the first steam powered 'rotary engine'. Bet you would not see it for exhaust steam.

Mike

[Jasonb]

You don't need that many, and someone got in a long time before me Uniflow type cylinders on this one.

[Krypto]

Thanks for the build posts!  I was trying to figure-out how this thing worked and not having much luck.

[Jasonb]

Basically steam or air come up through the fixed base. The groove shown being cut in the flywheel bottom lines up with a passage in the base so collects the air. It then passes up the hub and out along a spoke, dodging around the cylinder pivot to the inlet. Exhaust just blows out teh bottom of teh portface. There is a spring set into a recess in the top of the flywheel which applies pressure to the two mating faces much like the spring that pulls the cylinder down onto the portface. The crank can be adjusted up or down to compress that spring as needed.

When running the action of the piston moving down pushes against the fixed crank which pushes the flywheel round, the momentum in the flywheel pushes the piston back in on the exhaust stroke and it starts all over again.

If I were doing it again I might opt for a radial joint for the air rather than a face to face as the spring pressure adds some drag. Run the spoke hole right through to the bore, bring the air up the middle of the crankshaft and out the side, cut a groove around the crankshaft.

[Jasonb]

Here's one for Mike. I'll have to see what it costs to print the cylinders if you want a 9-cyl radial

[crueby]

With multiple cylinders, probably  would be able to run it a lot slower since it would always have at least one in the power stroke? A needle valve on the inlet would give you fine control of  the air flow.

[Jasonb]

I did toy with the idea of a double acting cylinder which would have helped to slow it down, adding multiples would as you say allow the speed to be reduced further.

I do have this one tucked away for when I feel the need for a twin. Sold commercially by Boucher and also detailed in Popular Mechanics as an engine for "Poly-wog"