Coomber Style Elliptical Rotary Cylinder Steam Engine
USA - Manufacture date: 2006
Bore = 1.25", Stroke 1.75 ", Flywheel diameter = 8"
Style: Elliptical , Rotary Cylinder

13" length x 9" width x 11" height
(includes base)

The Coomber Elliptical Style Engine

his collection is obviously made up of engines with unusual designs and a wide variety of different  mechanical functions. As you might have noticed, I try to collect machines with the widest variety of mechanical movements in mind. The Coomber Elliptical Rotary design is a perfect example of this tendency. The original Coomber design is a kit which came from specifications provided by the legendary steam engine guru, Tubal Caine. This particular engine is based on Caine inspired drawings offered by A-1 Machining, of Flushing Michigan, which later were adapted for CNC by Carl Hoyer, in California. The CNC adaptation allowed him to add the wonderfully smooth contours, curves and beautifully executed brass inlays to an already very nice design.

As with many things in my life, this engine came to the collection in an unexpected way. I had seen the builder of this engine offer his creations on Ebay at a time when my toy funds were less than flush. I figured they would sell off quickly, so I continued searching for the "casting kit" version I was more familiar with.  A fellow collector and friend  had recently bought this engine for less than it was offered on Ebay, but now he was looking to pick up a more desirable, engine and wanted to sell this one to free up his own toy funds. A deal was struck and after some clean up and a bit of work to fix a few minor alignment problems, mostly due to shipping, this well made bar stock engine is now the perfect display partner for the ever flamboyant Rectilinear engine.

Detail of Curves, Contours and Inlays

View of the Cylinder Details

The cylinder of this engine is mounted on the centerline of  its axis and rotates inside a fixed ring which is offset above the centerline. This offset guide ring acts to control the cylinder rod's travel. By the ring being located above the centerline, one end of the cylinder rod is allowed to extending as it rotates to the top of the circular guide. As one end of the rod extends, the other fully collapses as it reaches the bottom of the circle. This action provides the cylinder with a cyclical stroke which turns the motor's shaft and flwheel to provide its motive force. Switching is via a pair of fixed ports running inside the length of the main shaft. To say it has an unusual mechanical action is a bit of an understatement. It is really quite entertaining to watch in action.

This engine will soon undergo a tear down and it will then be polished up a bit. Nothing is wrong with Carl's workmanship, but the engine has been shipped around enough to acquire a few small nicks and dings. These will be removed and the engine will once again look just as fine as the skills that brought it to life.


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