This publication brings an interesting engine (rather a project, since we only know the Spanish Patent -Number 86515-923-) and its practical construction is not known either.

-And it is interesting because here we have treated the three main-type sliding-sleeve engines, Burt, McCollum and Knight.

-But it is that the Igartua uses a rotary piston, describing a "Helioidal" route as it is said in the engine description.

-In its turn the piston faces ports with the cylinders.

-But it is better to show the patent illustration:

“Igartua engine”

The rod connection with the crankshaft is provided with gear that causes the piston to turn.

-The connection with the piston is through a cardan joint.

-When the engine turns, so does the piston on itself, uncovering the different ports.

It works with the four-stroke cycle, that is, one piston stroke for every two crankshaft strokes.