A valve (the tilting valve) is secured on the small end of the connecting rod.
The connecting rod together with the tilting valve perform two motions: they reciprocate with the piston and they swing (oscillate) relative to the piston about the wrist pin.
The piston has a properly formed port (the piston port) that sealingly fits with the tilting valve. The tilting valve opens and closes the piston port allowing, or stopping, the communication of the spaces at the two sides of the piston port.
The tilting valve is not in contact with the piston port; a small gap (like 0.05mm) between the tilting valve and the lip of the piston port enables wear-free and friction-free operation without spoiling the sealing (the pressure difference at the two sides of the tilting valve is small).
The geometry of the "tilting valve / piston port" defines the timing of the opening and closing of the piston port.
Among the advantages of the connecting rod tilting valve are the simplicity, the high flow capacity, the small dead volume of the scavenging pump, the reliability at extreme revs, the efficient piston cooling, the fact that it adds no additional moving parts to the basic mechanism.
OPRE engine with tilting valves
In the Opposed piston Pulling Rod Engine ( OPRE ), below, the compressed air or mixture from the two scavenging pumps, through ports made on the casing, enters into the combustion cylinder and forces the burnt gas out of the exhaust port.
The balancing (vibration-free quality) is perfect.
In case of divided load applications (like in a Portable Flyer with two counter-rotating props secured on the two crankshafts, or like in an outboard engine driving two counter-rotating screws, or like in a power gen-set having two counter-rotating electric generators secured on the two crankshafts) the basis of the engine is perfectly rid of inertia vibrations of any kind and order, the basis of the engine is also perfectly rid of power pulses vibrations of any kind and order.
The scavenging is cross-uniflow: the inlet ports and the exhaust ports are disposed anti-diametrically.
The two crankcases run non-pressurized.
The thrust loads are taken at the scavenging end of the piston wherein the cylinder and the piston are substantially cooler (more reliable operation with lower lube consumption), and wherein the cylinder liner is rid of ports.
With the "combustion" side of the piston being rid of thrust loads, and with the wrist pin not hiding the backside of the piston crown, the piston and the cylinder run cooler and more reliable.
The substantially longer piston dwell around the combustion dead center:
enables higher revs and thereby higher power to weight ratio (higher specific power).
The piston of the PRE remains at the top 10% of its stroke for some 35% longer time; for RC/model engines, this means that at 40,000 rpm the conventional gives to the combustion the same time (absolute time, in seconds) given at 55,000 rpm by the OPRE (Opposed piston Pulling Rod Engine); for normal size engines, this means that at 4,000 rpm the conventional gives to the combustion the same time (absolute time, in seconds) given at 5,500 rpm by the OPRE (Opposed piston Pulling Rod Engine).
OPRE Tilting prototype:
333 cc, bore 84mm, stroke 30+30=60mm
(same bore to stroke ratio with BMW's boxer R1200GS of 2013)
weight: 8.5Kp (19lb) without the exhaust pipe and the carburetor
Tilting Valve gif-video:
The lightweight, the vibration-free operation,
the reaction-free frame, the reliability etc,
are among the characteristics that make the
OPRE Tilting comfortable for Portable Flyers:
Click HERE (or on the following image) for a youtube video showing the first OPRE Tilting prototype running at low revs:
Click HERE (or on the following image) for a youtube video showing the first OPRE Tilting prototype running at medium revs:
Click HERE (or on the following image) for a youtube video showing the internal parts and the engine assembly:
The above parts are the only parts of the OPRE Tilting engine of the following youtube video (manual cranking; click on the image):
The frame is shown green, the saddle red, the belts brown:
OPRE tilting engine with propeller speed reduction
For more conventional applications (like small airplanes, ultralights etc) a propeller speed reduction may be required:
In the above arrangement all the gear-wheels are supported on the two crankshafts.
The unique propeller (not shown) is secured on the red gear and rotates 3.33 times slower than the crankshafts.
2,500rpm for the propeller, 8,300rpm for the engine; with 30mm piston stroke (i.e. 60mm combined stroke) the mean piston speed at 8,300rpm is only 8.3m/sec.
With another set of gearwheels at the other side of the OPRE Tilting engine, another slow-revving counter-rotating propeller can be driven. In this case the synchronizing gearing runs unloaded (each crankshaft drives its own propeller) and there is no reaction torque on the basis of the engine (the frame of an "ultralight" becomes ultralight).
In another approach the two crankshafts of the OPRE Tilting engine drive, by means of sprockets and toothed belts (a common practice in small high-revving aero engines, like Simonini, like Rotax
etc), two counter-rotating large diameter intermeshing propellers mounted at the same side of the engine and revving at substantially lower, than the engine, revs):
Click here for a controllable "exe" windows animation
At operation, the two synchronizing gearwheels of the OPRE Tilting engine run unloaded (each crankshaft drives its own propeller).
The basis of the above propulsion unit needs not to provide any reaction torque; besides being perfectly vibration-free (including all types of inertia and combustion vibrations), it also has zero gyroscopic rigidity.
Here is another arrangement of the OPRE Tilting:
The (single) OPRE Tilting engine has on its casing two "arms" whereon a holed pipe (yellow) is secured.
The one crankshaft drives, by means of a reduction gearing (comprising a pair of sprockets and a "short" toothed belt (not shown)), a propeller which is rotatably mounted on the holed pipe at the one side of the engine,
the other counter-rotating crankshaft drives, in a similar way, another propeller which is also rotatably mounted on the (yellow) holed pipe, but at the other side of the engine.
The two propellers are contra-rotating.
Through the holed pipe they pass the fuel and the control (like: the gas cable, a cable for the release of a parachute, etc).
Here is the engine with the arms whereon the holed pipe is to be secured; at right is the synchronizing gearing and the transmission to the one propeller:
The diameter of the propellers is as large as desirable.
The basis of the engine (say, the flange or the pipe whereon the engine is secured) is rid of gyroscopic rigidity, of vibrations and of reaction-torque.
The flange at the end of the (yellow) pipe can be secured on the frame at the back of a parachuter replacing the conventional propulsion unit.
If the flange at the end of the holed pipe is secured on the nose of an ultra-light or of a small airplane, it is a complete propulsion unit having significant advantages.
If the holed pipe is substantialy extended, then a simple Portable Flyer (say, a "Witch's Broom" Portable Flyer) is made:
a second OPRE Tilting engine with its own pair of contra-rotating propellers can be secured higher on the holed pipe.
The following Portable Flyer uses two OPRE Tilting Valve engines, each driving a pair of counter-rotating intermeshed rotors through a reduction gearing (sprockets / toothed belt).
The hubs of the rotors are hollowed.
The frame extends from bellow the lower rotors to above the top rotors, ending in cone-shaped cages improving the air flow and containing rescue parachutes for emergency landings.
At horizontal flight the frontal area is minimized (the engines and the pilot / rider are "in line": the one engine is hidden behind the other, the pilot is hidden behind the engines) allowing extreme maximum velocities.
In the following arrangement two OPRE_Tilting engines (which are quite short engines relative to their capacity) are arranged "axially" to form the basis of the caging / frame at the ends of which are rotatably supported two pairs of rotors.
Each OPRE Tilting engine drives, by a pair of tooth belts, two synchronized counter-rotating rotors; the one tooth belt is substantially longer than the other.
There are two completely independent "propulsion units" (each comprising an engine and two counter-rotating rotors), with each propulsion unit being capable, alone, to safe land the Portable Flyer.
In the Osprey the malfunction of both engines, or the collapse of the one rotor, or the failure of the transmission to one rotor, may turn out fatal, especially during a vertical take-off or landing.
In comparison, the Portable Flyer with the two OPRE Tilting engines is safer.
The failure of the transmission of the one propulsion unit of the
Portable Flyer is not of vital importance because the other
propulsion unit, alone, has its own transmission and is capable for
the safe landing of the vehicle.
Even in the case wherein both engines fail, or in the case the Portable Flyer runs out of fuel, the Portable Flyer can still, using the rescue parachute(s), land safely (more at PatTol).