Pattakon
Greece

OPRE
Opposed Piston Pulling Rod Engine

Click on the photo below to download the relevant video (QT format, 4.6 MB) showing the engine free on the desk, running on Diesel fuel (compression ratio 17:1, direct injection, rid of glow plug, rid of electrical system).
The additional big flywheel is secured on the "exhaust side" flywheel. It makes easier the manual cranking, it makes possible the true low rev operation and allows power/torque measurements.


Click on the following images to enlarge.


Bore: 80mm.
Stroke: 100mm (50+50).
Combustion capacity: 503cc.
Pumping capacity: 581cc.
Total width: 505mm.


* The oil pump is driven by the "intake side" crankshaft (it is installed inside the cover/bearing behind the one big gear).
* The high pressure fuel pump is driven by the "exhaust side" crankshaft (by means of a cam lobe behind the other big gear).
* The built-in scavenging pumps (two reciprocating piston compressors) add no extra cost or friction and operate efficiently throughout all revs. The ratio of the "combustion bore" to the "scavenging pump bore" defines the scavenging-supercharging ratio.
* The balance is perfect. In case of symmetrical load - like twin electric generators, twin propellers, twin rotors - the base of the engine is rid not only of inertia vibrations of any order, but it is also rid of "power" (combustion) vibrations of any order too.
* The lubrication (and the oil consumption) is as in four stroke engines. The oil rings never pass over the ports and flooding with oil is needed only at the compressor side of the piston (the cool side) where the thrust loads are taken.
* The total weight of the prototype (the big flywheel excluded) is 22 Kp (a 15 Kp total weight seems feasible).
* The long dwell of the pistons at combustion offers some 40% more time to the fuel to get prepared and burned efficiently. In other words this engine can burn efficiently the fuel at 40% higher revs (i.e. Diesel with peak power at more than 6000 rpm).
* The synchronizing gearing is nothing more than the couple of small "free" gears (the big gears are balance webs).
* At the same revs the piston speed is half of the conventional engine of same stroke (less friction).

The two stroke operation, the perfect balancing, the built-in scavenging pumps, the true compact dimensions, the light weight, the simplicity (reliability), the smaller friction due to the half piston speed, the low cost, the ability for higher "efficient" revs (more power), the four stroke lubrication, the easy/light/cheap synchronization of the two crankshafts etc, etc make this engine a true alternative for all applications.

A 500cc two stroke can easily make some 80 Nt*m (8 Kp*m) torque.
At 6000 rpm this torque makes some 50 KW (70 PS).
50 KW from 20 Kp means 0.4 Kp per KW.
And 0.4 Kp/KW with direct injection Diesel efficiency sounds interesting, especially for an engine with such a low cost.

In a nutshell, the OPRE engine is the classical "free piston engine" without its problems.


Click on the image below to download a WMV video (700 KB) with the engine driven by two electric drills (balance quality).


Click on the image below to download the PRE17.exe animation (1.2 MB) of the above engine.

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Relevant Links:
PRE principle-animations-plots.
OPRE prototypes (dimensions, materials etc)

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mailto:ppe@pattakon.com

Pattakon Greece