The above looks very much like the "counter-piston" Mobylette engine by Motobécane - we have discussed it a while ago ( with T54) but I need to find the post . The idea was to use the bottow "non-powering" piston both to compress the intake gases before sending them in the proper chamber , and to act as an "inertia inducer" and add torque....don't know if my technical blurb makes any sense......
I found it.....from 2005, buried deep in the original "huge" Motorcycle Nostalgia thread
The most original ( by this, I mean never having been seen on any other prototype ) part of this Gilera project of yours is indeed the supercharger . I think that a Peugeot (?) scooter (!) went on sale about a year ago in France, with some sort of mechanical supercharging similar to your idea.....you should have registered a patent !
This idea also brings back a very faint memory about another system , with the same goal of increasing pressure of the intake gases .....and not seen on a Grand Prix bike, mind you, but on a french blue "Mobylette" 50cc moped....Don't you remember, T54 , the "Double Piston" engine that went , I'm fairly sure, into production at Motobécane ? Basically, they had a "counter-piston" facing downwards, whose conrod was linked to the same cranck "axle" ( palier in french ) as the "powering" piston, and therefore was moving up when the other one was going down . That piston ( larger bore and smaller stroke than the "real" one ) was sucking in the gases from the carb intake into a cylinder , and then pushing them , compressed , into the cranckase, where they of course were accelerated again by the crank like in all 2-Strokes . The effect of the "double piston" was double , first acting as a compressing device, but also the increased masses in movement made it act like some sort of "balancing mass" and increasing the torque .
Of course the Mobylettes were limited by law to a maximum speed of 45 kms/h , so no high performance was sought by this technology, but only increased acceleration, and increased power for climbing hills without having to seek help from the pedals...
Anyway, another funny idea....and my apopogies for the poorness of my technical english !
To which T54 replied :
I do indeed remember the Motobecane twin-piston design. the main problem found is that the torque gained was somewhat negated by increased mechanical friction and higher fule consumption. I remember that it did not last long until theyr dropped the idea.
To be efficient, a compressing mechanism must be friction-less except for... the forced air molecules.
The proposed engine had quite a few new ideas: getting rid of the conventional exhaust port allows for less piston slap and tighter clearances. Using a carbon case allows for less temperature distortion as aluminum or magnesium does, again making tighter clearances possible.
The total weight reduction by using a carbon case, carbon wheel halves, magnesium suspension uprights and in fact very little metal structure should be in the magnitude of 25% of total weight of a conventional machine.
By blocking any air flow to penetrate the inside of the engine compartment, that could also show an enormous gain in lowering drag.
and to be complete, the discussion had started when T 54 produced some sketches about a project he had imagined, which I think fits well on this thread :
I found and scanned the pencil sketch of the Gilera (not Garelli of course, me stupid!) mentioned above. It is exactly 10 years old.
It has lots of interesting ideas for a single lunch... Please forgive the poor quality as the original sketch was drawn over a piece of computer line paper, because that is all what the restaurant could provide!
The basic design is one of extreme aerodynamics. Note that the pre-war record-setting style helmet has found its way in new "hunchback" leathers since.... The front upright (there is no "fork" to speak of) is a one-piece streamlined cast-magnesium part that also includes the front brake calipers. The wheels are also streamlined but allow for clean passage of side winds. There is no brake rotor, the wheel rim made of two pieces of carbon fiber bolted together in the rim and center act as a disk. There is virtually no frame, see below. The engine IS the chassis and bolts directly to the front and rear suspension. The engine drives the rear wheel through a constant-tension chain as the drive gear is running near the center of the one-sided swing arm. The front suspension is by double wide A-arms and a single shock is actuating the adjustable system through a bellcrank. The steering is hydraulic with adjustable ratio so as to allow the driver large amounts of movement without upsetting the basic stance while cornering, allowing much finer control at the limit. The engine is very different: it is a single cylinder, 2-stroke unit with a single reed valve intake feeding a gear-driven turbine that compresses air and fuel to about 2.5 crank speed (see schematic on picture # 3). There is no conventional exhaust port but no less than 4 electronically controlled segmented exhaust valves lead to a pair of expansion chamber located on top of the horizontal cylinder. This allows the piston to run freely with at no time, the single ring "hitting" a port.
Of course the compressor is borderline legal, but if you read the regulations, only EXTERNAL compressing devices are forbidden...
The front suspension supporting unit is made of two pieces of stamped sheet-steel. They are bolted on top of the engine's crankcase at their bottom edge, and to a small tubular subframe working in tension and supporting the driver's seat and faux-tank anatomically designed to receive the torso, arms and chin comfortably. it means that the entire front suspension can be unbolted from the engine in less than two minutes, for an eventual replacement with different settings. The cast-magnesium single-sided swing arm is bolted directly onto the engine case made of carbon fiber. It is a one-piece molding with external covers from which one can slide the crankshaft and a cassette gearbox with integrated clutch system more akin to a torque converter. The swing arm axle rotates at drive-gear speed inside engine oil-lubricated bearings and as the front upright, includes a brake caliper acting on a "disk" protruding from the carbon fiber rear wheel rim. The single shock/spring unit is simply attached to the engine crankcase. over 80% of the torsional and longitudinal effort is carried by the carbon crankcase just like an F1 gearbox. Indeed, BAR now has a carbon gearbox doing exactly the same job, and quite successfully at that!
This arm assembly design allows the chain to be in constant tension, giving much more precise transmission especially under downshifts. The pressurized rubber fuel cell fits inside the front suspension system and feeds the single 38mm indirect fuel injection throttle body. Two surface coolers are part of the outer fairing to keep the engine bay enclosed and not subject to aero drag. The filtered air is pressurized by a small ram air intake.
A view of the centrifugal compressor run by a set of four thin aluminum hubs with nylon spur gears. Legal? according to the regs, yes! But anyone knows that regulations may change quickly when someone has a true mechanical advantage...
So, gearheads, what do you think of this brainstorm and is Italian food responsible for demented ideas?