investigate PTFE as a friction reducer? look at the tolerances the piston/connecting rod/ gudgeon pin liner operate to.... what texts have you looked at so far.... crazy as it may seem, TBASE (tuning the A Series) by Vizzard gives a good overview
There is an annual engine award given http://www.ukipme.com/engineoftheyear/
Enjoy
Dr B
Hi!: I'd say a good approach is the one implemented by Bristol in their Air-Cooled line of engines, one of the top performing and longer TBO in WWII: Single Sleeve-Valve, Burt-McCollum type distribution. As the sleeve is in a non-stop movement while the engine is running, the poor/nil lubrication linked to piston stroke TDC and BDC is eliminated, the Sleeve also provides with the best type of movement for distributing oil. Basic info and referencies for S-V engines can be found in Wikipedia.
According to Mike Hewland in a 1974 interview in Car&Driver, sleeves didn't need an individual lubrication supply, and oil use of their 500 cc, 72 HP, single cylinder prototype was reported as lower than in the contemporary popett valve engines.
Solid lubricant aditives, as MoS2, are also practical in reducing the wear of critical parts. Hope it's useful. Salud +
Wankel Rotary Combustion Engines, having a non-stop, same direction movement witth changes only in speed of seals relative to housing, also can reduce this type of wear and poor lubrication, but as in 2-Strokes, separate oil dosing pumps may loss fed, and some oil added to gasoline is advised by many users.
Smoke from engines using oil-gasoline mix is higher than with conventional independent lubrication, but a review of 2-Stroke emissions was published in a SAE Journal around year 2000, showing that a 3-way catalyst, with air injection in its middle section, can adequately clean 2-Stroke exhaust. Wankel remain more efficient in fuel use than 2-Strokes, Wankel are better also in engine life, and production costs may not differ too much, just the technology remain misterious and dubious for many people in the motor industry. Regards
The best approach in Single-Sleeve Valve engines seems the one tested by Harry Ricardo in the last times of its development, in a 2-Stroke Compression Ignition Engine (You're aware of recent data published in SAE, Loop Scavenging is always better than Uniflow scavenging for Two-Strokes): leaving the Sleeve open, acting as a second piston with a surface of 10% of the surface of the central piston, and contributing with 3% to the output power via the Sleeve-Driving mechanism and the crankase. This approach (1954 and 1969 editions of: 'The high-speed internal combustion engine') eliminates the upper rings and the complexities of the so called 'Junk head' of SSV engines. As long as tolerances and space between piston, cylinder and Sleeve are kept to a minimum thickness of the oil layer, Sleeves are transparent to heat. Thanks. Salud †
SAE paper 2014-32-0115: 'Advanced low friction engine coating applied to a 70 cc high performance chainsaw', that seems having found a solution to the requirements for a Cylinder Liner coating meeting the requirements depicted in the SAE book by professor T Suzuki: 'The romance of engines', could be a proposal. The SAE paper 760642, by Yanmar Diesel, is about a Rotary Combution Engined ChainSaw were this coating may be also of benefit. Dolmar-Sachs sold for a while a similar RCE Chainsaw, the advantanges from this low friction material could also be seen in larger engines, but for small engines, the advantages of a low-friction, high lubrication coating are more important in a relative way. Thanks.
Mr Taurozzi, in Argentina, designed a piston-rod operating mechanism without load on cylinder walls, requiring no lubrication: 'Motor pendular', you can have a look at it in YouTube: 'Taurozzi engines', the concept was developed, and seems in widespread use, for compressors in medical machines, where the possibility of lubricating oil entering the air flow, then the lungs of a patient, could be lethal. https://youtu.be/jIpsSQgr5E8
This engineer provides compressors to Savoia Cars: http://www.savoiacars.com/principal_in.html
if it's interesting to you, perhaps you may contact mr Taurozzi through Savoia cars.
An interesting General Aviation Turbine design could be located also in YouTube, with the search terms: 'Turbina argentina Labala', it has very few moving parts. Sorry, most is in Spanish
https://youtu.be/blt-jSWzsSI Regards, + Salut
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