Hallo,
S-öl ist das Todesurteil für jeden COX dessen Pleuel per Kugelgelenk (balljoint) mit dem Kolben verbunden ist.
Dieses Gelenk ist nur Rizinusöl tauglich , durch S-öl herrscht dort mehr Hitze , erhöhter Verschleiß bis zum Bruch.
Cox .049 .051 Piston Reset Tool
coxengines.ca
Die Synthetik-Öl-Hasserei nimmt bei dir ja schon manische Züge an. Jedesmal, wenn es um S-Öl geht, schreibst du Hasstiraden.
Was du hier jetzt schreibst, stimmt so nicht, denn das Rizinus-Öl kommt schlechter als das Synthetik-Öl weg. Lies dir deinen ersten Link nochmal durch!
Hier die wichtigsten Ergebnisse des RC-Groups-Kollegen, den man im ersten Link nachlesen kann, die ersten paar Ergebnisse habe ich rot gefärbt. Es lohnt sich bis zum Schluss zu lesen!
The base fuel used was 15% nitromethane, 20% castor oil by volume.
The base fuel engine failed 8 hours into the 10 hour endurance test by wearing the connecting rod through the crown of the piston. The wearing surfaces of the ball and socket were not "varnished". The same test run with a
synthetic oil in place of the castor ran for the full 10 hours without failure although the rod and piston joint showed .008" of wear. The flight cycle testing engine
failed on the castor mix at 4.4 hours by the same piston failure, the rod had just broken the surface of the piston crown and affected starting, although the engine would still start via an electric starter. Again no "varnishing" was present in the joint. The synthetic oil engine passed the 100 flight cycles, but showed slightly more cylinder wear near the exhaust ports and a similiar .008" of wear in the ball/socket joint. So from the first basic tests it was clear that the ball/socket joint does not run hot enough with 15% nitro fuel to cause castor oil to polymerize, "varnish" and prevent metal to metal contact, which is of course castor's key strength as its anti-wear capability in liquid form is lower than other oils. The synthetics while better in the liquid form at anti-wear, do not have the capability to protect hot areas such as the cylinder near the exhaust port as well as the castor. A third test was run with 15% nitromethane fuel, 2% castor oil and 18% synthetic. The engines passed both the 10 hour endurance and 10 hours of flight cycle and both showed about .008" of wear in the ball/socket joint. Slight varnishing around the exhaust ports showed the castor was doing its job protecting that specific area, otherwise the engines were spotless inside. In a final effort to reduce the ball/socket wear an oil made up of 8% castor, 90% synthetic oil, and 2% tricresyl phosphate was used at the same 20% as previously with 15% nitromethane. The engines using this fuel passed both tests, with just under .002" ball/socket wear, slight varnishing around the exhaust ports, and overall excellent condition. This test was repeated with 16% oil volume with no degredation in wear and a 6% increase in RPM. To go back to determining the failure mode of the all castor fuel 30% nitro fuel was blended with 20% castor oil. The engine though needing to be de-varnished every 2 hours passed the 10 hours of testing without a ball/socket failure. The crankpin and crankcase wear was however higher than any other test. I did a final test using 20% of my synthetic/castor/TCP mix and 30% nitromethane, the engines ran the full 10 hours without needing a de-varnish, and the ball/socket and crankpin joint were in excellent condition. So from my little bit of testing, I have concluded that for my Cox design sport engines, a fuel mixture with castor/synthetic oil/and TCP will provide excellent service with as low as 16% total oil volume however I did not test the 30% nitromethane fuel at that oil level. This eliminates the gumming of engines in storage, sticking reeds etc. Anyway hope this is entertaining for people!
cu,
Rüdiger