Guest deanfi Posted November 21, 2019 Share Posted November 21, 2019 new one to me , its a old engine " The Lycoming O-1230 hyper engine" very interesing site https://oldmachinepress.com/2018/04/20/lycoming-o-1230-flat-12-aircraft-engine/ Link to comment Share on other sites More sharing options...
skippydiesel Posted November 21, 2019 Share Posted November 21, 2019 Very interesting. Thanks Link to comment Share on other sites More sharing options...
facthunter Posted November 21, 2019 Share Posted November 21, 2019 Long cranks with lots of cylinders hanging off them are hard to manage design wise for torsional harmonics as the crankshaft a relatively long and light unit. Most aero engines don't allow for much development or else the original design was too heavy. An aero piston engine is a contest between LIGHTNESS and producing power reliably for a reasonable design life. Nev 1 Link to comment Share on other sites More sharing options...
Guest deanfi Posted November 21, 2019 Share Posted November 21, 2019 I imagine cyclinder cooling on the back half would be problematic, it was a bit of a problem on the Lycoming flat 8 in the commanche though I believe they overcame it with better ducting Link to comment Share on other sites More sharing options...
Thruster88 Posted November 21, 2019 Share Posted November 21, 2019 I imagine cyclinder cooling on the back half would be problematic, it was a bit of a problem on the Lycoming flat 8 in the commanche though I believe they overcame it with better ducting Not a problem with liquid cooling 1 1 Link to comment Share on other sites More sharing options...
Guest deanfi Posted November 21, 2019 Share Posted November 21, 2019 Not a problem with liquid cooling Duh ! I was having a senior's moment thinking about the wrong engine Link to comment Share on other sites More sharing options...
skippydiesel Posted November 21, 2019 Share Posted November 21, 2019 Long cranks with lots of cylinders hanging off them are hard to manage design wise for torsional harmonics as the crankshaft a relatively long and light unit. Most aero engines don't allow for much development or else the original design was too heavy. An aero piston engine is a contest between LIGHTNESS and producing power reliably for a reasonable design life. Nev Its only 7 cylinders long, however I do agree with you. Strange how they went to so much bother to design a very flat/low frontal area engine and then stuck a whacking great magnito & starter motor on top, completely screwing up the original concept Link to comment Share on other sites More sharing options...
facthunter Posted November 22, 2019 Share Posted November 22, 2019 FLAT motors don't share crankpins, like VEE motors and radials do. Crankshaft "stiffness" is always an issue , creating "don't use" rpms to avoid harmonics wrecking the show. Also harms redrives. quills etc..Nev Link to comment Share on other sites More sharing options...
Geoff_H Posted November 23, 2019 Share Posted November 23, 2019 Actually as a general rule speed harmonics tend to reduce dramatically as the number of cylinders increases. I remember being taught in 3rd year of degree that a V12 was regarded as the first "fully" balanced engine, well the vibrations were considered insignificant. I don't know about this engine but I am not about to get the books out to calculate the effectiveness of this configuration. Interesting to note that there is a theory that a 'square 4" with contra rotating shafts should be considered extremely well balanced,. mmmm how heavy would that be? Link to comment Share on other sites More sharing options...
Mike Borgelt Posted November 23, 2019 Share Posted November 23, 2019 Radial engines are good. Next time you see one have a careful look. Most of it is power producing bits (cylinders). Link to comment Share on other sites More sharing options...
Guest deanfi Posted November 23, 2019 Share Posted November 23, 2019 Quite interesting old nasa film about propeller whirl instability, Start around the 2 min mark https://youtu.be/j6Q5ggtV-y8 Link to comment Share on other sites More sharing options...
pmccarthy Posted November 23, 2019 Share Posted November 23, 2019 Actually as a general rule speed harmonics tend to reduce dramatically as the number of cylinders increases. I remember being taught in 3rd year of degree that a V12 was regarded as the first "fully" balanced engine, well the vibrations were considered insignificant. I don't know about this engine but I am not about to get the books out to calculate the effectiveness of this configuration. Interesting to note that there is a theory that a 'square 4" with contra rotating shafts should be considered extremely well balanced,. mmmm how heavy would that be? Ariel square four was a quite successful bike, used by police. Link to comment Share on other sites More sharing options...
facthunter Posted November 23, 2019 Share Posted November 23, 2019 It's smooth but not without problems. The reversing of the rotation does cancel out a lot of forces. If you seek challenges play with one.. Nev Link to comment Share on other sites More sharing options...
facthunter Posted November 24, 2019 Share Posted November 24, 2019 Torsional harmonics are generally not felt outside of the engine but really play havoc with the life of it if not taken into account with harmonic balancers or "live" Counterweights and/or avoiding the critical RPM settings.. There was a lot of promoting of the V 12 configuration at times but it's not immune from the problem of the crankshaft length/thickness ratio issue (Stiffness) It has a good piston mass inertia/flywheel effect where only a couple of Pistons are stopped at any point in time as compared with any in line or flat 4 which are the worst. where all are stationary at the same time, twice per revolution.. That could be what the lecturer was referring to and there is an optimum angle for the Vee for that effect to be best achieved.. Nev Link to comment Share on other sites More sharing options...
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