Ok I tried to stay out of this but, as some of you know I am putting a Suzuki G15 in my KR2S. Full disclosure I am a dealer for Aeromomentum. Forgetting that, I think the Suzuki is a great option for a KR. Great performance, light weight, great fuel economy, overhaul is very affordable. Can't beat the price. This basic engine has been around for decades and proven to be tuff. These engines are all brand new not rebuilds. I am not going to write a novel on this net about it, but if you want more information on it contact me. Mine will be in this year for sure.
On Tue, Oct 22, 2019, 6:23 PM donald january via KRnet <krnet@list.krnet.org> wrote: > If you can get your hands on "Converting Auto Engines for Experimental > Aircraft" Second Edition by Richard Finch I recommend it for good reading > and great insight. FWIW > > On Tue, Oct 22, 2019 at 2:56 PM Daniel Branstrom via KRnet < > krnet@list.krnet.org> wrote: > > > I am not an engineer, and my comment here is based on some reading and > > observations that I have made over the years in aviation. My opinion is > > worth the electrons that were used to produce this post. > > > > In every machine that has rotating parts, torsional harmonic vibration > > is present. I'll call it THV. If a vibration coincides with an operating > > range of the machine, the THV can destroy the machine. If the frequency > > is above or below the operating rotation, it becomes much less of a > > problem. In an automobile, THV is damped by the rubber tires, and the > > greater rotation mass of the flywheel, and, often, automatic > > transmissions. On an airplane, the power pulses go undampened to a > > propeller, which has its own harmonic vibration that can be fed back to > > the engine at certain frequencies and can destroy the engine. Wooden > > propellers tend to dampen this because of their composition. > > > > Aircraft engine manufacturers take torsional harmonic vibration into > > account when designing their engines. That's why some certified direct > > drive engines come with a warning not to operate them at certain rpms > > with certain propellers, or they have counterweights to smooth things > > out. Rotax engines, for example, have a coupling that dampens THV. > > Engines are certified in aircraft with designated propellers for that > > reason. > > > > Torsional harmonic vibration can snap crankshafts and destroy reduction > > drives. It is similar in concept to aerodynamic flutter in flight > > controls. The THV does not disappear where the power pulses are > > overlapping, so that all of the forces going in same direction as they > > are in 6 or 8 cylinder engines, but at least all of the force going to > > the prop is in one direction. 4 or less cylinder engines have periods in > > their rotation when there is a backward force on the power output. The > > inertia in the engine, as well as flywheels or propellers keep the > > engine turning. > > > > There are very few companies that have been successful in experimental > > aviation with reduction drives. That doesn't mean that there aren't good > > ones out there, but the amount of engineering and manufacturing skill > > needed to build them can be immense and costly, and they have to have a > > big enough market to be profitable. It's also my opinion that as the > > power of the engine goes up, the forces on any reduction drive go up > > exponentially, and that's why it's easier to make a drive for an engine > > developing under 100 hp (which seems to be the dividing line) than one > > that has more power. It's for those reasons that I don't believe you > > will see a Rotax 200 hp engine. > > > > Years ago, there was a manufacturer of a redrive that was used on large > > engine conversions. It seemed to be a good one, with few problems, but > > when the drive was manufactured by someone new, the drives started > > breaking. I credit the problems to manufacturing technique. > > > > I have flown behind a Cessna 175, which has a geared engine. It was > > excellent both in climb ability and cruise speed, I found it close to > > the performance of a 182, and it had a fixed pitch propeller. The 175 > > got a bad reputation, I believe, because pilots tried to operate it like > > an ungeard engine. The engine was designed to run at above the red line > > of ungeared engines, and operating it at low ungeared rpms is very hard > > on it. Also, it was not good practice to let the prop drive the engine. > > > > Consider the reputation of anyone making a reduction drive, and look for > > reports of people that have problems with it. Google engine problems or > > engine issues, and look at what other engines they have sold in the past. > > > > That's my 2 cents. Your mileage may vary. > > > > Dan Branstrom > > > > > > _______________________________________________ > > Search the KRnet Archives at > > https://www.mail-archive.com/krnet@list.krnet.org/. > > Please see LIST RULES and KRnet info at http://www.krnet.org/info.html. > > see http://list.krnet.org/mailman/listinfo/krnet_list.krnet.org to > change > > options. > > To UNsubscribe from KRnet, send a message to krnet-le...@list.krnet.org > > > _______________________________________________ > Search the KRnet Archives at > https://www.mail-archive.com/krnet@list.krnet.org/. > Please see LIST RULES and KRnet info at http://www.krnet.org/info.html. > see http://list.krnet.org/mailman/listinfo/krnet_list.krnet.org to change > options. > To UNsubscribe from KRnet, send a message to krnet-le...@list.krnet.org > _______________________________________________ Search the KRnet Archives at https://www.mail-archive.com/krnet@list.krnet.org/. 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