Try to find a set of lifters for a 3 cylinder Geo engine. I did 5+ years ago and couldn't find them then. I bought every one I could find at every dealer in KC and still couldn't get a full set.
There must be hundreds of Geo/Suzuki G10 three cylinder engines flying so the guy who said they should never be used in an airplane is 100% wrong, in fact they have a history of reliability and success. Gearbox and belt redrives are available to bolt on to them so you don't have to fool around making your own or adapting a drive made for a different engine. There is an excellent Yahoo Geo/suzuki engine group Yahoo! Groups that you should join.So far on the pages of this forum I have found the opinion that the 1000cc three cylinder Metro/Sprint engine has excessive vibrations and should never be used in an airplane, and another in direct conflict that says the three cylinder engine is a great engine. Both can’t be totally correct. Since I already have a 3 cylinder sitting here waiting to be used for something, I have an interest in a valid answer. There either must be a fatal flaw for aircraft use, or there must be a range of correctness, with some common or theoretical mods to reduce some of the bad traits to an acceptable level. So some useful questions to those who may have answers are:
Does use of the Suzuki three cylinder also mandate using the stock (heavy) flywheel to tame engine harmonics? Are there any alternative mechanical means to reduce vibration (like torsional dampers) that might do the same thing at a lower weight penalty? Would three bladed props offer a reduction in resonances? Would wood props be the best choice for direct drive?
There was also one, and only one, mention of using this engine direct drive rather than with a PSRU. The tradeoff of the PSRU’s greater thrust vs lower weight and complexity of direct drive is clear and would probably be a subjective decision. The question is really whether the engine produces enough torque at 3000-3400 rpm to be a useful choice, compared to the engine weight and other competing engines. Assuming the torque curve of the 1300 would be similar to the 1000, the torque curve over this rpm range is almost flat. (re post #4 at Technical Discussion Areas/Auto conversions/Suzuki 1.3 hp torque).
Are there any successful examples of direct drive 3 cylinder Suzukis in airplanes?
Regarding resonant frequencies… virtually all engines have some harmonic resonances, so the question is more one of degree. And there are some certificated aircraft that have resonant frequencies that the operation manual simply says to avoid. Also associated with the engine’s harmonics are the combined prop/engine resonances. Elsewhere on this forum, someone mentioned this, but did not add that prop indexing on the crankshaft is a significant factor. Yet another comment said that opposed engines should have the prop aligned with the cylinders to avoid the engine/prop resonances that indexing elsewhere would produce. Could someone with more knowledge than I address some of these questions?