The smaller displacement engines can revup more just look at the small car engines that turn those rpms. I must say that I have no desire to fly such an engine and setup as I am a very practical person and the .40/.60 size engines seem to be the most practical engines for me. The only small engine that tempts me is the little Saito 30.
I remember seeing a photo of a .61 two stroke belt driving a large prop on someone's pattern plane, back in the days when F3A rules limited two strokes to .61 (10 cc) and four strokes to 1.2 (20 cc) displacement. It is my opinion that unless you are restricted to a certain displacement by competition rules, it's better to just direct drive the prop with a larger engine. (the KISS rule, keep it simple, stupid!)
buzzingb... Gear reductions are not restricted to small, high revving engines. This is an OS .61. The gear reduction on this engine was before 4-strokes became common but noise issues were getting to be very restrictive. Folks figured out that the high prop tip speed was producing more noise than the engine and turning the prop slower helped. As B.L.E pointed out, rules in the pattern world at the time also partially drove the development of these engines.
You did know the Satio .30 is out of production?
Bill Vail
www.RCScreenProtectors.com