ekimneirbo
Well-Known Member
On another thread about engines, some references were made that Formula 1 Racing O-200 engines were able to generate more HP when run at higher rpms from 4000/4200. This is a specialized situation but it does point out that the ability to have or create more horsepower at higher rpms and using a SMALLER diameter propellor can work. The combination must generate a result where the loss of efficiency of the smaller prop is offset/overcome by the additional HP and RPMS being used.
Many of the builders using conversion engines used today seem to feel that they must use a reduction drive and keep their propellor speeds at 2700 rpms max. I feel that reduction drives aren't really needed and that a smaller prop at a higher rpm can provide adequate or very close to comparable efficiency if selected properly. Unfortunately I don't have the expertise or patience to wade thru the technical jargon. There are people like Gary Spencer , Steve Wittman and others who have done it successfully.
I don't particularly want to use 4000 or more rpms. I would prefer something at 3500-3200 rpms.
The article attached below seems to be along the lines of what I'm looking for.
I realize that the size of the airplane and the size of the engine chosen will have a large input on doing this.
I'd like comments on what this article outlines and suggestions . I just think that the standard idea that
larger is better so its the only way to go ..........is overstated. I think there can be a loss of efficiency
but it can be offset mostly or the amount of loss maybe isn't that bad. You tell me.
One direct question. Will adding a 3rd blade increase area and offset diameter? I know fuselage size and shape
comes into play by blocking some of the airflow.
http://a.moirier.free.fr/H%E9lice/Conception%20h%E9lice/Th%E9orie/4200%20RPM%20Props.pdf
Many of the builders using conversion engines used today seem to feel that they must use a reduction drive and keep their propellor speeds at 2700 rpms max. I feel that reduction drives aren't really needed and that a smaller prop at a higher rpm can provide adequate or very close to comparable efficiency if selected properly. Unfortunately I don't have the expertise or patience to wade thru the technical jargon. There are people like Gary Spencer , Steve Wittman and others who have done it successfully.
I don't particularly want to use 4000 or more rpms. I would prefer something at 3500-3200 rpms.
The article attached below seems to be along the lines of what I'm looking for.
I realize that the size of the airplane and the size of the engine chosen will have a large input on doing this.
I'd like comments on what this article outlines and suggestions . I just think that the standard idea that
larger is better so its the only way to go ..........is overstated. I think there can be a loss of efficiency
but it can be offset mostly or the amount of loss maybe isn't that bad. You tell me.
One direct question. Will adding a 3rd blade increase area and offset diameter? I know fuselage size and shape
comes into play by blocking some of the airflow.
http://a.moirier.free.fr/H%E9lice/Conception%20h%E9lice/Th%E9orie/4200%20RPM%20Props.pdf
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