2000 Posts and climbing!!!
Join Date: Dec 2005
Re: Correct Engine RPM, set?
Yes, I have understood that manufacturers have to limit blade tip speed, and it is lower for residential than for commercial machines. As residential lawn mowers are all direct drive, that is the blade is directly attached to the crankshaft there is a simple relationship between the RPM and tip speed. Let's see I if I can do the math:
2"pi"R (R = Radius, is 11" for a 22" mower) is the Circumference, is 69 Inches. and if limited to 19K feet per minute, or 209K inches per minute, I get RPM(max)=209,000/69 = about 3,000 RPM, hum if I didn't make a mistake, this sound a bit high. Well, as I compute it I'd not want the engine to run higher than 3K RPM, still need a tach to find the RPM.