Pretty Close
I took a ruler and measured the diameter ratios of the pulleys/sprockets from the pictures and came up with the following approximations:
First reduction = 2.4 : 1
Second reduction = 2.8 : 1
Chain reduction = 4:1
Total reduction is therefore about 27 : 1
Assuming a tire outer diameter of about 32 inches, one revolution of the rear tire would be about 100 inches of distance traveled. For a speed of 30 MPH, the saw would be turning:
(30 mi/1hr)(1hr/60min)(5280 ft/1mi)(12in/1ft)(100in/tire rev)(27)=
8550 RPM
Certainly in the ballpark...and why wouldn't it be?
The ex-blabbermouth