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View Full Version : Gravely @ 7.8/hr v.s. Ferris @ 5.1/hr ...


CP Estates
03-03-2006, 07:07 PM
:confused: Why such a difference? The Gravely is a 60" with a 25hp and the Ferris is a 61" with a 25hp.

jtkplc
03-03-2006, 07:51 PM
2 things...

The equation for finding acres per hour is "Ground Speed X Deck Width / 99 for 100% efficiency (which is impossible) or /120 for 80% efficiency."

The Gravely goes 13 mph and the Ferris you mentioned only has a top speed of 10 mph. Ferris used 80% efficiency in their equation, while Gravely used 100% efficiency in theirs.

Gravely
13 mph X 60" deck / 99 = 7.8787...

Ferris
10 mph x 61" deck / 120 = 5.0833...

Make sense?