Solving Gearbox Ratio for 12" Wheel Travel @ 2mph

[SevenToFive]

I need to figure out a gearbox ratio to get a 12 inch wheel to travel at 2mph. If I remember right the equation should be 1foot * 3.14*gearbox output rpm*60 then all divided by 5280 to get the final mph. Am I on the right path? Then I need a gearbox output around 58rpm.

Thanks to all of you who reply.

 

[Bystander]

I need to figure out a gearbox ratio to get a 12 inch wheel to travel at 2mph. If I remember right the equation should be 1foot * 3.14*gearbox output rpm*60 then all divided by 5280 to get the final mph. Am I on the right path? Then I need a gearbox output around 58rpm.

You're close to the "right path." Just one little adjustment.

 

[Baluncore]

Do it backwards.
12” diam = 1 ft wheel, at 2mph.
wheel circumference = Pi * diam = Pi feet.
2 mph = 2 * 5280 feet per hour = 10560 ft per hour
revs per hour = 10560 / Pi = 3361.35
revs per min = 10560 / ( 60 * Pi ) = 56.02 RPM