[Yak] Converting Gear inches at some RPM to MPH

[Bob Thomas]

Chuck,

Here's the way I see it.

Gear inches is the diameter of wheel equivalent to the that provided
by your gearing.

In one revolution it moves forward pi x diameter

So take a 100 gear inch wheel at 80 rpm

100 inches (diameter) x 3.14 (pi) x 80 rpm x 60 (minutes in an hour) =
1,507,200 inches per hour

now change that to mph by dividing by inches per mile = 5280 x 12 = 63,360

1,507,200/63,360 = 23.78 mph

which is  a really good clip for a recreational cyclist to maintain for an hour

Looks like you were leaving out Pi and not converting the mph to
inches per mile.

Bob Thomas
Morris NY
pocket rocket owner
http://tdf2004.home.mindspring.com


>From: charles voigtsberger <charles_e_voigtsberger at yahoo.com
>Subject: [Yak] Gear inches
>
>Logic tells me if you know gear inches, you should be
>able to get to miles per hour fairly easily. Gear
>inches equal number of lineal inches traveled with one
>revolution of the pedal. Gear inches x rpm x 60
>divided by 5280 should give you miles per hour.
>Somehow that formula is not working out for me, so
>obviously I am overlooking something.
>Chuck Voigtsberger
>Ventura CA