# How to: compute Watts and Calories for for a bicycle, up a hill

At 6'5", 300 lbs. and old as dirt, I am a walking and rolling testimate to F=ma. This part of my project is difficult for me, because I have never taken a physics class. All the examples I have in books and PF, deal mostly with force moving down a hill. I am trying to compute Watts and Calories, while riding at any measured angle.

I am using a BS2p basic stamp reading an 2 axis accelerometer, 2 hall sensors and a gear tooth sensor. A math coprocessor handles the math. With my current set-up the BS2p determines what gear I am in, at any time, or if I am coasting. Every calculation is started after the front wheel completes a rotation, but I have no idea if it is accurate.

Watts = ma*gr*pcl*s*sin(theta) + Rr (so long as theta is never zero) If theta = 0, then Watts = ma*gr*pcl + Rr

Calories = watts*0.2388459

m = Mass = 145kg
a = Pedal Speed = 22pi/9 rad/sec
gr = Gear Ratio = 44 : 18 (2.44 to 1) (This is gear ratio I use the most)
pcl = Pedal Crank Length = .175m
s = Front tire circumference = 2.2m
Rr = Rolling Resistance ??

I left gravity out, because I felt it would be part of Rolling resistance. Once the initial equation is working I figured on gathering Rr by comparing computed and measured data

thanks

Bill M.

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