How do I convert torque to watts and other PM/math questions?

Triathlon Forum
1

O.k. I have an SRM. Lets say I want to cacluate how much a chnage in offset of 20 affects my power (and other misc. math things). Its math geek type stuff but I am curious…so bear with me please.

  1. My offset is 630 Hz.
  2. My slope is 25.1 which means delta 25.1 Hz = 1 Nm.
  3. My cranks are 172.5 mm.

Problem #1: If I hang a 10 pound weight on my pedal (which I think needs to be at 3 o’clock) and recheck offset, it should read:

offset + ((formula for torque in NM) X slope Hz/Nm)) =

630 + ((10 lbs X 172.5 mm X 0.00444822)X25.1 = 822.6 +/- 2%

Problem #2: My Garmin computer calculates power by an equation that has to do with torque and cadence - what is that equation?

Extra credit: So if I am riding and my computer says “200 watts” at a cadence of 80, but my offset has gone up from 630 to 640 due to temperature changes, what is my true power output?

Thanks,

Dave