Here is some data from the Robitronic Manual.
"In addition to that of the flywheel, the moment of inertia of the motor armature must also be considered for a measurement. The value above is an average of various commonly available armatures. The value should not be changed initially, but can be adapted for special applications. The factory setting is 4.20 x 10e-6 kgm2 "
The factory flywheel has a moment of Inertia of 45 x 10e-6 kgm2
This is calculated from the following formula
Inertia = 1/2 mass x Radius^2
I don't have the flywheel in hand to measure it. There is a robitronic thread. If you ask there for the radius and width you could calculate the mass with the formula. Here is a picture of the instrument if you just want a rough estimate.
You need to convert dimensions to meters and will get a mass in kilograms if you use the above formula.
If you would like more accurate power measurments on P2K type stock motors then you can use 3.0 x 10e-6 kgm2 for the inputed Moment of Inertia of the armature. Most people don't make this change.
Photo courtesy of Robert Schachuber.
Last edited by John Stranahan; 01-03-2006 at 05:30 PM.