Here I will try to put in perspective, the amount of power we can expect from a gravity driven (perpetual motion) wheel.

Since there is much know data about the successfull Besslerwheel, the numbers are there to play with.

Know facts from Besslers latest and biggest wheel are :

Diameter : 3,65 m
Weights  : 9 Kg
RPM      :  20
Load      : 34Kg pulled around the axle
Axle diameter : 15,24 cm

Power exctracted from the machine at 20 RPM will then be :

F*Dpr.sek =
34kg*9,8m/s^2*3,14*0,1524*20/60 = 53,2Watts

What we don`t know is how many weights he used.
It is known that the weights worked in pairs (of two?)
And that about 8 bumps where heard pr. revolution.

1. It could be that he used 8 , 9 Kg weight, and 8 weights working in pairs with the first 8 (somewhere from 3 to 9 Kg) (totally 16  weights)

2. He could also have used 4 , 9Kg weights and 4 weights somewhere from 3 to 9Kg.

This is my basic theory !

Anyway I got a formula for calculating the Power from his latest design that looks like this :

  
(Where d = diameter and m = the weight of one of the (biggest) weights.)

In this case the formula adds up to 54 Watts !!