I am writing this blog to show how I balanced the propellers on my FMS B-25. Balancing propellers decreases vibration and more efficiently provides thrust. This is especially important for my B-25 as I am running the props on 4 cells (4s) instead of the stock 3 cells (3s). Although it may look complicated, balancing is very easy once you know what you're doing.
The first step is to get a prop balancer such as the Dubro Tru-Spin Prop Balancer http://secure.hobbyzone.com/DUB499.html. This is what I use and everyone else I've seen says that it is the best. I will be assuming you are using this for the instructions. You will also need some sandpaper (150 and 300 grit paper work well).
Assemble the propeller onto the balancing shaft in between the two metal cones. Make sure that the prop is evenly fitted between the cones. Make sure that the aluminum wheels are the same height away from the base, use a wide ruler to calibrate the heights and then tighten the hubs to the vertical rods.
Place the propeller and balancing shaft combo onto the aluminum wheels and allow the prop to rotate until it comes to rest. One rotor will be closest to the bottom, another in the middle, and the last rotor at the top. The bottom rotor is the heaviest and will need to be sanded the most. The middle rotor is the 2nd heaviest and will be sanded a little. The rotor pointing away from the base at the top will not be sanded at all.