Wind Turbine Project: Balancing the Wind Blades
I'm now ready to get the blades up in
the air. I have to make sure they are balanced or else they will
wobble at high RPMs. This uneven rotation could cause excessive
vibration and failure of the blade hub or tower. Ideally I would
like to do a dynamic balancing, but I don't know where I can do
this. Therefore, I chose to do a static balancing of the rotor
and blades.
The physics of the scale balance depends on the location of the center of gravity relative to the fulcrum. Here, the fulcrum is at the spline shaft. If the center of gravity is above the fulcrum the setup is unstable and will tip and continue to move until it can go no further, or the new center of gravity finds an equilibrium. If the center of gravity is at the fulcrum the apparatus will tip and remain in this position. If, however, the center of gravity is below the fulcrum the apparatus will oscillate until the center of gravity is at the lowest point. If the center of gravity is too low then the balance will be "dead" and not function. At the right point, the lower center of gravity will prevent the apparatus from excessively tipping, allowing one to add weights to the three arms until the center of gravity is in the center and all three blades are at the same height. If one tips the setup when balanced it will oscillate and eventually return to the balanced state. I inserted the shaft at the bottom with some weight to lower the center of gravity.
I fashioned a plug that will fit into the spline shaft of the rotor. Using a lathe I put a hole in the dead center and attached a knotted string.
Using this device I can suspend the whole rotor, hub and blades and
balance them like a scale balance.
The physics of the scale balance depends on the location of the center of gravity relative to the fulcrum. Here, the fulcrum is at the spline shaft. If the center of gravity is above the fulcrum the setup is unstable and will tip and continue to move until it can go no further, or the new center of gravity finds an equilibrium. If the center of gravity is at the fulcrum the apparatus will tip and remain in this position. If, however, the center of gravity is below the fulcrum the apparatus will oscillate until the center of gravity is at the lowest point. If the center of gravity is too low then the balance will be "dead" and not function. At the right point, the lower center of gravity will prevent the apparatus from excessively tipping, allowing one to add weights to the three arms until the center of gravity is in the center and all three blades are at the same height. If one tips the setup when balanced it will oscillate and eventually return to the balanced state. I inserted the shaft at the bottom with some weight to lower the center of gravity.