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Old 09-03-2011
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PorFin PorFin is offline
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Doc,

Here's a suggestion for a temporary fix. I've never tried it, but in principle it should work.

As I2F suggested, the lead tape is the easiest solution. You adhere strips to each blade, and then cut off small sections until the blade is perfectly balanced. The tape is thin, and doesn't significantly disturb the airflow over the blades. Lead tape is not that difficult to come by normally, but since you're in Oceania I can't imagine what a challenge it may be trying to find it.

So the expedient solution is to take your old hub, and start balancing it with the new blades installed. It will be tedious, but start with equal weight pieces of lead taped to the hub between the blades. From this point, follow the procedure recommended for the KISS generator -- except that you'll be decreasing the size of the hub-mounted weight instead of the blade-mounted tape. Since the position of the weights are closer to the center, they will be less sensitive to adjustment than tape would be further out along the arm of the fulcrum (i.e., out on the blades themselves.)

Once you've achieved balance, carefully mark EXACTLY where the weights are on the hub and then epoxy or polysulfide the weights to the hub. This should work, but for extra credit (and peace of mind) continue...

Obviously, you're trying to keep the wieghts as small as possible to minimize the risk of these puppies coming loose when the blade's spinning. While centrifugal forces will be less prevalent closer to the hub, they will exist.

After you've found balance you could then carefully remove and measure the individual weight of each piece of lead and tape to determine what your differential is at each point on the hub. You'll wind up with two numbers that are not zero -- this will be the mass of the wieghts you'll need to make and adhere to the hub.
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