Balancing props with DynaVibe is usually pretty easy, even for first-time users. Once in a while, however, we hear from customers who are having problems balancing, so based on some support exchanges, we've put together some troubleshooting tips when the balancing process is more difficult.
Here's the typical scenario: a customer consults the DynaVibe manual, follows the instructions and adds weight where the procedure indicates, but subsequent runups show that the balance hasn't improved, and/or that the location where the weight should be added has moved. After repeated runups, there seems to be no progress being made toward getting the prop balanced.
There are a few “gotchas” that may impact how easily the balancing process proceeds.
First, make sure you are aligning the reflective blade tape with the phototach, using the position of the accelerometer as zero degrees, with the accelerometer cable pointing up to the zero degree position. Then go in the direction of rotation to the angle indicated; that's the heavy spot. When the pusher is backwards, as in a Long EZ, sometimes people get confused, but if you follow those steps, it doesn't matter which side of the plane you are on or which way the motor is spinning. Just point in the direction that the wire is coming out of the accelerometer and then go in the direction of rotation to the heavy spot (add weight opposite).
Second, RPM readings must be completely stable. If you see the RPM jump from 2200 to 1100 then back, or if you see more than a 50 RPM variation in tachometer readings, there is probably an issue with the tachometer. If you experience a tach variation of this nature, contact us and we can make some suggestions.
Third, check the spinner if your airplane has one. "Chasing" the angle during the balancing process is a classic indicator of a spinner that is shifting while running. If you can feel the spinner move by pushing laterally on the spinner, then it will be hard to balance. If your airplane doesn't have a spinner, do a very thorough job of looking for anything else that is loose: cowling rubs, exhaust pipe contact points, or anything that may be causing erroneous readings.
Fourth, are you running a long prop extension? If so, pay close attention to where you mount the accelerometer. It should be at the very front of the engine (or the very back of the engine for a Long EZ), otherwise, the accelerometer placement could give unusual results.
Fifth, check your static RPM. If your static RPM is lower than your cruise RPM, the low static RPM can be an issue if the mounts are stiff.
Sixth, and finally, the blade pitch of the prop could cause difficulty balancing, so you may need to verify the blade pitch on each of the blades to make sure they are all setup the same way. If balancing isn't going smoothly it is a good idea to verify that all the blades are pitching the same (and in track the same).
We love hearing from our customers, so if you have a question, comment or problem, please don't hesitate to contact us: firstname.lastname@example.org or 405.896.0026.