How to Balance

Balancing your aircraft is usually a straightforward process. There are certain circumstances that may make balancing the aircraft more difficult, but in general, the process can be completed in a couple hours.

Step 1. Remove Cowling

Remove the cowling to gain access to the area immediately behind the propeller. For typical power plant installations, this would require removing the upper cowling of the aircraft, giving access to the top of the engine.

Step 2. Mount the Accelerometer and Optical Pickup

The accelerometer and optical pickup are typically mounted on the top of the engine, approximately six inches behind the back of the propeller. The accelerometer is mounted vertically while the optical pickup is mounted such that the optical beam is pointed at the back of propeller, with one of the propeller blades in the 12 o'clock position. A common mounting technique is to remove one of the case bolts along the top of the engine and then replace the bolt with the accelerometer and optical pickup mount installed under the bolt. Position the optical pickup such that the beam is visible on the back of the propeller. The beam should be perpendicular to the blade.

Step 3. Mount reflective tape on the propeller

By placing the small piece of reflective tape (provided in the kit), on only one blade, that blade can now be considered the “Master” blade. Position the tape such that the optical pickup strikes the reflective tape and turns on the small light at the back of the optical pickup.

Step 4. Secure Cabling

Secure all cabling from the accelerometer and the optical pickup to the engine and aircraft using tape and zip ties as needed. Route the cabling into the cabin of the aircraft. Cables should not be allowed to hang free as they may become entangled in rotating equipment. For pusher aircraft and rotorcraft, this can be particularly dangerous. The cabling should be secured in all cases and any doors or loose cowlings should be thoroughly secured to prevent damage during engine runup.

Step 5. Attach the DynaVibe

Attach the DynaVibe dynamic balancer to the accelerometer and optical pickup cables from the engine compartment. The cables are keyed, so look closely at the connectors before plugging them into the DynaVibe.

Step 6. Get Ready!

The next step is to organize the area prior to starting the engine. The DynaVibe should be placed near by in a location that will prevent it from falling or shifting during operation. A notepad and pencil/pen should be readily available to write down vibration readings while running if you're going to take multiple readings.

Step 7. Start Your Engine

Start the engine normally, watching for any shifting in cabling or equipment. Let the engine warm up to reduce wear during the high RPM data collection. Slowly increase the RPM of the engine until it has reached the desired RPM (usually peak static RPM, or cruise RPM). Verify that the DynaVibe RPM reading is accurate relative to the displayed RPM. If the RPM is erratic or incorrect, this may indicate that the optical sensor is not properly in-line with the reflective tape.

Step 8. Confirm DynaVibe Readings
Balancer - Real Time Display

The DynaVibe will now display the measured RPM and IPS-phase in real-time. Be sure the engine RPM remains constant during this process. The readings should settle down after a few seconds. If the readings are erratic, check the setup for lose connections, verify the alignment of the optical tach and tape, and be sure all wires are routed away from spark plug wires and sources of other electrical noise. For more troubleshooting tips, see the DynaVibe FAQ and manual.

As shown in the picture on the right, the DynaVibe displays the RPM, Vibration Amplitude in Inches Per Second (IPS), and Vibration Phase Angle (i.e. 133 degrees)

 

Step 9. Press the Averaging Button
Balancer - Real Time Display

Press the averaging button on the top right of the DynaVibe to start the balancer averaging multiple readings over several rotations. This process will take a few seconds at high RPMs and longer at lower speeds. A bar graph will display the progress of the averaging process. Note that the engine RPM should be steady during this process for maximum accuracy.

 

 

 

 

Balancer - Real Time Display

Once the averaging process is complete, the balancer will display the averaged values and hold it on the display The "average hold" mode is indicated by "AV" in the upper right of the display.

To switch back to the "real time" mode, press the average button again.

 

Step 10. Throttle back

Slowly return the engine to idle, allow the engine to run at the lower RPM for a minute to circulate oil and cool.

Step 11. Clock the Prop and Add Weight

Confirm that the ignition is off and mixture is full lean, then rotate the propeller until the small light at the back of the optical pickup comes on. This is the 0 Degree position. The angle indicated by the DynaVibe is the angle where the prop assembly is heavy. The angle is measured from the zero position to the indicated angle in the direction of propeller rotation. When the heavy point is identified, remove weight from this point. If there is no weight to remove from the heavy location, then add weight on the opposite side of the propeller (indicated angle +/-180 degrees).

Step 12. Repeat

Repeat steps 7 through 12 until the engine is below approximately 0.20 IPS. You should notice a substantial improvement in vibration levels once below that level.

Questions? Contact us at sales@rpxtech.com