So, you buy a new engine, a new prop, bolt her on and think everything is playing friendly together under the cowl. WRONG!! I mean how bad can it be, everything feels fine. Well let me tell you, it aint. Read on.
After some advise from the aerobatic guys at the airport, they convinced me to go ahead and spend the $200.00 to get a dynamic prop balance. Why? Well engine life, prop life, airframe life, and overall comfort are the reasons. Here is how it works.
First, find a reputable prop balancing guy. They are not created equally. My guy was Andy, he did a terrific job. Second, be prepared to pull the top cowl. Yes them pesty pins have to be pulled out.
Then a little transducer gets bolted to the engine, close to the prop. It will measure the "throw" of the engine. Meaning how much the engine is moving. Just like a tire balance.
Next a little light pickup is taped to the cowl with a piece of reflective tape on the prop. This is how the computer knows where the prop is in relation to the vibration it picks up.
Here is what the little gismo looks like. It tells you the "throw" in inches, and how many degrees from the reflective tape on the prop the weight needs to go.
Tape the wires back
And run the engine. Here are my findings
1st run, as flown from day 1, no changes, was .35". Meaning the engine is moving in the cowl, near the prop .35". What's that mean? An average factory delivered new piper archer moves .25". So I have roughly 50% more movement than that. Still, not bad. But I was disappointed to see it off that far off. I was now suspecting that his little gismo computer was scamming me. I kept a close eye on all this as the next few runs unfolded.
Next we added the weight to the flywheel, just nuts and bolts, weighed precisely with a little digital scale, to the gram. Several runs were made, all at 2000rpm as this was where is greatest "throw" was found to be.
Finally, the little gismo was reading .025" WOW!!...... Now really, can this be? Again I had suspicions of being scammed. He said anything under .1" is very good and he usually gets it to .05". OK...so I paid him, reluctantly, as I thought I was getting scammed by a little computer.
Results.... WOW!! What a difference. I didn't think it was out of balance before I started, but now, it is so much smoother. Quieter, and I feel better knowing that my engine, prop and airframe are happier too.
So go ahead, get it done, you will be glad you did.
To get your prop balance done in the Atlanta area, Freeman Aviation