I have been a believer in Dynamic Prop Balancing ever since I had the Val’s prop balanced shortly after she was flying. I frequently have pilot passengers remark on the smoothness of the engine in cruise, and I think that the balancing is a large part of this. I have often wondered if the balance might shift over time with wear, but haven’t had a chance to just check it, and still don’t know for sure. But I WAS able to take advantage of a great offer by Walt Aronow up in Fort Worth to get Louise’s prop balanced today, and learned a bit about how it might shift.
Louise had her prop balanced about four years ago during an annual, and told me then that she really couldn’t’ feel any difference afterwards. Shortly thereafter, she had a strange grove appear in the prop hub that might have been caused by the spinner (even though it had plenty of static clearance), and had it dressed out by a prop shop. This entailed removing and replacing the prop, as well as some material removal near the root of one blade. Ever since then, we have talked about getting it rebalanced to see if there had been a significant shift, but never quite got around to it until Walt’s discount for this month ($150, with $25 of that going to VAF as a donation) appeared to us to be an offer we couldn’t refuse. That plus it was a gorgeous day to fly across Texas, and Louise was out of town, so I would be the one to do the flying!
Doug met us when I arrived after an uneventful trip up from Houston, and offered to take a few pictures as we went.
http://picasaweb.google.com/VansAirForce/PropBalance_WaltPaul#
Cowl removal was quick, and before we got started, Walt volunteered to grease the prop since we had things opened up. After that, he began to set up for the tests. I could tell right away that he had the latest equipment for the job – compact, rugged, and simple to attach. The last time I had the Val done b a traveling balancing fellow, his equipment looked like it had been salvaged from a castle laboratory in Transylvania, right down to an X-Y plotter and an oscilloscope. Walt’s gear looked like it could land on a beach with Navy Seals and not be damaged. A small accelerometer was bolted to the engine spine, and a light sensor attached to the top of the Number 2 Cylinder rocker arm cover screw. A patch of reflective tape on the back of the prop blade for the light sensor to detect the blade finished things up. Walt taped the cables along the leading edge of the wing so that he could stand well clear, and we were set to go.
After that, my job was simple – run the engine up to cruise RPM and hold it there while took a ten second vibration sample. Full aft stick for this, please (and a rope tied to the tail wheel and secured to Walt’s truck as well…)! After each of the four runs, Walt did some magic and calculated the weight and location of the required balance weights, which are nothing more than AN bolts, nuts, and washers attached to the flywheel holes. The system tells him how much weight to attach to which positions, and he goes through his hardware collection using a sensitive gram scale to find combinations that give him what he needs. Each run was better than the last, and we ended up with a balance of 0.024 inches/second – about as close as you can actually measure. And there was no question that the engine was smoother after the balancing. We started out at about 0.24, so that was an order of magnitude improvement.
The whole thing took about two hours, which gave us plenty of time to drive over to Justin, TX with a gang of the 52F regulars for a great Chicken Fried Steak (That phrase is always capitalized in Texas for some reason…) and a bunch of pilot talk before I saddled up for the smooth trip back to Houston. Clearly an improvement well worth the cost – even if you factor in the fuel for the trip. But hey, it was a nice day, so who am I kidding – I would have been flying anyway….
Thanks Walt for a great job at a great price – and to Doug for the photos!
Paul
Louise had her prop balanced about four years ago during an annual, and told me then that she really couldn’t’ feel any difference afterwards. Shortly thereafter, she had a strange grove appear in the prop hub that might have been caused by the spinner (even though it had plenty of static clearance), and had it dressed out by a prop shop. This entailed removing and replacing the prop, as well as some material removal near the root of one blade. Ever since then, we have talked about getting it rebalanced to see if there had been a significant shift, but never quite got around to it until Walt’s discount for this month ($150, with $25 of that going to VAF as a donation) appeared to us to be an offer we couldn’t refuse. That plus it was a gorgeous day to fly across Texas, and Louise was out of town, so I would be the one to do the flying!
Doug met us when I arrived after an uneventful trip up from Houston, and offered to take a few pictures as we went.
http://picasaweb.google.com/VansAirForce/PropBalance_WaltPaul#
Cowl removal was quick, and before we got started, Walt volunteered to grease the prop since we had things opened up. After that, he began to set up for the tests. I could tell right away that he had the latest equipment for the job – compact, rugged, and simple to attach. The last time I had the Val done b a traveling balancing fellow, his equipment looked like it had been salvaged from a castle laboratory in Transylvania, right down to an X-Y plotter and an oscilloscope. Walt’s gear looked like it could land on a beach with Navy Seals and not be damaged. A small accelerometer was bolted to the engine spine, and a light sensor attached to the top of the Number 2 Cylinder rocker arm cover screw. A patch of reflective tape on the back of the prop blade for the light sensor to detect the blade finished things up. Walt taped the cables along the leading edge of the wing so that he could stand well clear, and we were set to go.
After that, my job was simple – run the engine up to cruise RPM and hold it there while took a ten second vibration sample. Full aft stick for this, please (and a rope tied to the tail wheel and secured to Walt’s truck as well…)! After each of the four runs, Walt did some magic and calculated the weight and location of the required balance weights, which are nothing more than AN bolts, nuts, and washers attached to the flywheel holes. The system tells him how much weight to attach to which positions, and he goes through his hardware collection using a sensitive gram scale to find combinations that give him what he needs. Each run was better than the last, and we ended up with a balance of 0.024 inches/second – about as close as you can actually measure. And there was no question that the engine was smoother after the balancing. We started out at about 0.24, so that was an order of magnitude improvement.
The whole thing took about two hours, which gave us plenty of time to drive over to Justin, TX with a gang of the 52F regulars for a great Chicken Fried Steak (That phrase is always capitalized in Texas for some reason…) and a bunch of pilot talk before I saddled up for the smooth trip back to Houston. Clearly an improvement well worth the cost – even if you factor in the fuel for the trip. But hey, it was a nice day, so who am I kidding – I would have been flying anyway….
Thanks Walt for a great job at a great price – and to Doug for the photos!
Paul
Last edited: