StarJar
Well-Known Member
A couple years ago I built a plane with a VW engine that initially had a little bit of excessive vibration. I was on a shoestring budget, and knew I needed to balance the prop. For a few nights I thought hard about it and an idea popped into my head, but I wasn't sure it would work.
I got a piece of chalk and a stick about 4 ft. long, and duct taped the chalk to the end of the stick. Then I tied the tailwheel to a post, chocked the wheels, set the brake, removed the cowling, and ran up the engine to about 2,000 rpm. Then I took the chalk-stick and stood next to the engine behind the blowing prop. I moved the stick, with the chalk on the end, closer and closer to the spinning prop flange, while bracing it against the front exahust stack . Then I let the chalk just barely touch the spinning flange, for like, less than a second.
Then I shut down the engine and looke at the flange. There were white chalk marks on one side of the flange. I figured that must be the heavy side, and the flange was getting pulled in that direction as is spun. At this point a smile appeared on my face. Then I added a few washers to the other side off the flange and then ran the engine again. The engine vibration was gone and everything ran smooth! I looked around for wittnesses but there were none.
Anyway, maybe this has been done before, but I had never heard about it, and it was quick, cheap, and fairly easy. As I post this, I am hoping to save some people some money, but would really regret it, if someone got hurt. If you have larger engine, and want to try this, you should be very carefull, since even the VW produces a pretty strong blast of air. You could probably use a longer stick, and put a c-clamp on the lower cowling which you could put the stick through to brace it more securely in the blast, and then stand outside the prop arc as you move the chalk slowly toward the flange and touch it. This way you don't have to fight the prop blast with your body as you manuevre the chalk stick.
Note; if you painted the flange outer-edge black, the chalk marks could probably be seen better and more accurately. Also I kind of got lucky with my first washers, since it's kind of a guess how many to add.
Please don't send money, but if you think it's cool let me know. Also if you've heard of it being done this way before, or see a safer way to do it, you are also encouraged to reply. Thanks
added on April 6: Use the beginning of the chalk line, because there is a lag in the actual vibration.
I got a piece of chalk and a stick about 4 ft. long, and duct taped the chalk to the end of the stick. Then I tied the tailwheel to a post, chocked the wheels, set the brake, removed the cowling, and ran up the engine to about 2,000 rpm. Then I took the chalk-stick and stood next to the engine behind the blowing prop. I moved the stick, with the chalk on the end, closer and closer to the spinning prop flange, while bracing it against the front exahust stack . Then I let the chalk just barely touch the spinning flange, for like, less than a second.
Then I shut down the engine and looke at the flange. There were white chalk marks on one side of the flange. I figured that must be the heavy side, and the flange was getting pulled in that direction as is spun. At this point a smile appeared on my face. Then I added a few washers to the other side off the flange and then ran the engine again. The engine vibration was gone and everything ran smooth! I looked around for wittnesses but there were none.
Anyway, maybe this has been done before, but I had never heard about it, and it was quick, cheap, and fairly easy. As I post this, I am hoping to save some people some money, but would really regret it, if someone got hurt. If you have larger engine, and want to try this, you should be very carefull, since even the VW produces a pretty strong blast of air. You could probably use a longer stick, and put a c-clamp on the lower cowling which you could put the stick through to brace it more securely in the blast, and then stand outside the prop arc as you move the chalk slowly toward the flange and touch it. This way you don't have to fight the prop blast with your body as you manuevre the chalk stick.
Note; if you painted the flange outer-edge black, the chalk marks could probably be seen better and more accurately. Also I kind of got lucky with my first washers, since it's kind of a guess how many to add.
Please don't send money, but if you think it's cool let me know. Also if you've heard of it being done this way before, or see a safer way to do it, you are also encouraged to reply. Thanks
added on April 6: Use the beginning of the chalk line, because there is a lag in the actual vibration.
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