Tom(?), It is certainly possible to put the prop on the crankshaft in a different position than the one in which it was previously installed. And the orientation of the prop on the crank can affect the vibration of the prop/engine combination. You can search the Ercoupe archives and read lots of discussion about this topic. My Alon service manual tells one how to index the prop, unfortunately, you can't index it exactly where they say to put it, because the bolt holes just don't line up that way. Another thing to look for is anyplace where the engine, exhaust, carb air box, etc is hitting the engine mount, cowling, firewall, etc. This can also cause a change in vibration. Sometimes a heat muff gets reoriented slightly during annual and hits the cowling, which will not only cause some vibration to be transmitted into the airframe, but can also eat a nice hole in the cowling, too. (At least it can on an Alon.) I would research the archives and read about prop indexing, and also inspect for anything that is not properly clearanced from the airframe. Of course, carburetion, intake leaks, etc can also cause vibration. Hope this is of some help. Best Regards,
Wayne DelRossi Alon Aircoupe N5618F "Life begins at 50...... knots." **************It's only a deal if it's where you want to go. Find your travel deal here. (http://information.travel.aol.com/deals?ncid=aoltrv00050000000047)
