Prop Balancer Revisited
By John Steere, EAA 301134, email@example.com
John Steere’s beautiful BD-4 appeared in a recent issue of Experimenter. John has enjoyed hundreds of hours flying his supercharged Ford (T-Bird) V6 powered experimental aircraft, including multiple trips to Oshkosh. As an avid reader of CONTACT! Magazine, he read the article on propeller balancing we first published in CONTACT! and again in last month’s Experimenter - and took it to the next level. He is sharing that info with us.
I read with considerable interest the article “Sensitive Static Prop Balancer,” by Paul Lipps. Balance has not been a concern with my three-blade Warp Drive prop because it runs very smoothly, but I had a significant out-of-balance condition on both of the main gear wheels on my BD-4. It looked like fabricating a wheel balance rig would be my next project, but after reading Paul’s article it became evident that the prop balancer could be used for both prop and wheel balancing with a simple adaptation.
Like most true experimenters, I didn’t follow the plans exactly. The differences are of little consequence and simply suit my preference and available materials. The tube is 1-inch aluminum from the ACE Hardware aviation department. The ferrule was changed from aluminum to plastic, and the diameter in the center was reduced by 1/16 inch. This creates space to wrap a piece of low-density foam tape around the center of the ferrule.
The foam tape provides enough friction against the inside of the tube to ensure the ferrule will not move unless deliberately repositioned. The aluminum cap was eliminated by turning the indicator disc’s outside diameter (OD)to match the tube OD. While on the lathe, a wire retainer disc was turned with a counterbore large enough to accept a knot tied in the end of a piece of 0.032-inch stainless safety wire.
To adapt the balancer for my wheels, simple plastic adapter rings are positioned on the tube OD in positions that line up with the inside of the wheel bearings. The inside dimension of these adapter rings provides a snug fit to the tube so they will stay in place while sliding the assembly through the wheel bearings.
Rather than taking the time to make that nice-looking steel stand shown in the article, aircraft hardware bits from my spare parts bin were attached to the opposite end of the safety wire. This allows the balancer to be suspended in space by clamping the nut in the end of my drill press chuck. The spindle return spring on the drill press is sufficient to hold the wheel in place without clamping the drill press’s spindle.
It works great! Thanks to Paul Lipps and the gang at CONTACT! Magazine for the excellent article.