[Danijel0frk's] friends may call him unbalanced, but his propellers are always spot on. His well-balanced props are thanks to this magnetic balancer he built from scrap PC parts and pilfered office supplies. Propeller balance has always been important for radio controlled models. Flying for hours with a poorly balanced prop can wreak havoc on an air frame and the radio equipment within. With today’s drones and R/C vehicles carrying cameras, accelerometers, and gyros, propeller balance has become even more important. A vibrating propeller can ruin a picture at best. At worst it can throw gyroscope and accelerometer readings off and cause a crash.
[Danijel0frk's] balancer is based upon several commercial designs. A steel shaft from a CD-ROM drive is cut and the ends ground to points. A propeller to be balanced is mounted to the shaft. Propellers don’t all have the same hole size so two pen tips are pressed into service as self centering mounts. [Danijel0frk's] picture shows one tip pointing toward the prop hub while the other points away. The balancer will work better if both tips point inward, ensuring the shaft sits directly in the center of the propeller hub’s hole. Hard drive magnets suspend the prop and shaft from a drive rail and wood frame. We should note that this type of balancer will only perform a static balance. Dynamic balance would require the propeller to be spinning on a motor with force sensors on the shaft. To perform a static balance, material is added to or removed from the propeller until it balances in any orientation. Click past the break for a good tutorial video on balancing.