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A prop balancer is a device used in the aviation field to balance airplane propellers. This device allows the propeller to be balanced by showing the operator which side of the propeller is heaviest. The propeller is placed on a shaft and then the shaft is placed into the balancer. The propeller is then placed into a horizontal position and released. The heavy side of the propeller will sink to the bottom.
Once the propeller has been placed on the prop balancer and the heavy side has been identified, there are several ways the propeller can be balanced. Some metal propellers have an area of heavy metal near the hub which can be drilled to remove weight and balance the prop. On wooden models, the heavy side of the propeller can simply be sanded until the prop levels.
A prop balancer is an extremely important tool. An unbalanced propeller can cause engine and airframe damage that could lead to a crash. An out-of-balance propeller will cause the airplane to vibrate and be hard to control. A propeller that has not been balanced also could break during use. In some instances, the heavy end could crack and break off in flight without notice.
A prop balancer can be built at home with modest tools. All that is needed is a perfectly straight rod–heavy enough to support the propeller, two stands that will support the rod evenly and a way to secure the propeller that is evenly weighted on both sides. Mount the prop on the rod, set it on the stands and let gravity do its work.
A prop balancer is a critical tool in model airplane building as well. There are many different types of prop balancers to choose from in scale model building. It is certainly still critical in model airplane building since there is no pilot to counter the effects of an out-of-balance propeller. If considering a model airplane build, invest in a quality prop balancer designed for the purpose of model building.
Outboard boat motors as well as ship propellers are also balanced on a prop balancer. An out-of-balance boat propeller could cause bearing failure as well as seal leakage on thru-hull propeller shafts. Skilled propeller repair personnel are not very common in most places; however, once located, will typically require an appointment as they are usually busy. Many out-of-balance props not only need balancing, but require straightening as well.