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Dynamic balancing is the practice of spinning an object at a high rate of speed and adjusting the balance or removing the vibration by subtracting or adding weight. This is the most common method of balancing a drive shaft, an engine crankshaft or an automobile tire. Once the object has been brought up to a predetermined speed, a computer reads the material that the dynamic balancing machine's on-board sensors provide. The recommended amount of weight to counter-balance a heavy or light spot is then added or removed from the item being balanced.
Dynamic balancing is preferred over static balancing in most high-performance situations due to its extreme accuracy. In most cases, the object can be perfectly balanced within one or two grams. Mallory metal, which is a very heavy metal as well as extremely expensive, is typically added to crankshafts in order to balance them. The Mallory metal is inserted into a pre-drilled hole and welded in place. Fine tuning is accomplished by drilling small holes in the crankshaft's counter weights and removing small amounts of weight.
By spinning an object at or near normal rotational speeds, dynamic balancing replicates real-world performance and assures that an object will perform at its best when installed. If not for the dynamic balancing of drive shafts and crankshafts, extreme cases of wear would include bearings burning up in a very short time, engine blocks tearing apart because of vibration, and the vehicle itself could actually ripping itself apart. Dynamic balancing of tires allows the tire to last for many thousands of miles without cupping or wearing the tread unevenly.
In many machines, multiple parts and often entire assemblies undergo dynamic balancing. Outboard boat engines undergo balancing so that the vibration levels transmitted to a user's hands are minimized. Fishing reels are balanced to provide comfortable cranking with a minimum of vibration passed along through the handle. Even high-end countertop electric mixers are balanced to allow for steady and quiet counter-top mixing of ingredients.
While a must for most high-performance applications of anything that spins or goes around, dynamic balancing finds its way into everyday household items that may not be considered high performance. Electric mixers, blenders, beaters and rotisseries are balanced to provide smooth, long-lasting operation. Items found in the garage such as electric saws, drill motors and lathes undergo balancing to provide long-lasting and durable tools.