Thursday, January 7, 1999

Dual Plane Balancing

We receive lots of calls about balancing and one of the first questions is always, "What is DUAL PLANE BALANCING".
If you read the book on it, and you had a background in engineering and physics, you could get a good understanding of it. The two terms that are used in the explanation are Force and Couple balancing. What we are going to attempt to do is reduce all of this down to a non-technical explanation.
Lets go back many years to tire balancing. Your rim and tire assembly was mounted on a shaft and then placed on a frame with the shaft resting in a ball bearing V fixture. The tire assembly would then rotate around until the heavy part came to rest at 6 o’clock. A wheel weight was then placed at 12 o’clock on one side of the tire. You kept adjusting this weight until the tire would not move regardless of how you repositioned it in the V fixture.This process is called, Static or Force balancing.
Then an improvement was made in this process. Instead of putting all the weight on one side of the rim, it would be split with ½ of the weight going to the inside. This was the first form of Couple balancing in the tire industry. Not perfect, but an improvement.As years went by, and the advent of much wider tires came into being, the need for Couple balancing increased.
We know have electronic tire balancers that spin the tire assembly and calculates the amount of weight needed to Force balance. Then it calculates what amount goes on the inside of the rim and what goes on the outside. This is Dual Plane balancing of a tire.
How does Dual Plane Balancing apply to the Briggs Crankshaft ?
A bob weight is attached to the rod journal of the crankshaft that represents 100 % of the rotating weight and a percentage of the reciprocating weight. This assembly is then placed on the ball bearing V’s of the balancer. It is then spun up to the operating RPM. Now the balancer can read both sides of the crankshaft and precisely tell the operator the amount of weight that needs to be added or removed from the left or right counter weight.This completes the Force and Couple (Dual Plane) balancing.
Special Note:If you change the connecting rod and/or piston, wrist pin and rings, the crankshaft may need re-balancing.