Great discussion. It remains widely believed that dropping a pound in weight will result in an increase in ball speed and an increase in revs off the hand. The reality though, is different (in the majority of cases). It is definitely true that a freely swinging armswing
(absent any applied force by the bowler) will not result in any increase in ball speed. However, this is also true in the majority of cases where force is applied in the swing cycle.
If the bowler applies acceleration in the backswing, a higher arc is created. Unless the swing "flattens" on the downswing, any acceleration applied will be directed INTO the lane and as a result, any excess acceleration will be absorbed into the lane, resulting in an actual LOSS in ball speed. However, it is true that an acceleration which is applied to the ball PRECISELY at the point when the arm is perpendicular to the approach, and especially if the acceleration has a slightly UPWARD direction, will result in a small increase in ball speed.
Also, balls that have mass removed from OUTSIDE the core WILL roll faster
than a similar ball that is overall, heavier than the ball that had the mass removed, even if rolled by a bowler who relies completely on a gravity-fed armswing. However.
ball manufacturers already know this. This is why there are different RG and differential values for balls that come in a variety of weights. If you look at most ball specs, you will see that in general, RG values INCREASE as ball weight drops. As a ball's RG increases, it becomes harder to "rev-up", because the center of mass has been moved farther out from the axis of rotation. Yes, a lighter weighted ball might seem"easier" to rev up, but it has to rev up a core that is..... actually harder TO rev-up. This is especially true when dropping from 15# to 14# in weight, for reasons that would take even longer to explain on this post. So, in summary, there is most often, little if no, difference in the amount of RPMS than can be generated by dropping down a pound in weight. But there is a much more realistic explanation on why dropping a pound in weight can in some cases, improve a bowler's performance, but increased ball speed and the ability to generate more revs are not among the reasons.
The real reason why some bowlers experience an improvement in performance by dropping in welght is because just a single drop in ball weight (a pound), has more
effect on the body's LEGS and their ability to carry a load, shot after shot, game after game, block after block. It is precisely due to leg fatigue that will often cause a bowler to increasingly rely on using their upper body to control and propel shots downlane. As the legs tire, bowlers increasingly resort to more muscle in the swing.
A muscled swing is a SLOWER swing. It also allows for more "grab" in the release, resulting in LESS revs being applied to the ball. A lighter ball will delay the onset of leg fatigue, allowing the bowler to rely on a more relaxed swing and grip as time goes on. Our legs begin to tire LONG before we feel it. It shows up when we begin to use our upper body more and more to execute shots.
Also a side note on the belief that a lighter ball can result in an increase in foot speed. Going to a lighter ball will also not normally have any effect on ball speed. In fact, it is often quite the opposite. A heavier ball will actually cause a slight INCREASE in foot speed when any of the following conditions apply:
1. The bowler utilizes an extended pushaway (vs. a hinged pushaway)
2. The bowler's legs are not conditioned enough to "carry" the ball's weight
throughout the approach.
In both of these instances, a bowler's foot speed will actually INCREASE--more so than if the same bowler was swinging a lighter-weighted ball.