Adding Weight to Reduce Swingweight? Origin of the Myth!

[travlerajm]

The laws of physics make it impossible for swingweight to be decreased by the addition of weight anywhere on the racquet.

However, when weight is added to the buttcap, many players feel that they can generate more racquet head speed on topspin groundstrokes. The reason is that swingweight (rotational moment of inertia) is not the only thing that limits racquethead speed.

On a topspin grounstroke, the racquet head is accelerated against the force of gravity. Adding a counterweight to the butt makes it easier for the wrist to accelerate the racquet head upward against the force of gravity. The increased inertia slows the forward acceleration, but the decreased moment can increase the vertical acceleration. It is analogous to using a counterweight to make it easier for a motor to lift an elevator.

So it is indeed possible to add weight to make it easier to swing a racquet faster, even though swingweight is still increased!

 

[bertrevert]

great I'm going to try this because precisely what you describe is happening I just cannot seem to whip the racquet head through fast enough. So I will add lead under the grip at the buttcap, or perhaps take off the cap and use bluetack to add some inside.

 

[kinsella]

Tjam:

I cannot buy that adding mass reduces the energy required to move that mass. Physics does not permit it. The "force" required to accelerate the racquet is not opposed to gravity, but "inertia." Opposing gravity is just how you keep it off the ground. The mass of a racquet is only the same as its weight when it is on earth. A weightless racquet in an orbiting space shuttle has the same mass that it had on the ground. The law of "inertia" tells us that a body in motion tends to stay in motion and a body at rest tends to stay at rest. The energy required to accelerate an object does so by overcoming inertia. The amount of inertia relates to an object's mass, not its weight.

Perhaps adding butt-weight allows a player to get used to having more weight to move generally. Then the swing seems easier, despite a very small increase in SW, because swinging calls for less "extra" energy compared just holding it or volleying after the mod.

Many people pick up my racquets, swing them a little and pronounce them head heavy when they are 12 oz and 4 pts HL! My sticks are simply heavier than what they are used to. Subjective descriptions can be unreliable. This goes for SW, too.

 

[ATXtennisaddict]

I'm gonna put a ton of lead in the butt tomorrow and see what happens. It's a prince racket so I'm gonna stuff the weight under the buttcap. Is that acceptable (compared to 'on the handle'?)

 

[travlerajm]

This effect works alongside several other effects that give the illusion that it is easier to swing the racquet upwards when you add weight to the butt. But for now, let's forget about the other effects, and consider only the effect in the OP.

Consider the extreme theoretical case of what would happen if you added several pounds of concentrated mass to the butt. In that case, the racquet head would pop up by itself due to the force of gravity, since the wrist would act as the fulcrum of the "seesaw." In that case, clearly no force is needed (from the wrist joint) to accelerate the racquet head upwards, because gravity does the work.

When you add a small amount of weight to the butt, you are simply giving your wrist a gravity assisted boost. Of course the acceleration at the elbow joint will be more difficult, but it will be easier for the wrist.

 

[travlerajm]

great I'm going to try this because precisely what you describe is happening I just cannot seem to whip the racquet head through fast enough. So I will add lead under the grip at the buttcap, or perhaps take off the cap and use bluetack to add some inside.

If you add a couple of ounces to the the butt, you may need to reduce the tension by 5-10 lbs to compensate for the lower power level.

 

[Shroud]

The laws of physics make it impossible for swingweight to be decreased by the addition of weight anywhere on the racquet.

However, when weight is added to the buttcap, many players feel that they can generate more racquet head speed on topspin groundstrokes. The reason is that swingweight (rotational moment of inertia) is not the only thing that limits racquethead speed.

On a topspin grounstroke, the racquet head is accelerated against the force of gravity. Adding a counterweight to the butt makes it easier for the wrist to accelerate the racquet head upward against the force of gravity. The increased inertia slows the forward acceleration, but the decreased moment can increase the vertical acceleration. It is analogous to using a counterweight to make it easier for a motor to lift an elevator.

So it is indeed possible to add weight to make it easier to swing a racquet faster, even though swingweight is still increased!

would this affect the kick serve the same way?