Tech Talk

Torque comes up all the time in shaft selection. What is torque? Is it important? What”s the right shaft torque for you? Should you even care?Torque is a feature in shaft selection and you can usually find a shaft’s torque in the catalog of the shaft or club manufacturer. But, what is torque?

The basic definition for torque in a golf shaft is a measure of the shaft”s resistance to rotational twisting. Many golfers who come to our shop ask questions like:

“What rotates? How does torque work?”
“Is low torque better than high torque?”
“Is torque important?”
“What shaft torque is right for me?”

We sought out the experience and knowledge of our contacts at Titleist, Harrison Shafts, Fujikura and A.J. Tech to get answers to these questions.

What rotates? How does torque work?

The mass of the clubhead is much greater than the mass of the shaft tip. The clubhead resists being put into motion at the takeaway and resists reversing direction during the downswing. This resistance causes the shaft to flex and the tip to twist. As the tip twists the clubhead rotates.

Referring to the Harrison Shaft website (www.harrison.com) article about shaft lead and lag:

“On the down swing, at around the 10 to 11 o'clock hand position, a golfer will generally engage his initial load. “Load” is the force you exert to bring the club down toward the ball. In response, the golf shaft will lag. Shaft lag results as the golf shaft bends backwards in the direction of the swing plane.”

This causes the clubhead to rotate out.

“Upon reaching the peak of his initial load, the acceleration rate will drop while the player's swing speed continues to increase. Therefore, at around the 9 o'clock position, the shaft will transition into a leading position, bending forward in the direction of the swing plane.”

This causes the clubhead to rotate in.

Since the center of gravity (COG) of the clubhead is not in line with the axis of the shaft, there is both a bending and twisting force applied to the shaft during the swing. The lower the torque value the greater the shaft”s resistance to rotational twisting and, consequently, the less the clubhead will rotate as well.

“Is low torque better than high torque?”

The answer to this depends on your swing. Torque values are not measured like shaft weight or kick point. Shaft weight is measured with a gram scale. Kick point is measured with a flex machine. These values are not arbitrary. Torque is different.

Torque is measure by clamping a shaft at both ends and then twisting the butt end (where the grip goes). The number of degrees the tip of the shaft rotates from this twisting is the measure of torque. So a torque value of 4.5 means the tip rotated 4.5 degrees when the shaft was twisted. However, who decides how much pressure or force is applied during the twisting? Obviously, a force of 50 pounds twisting the shaft will rotate the tip more than a force of 5 pounds. There is no standard measure of force used to determine torque, which means that it may be “relative” to the force of your swing.

Since the center of gravity (COG) of the clubhead is not in line with the axis of the shaft the shaft will bend and twist in every swing, regardless of speed. However, the faster the swing tempo the more the shaft will move.

Again, from the Harrison Shaft website article:

“During the swing the golf shaft will stay leading unless the golfer engages a second force, commonly known as delayed release or wrist snapping, at 7 to 8 o'clock hand position. A moderate delayed release will likely bring the golf shaft to a relatively straight position. The shaft will lose power at this point. A strong delayed release will cause the shaft to lag again. This results in a powerful kick to the ball at impact."

In general, the golfer with the quicker tempo and faster swing speed will benefit from a lower torque shaft if he can release his hands properly. The stronger his delayed release the faster the shaft recovery he needs to optimize the performance of his club. A higher torque shaft won”t get the clubhead square quickly enough for his swing.

Golfers with moderate swing speeds or smooth tempos don”t generate as much force as their faster counterparts. For these golfers a low torque shaft will tend to lead forward at impact and may not let the clubhead rotate enough to provide the kick they need to get extra distance. For slower golfers or golfers who cannot release their hands quickly a low torque shaft is likely to cost them distance or reduce the playability of a club.

“Is torque important?”

There are four criteria for evaluating a shaft: 1) Weight 2) Flex 3) Torque 4) Kick point. Torque ranks third in importance. A lower torque shaft that resists bending and twisting will prevent the clubhead from rotating and that should result in more consistent ball dispersion.

We know that torque measures are somewhat arbitrary. This factor reduces torque”s importance as a reliable indicator of shaft value. Nonetheless, the more expensive shafts have torque measures less than 5 degrees, irrespective of weight and flex. If you are willing to spend $50 (or more) for a replacement shaft, or $30 (or more) upcharge for a non-stock shaft then torque is probably important.

What shaft torque is right for me?

As clubheads have gotten bigger the tendency for the clubhead to rotate has also increased. Yet, getting a shaft with the lowest torque—a shaft with the least amount of twisting—may not be the answer to getting longer, straighter drives.

In general, a good rule of thumb about shaft selection is as follows:

Low clubhead speed + consistently square ball strike
=>medium torque, light to medium weight, light to regular flex

Low clubhead speed + inconsistent ball strike
=>Med/high torque, light to medium weight, light to regular flex

Moderate head speed + consistently square ball strike
=>medium torque, medium weight, regular flex
Moderate head speed + inconsistent ball strike
=> med/high torque, medium weight, regular flex

High clubhead speed + consistent ball strike
=>low torque, heavy weight, stiff flex
High clubhead speed + inconsistent ball strike
=>medium low torque, medium heavy weight, stiff flex

Low torque values are less than 3.0 degrees. In general, shafts with torque values under 2.5 degrees are too difficult for most golfers to use.

Medium torque values are between 3.0 and 5.0 degrees. These are the most common torque values available in high quality shafts.

High torque values are over 5.0 degrees, and are common in inexpensive shafts.

The better golfer you are, regardless of swing speed, the more you will notice differences in torque.

At Klees Golf Shop we carry shafts from Fujikura, Graphite Design, UST Pro Force, A J Tech, Grafalloy and Harrison. We have nearly 100 years of experience shafting clubs and know what works and what doesn”t. We also have a Accusport Vector Pro launch monitor to help you test which shaft is best for your swing.

If you have a question about a shaft or would like to schedule an appointment to use the Vector Pro, call us toll free at 866-241-9687. Ask for Charlie.

Much of the information in this Tech Talk article came from the following sources:

Dave, Harrison Shafts
Chad, Fujikura Shafts
Al, A.J. Tech
Chris McGinley, V.P. Marketing, Acushnet Golf
 

Bounce--or bounce angle--measures the angle of the back edge of the sole to the leading edge of the face. Sure it's confusing--that's why we've included a diagram.

Bounce or bounce angle measures the angle of the back edge of the sole to the leading edge of the face. If you put a clubhead on a countertop (upright) and look at the sole straight on you'll notice that the back of the sole is off the countertop, just like the leading edge of the face. The relation of these two edges is called bounce angle.

The illustration below shows how a wider sole with less bounce angle has the same “effective bounce” as a narrower sole with a greater bounce angle.

and wedges (wedges with 54 to 57 degrees loft) typically have 10 to 14 degrees of bounce so that they can easily sweep through the sand, tall grass or soft ground. Gap wedges (wedges in the range of 51 to 53 degrees of loft) have 0 to 10 degrees of bounce, and Lob wedges (wedges with 58 to 64 degrees of loft) have 4 to 14 degrees of bounce. Some players use a 60 degree wedge with a lot of bounce in the sand while others will use a 60 degree wedge with relatively little bounce in the fairway.

Golfers who strike down at a sharp angle when hitting the ball with a wedge can put a lot of back spin on the ball. These players might benefit using wedges with very little bounce (less than 8 degrees), but they are a minority of golfers. Most golfers are better off with more bounce (10 to 14 degrees), not less.

High Moment of Inertia or MOI is the what's HOT in driver head design. It's also what's been increased in putter head design, wide soled irons and any other item where more mass has been added to the back, side or bottom of the clubhead. So what is MOI?If you are thinking about getting one of the new square drivers you might be interested in what the hype is about. A good place to start is Tom Wishon's article about MOI vs Head Shape in his October, 2006 eTECH Report. enewsletter

Here is an overview of the physics pertaining to MOI. For those of you who did not study mechanical physics a quick review of some basic principles is useful for understanding MOI.

1. A body at rest stays at rest and a body in motion stays in motion unless an outside force intervenes. In a golf swing the clubhead is the force that acts on the ball (which is at rest) and the ball is the force that acts on the club head (which is in motion).

2. If a net force acts on an object it will cause an acceleration of that object. This is Newton's 2nd Law of Motion. Newton's 3rd law states that if one object exerts a force on a second object--e.g., a club head hitting a golf ball--the second object (golf ball) exerts an equal and oppositely directed force on the first object (club head).

3. Moment of inertia (MOI) is defined as a point mass about the center of rotation and is calculated to determine an object's resistance to rotation. Moment of inertia is also called rotational inertia.

The greater the mass is away from the center of rotation the more resistant it is to rotating. For example, when a figure skater pulls in her extended arms her moment of inertia decreases and she spins or rotates faster. (You might read the term moment arms" in conjunction to MOI. The "arms" allude to the figure skater, which is an easy visual for understanding this concept).

The club head's interaction with the golf ball produces a whole set of physical challenges. First, the force of the club head causes the ball to go into motion and accelerate. The force has to be applied so that the ball is launched at an angle that causes the acceleration to keep the ball going forward.

Second, the force of the ball on the club head causes it to rotate. When the clubface rotates the ball accelerates right or left depending on the rotation. We can't control the force of the ball so the club makers want to control the effects of that force, by controlling the flex and torque of the shaft, as well as the MOI. Ways to increase MOI, which increases the resistance to rotating, include adding mass to the club head; distributing the mass over a larger area; adding weight to the perimeter, and concentrating the weight away from the face.

The center of gravity (COG) of the club head is positioned to minimize rotation during the swing and optimize the launch angle when the club face hits the ball. The COG of the current generation of 460cc drivers tends to be low and deep or toward the back of the head.

So, why do all of the drivers claim to have a high MOI and "optimal" COG and yet few players can hit equally well with all the drivers?

The physical differences between one person's swing and someone else's are the wild cards in the equation. This is why a launch monitor is probably the only way a golfer can really determine the best driver"head/shaft/grip combination"for his swing.

References: http://www.grc.nasa.gov/WWW/K-12/airplane/cg.html; Titleist, Cleveland Golf and Nike Golf; /Cliffs Quick Review Physics, copyright 1993