Overall length vs Clubhead Speed

[Ginker]

Wondering what effect cutting down a driver will have on clubhead speed.. and anything else for that matter.. thnx

[jvincent]

IF, and it's a very big if, you can keep your hands moving at the same speed for any driver length, the clubhead speed will change about 6% for every 1% if increase or decrease since it's moving in a circle.

The reason it's a big if is that most people can't get their hands moving as fast with a longer club so the net gain in clubhead speed is smaller, if any. And there are also cases where going shorter actually results in higher clubhead speed.

Total weight also plays a big role.

[Ginker]

I am thinking of playing my driver at 44" Just wondering what all will be affected by the shortening of the shaft. I am correct in assuming that since the 1 inch will come off the butt end it will not affect the flex?

[Chieflongtee]

Maybe slightly(flex). The sw might have to be readjusted. You might end up hitting it farther since the odds of you hitting the centre of the face will be greater.

[BC MIST]

the clubhead speed will change about 6% for every 1% if increase or decrease since it's moving in a circle.

Do you have the source for this ratio? It does not make sense to me.

If we get 2.5 yards (app) per mile per hour of club head speed, and I swing a 45" driver, 100 mph, the ball flies 250 yards. Then, if I shorten the club to 43.2" my swing speed will be 78 mph and the ball will go 195 yards, all other things being equal. This is based on the 6% loss of club head speed per 1% decrease in length.

BUT, if I can swing a 43" driver 100 mph, it goes 250 yards. By lengthening the club to 45.2", my swing speed goes to 134 mph and the distance is 335 yards. THERE IS NO WAY THAT THIS HAPPENS. To make this ratio even more absurd, extend my driver to the conforming limit of 48" and I will swing the club at 190 mph, flying 475 yards. Wouldn't this be nice?

By shortening the driver 1", the butt flex will be stiffer, but the tip flex will not change. If you (SC) have a rapid transition move at the start of the downswing, the stiffer butt won't hurt. If you have a smooth transition, the shaft will definitely feel stiffer. There should be no change in the ball's trajectory because the trajectory is more greatly influenced by where the wrist cock axis releases.

By shortening 1", the swingweight goes down, the MOI goes down, unless you add some lead tape to the back of the head or a tip weight, if the club is to be reassembled.

[jvincent]

Do you have the source for this ratio? It does not make sense to me.

Since the club is now 1% longer, the radius of the circle that the clubhead travels is 6% (2*pi*1%) longer.

However, the starting assumption was that the angular velocity of your hands stayed the same, which means the angular velocity of the clubhead stays the same, which means its linear velocity (AKA clubhead speed) increases.

It's very unlikely that you could actually swing two clubs at different lengths at that same angular velocity without also changing the weight.

[Chieflongtee]

If the club is shortened by 1 inch and the swingweight is not adjusted the butt frequency of the club will go up by 7 cpms. If the club is shortened by 1 inch and the swingweight is readjusted the change in frequency will be about 1 cpm. The swingweight can also be reajusted with the use of rat glue. In this particular case 12 grams would have to be added to restore the original sw.

[Ginker]

Since the club is now 1% longer, the radius of the circle that the clubhead travels is 6% (2*pi*1%) longer.

However, the starting assumption was that the angular velocity of your hands stayed the same, which means the angular velocity of the clubhead stays the same, which means its linear velocity (AKA clubhead speed) increases.

It's very unlikely that you could actually swing two clubs at different lengths at that same angular velocity without also changing the weight.

WOW.. lol. I thought I was back in highschool physics reading that.. Very nice JV

[Started2k3]

Since the club is now 1% longer, the radius of the circle that the clubhead travels is 6% (2*pi*1%) longer.

However, the starting assumption was that the angular velocity of your hands stayed the same, which means the angular velocity of the clubhead stays the same, which means its linear velocity (AKA clubhead speed) increases.

It's very unlikely that you could actually swing two clubs at different lengths at that same angular velocity without also changing the weight.

Not correct.

Circumference = 2*pi*r

Big circle:
C2 = 2*pi*r2
Small circle:
C1 = 2*pi*r1

divide the big circle by the small circle:
C2/C1 = (2*pi*r2)/(2*pi*r1)

Simplify:
C2/C1 = r2/r1

So if r2 is 1% larger than r1, then C2 is 1% larger than C1 and velocity2 is 1% faster than velocity1.

So the rate is 1% gets 1%.

If you would like I can do the same calculation from an angular velocity pov.

Charles

[Ginker]

Not correct.

Circumference = 2*pi*r

Big circle:
C2 = 2*pi*r2
Small circle:
C1 = 2*pi*r1

divide the big circle by the small circle:
C2/C1 = (2*pi*r2)/(2*pi*r1)

Simplify:
C2/C1 = r2/r1

So if r2 is 1% larger than r1, then C2 is 1% larger than C1 and velocity2 is 1% faster than velocity1.

So the rate is 1% gets 1%.

If you would like I can do the same calculation from an angular velocity pov.

Charles

[Chieflongtee]

[Started2k3]

What's the problem?

[dreaded_snowman]

What's the problem?

Just tell 'em you do that math during your backswing on all par 5's.

[jvincent]

Puts a Physics smackdown on me.

That's what I get for not doing the math first.

[Started2k3]

Just tell 'em you do that math during your backswing on all par 5's.

Everybody should have their own "ClearKey".

That's what I get for not doing the math first.

Like BC said earlier "It does not make sense to me." Which makes him the first to intuitively see the error. I thought the same thing, and verified the math. I have this responsiblity because my wife is a high school math teacher and if I let something slip by I will never hear the end of it.

I am sure that if this error went unchecked, it would be quoted on TGC in a couple of weeks.

Charles

[Chieflongtee]

[

What's the problem?[/QUOTE]

There is no problem. I am simply amazed by your knowledge.

[jvincent]

I am sure that if this error went unchecked, it would be quoted on TGC in a couple of weeks.

It might still make Golf Digest.

As an excuse for failing Physics 101, I was applying the 2*pi*r factor because I was thinking purely of angular velocity being translated to linear velocity and "forgot" that this would cancel out when looking at the ratio of the two clubhead speeds.

Thankfully, those brain cells are no longer required in my day job as they have long since been rendered dormant by alcohol.

[BC MIST]

Like BC said earlier "It does not make sense to me." Which makes him the first to intuitively see the error. I thought the same thing, and verified the math.

Whew!! I thought that after 30 years of teaching math, I had lost it.

[covanant]

I have a headache

[mcgoo]

Very impressive, could you translate the math to golfer's language, how much yardage would be lost? I have wondered what the yardage impact would be of shortening my driver. I know I would be straighter.

[jvincent]

Without using math, since I clearly suck at it right now, it's hard to say if you will lose distance by going shorter.

You may actually be able to swing the shorter club faster, which would mean more distance.

Similarly, even if you swing the shorter club at the same speed or slightly slower, if you hit it in the center of the face more often, you will gain distance.

[covanant]

The last driver i had at 44 inches was alot straighter,but did notice a lower trajectory and less distance but not much.

[Started2k3]

Very impressive, could you translate the math to golfer's language, how much yardage would be lost? I have wondered what the yardage impact would be of shortening my driver. I know I would be straighter.

If BC (negligible accuracy change assumed) was to shorten his driver by half an inch (~1%), then he would lose 2.8 yards based on the shorter driver alone.

However, he would gain a very small part of that back because he would now be able to swing the club with a higher angular velocity (equivalent term to rpm), because the moment of inertia for the entire club (MOI is the relationship between mass and its distance from the point of rotation) has decreased and this assumes that the torque/force that he can apply to swinging the club is the same.

So overall BC would probably barely be able to tell the driver is shorter based on the distance obtained.

If he was to increase to the RCGA limit of 48" he would only be able to obtain less than 16.6 yards. But he would argue at the expense of all his accuracy.

I hope this helps.
Charles

[Chieflongtee]

[QUOTE=Started2k3;1387=(MOI is the relationship between mass and its
Charles[/QUOTE]

Can you explain the MOI formula in simple terms?

[Chieflongtee]

THis is the formula but I still don't get it:
MOI is calculated by squaring the length of the club and multiplying that number by the sum of the head weight and the shaft weight divided by 3. MOI = L^2 x (H + S/3). Using a 124 g shaft, a 52 g grip, head weights starting at 231 g in the 2 iron and increasing in 7 gram increments to 287 g in the PW , the MOI of this set range from 311,506 in the 2 iron to 295,831 in the PW, a difference of roughly 16,000. Obviously these clubs are not matched by MOI. Interestingly, too, the balance points of this set range from 28.9” to 27.7”, not matched, and the overall weights are different, not matched, but the swingweights are matched at C-8.

[mcgoo]

Thanks for the translation.Therefore assuming a linear relationship, if I reduce my shaft length from 45" to 40" I will loose 5 x 1.8 yards, less "a little bit" from the resulting decrease in the MOI, say a yard.

Will I gain the 8 yards from the improved accuracy of the shorter shaft?

BC Mist; is this a high school trig question?

[BC MIST]

Several years ago I went to a Golfworks clubmaking seminar where the results of a distance versus length "study" were revealed. Golfers hit drivers from 42" to 47" in .5" increments.

The results were predictable. The longest drive came from the driver of the longest length, BUT, the LONGEST AVERAGE DRIVE came from the 42.5" driver and the reasons should be obvious.

At the end of the day then, shorter is better,( as it is easier to hit the ball BETTER or more consistently closer to the centre of the club face. Cutting the driver down by an inch or so won't cause much, if any distance loss, and should allow you to play more shots from the short grass.

From my perspective, golfers with a smooth tempo, swingers, can use a longer club, more effectively as they tend to hit the sweet spot more frequently than those golfers who have a fast tempo, hitters.

To contradict everything I just said, I cut my driver length from 47 7/8" to 46" this year, and my irons are shorter by about .5", and my fairways and greens hit are DOWN, albeit, only fractionally. Gee, I wonder if it could be my swing.

[Started2k3]

Can you explain the MOI formula in simple terms?

Probably not.

THis is the formula but I still don't get it:
MOI is calculated by squaring the length of the club and multiplying that number by the sum of the head weight and the shaft weight divided by 3. MOI = L^2 x (H + S/3). Using a 124 g shaft, a 52 g grip, head weights starting at 231 g in the 2 iron and increasing in 7 gram increments to 287 g in the PW , the MOI of this set range from 311,506 in the 2 iron to 295,831 in the PW, a difference of roughly 16,000. Obviously these clubs are not matched by MOI. Interestingly, too, the balance points of this set range from 28.9” to 27.7”, not matched, and the overall weights are different, not matched, but the swingweights are matched at C-8.

The physics definition of moment of inertia for a point mass (very very small object rotating around an axis) is:
MOI = m*r^2
m = mass of the point in kg
r = radius of point mass from axis in meters

Unfortuneately we have to deal with the real world where objects actually have volume. Which greatly complicates the calculation, by splitting up the solid object (like a clubhead) into a set of point masses that can then be summed to get MOI (get out your grinder and slowly remove layers on your favourite club head).

On the bright side, small objects (like a clubhead) end up having an equation that is very similar to the point mass equation. This is where you get the H*L^2 part of your MOI equation.

Luckily scientists have already gone through a lot of calculations for us so we know what the equation for a thin rigid rod is which gives us the secont part of your equation: S/3*L^2

Adding these together we get:
MOI = H*L^2 + S/3*L^2
or
MOI = L^2 x (H + S/3)

RE YOUR CALCULATION: The grip weight is left out of the calculation because its influence on MOI will be constant so long as you are using the same grip for all clubs (ie same maker and of similar mass). Also if you include the grip mass to the shaft mass you will be distributing the grip mass accross the entire length of the shaft during the calculation.

Using your numbers I get values like:
40" 2 iron -> MOI = 281,118
36" PW -> MOI = 271,072 (shaft weight is reduced from tip trimming to 111.6g)
Still a large margin, which is why you would then need to add tip weight to push up the MOI for the shorter clubs. This would range from 0.5g for the 3i to 12.1g for the PW. I believe that if you actually want to MOI your clubs you should have a scale that measures to the 0.1 of a gram.

I hope this helps.
Charles

references:
http://en.wikipedia.org/wiki/Moment_of_inertia
http://en.wikipedia.org/wiki/List_of_moments_of_inertia

[Started2k3]

Several years ago I went to a Golfworks clubmaking seminar where the results of a distance versus length "study" were revealed. Golfers hit drivers from 42" to 47" in .5" increments.

The results were predictable. The longest drive came from the driver of the longest length, BUT, the LONGEST AVERAGE DRIVE came from the 42.5" driver and the reasons should be obvious.

At the end of the day then, shorter is better,( as it is easier to hit the ball BETTER or more consistently closer to the centre of the club face. Cutting the driver down by an inch or so won't cause much, if any distance loss, and should allow you to play more shots from the short grass.

From my perspective, golfers with a smooth tempo, swingers, can use a longer club, more effectively as they tend to hit the sweet spot more frequently than those golfers who have a fast tempo, hitters.

To contradict everything I just said, I cut my driver length from 47 7/8" to 46" this year, and my irons are shorter by about .5", and my fairways and greens hit are DOWN, albeit, only fractionally. Gee, I wonder if it could be my swing.

Do you know if the flex of the shafts were taken into account during this study? Because if the shafts were only butt trimmed then the flex (frequency) would increase which in my opinion would make the shaft more predictable hence greater accuracy.

[sammypvt]

Do you know if the flex of the shafts were taken into account during this study? Because if the shafts were only butt trimmed then the flex (frequency) would increase which in my opinion would make the shaft more predictable hence greater accuracy.

Whoa this is getting way out of hand, the original q was what would happen if he shortened the shaft.
As a general rule of thumb, and I mean general, if you shorten the shaft by 1 inch, the headspeed will decrease by no more than 2 mph and in some cases less, this translates to 3 to 5 feet of distance. The tradeoff here is that a shorter shaft will alter the swing weight, but that is only feel anyway and can be compensated by tape or backweighting, (according to lengthening or shortening) however center hits are greatly increased. Several years ago 43 inches was the norm, nowadays 45 and even 46 is regarded by 28 hcpers as acceptable. Fact is that by reducing the length, the fairways become more achievable. I am a fromer tour pro that used to play at 43 inches, I went up to 45 and now at 54 yrs old I am back to 43.5. Most tour pro,s today are cutting back and feeling the results of more fairways hit.
Here is a fact to ponder. If you asked a pro what he would like to loose and get back in return he would say..... take away a few yards in length and give me accuracy in return. Now ask a 28 hcper the same q, dont you think he would say, stuff the accuracy, give me distance. I rest my case.