What is Zero Torque? A Putter Torque Analysis. LAB, Axis1... A Call to Engineers

[joostin]

On 11/17/2023 at 11:07 AM, HighHooks said:

What is torque and zero torque on a putter?

 

• Torque is the amount of twisting force transmitted to the hands by the putter head while in the address position plus the additional twisting force exerted by striking the golf ball.

 

• The only way to achieve zero torque on a putter is to place the CG of the head and the axis of the shaft exactly on the center of the striking face. (the point where the ball meets the face)

 

• The further away the CG of the head or the axis of the shaft are from the center of the striking face, the more torque will be transmitted to the hands-on off-center hits

Just want to address this.  I know this is coming from the Axis1 inventor, but I have to disagree with the 2nd and 3rd points.  While I see the forward head CG as beneficial in certain aspects mentioned on page 1 of the thread, for impact torque alone it's not limiting it or zero-ing it out.

 

No one will zero out torque on off-center hits, no matter if CG is on the face or behind.

 

Also, in general I think think the term "torque" is probably being confused or misconstrued for a lot of people.  They hear "zero torque" without realizing there are all these different torques involved.  Some can be zero, some cannot. 

 

Here's a look at impact on a toe side strike:

 

 

If you strike inline with the head CG, there's no impact torque (force vector normal to the face crosses the CG, so there's a zero moment arm, d).  It doesn't matter if the CG is forward or rearward - any putter.

 

Yes, other torques can be zero as shown on page 1 of the thread.  Others can't be zero, including those from off-center hits.

[ElephantTusk]

4 hours ago, Stuart_G said:

 

That's part of it of course, but I also think the approach looks at an over-simplified view of the dynamics and biomechanics of the swing itself.  Possibly making some assumptions that might be best if they were not made.  Hard to say for sure though since little is said or published about that aspect of things.

 

Check. Agreed, and ultimately why I dug up the patent earlier in the thread. It's not perfect, but it's the most precise bits  of information I have seen to work from.

 

Those coordinates specified should be enough to derive the properties of the putter when in motion (e.g. if you make a pendulum stroke about the putter's lie angle, what are the resulting torques at the start of the backswing and downswing). It's been years since I've worked to solve a problem like that (so hopefully someone beats me to it!), but plan to attempt it in a few weeks when some of my prior commitments slow down.

[ThinkingPlus]

6 minutes ago, ElephantTusk said:

Check. Agreed, and ultimately why I dug up the patent earlier in the thread. It's not perfect, but it's the most precise bits  of information I have seen to work from.

 

Those coordinates specified should be enough to derive the properties of the putter when in motion (e.g. if you make a pendulum stroke about the putter's lie angle, what are the resulting torques at the start of the backswing and downswing). It's been years since I've worked to solve a problem like that (so hopefully someone beats me to it!), but plan to attempt it in a few weeks when some of my prior commitments slow down.

I agree that is a good approach. Pendulum motion with force due to gravity as the driver. Coordinate system will be key. It's complicated by the lie angle of the shaft. I think the motion must be constrained to the lie angle plane, but that might be omitting some relevant effects. Not sure.

[bladehunter]

On 11/18/2023 at 4:59 PM, Soloman1 said:

 

Thanks for being a volunteer moderator and thought leader to keep us in check.

 

Topics resolve into other things after the meat has been said. I’m a Mechanical Engineer who makes putters. How about you, sparky?

Having read this whole thread , I almost choked with laughter just now when I read the post before this one.  To say you’ve forgot more than most know ( about a lot ) is a gross understatement … if you or @ThinkingPlus speak, I’m listening.  And I’m one of the hardest heads here 😉.    
 

good stuff all.  

[Soloman1]

6 minutes ago, bladehunter said:

Having read this whole thread , I almost choked with laughter just now when I read the post before this one.  To say you’ve forgot more than most know ( about a lot ) is a gross understatement … if you or @ThinkingPlus speak, I’m listening.  And I’m one of the hardest heads here 😉.    
 

good stuff all.  

 

Thanks.  @ThinkingPlus is wicked smart and the place is lucky to have her around.

Hey, you’re not so hard headed. You’re full of curiosity and details. That’s good!

[ThinkingPlus]

1 minute ago, Soloman1 said:

 

Thanks.  @ThinkingPlus is wicked smart and the place is lucky to have her around.

Hey, you’re not so hard headed. You’re full of curiosity and details. That’s good!

Actually, I might just be wicked.

[ElephantTusk]

For the record @bladehunter, @Soloman1 , @ThinkingPlus, I never suggested anyone was dumb! I guess I touched a nerve though 😉

 

If anyone cares to play along, I'm still not so sure that the putter has been explained/understood correctly, however. Zero-torque does not seem to be accurate about any of the relevant axes as far as I can tell.

 

Based on the videos of the revealer, the patent, and the fact that it has some non-zero amount of toe up properties (instead of face balanced or toe hang), I'm actually thinking (hoping?) the putter may be balanced in such a way as to produce an "autocorrecting" torque that keeps the face (nearly) perpendicular to the path of the stroke. This requires some torque generated clockwise rotation when force is applied to start the backswing, and proportional counterclockwise rotation when force is applied on the downswing.

 

The approach I'm working through is to look for necessary conditions to generate rotation that is exactly perpendicular to the tangent of the ellipse that results from projecting an inclined circle (this is the lie angle part) to the ground (e.g. xy axis, depending on your coordinate system). I'm using this as a definition of what golfers typically mean by "square to the path", and I don't think a zero torque putter would actually stay square to that path.

 

So the question is: can a putter be balanced in such a way as to have the face always be perpendicular to that lie-angle specific ellipse without any rotation being applied by the golfer?

[ThinkingPlus]

7 minutes ago, ElephantTusk said:

For the record @bladehunter, @Soloman1 , @ThinkingPlus, I never suggested anyone was dumb! I guess I touched a nerve though 😉

 

If anyone cares to play along, I'm still not so sure that the putter has been explained/understood correctly, however. Zero-torque does not seem to be accurate about any of the relevant axes as far as I can tell.

 

Based on the videos of the revealer, the patent, and the fact that it has some non-zero amount of toe up properties (instead of face balanced or toe hang), I'm actually thinking (hoping?) the putter may be balanced in such a way as to produce an "autocorrecting" torque that keeps the face (nearly) perpendicular to the path of the stroke. This requires some torque generated clockwise rotation when force is applied to start the backswing, and proportional counterclockwise rotation when force is applied on the downswing.

 

The approach I'm working through is to look for necessary conditions to generate rotation that is exactly perpendicular to the tangent of the ellipse that results from projecting an inclined circle (this is the lie angle part) to the ground (e.g. xy axis, depending on your coordinate system). I'm using this as a definition of what golfers typically mean by "square to the path", and I don't think a zero torque putter would actually stay square to that path.

 

So the question is: can a putter be balanced in such a way as to have the face always be perpendicular to that lie-angle specific ellipse without any rotation being applied by the golfer?

I believe their design is intended to maintain the putter face square to the lie angle plane. Given the shallow arc of a putting stroke, the arc and the tangent line would be more or less the same over the stroke. Also, for what it's worth, my B.2 has the shaft inserted into the putter head such that the tip is more or less coincident with the center of the putter face and presumably the CG of the head. I casually measured to a couple mm.

[Soloman1]

Depends on the 3D path and player, too. Not all strokes follow the lie angle. Moving the head CG down and forward helps some players keep the face more perpendicular to the horizontal arc.

 

Can you make an automatic putter? Not until you make an automatic person.

 

Simple center-shafted putters with a double bend shaft are pretty forgiving, but the visual orientation of the shaft, head and ball isn’t pleasing to some.

 

You’d need local and global coordinates because the system is more than just the head.

[nsxguy]

2 minutes ago, Soloman1 said:

Simple center-shafted putters with a double bend shaft are pretty forgiving, but the visual orientation of the shaft, head and ball isn’t pleasing to some.

 

I don't think I've ever seen a CS putter with a double-bend shaft.

 

Is there such an animal ?

[ElephantTusk]

5 minutes ago, Soloman1 said:

Depends on the 3D path and player, too. Not all strokes follow the lie angle. Moving the head CG down and forward helps some players keep the face more perpendicular to the horizontal arc.

 

Can you make an automatic putter? Not until you make an automatic person.

 

Simple center-shafted putters with a double bend shaft are pretty forgiving, but the visual orientation of the shaft, head and ball isn’t pleasing to some.

 

You’d need local and global coordinates because the system is more than just the head.

 

Yeah, I mean obviously no one is following a perfect pendulum every time, and alignment also matters, and green reading matters, and too much coffee makes your hands shake and that matters, and the attractive person on TV selling the newest hyper-TORQUE (TM) putter matters to your psychological state when hitting a putt, and so on.

 

I'm literally just curious about the properties of the LAB and Axis1 putters! I naively thought this was a thread about that topic, but as aptly noted I'm also not a moderator so I may have been confused. I don't know how else to make it clear my intention was to ask physics and engineering questions about the putters being sold, not about how golfers can make more putts or trying to flex/doubt one's mental acuity.

 

Internet forums have never really been my thing, and I'm remembering why. I'll leave you all the ball and just go home 🙃 (metaphorically speaking). Happy holidays all, and good luck with your golf, life, and careers in 2024! I'll probably be back eventually, but going back to lurching for awhile.

[ThinkingPlus]

1 hour ago, Soloman1 said:

Depends on the 3D path and player, too. Not all strokes follow the lie angle. Moving the head CG down and forward helps some players keep the face more perpendicular to the horizontal arc.

 

Can you make an automatic putter? Not until you make an automatic person.

 

Simple center-shafted putters with a double bend shaft are pretty forgiving, but the visual orientation of the shaft, head and ball isn’t pleasing to some.

 

You’d need local and global coordinates because the system is more than just the head.

Setting up the problem in such a way as to provide non-trivial, meaningful results without rendering things intractable is the trick. To first order, just understanding what the torque about the lie angle axis would be ignoring the shaft mass would be a good step. After that you can jump in the rabbit hole with both feet adding in the shaft inertia and grip inertia.

 

My primary reason for liking the L.A.B. approach is regardless of what I do with my stroke, their putter isn't adding any rotation. It's especially annoying realizing the added rotation changes with length of putt. If I miss a putt, it's all on me.

[Soloman1]

10 minutes ago, ThinkingPlus said:

Setting up the problem in such a way as to provide non-trivial, meaningful results without rendering things intractable is the trick. To first order, just understanding what the torque about the lie angle axis would be ignoring the shaft mass would be a good step. After that you can jump in the rabbit hole with both feet adding in the shaft inertia and grip inertia.

 

My primary reason for liking the L.A.B. approach is regardless of what I do with my stroke, their putter isn't adding any rotation. It's especially annoying realizing the added rotation changes with length of putt. If I miss a putt, it's all on me.

 Yes, a good benchmark.

[bladehunter]

2 hours ago, ThinkingPlus said:

Setting up the problem in such a way as to provide non-trivial, meaningful results without rendering things intractable is the trick. To first order, just understanding what the torque about the lie angle axis would be ignoring the shaft mass would be a good step. After that you can jump in the rabbit hole with both feet adding in the shaft inertia and grip inertia.

 

My primary reason for liking the L.A.B. approach is regardless of what I do with my stroke, their putter isn't adding any rotation. It's especially annoying realizing the added rotation changes with length of putt. If I miss a putt, it's all on me.

I’ll say me too at the risk of a faux pas! 😂.  
 

I won’t pretend to know the term to explain it. But how I see it is this. One of my tendencies was adding loft at impact.  Or a flip.  Right hand driven strokes have this tendency.  Also.  I’m a tall  guy who prefers to have my eyes over the ball.  head over and slightly behind is where I can “ see “ down the line.  Less distortion.  Think about Adam Scott’s stance etc.  I see the putting  stroke  better when it’s straight.  I’m thinking about what the clubhead does. Not what my hands etc do.  Same as my full swing.  I want the clubhead on the line a long time , and the face not rotating.  So this Lab armlock in a shorter length works. (  at 39 inches for a 6-3 guy ).With a very upright lie  angle (78 degrees) . It’s a locked in stance , my head has no choice but go in place , and I can’t reach if I am inside of the ball. I’m on the train tracks. And the train doesn’t manipulate the face going back or going through.

 

 No way an axis heel shafted putter could ride as true as this one does. It’s blind to be weighted to one side or the other.  
 

 According to decade I’ve picked up 4 shots a round Strokes gained putting since the last iteration of this putter was fit to me. It took 3 putters a good coach and a month to get it perfect.  But now it’s just automatic.  
 

People I’ve seen not have success with a lab putter are those who try to play it with an arc. They get a flat lie angle and don’t see the full benefit.  ( my opinion ). Upright is the way it works best.  But I know I’m biased there.  

Edited November 25, 2023 by bladehunter

[5hort5tuff]

17 hours ago, bladehunter said:

No way an axis heel shafted putter could ride as true as this one does. It’s blind to be weighted to one side or the other

 

What about a center shafted putter with the same specs? 

 

I often wonder with all the successful LAB putters used on tour  being broomstick or armlock, why arent the other companies circling back and offering broomsticks again?  

 

How much of the success is the LAB tech vs the long putter?  

[bladehunter]

26 minutes ago, 5hort5tuff said:

 

What about a center shafted putter with the same specs? 

 

I often wonder with all the successful LAB putters used on tour  being broomstick or armlock, why arent the other companies circling back and offering broomsticks again?  

 

How much of the success is the LAB tech vs the long putter?  

Not even close.  A center shaft putter is usually toe down in balance. Or headed to toe down.  That means  it opens itself up going back , and slams shut coming back to the ball .  Trying to make them the same without the balance and onset shaft is like the guys who are buying a $40 lightweight driver shaft and hoping  it gives autoflex ballspeed. It won’t.  The tech may not be worth the $. But there is some tech there. I tried it both ways.  

I think the success on tour is same as what I saw.  Guys who were at their last hope coupled with a tall build , an upright lie angle that got them into a position they’ve never been in before.  Then the tech just made the stroke easy-er.  Confidence coming from making a couple.  Then they believe in themselves again.  Poof. Magic happens.  What the actual problem is to begin with ?  Don’t know.  But I suspect tall has a small amount to do with the struggle.  You rarely see a short  guy with the yips. Theyre way closer to the ball and connected  to the stroke with a “ normal “ length putter.
 

 I think armlock or broomstick gets those all guys  down over the ball , like no other putter can.  But that’s just a guess and opinion.  
 

I’ve used it all. Have a $10k Cameron 009 in the closet ( I didn’t buy it , long story ) and I get crap almost every round for this putters looks. So it’s absolutely  because of results. It’s  not because I think it’s expensive or for vanity.  Anything But. I make a ton.  I believe it’s  the total package of traits.  Because I had many armlocks before and never made a thing.  I had 2 lab mezz regular putters before this one and progressively made more. Direction was instantly good.

Edited November 26, 2023 by bladehunter

[ThinkingPlus]

2 hours ago, HighHooks said:

I'll see if can get a response from Luis Pedraza on this and circle back if I get a response.

 

That being said on off center hits axis1 is the only company that has posted indy robotic testing using Qunitic posted earlier in this thread which shows that shows minimal twist and ball speed loss on off center hits.  

That's not what we are discussing. The torque in question causes the putter head to rotate about the shaft by just swinging it. We are not talking about impact torque on mishits.

[ThinkingPlus]

7 hours ago, HighHooks said:

This is what he said......

 

"No one will zero out torque on off-center hits, no matter if CG is on the face or behind."

 

Thats what I was responding too. 

 

 

 

 

 

 

OK. I guess I missed that.

[joostin]

17 hours ago, HighHooks said:

 

I got a response from Luis Pedraza founder of axis1. 

 

 

"@Joostin is correct, every putter will experience some degree of torque on off center hits unless other forces are created to minimize that initial force.

 

However, in order not to introduce additional variables that lead to more confusion,  assume  the ball has been properly struck on the center of the striking face and then compare how torque affects the performance of the various putter approaches. (See attached illustrations.)

 

To reiterate: Torque is the amount of twisting force transmitted to the hands by the putter head while in the address position plus the additional twisting force created by striking the ball. "

 

 

 

Thanks for following up with him!  It's great that he also provided diagrams.  Here's my take... and I'm just trying to be objective with the physics, not biased, because as mentioned I really like what all these guys are doing (and obviously as a company founder what he says holds more weight to people than a golfwrx poster lol).

 

If we're looking down the grip axis (saying grip axis not shaft axis because of LABs forward press grips), that's correct, but a couple things:

 

The face balanced grip axis and the LAB grip axis would be inline with the ball and head CG like this (that's how the face balance putter is face balanced):

 

 

The torque he shows is correct for the weight being off axis when held in the hands, exactly what I was showing on this diagram from page 1:

 

Torque from impact though, on center strike should still be negligible for all, even for the toe hang putter.  Tutelman's analysis of shaft effect with a driver in this site would still apply to putters but to a lesser extent:  https://www.tutelman.com/golf/ballflight/gearEffect3.php#shaftTorque

 

Looking at the toe hang putter diagram, the force at impact applying torque around the grip axis would be true for a static force.  However for ball impact that lasts half a millisecond it's a bit different because the head MOI would be the biggest contributor to resistance to twisting over the shaft.  Going through Tutelman's equations let's take a putter with head MOI of 5,000 g-cm² and a ball speed of 10 mph that's struck 1/2" off-center (btw "x" below is the distance hit off-center so at x=0, the torque becomes zero).

 

Torque applied to the head by the ball is approx.:

T = .771*x*V_ball (derived from the collision impulse and using the mix of typical units - g-cm², in, mph)

T = 3.855 lbf-ft

 

Torque on the head from the shaft due to twist, assuming a low torque shaft rated at 1° twist at an applied 1 lbf-ft is approx.:

T = 72.4*x*V_ball / τ_shaft*MOI_head

T = 0.072 lbf-ft

 

Torque on head due to impact impulse is 53X greater than torque on head from shaft twist.  Yes there's shaft torque but it's pretty small, and shaft companies like BGT advertise their shafts' benefits with convincing data.  Head MOI will dominate though.

 

Going back to the putter comparison, the face balanced putter people can argue that their putters, when in forward motion will tend to self orient because the applied force from the hands lead the CG.  The face balance test shows stable equilibrium, which relates to the hand force leading the head CG with a square face.  Zero torque people will argue that the face balanced putter CG creates the unnecessary torque shown on the diagrams that a person has to counteract.

 

Toe up putter people also can argue that their putters demonstrate stable equilibrium holding the putter with the face square (no torque in that sense), but zero torque people will argue that there is still torque when in motion, which is true.

 

LAB interestingly is zero torque in certain aspects, but with their forward press grips, it's actually bringing torque back around the grip axis.  Their Revealer only holds by the grip butt vent hole, bypassing the orientation of the grip axis - which Axis1 can argue against!

 

I still have to wrap my head around the LAB patent verbiage (esp. their lie angle radian claim)... but all interesting stuff going on.  I don't think there's a right or wrong because it all comes down to feel and how a person gets along with putters of different kinds.

 

@HighHooks Adding that if Axis1 made their own "Revealer", but instead of hooking in the grip vent hole, they'd use a low friction cylinder to grab onto the grip, they'd be able to show a LAB with a forward press grip flopping around in the swing... Just to balance out everyone's claims 😆.

Edited December 2, 2023 by joostin

[Stuart_G]

3 hours ago, joostin said:

Looking at the toe hang putter diagram, the force at impact applying torque around the grip axis would be true for a static force.  However for ball impact that lasts half a millisecond it's a bit different because the head MOI would be the biggest contributor to resistance to twisting over the shaft.  ...

 

What really makes it different is that while that particular torque can exist in dynamics as well as statics, in a dynamic situation it really has nothing to do with impact forces from the ball.   As long as impact is inline with the c.g., impact itself will result in no additional torque being generated.  Instead the torque from a non-zero torque putter is all about the acceleration (rotational and linear) of the head by the hands through the shaft.   And as long as the acceleration by the hands is constant or changes very gradually, that torsional force will also be very constant or change minimally through the stroke. 

 

Which - if applied to more commonly used (or encouraged) putter mechanics, means that the biggest influence of the zero-torque head will occur in transition, and the least amount of influence will occur near and at impact.   Which makes it pretty easy (IMO) for players to compensate in way that results in minimal to no influence on the results.   Now how comfortable they feel making that compensation is a separate question that certainly can very a lot and make one prefer one option over the other.

 

Edited December 2, 2023 by Stuart_G