My Study of OBFL versus NBFL

[Region3]

Without wishing to start an argument, i woudl be interested in the background to this, and any video clips up close. From a simplistic point of view, any club (irrespective of loft) with a downwards component of velocity at impact must transfer a downward component of momentum to the ball, so that implies a reaction from the ground, and hence potentially some "compression".

Admitting my ignorance here - not trolling

If we accept that the NBFL are correct and that the ball's initial direction is 85% influenced by club face direction, then you can apply that to vertical launch as well.

To 'compress' the ball into the ground (which sounds odd enough as it is because the ball is a lot harder than the ground) the club would have to have an effective loft at or around 0°.

Even with a 3 iron that's a lot of forward shaft lean at impact.

When I first heard the term 'compressing the ball against the ground' I thought "how does the ball ever come out of a fairway bunker or soggy ground", and decided not to believe it.

 

[SocketRocket]

That doesn't say that I said the 'new' laws don't work. My stance throughtout this debate has been that the laws of physics dictate how a ball flies and those laws haven't changed. All that has changed is our understanding due to modern technology ie. slowmo cameras etc.

I have never stated the 'new' laws are wrong.

OK, let me ask you a question. Do you agree that the way ball shaping was taught, where the clubface decided where the ball would end and the swingpath decided the direction the ball started, was wrong?

If you answer 'yes' then we can agree on the subject.

 

[sev112]

Super Slo Mo clips are around even on you tube I think. The ball does not at any point compress into the ground or get pushed downwards. I'm sure you can prove me wrong if your ay good at topping the ball on a regular basis.

But this is what a lot of people used to think happened and a lot still do. That is the only reason I mentioned it. Didn't mean to hi jack any part of this thread.

One needs broadband to be able to watch clips - unfortunately, high tech IT solutions such as moving pictures haven't got to Wokingham just yet

 

[bobmac]

One needs broadband to be able to watch clips - unfortunately, high tech IT solutions such as moving pictures haven't got to Wokingham just yet

If you do a search for 'Clip Extractor' you can then download clips off you tube onto your hard drive and watch them at your leisure.

 

[Swinger]

One needs broadband to be able to watch clips - unfortunately, high tech IT solutions such as moving pictures haven't got to Wokingham just yet

Just take my word for it then!!:thup:

 

[sev112]

SO i've been doing some more physical experiments, and this time i've been looking at what all you lot s are debating about vertical motion.

Now, it tunrs out that it is easier to repeatedly "fire" a ball at a staionary head (in my hall) than try and consistently/repeatedly swing the club at the ball.

Now "physics" tells us that it is the relative "cmoing-together" speed of the ball and club that matters, so it shouldnt matter if the ball is shot at the club or the club hits the ball.

So chaps, here is the interesting question that i would like the OBFL supporters, the NBFL supporters and the NF'ingL supporters to debate :...
i have a stationary 45 degree Pitching wedge fixed on the floor of my hall.
i fire a ball at the club at a height of 1 cm above the floor straight at the sweetspot of the PW, at circa 100mph

At what angle (from the floor) will the ball come off the face of the club ?
- straight back at me
- at less than 45 degrees
- at 45 degrees
- at greater than 45 degrees
- at 90 degrees

Enjoy

 

[USER1999]

Initially 45 degrees, but drops rapidly?

Do you have any windows left?

How do you fire a ball 1cm off the floor at 100 mph? Unless you have gibbo there with a driver in his hands?

 

[Foxholer]

OK, let me ask you a question. Do you agree that the way ball shaping was taught, where the clubface decided where the ball would end and the swingpath decided the direction the ball started, was wrong?

Given the Cochran & Stobbs specified things happened as per NBFLs in 1968 AND that that (In Search of the Perfect Swing) was recommended reading for British PGA training, shouldn't you be limiting your 'way ball shaping was taught' to '... was taught in America'?

 

[sev112]

Initially 45 degrees, but drops rapidly?

Do you have any windows left?

How do you fire a ball 1cm off the floor at 100 mph? Unless you have gibbo there with a driver in his hands?

Cant get to 100 mph, but i didnt want to confuse the quiz by using an artificially low speed

I'll wait for a few more answers before i (argumentatively) suggest that O Level Physics text books say the answer is in fact 90 degrees ! Hence my trick question

 

[USER1999]

Cant get to 100 mph, but i didnt want to confuse the quiz by using an artificially low speed

I'll wait for a few more answers before i (argumentatively) suggest that O Level Physics text books say the answer is in fact 90 degrees ! Hence my trick question

Trick questions, hmmm, yes, the ball will ping off the face at 90 degrees, I guess, so in theory, it should hit the ceiling directly above the club face. Ping down, and then the spin will shoot it off and break a window.

 

[sev112]

Trick questions, hmmm, yes, the ball will ping off the face at 90 degrees, I guess, so in theory, it should hit the ceiling directly above the club face. Ping down, and then the spin will shoot it off and break a window.

No - it went through the ceiling, hence the need to experiment at lower speeds

 

[Region3]

In a frictionless collision it would come off at 90°, like light reflecting off a mirror at 45°, but friction means that the true angle will be less than 90°, although I wouldn't like to guess what that angle is.

Thinking about it from a 'playing the shot' perspective, I don't think the real answer is much more than the angle of the wedge, although I do hit the ball quite low.

From your experiment though, do you agree that you're never going to 'compress the ball into the ground"?

I think you can turn the canon down to about 70mph as well. I don't know anyone that has a 100mph club speed with a wedge.

 

[SocketRocket]

Given the Cochran & Stobbs specified things happened as per NBFLs in 1968 AND that that (In Search of the Perfect Swing) was recommended reading for British PGA training, shouldn't you be limiting your 'way ball shaping was taught' to '... was taught in America'?

Whats that got to do with the price of fish? This is the way it is still taught in the USA. It was also taught this way in the UK until around 1980 or there abouts (Bob will know when).

Still nitpicking then Foxy! The date it changed here was not the point under discussion.

 

[SocketRocket]

Right! sorry about the distraction from Foxy.

The golf ball is not solid like a ball bearing, it has elasticity and when hit or hitting an object like a golf club head it will deform against it's surface, start sliding up it then spring off as it is restored to its original shape (Coefficient of Restoration).

It is the sliding effect that creates the spin and the small deviation angle that will stop it deflecting normal to the inclined surface (Refraction). So it will deflect mainly normal to the slope but slightly towards the approach angle.

 

[sev112]

In a frictionless collision it would come off at 90°, like light reflecting off a mirror at 45°, but friction means that the true angle will be less than 90°, although I wouldn't like to guess what that angle is.

Thinking about it from a 'playing the shot' perspective, I don't think the real answer is much more than the angle of the wedge, although I do hit the ball quite low.

From your experiment though, do you agree that you're never going to 'compress the ball into the ground"?

I think you can turn the canon down to about 70mph as well. I don't know anyone that has a 100mph club speed with a wedge.

Aha - a clever man - at long last one comes along
It is (almost) coincidental that the "real" ball direction is "similar" to face angle - it is not a "Given" as some of the NBFL'ers suggest or possibly imply. It is a function of the (stiffness of the) materials involved in the collision and the relative magnitude of the friction force developed in relation to the meomentum vector of the club approaching the ball. The ball will only follow the face angle (sideways or vertically) if the face angle is perpendicular to the clubhead path; any skew and then then friction components come in. It's fundamentally (but not the only) way that D-plane can work.

In regard to the other question about "compression" - i will slightly reword the question
There are 2 facets that are different to the lateral (ball flight) case :
- there is a force (ball weight due to gravitational acceleration) ALREADY acting on the ball before the club gets anywhere near it
- if the clubhead aproaches the ball with any form of downward motion, then the friction imposed must have a (small?) component of downward momentum which is transferred to the ball, and because the ball is already in contact with the ground, it imposes a force on the ground. (this would not be there if the clubhead approaches the ball horizontally hovever, as you say)


The experiments were sending the ball off on a much higher trajectory than i expected (hence the question above) - i think this is because at the speed i am sending the ball at the club (much much less than the 70 to 100 mph - much closer to about 20 to 25mph i think) i am not getting as much force (and hence friction) at impact

Time for bed i think

 

[Val]

Still going I see

 

[Foxholer]

Whats that got to do with the price of fish? This is the way it is still taught in the USA. It was also taught this way in the UK until around 1980 or there abouts (Bob will know when).

Still nitpicking then Foxy! The date it changed here was not the point under discussion.

Actually, Bob could well be in an excellent position to confirm when/if the British PGA promoted which 'laws'. Or even which ones he originally taught and if/when he changed (if he needed to).

If accuracy = nit-picking, then I'll happily plead guilty.

As for those (still) teaching OBFLs, it seems to me that there are sufficient 'modern gurus' and others that are publicising the NBFLs to ensure a fairly quick transition to the correct approach. It certainly took some time to convince the authorities/folk the truth about the universe rotating about the (flat) Earth.

 

[SocketRocket]

The leading edge of the club passes under the balls equator and contact between the clubface and ball will be in an approximate position between the balls equator and bottom edge, this will be a lifting action on the ball. To push the ball in the direction of the ground the face of the club would need to contact the ball above it's equator which is not possible with loft. Well, it is possible but only by topping the ball with the leading edge which is not the intent.

 

[Foxholer]

Right! sorry about the distraction from Foxy.

The golf ball is not solid like a ball bearing, it has elasticity and when hit or hitting an object like a golf club head it will deform against it's surface, start sliding up it then spring off as it is restored to its original shape (Coefficient of Restoration).

It is the sliding effect that creates the spin and the small deviation angle that will stop it deflecting normal to the inclined surface (Refraction). So it will deflect mainly normal to the slope but slightly towards the approach angle.

Sorry SR, but so much of this post is absolute tosh! Some of it is correct, but cannot be taken as 'truth' given how much is wrong!

 

[Region3]

- there is a force (ball weight due to gravitational acceleration) ALREADY acting on the ball before the club gets anywhere near it
- if the clubhead aproaches the ball with any form of downward motion, then the friction imposed must have a (small?) component of downward momentum which is transferred to the ball, and because the ball is already in contact with the ground, it imposes a force on the ground. (this would not be there if the clubhead approaches the ball horizontally hovever, as you say)

Sorry, I can't be having that (if I understand you right).

If I can assume that the 85/15 rule still applies (face direction/club path) then even if I could swing down on the ball at 10° with a 20° 3 iron I would have to deloft the club to around 2°.

I haven't got a club near me but it doesn't sound practical to have my hands far enough in front of the club to make the face almost vertical at impact.


Just a quick non-sciencey question for anyone that thinks the ball compresses into the ground still....

Why do different clubs give different flights if every ball is smashed into the ground?
If it's because of the bounce back off the ground then why aren't long irons higher than short irons?