I don't do math good...physics question.

GolfrnutGolfrnut Members Posts: 7,103 ✭✭

Someone compute the math for me on this one. I'm back to experimenting with heavier weight shafts again. Overall, the heavier weight has been better for me in the back swing, a bad back has always been the issue. So I didn't do a breakdown when building test clubs (balance points, raw head weights, etc), so I just know the total weight differences (407g vs 434g) on the 6 irons. There might be a couple grams difference in head weight, but nothing more, and SW come out the same. Balance points between SF and DG, although not identical, are relatively the same. Results have me a bit puzzled. How much does shaft weight play into the total MOI of club and energy transfer potential? We all know the head weight does...but how much does the total weight/shaft weight play into it? I'm pretty sure it's a little more involved than the F=MA which is why I am asking for someone alot smart than me to solve. The interesting part of it is off-center hits seem to be noticably better on the DG vs my SF shafts...specifically toe side...which I find the most peculiar.

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Comments

  • cardoustiecardoustie haha, we don't play for 5's Members Posts: 11,606 ✭✭

    good post. I don't have the answers. I do know for me finding heavier graphite that feels similar to steel has helped with the back/elbows and hands

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  • GolfrnutGolfrnut Members Posts: 7,103 ✭✭

    @cardoustie said:
    good post. I don't have the answers. I do know for me finding heavier graphite that feels similar to steel has helped with the back/elbows and hands

    Haha..yeah, me neither. I have been in i95s for a while now. Have still kept the DG weight in my wedges. It's a give-take as my dispersion/consistency is a bit better with the heavier weight. Fatigue and the back is what made me move initially. Now I'm back to the debate of sacrificing my body for my golf game. :)

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  • Stuart_GStuart_G New HampshireMembers Posts: 22,876 ✭✭
    edited Apr 17, 2019 3:05pm #4

    @Golfrnut said:
    Someone compute the math for me on this one. I'm back to experimenting with heavier weight shafts again. Overall, the heavier weight has been better for me in the back swing, a bad back has always been the issue. So I didn't do a breakdown when building test clubs (balance points, raw head weights, etc), so I just know the total weight differences (407g vs 434g) on the 6 irons. There might be a couple grams difference in head weight, but nothing more, and SW come out the same. Balance points between SF and DG, although not identical, are relatively the same. Results have me a bit puzzled. How much does shaft weight play into the total MOI of club and energy transfer potential? We all know the head weight does...but how much does the total weight/shaft weight play into it? I'm pretty sure it's a little more involved than the F=MA which is why I am asking for someone alot smart than me to solve. The interesting part of it is off-center hits seem to be noticably better on the DG vs my SF shafts...specifically toe side...which I find the most peculiar.

    For MOI of the club, the contribution of the shaft is roughly 1/3rd of the total MOI - maybe a bit less. But that MOI does not really have anything to do in terms of energy transfer to the ball. So we can drop that line of though right away.

    As far as energy transfer from the club to the ball at impact, you're not going to find any equations to answer that question of the shaft contribution. Once we know the mass that contributes the equations to convert club head speed into ball speed are not that difficult but that assumes you know the mass of the club head to use in the equation. And that's really the question you are asking - how much of the shafts mass contributes and should be added to the club head mass. That's something that would need a full blown computer simulation to solve. It's generally considered pretty small - maybe a few inches of the tip - although I admit that's an educated guess. In theory the stiffness of the tip can make a difference in how much of the shaft contributes but even in the context of the differences in those two shafts, I wouldn't expect the difference to be that big.

    Now off center hits are a little different story. In that respect the torsional stiffness of the shaft and the MOI of the head (not club - are both those shafts using the same head model?) could make a bigger difference since there is much more rotational motion of the face - while the ball is still in contact with the face - as a result of the off center hit. The more the head (MOI) and shaft (torsional strength) resists the rotation of the face, the more energy can be transferred to the ball - instead of becoming potential energy stored in the shaft or rotational kinetic energy in the head. That's the theory - not sure how much of a difference I'd expect it to really make in reality though. I'd want to look at all the differences in data between the two clubs before coming to any conclusions (club head speed, ball speed, dynamic loft, etc..) since there is so many different ways the shaft can effect the swing and impact results.

  • GolfrnutGolfrnut Members Posts: 7,103 ✭✭

    @Stuart_G said:

    @Golfrnut said:
    Someone compute the math for me on this one. I'm back to experimenting with heavier weight shafts again. Overall, the heavier weight has been better for me in the back swing, a bad back has always been the issue. So I didn't do a breakdown when building test clubs (balance points, raw head weights, etc), so I just know the total weight differences (407g vs 434g) on the 6 irons. There might be a couple grams difference in head weight, but nothing more, and SW come out the same. Balance points between SF and DG, although not identical, are relatively the same. Results have me a bit puzzled. How much does shaft weight play into the total MOI of club and energy transfer potential? We all know the head weight does...but how much does the total weight/shaft weight play into it? I'm pretty sure it's a little more involved than the F=MA which is why I am asking for someone alot smart than me to solve. The interesting part of it is off-center hits seem to be noticably better on the DG vs my SF shafts...specifically toe side...which I find the most peculiar.

    For MOI of the club, the contribution of the shaft is roughly 1/3rd of the total MOI - maybe a bit less. But that MOI does not really have anything to do in terms of energy transfer to the ball. So we can drop that line of though right away.

    As far as energy transfer from the club to the ball at impact, you're not going to find any equations to answer that question of the shaft contribution. Once we know the mass that contributes the equations to convert club head speed into ball speed are not that difficult but that assumes you know the mass of the club head to use in the equation. And that's really the question you are asking - how much of the shafts mass contributes and should be added to the club head mass. That's something that would need a full blown computer simulation to solve. It's generally considered pretty small - maybe a few inches of the tip - although I admit that's an educated guess. In theory the stiffness of the tip can make a difference in how much of the shaft contributes but even in the context of the differences in those two shafts, I wouldn't expect the difference to be that big.

    Now off center hits are a little different story. In that respect the torsional stiffness of the shaft could make a bigger difference since there is much more rotational motion of the face - while the ball is still in contact with the face - as a result of the off center hit. The more the shaft resists the rotation of the face, the more energy can be transferred to the ball - instead of becoming potential energy stored in the shaft. That's the theory - not sure how much of a difference I'd expect it to really make in reality though. I'd want to look at all the differences in data between the two clubs before coming to any conclusions (club head speed, ball speed, dynamic loft, etc..) since there is so many different ways the shaft can effect the swing and impact results.

    Agree with all. I wasn't really ready to attribute it mainly to torsional stiffness alone as I think that is put a little too high on the pedestal in many cases, which is why I was wondering about the club mass (agree, MOI was a bad term) with the shaft weight difference. The thought crossed my mind, sure, I just don't know how much buy in I have on it. I don't recall if Tom's software has torque data in it, but you bring up a good point there of cheking the differences so I will try to do that this afternoon.

    No monitor data this time around. I just wanted to get some on-course testing in, specifically later in a round. It was just a peculiar thing I noted, and it wasn't so much a I hit club B further than A on a toe side miss, it was that I loss less distance with club B on a good vs bad shot than I did on club A.

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  • jvincentjvincent Members Posts: 494 ✭✭

    I haven't looked, but I'm willing to bet Dave Tutelman has answered this question on his site.

    I'm pretty good at math and physics but I'm not even close to being in Dave's league.

  • NRJyzrNRJyzr Allez Allez Allez Minnesota, USAMembers Posts: 6,184 ✭✭

    @Stuart_G said:
    Now off center hits are a little different story. In that respect the torsional stiffness of the shaft and the MOI of the head (not club - are both those shafts using the same head model?) could make a bigger difference since there is much more rotational motion of the face - while the ball is still in contact with the face - as a result of the off center hit. The more the head (MOI) and shaft (torsional strength) resists the rotation of the face, the more energy can be transferred to the ball - instead of becoming potential energy stored in the shaft or rotational kinetic energy in the head. That's the theory - not sure how much of a difference I'd expect it to really make in reality though. I'd want to look at all the differences in data between the two clubs before coming to any conclusions (club head speed, ball speed, dynamic loft, etc..) since there is so many different ways the shaft can effect the swing and impact results.

    And the clubhead MOI, the reason for perimeter weighting, is part of that equation. Not sure how much. I expect it's able to be tested, removing shaft as a variable.

    I also expect if it were ever tested, we golfers wouldn't have access to the results. LOL

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  • Stuart_GStuart_G New HampshireMembers Posts: 22,876 ✭✭

    @Golfrnut said:
    It was just a peculiar thing I noted, and it wasn't so much a I hit club B further than A on a toe side miss, it was that I loss less distance with club B on a good vs bad shot than I did on club A.

    If were an issue of shaft mass, you would expect to see the difference to be more uniform over both center hits and mis-hits. That's what lead me down the route of the rotational dynamics - and therefore club head MOI or shaft torsional stiffness. Club head MOI is certainly a possibility if they are different heads - torsional stiffness is a bit more tenuous.

    Of course, the mis-hit AND the distance loss could both be separate consequences of something else that happens much earlier in the swing - as opposed to one being a direct consequence of the other. e.g. the same 'flaw' that leads to the mis-hit is also effecting club head speed or dynamic loft or something else more in one club than the other. Which could be attributed to the total static weight or shaft weight difference. That's why I said I'd want to see more data on the swing.

  • NessismNessism To measure is to know... Members Posts: 18,190 ✭✭

    You're going down the rabbit hole big time with all this analysis. I prefer to keep things on simpler terms: the best energy transfer will occur with the club you strike the most solidly, and the club factor that leads to that is the club that brings out the best in your particular swing.

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  • GolfrnutGolfrnut Members Posts: 7,103 ✭✭
    edited Apr 17, 2019 4:40pm #10

    @Stuart_G said:

    @Golfrnut said:
    It was just a peculiar thing I noted, and it wasn't so much a I hit club B further than A on a toe side miss, it was that I loss less distance with club B on a good vs bad shot than I did on club A.

    If were an issue of shaft mass, you would expect to see the difference to be more uniform over both center hits and mis-hits. That's what lead me down the route of the rotational dynamics - and therefore club head MOI or shaft torsional stiffness. Club head MOI is certainly a possibility if they are different heads - torsional stiffness is a bit more tenuous.

    Of course, the mis-hit AND the distance loss could both be separate consequences of something else that happens much earlier in the swing - as opposed to one being a direct consequence of the other. e.g. the same 'flaw' that leads to the mis-hit is also effecting club head speed or dynamic loft or something else more in one club than the other. Which could be attributed to the total static weight or shaft weight difference. That's why I said I'd want to see more data on the swing.

    Same heads. I'm not that amateur :)

    And yeah, there always could be more. Even if I was using the monitor, without knowing ROC and about every potential variable out there, there's always going to be that chance that there are multiple effects at play here. Just curious if the mass change due to the shaft itself could be having effect, all else considered equal even though it might very well not be in reality.

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  • GolfrnutGolfrnut Members Posts: 7,103 ✭✭

    @Nessism said:
    You're going down the rabbit hole big time with all this analysis. I prefer to keep things on simpler terms: the best energy transfer will occur with the club you strike the most solidly, and the club factor that leads to that is the club that brings out the best in your particular swing.

    Just curiosity on my part. In the end, completely agree, sometimes you don't need to know the ins and outs...if it works, it works.

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  • Stuart_GStuart_G New HampshireMembers Posts: 22,876 ✭✭

    @Golfrnut said:
    Same heads. I'm not that amateur :)

    I am :-) When it comes time build a test club to check out a new shaft or even compare different shaft options, I use whatever head happens to be available and at hand - or on sale at golfwork that particular week. I think my current store of test clubs span about 6 different head models. Of course I'm more concerned about the general feel of the shaft and consistency of the results for center hits than I am about detailed numbers.

  • cxxcxx Members Posts: 3,059 ✭✭

    Most of this is from Tutelman's site. The strike duration is very small and you can treat the shaft like a rope. T showed that the shaft is a very small participant in the strike and can usually be ignored. The exception being the vertical gear effect in drivers. The MOI of the club is a sum of the club's mass times the square of the distance from the point around which you are measuring. You can compute the MOI from components by combining their MOI around their center of mass. It's not really worth it.

    I couldn't get your two clubs with the same swing weight to add up. The same swing weight would mean that both clubs would produce the same leverage at a measuring point when balancing the club on a fulcrum at 14" from the butt. The hireko info had data for 6 irons in i95 and DG that are suppose to be built to D1 with balance points of the shafts and built clubs. The SF club had a balance point closer to the clubhead but not by much.

    I'd stick with the one that works, DG, unless you are forced to change. I don't hit wedges that hard myself.

  • GolfrnutGolfrnut Members Posts: 7,103 ✭✭

    @cxx said:
    Most of this is from Tutelman's site. The strike duration is very small and you can treat the shaft like a rope. T showed that the shaft is a very small participant in the strike and can usually be ignored. The exception being the vertical gear effect in drivers. The MOI of the club is a sum of the club's mass times the square of the distance from the point around which you are measuring. You can compute the MOI from components by combining their MOI around their center of mass. It's not really worth it.

    I couldn't get your two clubs with the same swing weight to add up. The same swing weight would mean that both clubs would produce the same leverage at a measuring point when balancing the club on a fulcrum at 14" from the butt. The hireko info had data for 6 irons in i95 and DG that are suppose to be built to D1 with balance points of the shafts and built clubs. The SF club had a balance point closer to the clubhead but not by much.

    I'd stick with the one that works, DG, unless you are forced to change. I don't hit wedges that hard myself.

    Good info. My general question, as sort of dabbled into above, was how much it contriduted to the equation when we consider mass as a factor in the energy delivered in the strike. It's been discussed more than a few times how clubhead mass can effect how much energy is transferred, but I haven't really been able to find a whole lot about shaft contribution. I remember seeing what you referenced on Tutelman's site, I'm just not smart enough to figure out exactly what his angle of approach was with that. I took it as more of a reference to the idea on whether the "kick" or "deflection" at impact played a roll in the strike, but wondered if mass was also in the conversation.

    Interesting on the Hireko data. Didn't really know they had that tye of data avaialable. Will keep that in mind

    I'm very close to making a switch back to give it a full go. Sometimes I feel like they might be too heavy, other times they feel perfect...to the point where I'm against shooting for middle ground (DG120, SF125, etc). At this point, I'm not sure on whether to even go AMT or full weight on all. In my mind, I've been through a number of options.

    • Full weight R300s
    • AMT R300s
    • DG120s short irons, AMT long
    • AMT Short, DG120 long
      I haven't been through this debate for a number of years now.... :)
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  • GolfrnutGolfrnut Members Posts: 7,103 ✭✭

    @jvincent said:
    I haven't looked, but I'm willing to bet Dave Tutelman has answered this question on his site.

    I'm pretty good at math and physics but I'm not even close to being in Dave's league.

    I missed these post updates yesterday, not sure if my phone was **** up or what. As noted above, I couldn't find anything related to over all club mass effect. Head mass, yes...shaft flex...yes...but nothing that seemed directly related to shaft/overall club mass.

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    Callaway MD3 52* & 58* PM grind (both X100 8 iron SS)
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  • GolfrnutGolfrnut Members Posts: 7,103 ✭✭

    @NRJyzr said:

    @Stuart_G said:
    Now off center hits are a little different story. In that respect the torsional stiffness of the shaft and the MOI of the head (not club - are both those shafts using the same head model?) could make a bigger difference since there is much more rotational motion of the face - while the ball is still in contact with the face - as a result of the off center hit. The more the head (MOI) and shaft (torsional strength) resists the rotation of the face, the more energy can be transferred to the ball - instead of becoming potential energy stored in the shaft or rotational kinetic energy in the head. That's the theory - not sure how much of a difference I'd expect it to really make in reality though. I'd want to look at all the differences in data between the two clubs before coming to any conclusions (club head speed, ball speed, dynamic loft, etc..) since there is so many different ways the shaft can effect the swing and impact results.

    And the clubhead MOI, the reason for perimeter weighting, is part of that equation. Not sure how much. I expect it's able to be tested, removing shaft as a variable.

    I also expect if it were ever tested, we golfers wouldn't have access to the results. LOL

    I have a couple of iron heads that are the same that I use so I can side-by-side test. It helps take that question out of my head.

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  • jvincentjvincent Members Posts: 494 ✭✭
    edited Apr 18, 2019 4:57pm #17

    @Golfrnut said:

    @jvincent said:
    I haven't looked, but I'm willing to bet Dave Tutelman has answered this question on his site.

    I'm pretty good at math and physics but I'm not even close to being in Dave's league.

    I missed these post updates yesterday, not sure if my phone was **** up or what. As noted above, I couldn't find anything related to over all club mass effect. Head mass, yes...shaft flex...yes...but nothing that seemed directly related to shaft/overall club mass.

    Surprising.

    My guess on this is that you'd have to look at the relative effects of the mass of the shaft and the head in terms of delivering energy to the ball. Since the COM of the clubhead is, roughly speaking, in line with the impact vector it's going to have a much greater effect than the COM of the shaft which is far away from the impact.

    Also, since the COM of the clubhead is moving much faster than the COM of the shaft so looking at energy delivery (assuming equal clubhead speed) I'd guess that the shaft ends up being negligible. Just doing some quick math the COM of the head is probably 2X the speed of the shaft COM so that's a factor of 4 right there. The head is also about 3.5 to 4x the weight of the shaft, so there's another factor of 4 so you're up to the head weight being 16x more effective in delivering energy. But even then that would assume they were on the same vector as the golf ball launch, which they aren't.

    As a totally arbitrary example, let's say the shaft contribution is reduced by 50% because of the impact vector. Now you're at roughly 3% of the total energy being shaft related. So if you change the weight of the shaft by 20%, that's now 3.6% of the total energy in the system or an increase of 0.6% which I would call negligible.

    Looking at it now the calculus behind this is pretty straightforward but I think my rough numbers aren't that far off.

    That said, I'd bet that the effect of changing weights has more impact on the kinematics of the swing allowing you to swing faster (or slower) than on the physics of the collision.

  • buntabunta Members Posts: 541 ✭✭

    Bunch a Dechambeau's in here.

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  • jvincentjvincent Members Posts: 494 ✭✭

    I was Dechambeau'ing for as long as he's been alive.

    If anyone here is old enough to remember rec.sport.golf that's where a lot of Dave Tutelman's first stuff was posted. He's the original mad scientist.

  • GolfrnutGolfrnut Members Posts: 7,103 ✭✭
    edited Apr 18, 2019 6:03pm #20

    Came across a link from google images which is from Tutelman’s. It falls under the golf swing as opposed to a lot of the club data links I’m used too.

    https://www.tutelman.com/golf/swing/golfSwingPhysics2.php

    On first scan, I see "arm mass" mentioned, but nothing about shaft mass....

    It’ll take me a minute to process through it, but some of the answers may lie here.

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  • GolfrnutGolfrnut Members Posts: 7,103 ✭✭

    @bunta said:
    Bunch a Dechambeau's in here.

    Sometimes we get bored. :) Have to mix it from the "I need a high launch/low spin shaft" and "x vs y" shaft threads

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  • GolfrnutGolfrnut Members Posts: 7,103 ✭✭

    @jvincent said:
    I was Dechambeau'ing for as long as he's been alive.

    If anyone here is old enough to remember rec.sport.golf that's where a lot of Dave Tutelman's first stuff was posted. He's the original mad scientist.

    Speaking of that dude...I've heard him comment in the past that the increased head weight (mass) in the longer irons on the single length clubs will "make up" for lack of additional swing speed due to length. Anyone seen any studies done out there with respect to irons? Genuanly curious on whether he was blowing smoke or there was validity there. If you do say the 4, 5, 6 irons, obviously they have the same head weight, so how would head weight make up the distance across all those irons. Unless somehow the lower loft vs addition headweight acts as some sort of multiplier as you step to the longer and longer irons? The comments seem suspect, but keeping an open mind.

    I've seen driver studies, which only seem to show a few yards across the spectrum from what I have seen.

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  • jvincentjvincent Members Posts: 494 ✭✭

    For a traditional set the irons are .5" longer and 7g lighter per head. The end result is that the head is moving faster.

    In a single length, the head is heavier there is more energy due to weight, but that will be offset by less speed. It's more complicated than that though since loft and COG have an impact and single length lofts don't necessarily correlate to single length lofts.

  • Stuart_GStuart_G New HampshireMembers Posts: 22,876 ✭✭
    edited Apr 19, 2019 8:57am #24

    @Golfrnut said:
    Came across a link from google images which is from Tutelman’s. It falls under the golf swing as opposed to a lot of the club data links I’m used too.

    https://www.tutelman.com/golf/swing/golfSwingPhysics2.php

    On first scan, I see "arm mass" mentioned, but nothing about shaft mass....

    It’ll take me a minute to process through it, but some of the answers may lie here.

    That's just about the dynamics of the swing itself e.g. the generation of swing speed. Nothing there on the energy transfer to the ball at impact.

    @Golfrnut said:
    I've heard him comment in the past that the increased head weight (mass) in the longer irons on the single length clubs will "make up" for lack of additional swing speed due to length. Anyone seen any studies done out there with respect to irons?

    Use Tutelman's equation for estimating ball speed to get an idea of the potential there. More of of weight difference with the longer irons than we generally look at with a driver.

    assuming center face impact:
    Vball = V_clubhead * ((1 + e)/(1 + m/M)) * cos(loft)
    m = ball mass (0.045926 kg),
    M = clubhead mass (you fill in different values to see the different results)
    e = COR = .78 typical club today = .83 drivers today

  • Stuart_GStuart_G New HampshireMembers Posts: 22,876 ✭✭
    edited Apr 19, 2019 9:19am #25

    @jvincent said:
    My guess on this is that you'd have to look at the relative effects of the mass of the shaft and the head in terms of delivering energy to the ball. Since the COM of the clubhead is, roughly speaking, in line with the impact vector it's going to have a much greater effect than the COM of the shaft which is far away from the impact.

    Also, since the COM of the clubhead is moving much faster than the COM of the shaft so looking at energy delivery (assuming equal clubhead speed) I'd guess that the shaft ends up being negligible. Just doing some quick math the COM of the head is probably 2X the speed of the shaft COM so that's a factor of 4 right there. The head is also about 3.5 to 4x the weight of the shaft, so there's another factor of 4 so you're up to the head weight being 16x more effective in delivering energy. But even then that would assume they were on the same vector as the golf ball launch, which they aren't.

    Since the shaft can't really be considered a rigid body for this particular problem - the shaft COM really becomes irrelevant to the energy transfer to the ball at impact. The only valid approach would be a discrete look at the dynamics of each individual part of the shaft - but only for the short period of time that the ball is still in contact with the face. So due to that, it can't be just a "simple" length integral, it also has to be a time integral since anything that happens after the ball leaves will only effect the motion of the club head after impact and play no part in what happens to the ball. So you may be able to come up with the basic equations but there will not be any that will directly give an explicit result.

    In simple terms the elasticity of the shaft "slows down" the transfer of energy through the shaft to the head/ball to the point where much of it doesn't get there before the ball leaves the head. Then the fact that the shaft could have some pre-load (forward bend or some potential energy already stored) at the start of impact will complicate things even more.

    It's actually the same effect that makes one shaft feel softer or stiffer than another during the swing when the shaft is loaded. We accelerate the club head through the shaft, but the softer the shaft, the resistance of the head that we feel at the grip end is spread out over a longer period of time - giving us a 'smoother' feel. Although in that context the contact with the hands is continuous so we still get all the feedback.

  • GolfrnutGolfrnut Members Posts: 7,103 ✭✭

    @Stuart_G said:

    @Golfrnut said:
    Came across a link from google images which is from Tutelman’s. It falls under the golf swing as opposed to a lot of the club data links I’m used too.

    https://www.tutelman.com/golf/swing/golfSwingPhysics2.php

    On first scan, I see "arm mass" mentioned, but nothing about shaft mass....

    It’ll take me a minute to process through it, but some of the answers may lie here.

    That's just about the dynamics of the swing itself e.g. the generation of swing speed. Nothing there on the energy transfer to the ball at impact.

    @Golfrnut said:
    I've heard him comment in the past that the increased head weight (mass) in the longer irons on the single length clubs will "make up" for lack of additional swing speed due to length. Anyone seen any studies done out there with respect to irons?

    Use Tutelman's equation for estimating ball speed to get an idea of the potential there. More of of weight difference with the longer irons than we generally look at with a driver.

    assuming center face impact:
    Vball = V_clubhead * ((1 + e)/(1 + m/M)) * cos(loft)
    m = ball mass (0.045926 kg),
    M = clubhead mass (you fill in different values to see the different results)
    e = COR = .78 typical club today = .83 drivers today

    Gross... :)
    Joke's on all those math teachers that said I'd never have a calculator with me everywhere I go.

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