Back arm perpendicular- why?

[Patrick Johnson]

Simple mechanical theory using a pendulum stroke indicates that to minimize the up and down motion of your tip when a circular motion(the arc of the pendulum) is converted to linier motion through a fixed point, your bridge, the best place to hit the cue ball is when the pendulum is at the bottom of it's stroke with the least curving arcing motion. (slightly adjusted because the cue is rarely perfectly level and to support this theory the forearm should be at a perfect right angle to the stick when contact is made with the cue ball)

However, that is theory. Having watched strokes of the pro's for years, looked at the pictures and video's of many instructors, and watched many top local players, I note that with rare exceptions all commonly address the cue ball before shooting with the forearm anywhere from slightly to pronouncedly ahead of the "correct" right angle. Obviously the tip goes further forward to contact the cue ball so with the exception of the very few using a slip stroke they are using the same technique you are.

I think maybe the reason so many hit a little forward of perpendicular is that they can feel that's where their acceleration peaks. I think hitting the CB at the point where your acceleration peaks does two things: gives the most action for the effort and gives the best feel for speed control.

I've always heard that the stroke begins to "coast" when the forearm reaches perpendicular, but I've never quite believed it - the arm's physiology doesn't seem to me to dictate that.

I don't know any of this "scientifically"; just my impressions.

pj
chgo

 

[ShootingArts]

feel and comfort may be the issues

Some players have their wrists bent back, John Schmidt is one example I believe, so the grip to elbow line is still close to a right angle to the cue stick although the fore arm is a bit further ahead. However when you mention feel it makes me think of something else. With the arm bent slightly more forward it absorbs the impact with the cue ball a little better and the strike feels a little more comfortable. Not that the impact is a major issue but I wonder if we don't subconsciously seek to minimize it? Purest speculation on my part also, I have no idea why the position seems most natural.

Speed control is a very good point. Mine suffers if I hit the cue ball early with my forearm before perpendicular and isn't the best if I strive for a perfect pendulum and right angle between the cue and fore arm at impact. My best speed control is hitting the cue ball slightly late. When I set up to hit the cue ball with my fore arm at a perfect right angle my arm still feels cocked when I stop at the cue ball on my practice strokes and in the set position too. These are individual things for me and I don't know if they apply to other people.

I just had a thought that led me to step in front of my bathroom mirror. When I turn sideways bend over into a pool stance and move my upper arm into position letting my fore arm dangle I find that due to muscle tension my fore arm actually angles forward several inches when completely relaxed. It seems my true muscular neutral position isn't with my fore arm straight down but with it a few inches ahead of vertical. This is identical or very close to where I choose to hit the cue ball. I have to give this more thought but it may be the key.

Hu

I think maybe the reason so many hit a little forward of perpendicular is that they can feel that's where their acceleration peaks. I think hitting the CB at the point where your acceleration peaks does two things: gives the most action for the effort and gives the best feel for speed control.

I've always heard that the stroke begins to "coast" when the forearm reaches perpendicular, but I've never quite believed it - the arm's physiology doesn't seem to me to dictate that.

I don't know any of this "scientifically"; just my impressions.

pj
chgo

 

[JoeyInCali]

Not agreed on by most every top Straight Pool player
of the past 80 years.

Watch a few videos of them hitting break shots.

Dale

Stroke slippers?
A lot of them let that cue go.

 

[pdcue]

Stroke slippers?
A lot of them let that cue go.

No, it isn't a slipstroke. It is simply a smooth, controlled, follow-thru.
Steve Mez would often end the stroke with his elbow all the way down
by his waist.<when he still had one>

Dale

 

[spoons]

Thanks for the thoughtful replies everyone, there are some great tidbits in here.

I've long been a proponent of the importance of predictable results over raw ability, but obviously if I could combine the two, I'd like to do that.

I'm not sure what I'll do in the end, but I appreciate the perspectives of folks on here.

I think if there's one thing that would push me over the edge, it would be somehow knowing that I could achieve the same results with less effort. From what I'm reading here, it sounds like making contact peak acceleration is generally regarded as more important than the actual position along the pendulum swing. Right?

 

[crosseyedjoe]

Thanks for the thoughtful replies everyone, there are some great tidbits in here.

I've long been a proponent of the importance of predictable results over raw ability, but obviously if I could combine the two, I'd like to do that.

I'm not sure what I'll do in the end, but I appreciate the perspectives of folks on here.

I think if there's one thing that would push me over the edge, it would be somehow knowing that I could achieve the same results with less effort. From what I'm reading here, it sounds like making contact peak acceleration is generally regarded as more important than the actual position along the pendulum swing. Right?

Don't watch Mike Davis and Bustamante or you might think you are stupid for following instructional advice.

 

[Siz]

I wouldn't worry at all about cueing a little forward of perpendicular. It is behind perpendicular that is a real no-no IMO

 

[Bob Jewett]

... If your arm is perpendicular at contact it's easier to hit the cue ball at peak acceleration. ...

A small technical nit.... It's peak velocity you want, not peak acceleration. Velocity and acceleration are very different in physics, but many people confuse the two. If you hit at peak velocity, you have the most efficient and powerful stroke and likely the most consistent, as well.

 

[spoons]

Hi Bob. In a typical stroke, where would those two points fall? Or is that too loaded a question to answer in the context of this thread?

 

[Bob Jewett]

Hi Bob. In a typical stroke, where would those two points fall? Or is that too loaded a question to answer in the context of this thread?

The technical answer is pretty simple. For a typical stroke, the peak acceleration occurs at a time when the stick has about half its peak velocity. At peak velocity, there is zero acceleration. Those two statements are very basic physics, and hopefully no one will attempt to argue with them.

 

[spoons]

The technical answer is pretty simple. For a typical stroke, the peak acceleration occurs at a time when the stick has about half its peak velocity. At peak velocity, there is zero acceleration. Those two statements are very basic physics, and hopefully no one will attempt to argue with them.

Thanks. That makes sense to me.

 

[ShootingArts]

Thanks Bob

The technical answer is pretty simple. For a typical stroke, the peak acceleration occurs at a time when the stick has about half its peak velocity. At peak velocity, there is zero acceleration. Those two statements are very basic physics, and hopefully no one will attempt to argue with them.

Bob,

I definitely wouldn't argue with anyone saying acceleration has ended at peak velocity and I don't know enough to debate where peak acceleration would be during muscle contraction. I think the real questions were where would your fore arm be at peak acceleration and peak velocity. I may be mistaken but I think we are actually only interested in peak velocity. Any idea where this is reached in terms of the angle of the fore arm? Even a general range would be helpful.

Hu

 

[crosseyedjoe]

nothing . . .

 

[crosseyedjoe]

The technical answer is pretty simple. For a typical stroke, the peak acceleration occurs at a time when the stick has about half its peak velocity. At peak velocity, there is zero acceleration. Those two statements are very basic physics, and hopefully no one will attempt to argue with them.

No argument, if you're not talking about imparting the most power/force.

 

[Bob Jewett]

No argument, if you're not talking about imparting the most power/force.

But I am. You get the highest cue ball speed with the fastest stick speed. The acceleration at the instant of impact in not significant. This has been discussed extensively before, and you may want to look over Dr. Dave's recent articles on this for the details.

 

[Bob Jewett]

... I think the real questions were where would your fore arm be at peak acceleration and peak velocity. ...

Well, judging from how a lot of players are now choking up on the stick for break shots, I'm suspecting that maximum velocity happens somewhat after bottom dead center for those shots, but of course they are not exactly standard shots. I think that if you are looking for the best body position for maximum power, you need to get a sports motion professional involved. I don't know of any such study.

For the usual range of shots, I think you are not looking for maximum power; you are looking for consistency. On most shots, I can hit the ball much harder than I should.

 

[alstl]

The delivery of a pool cue reminds me of the old battering rams.

They would swing the battering ram back and when it was hanging perpendicular and parallel to the ground it would make impact, thus delivering maximum force.

Maybe it's just a coincidence but see a similarity.

 

[Patrick Johnson]

For the usual range of shots, I think you are not looking for maximum power; you are looking for consistency.

This topic is full of confusing terminology - acceleration, velocity, power - all with different meanings. So to clarify:

You get maximum stroke efficienty and consistency by hitting at peak velocity, and peak velocity occurs in every shot, soft or hard (it's not synonymous with maximum power). So even though on most shots you're not looking for maximum power, you are looking to hit the CB at peak velocity.

We're not sure whether peak velocity occurs right at perpendicular or a little forward of that, but we know it's somewhere around there and we also know that's where the tip is traveling with the least up-and-down variation. So there's a lot to say for hitting the CB at or maybe just a little forward of the perpendicular position.

pj
chgo

 

[ShootingArts]

What I was looking for

Well, judging from how a lot of players are now choking up on the stick for break shots, I'm suspecting that maximum velocity happens somewhat after bottom dead center for those shots, but of course they are not exactly standard shots. I think that if you are looking for the best body position for maximum power, you need to get a sports motion professional involved. I don't know of any such study.

For the usual range of shots, I think you are not looking for maximum power; you are looking for consistency. On most shots, I can hit the ball much harder than I should.

Bob,

I think you answered the question, I'd need to talk to a sports motion professional. What I was looking for was the maximum velocity for a given amount of effort. There is no question that we can almost always apply more power and speed than we need but where in the stroke do we get maximum velocity for minimum effort? Maybe the area from 98% velocity through peak velocity and back to 98% velocity.

Noting the true neutral position of my fore arm when I let it dangle freely earlier I suspect that this peak velocity area is a little forward of where I would have guessed looking at a purely mechanical model controlled by gravity. Standing with my arms hanging fully relaxed muscle tension keeps my arms hooked maybe ten degrees at the elbow. Just on a WAG, I'd think that my area of peak velocity on a soft to medium stroke might be from straight down to twenty degrees forward. In other words, centered around my arm's neutral position rather than the theoretical position indicated by a mechanical model and gravity. This agrees with your observations of break shots.

Just speculation on my part, as you say there are folks that specialize in this field and tune athletes to be their best. Doubt I could afford one's services to answer a question of only minor interest as I don't think it is the primary concern in developing a stroke. It would be a consideration, but not the major consideration.

Thanks for your answer,
Hu

 

[crosseyedjoe]

The delivery of a pool cue reminds me of the old battering rams.

They would swing the battering ram back and when it was hanging perpendicular and parallel to the ground it would make impact, thus delivering maximum force.

Maybe it's just a coincidence but see a similarity.

Yes, if you can make your arm a free swinging pendulum. It's not. You are using muscle contraction to mimic the pendulum movement.