Pivot Point

[SpiderWebComm]

Interesting. PJ and Colin disagreeing over what's feel and what's not.
*crunch* *crunch* *slurrrrrrrp*

I wonder who's right and who's wrong? *crunch* *crunch*
I wonder if someone will bet something? *slurrrp*
Can Colenso fade the diagrams and prove it's systematic? *crunch*

I can't wait to see. In the meantime, I must say... I'm tuning-in next time.

 

[Patrick Johnson]

There's a lot of aspects of the game where feel is involved but that doesn't mean that all systematization is superfluous as you make it sound.

I don't mean to make it sound that way. I just mean to point out that there's no such thing as a purely systematic system.

I don't expect you to approve of my methods of systematization for BHE as you're not completely familiar with it.

I don't approve or disapprove. I just try to describe it accurately.

... the feel is in executing the system rather than in adjusting away from where the system puts you in terms of proper alignment for the shot.

Feel is also used in "calculating" the aim, as I pointed out. As I said, this doesn't make the system useless or superfluous, it just changes how you should describe it in order to be accurate.

pj
chgo

 

[Jal]

Devindra,
If you want a really rough guide to working out your effective pivot point try this little formula.

Based on say a 'PURE' Pivot Point of 10". This is your baseline (shortest) bridge length.

Now add to this V x D x 0.3
0.3 = CFF = cloth friction factor
Where V = Velocity Rating ... 1= Top Speed. 5 = Slow (rolls about one table length). (Note that slower gives a higher number and the lowest number is 1.)
D = Distance in diamonds between CB and OB. Most the time you'll be playing these shots with less that 4 diamonds travel from CB to OB.

So, for a 2 foot (diamond) shot at medium-slow speed (4) you're looking at a bridge length around 10 + (2x4x0.3) = 12.4 Inches.

Hence, Effective Pivot Point = Pure Pivot Point + (V x D x CFF).

This doesn't take into account cloth slickness or cue elevation.

For a very slick cloth the cloth friction factor might be under 0.2, where a slow sticky cloth might be over 0.4.

This formula also assumes linearity, which won't always be true. On some shots the swerve might complete its arc early in the travel path. Other variables also mean it is not perfect, but it is a handy guide and should put you within an inch of the required pivot length for most shots, which should be accurate enough to make most shots.

Colin

Colin,

Glad to see you're still plugging away at this problem. It seems like a tough row to hoe, given all the variables, but it looks like you're making some headway.

Does your method of attack include the math and physics of it or are you working it out at the table?

Jim

 

[dr_dave]

Colin's squirt/swerve/throw BHE system

With most shots where one might consider using english in normal play, I reckon the calculations I make, although imperfect are within the margins of error. I simply trust them and pivot and cue through the ball.

I know the difference between feel and using a system. I use feel to estimate my pot angle and for years most of my english use was entirely feel.

It is even possible to use a purely systematic way to aim for standard potting if one were to make enough measurements and have a systematic method of placing the bridge relative to the CB. However, I believe, except for robots such systems are unlikely to be practical.

But BHE, the way I use it is quite practical I believe. It is for me and I'm not using any feel post initial aim.

I think it sounds a lot trickier than it actually is once you adapt to the system and learn the appropriate adjustments.

btw: I don't find elevation to be a significant problem. When draw is used the shots are usually quite firm, hence swerve is not highly significant. Most shots that would seem ridiculous to attempt with normal english methods are also difficult using BHE.

Colin,

I look forward to learning more about your system to account for squirt, swerve, and throw using BHE. When do you expect to share it publicly?

Regards,
Dave

 

[dr_dave]

squirt/swerve/throw effects

In the past BHE has been regarded as a good system, yet as we've discussed many variables make it complex and in need of adjustments.

What I am attempting to do is to formulate an adjustment system for BHE that is efficient and as accurate as possible. As a player I'm happy with its development and practical application.

FYI (to Colin and others), I have a listed of 35 squirt, swerve, and throw effects in the 2nd Q&A here:

http://billiards.colostate.edu/threads/aiming.html#compensation​

I can't imagine any system that would attempt to address all (or even most) of these effects without "feel;" but if you come up with a system that addresses many of the main effects, I think it will certainly be useful to the people who like systems. I certainly look forward to seeing what you come up with.

Regards,
Dave

 

[devindra]

I will practice and get a feel for adjusting my bridge length. When Colin gets the adjustment system worked out then it would help us alot.

Patrick, I'm curious to know if you use BHE. In most of the threads you seem to never agree on everything.

 

[Colin Colenso]

I don't mean to make it sound that way. I just mean to point out that there's no such thing as a purely systematic system.


I don't approve or disapprove. I just try to describe it accurately.


Feel is also used in "calculating" the aim, as I pointed out. As I said, this doesn't make the system useless or superfluous, it just changes how you should describe it in order to be accurate.

pj
chgo

No worries Patrick,
I think we basically agree on what is and what isn't feel. I'd be silly to argue aspects of the system I use without fully explaining it also.

Hopefully when I can explain it in more detail, with clear instruction, we'll both have a better sense of its practicality and its limitations.

Colin
ps. Spidey, put that pop corn away :frown:

 

[Colin Colenso]

Colin,

Glad to see you're still plugging away at this problem. It seems like a tough row to hoe, given all the variables, but it looks like you're making some headway.

Does your method of attack include the math and physics of it or are you working it out at the table?

Jim

Jim,
I work it out mostly at the table. Plotting some charts for various speeds and distances and then noticing variations on different tables. What math I've some is just a bit of quick brain work to fit into general observations. Even the formula I recommended above becomes silly at a distance of less than 1 foot, so I still need to work on the formula to make it relatively accurate while not too complex.

When I do it, I tend to see the charts in my head and know some set reference shots that I make adjustments for. eg. My medium speed 5 foot pivot point on table X (medium slickness) is 14 inches, however, I need to play it slower than medium speed, so I'll use a pivot point of 15.5 inches. If I want to power up I may shift the bridge up to 12 inches.

What I ideally need is 5 tables of different slickness and to compile an entire data set for each of them using cues of different pivot point lengths, but I don't have that luxury.

I do need to do more testing and spot anomolies as they arise and adjust the formulas such that these fit into the equations and make sense with what is known about the variables involved.

Note that I deal with throw as an entirely different aspect that requires a different adjustment in initial aim. I found that attempts to combine the create over complexity and also would lead the player to a confused understanding of the relationships of the different mechanical aspects.

Colin

 

[Jal]

...Note that I deal with throw as an entirely different aspect that requires a different adjustment in initial aim. I found that attempts to combine the create over complexity and also would lead the player to a confused understanding of the relationships of the different mechanical aspects.

Colin

Colin, I think it's a really good idea to separate out throw. As you well know, it follows a logic or pattern that's entirely divorced from swerve. Looking forward to any further work you might do, and wish to convey to the rest of us.

Jim