follow shot woes

Rarelymisses

AzB Silver Member
Silver Member
Here's the situation .... shooting a soft, straight-on follow shot with the expectation that the cueball will travel about 18" forward, but something strange happens at impact. It seems that one or both balls hop a little bit and the cueball only goes about 6" before stopping. There's nothing wrong with my stroke, so don't go there. This only happens occasionally (1 in 200 ?), but it can be devastating to a run. I suspect that this is the equivalent of a "skid" in the vertical plane. That is, I think there might be excessive friction during the contact and much of the rotational velocity of the cueball is transferred to the object ball, effectively killing the cueball. If friction is the cause, then what is the cure ? There will always be chalk imprints on the cueball, and object balls will always be somewhat dirty, so how does one compensate for this while playing ? Or is there something that I am missing to explain this phenomenon ?
 
Rarelymisses said:
Here's the situation .... shooting a soft, straight-on follow shot with the expectation that the cueball will travel about 18" forward, but something strange happens at impact. It seems that one or both balls hop a little bit and the cueball only goes about 6" before stopping. There's nothing wrong with my stroke, so don't go there. This only happens occasionally (1 in 200 ?), but it can be devastating to a run. I suspect that this is the equivalent of a "skid" in the vertical plane. That is, I think there might be excessive friction during the contact and much of the rotational velocity of the cueball is transferred to the object ball, effectively killing the cueball. If friction is the cause, then what is the cure ? There will always be chalk imprints on the cueball, and object balls will always be somewhat dirty, so how does one compensate for this while playing ? Or is there something that I am missing to explain this phenomenon ?

You've explained it already. It's skid. Tough to know it's going to happen though.

Fred
 
Ah, the hopping cue ball. I've read some theories about static electricity, and so on, but it seems that one thing that may be happening is the chalk from the shot just made when the cue ball rolls over and over manages to come in contact with the object ball at exactly the wrong moment, causing it to jump up a bit, as you've noticed, effectively killing the normal forward motion of the cue ball.

If you're shooting a straight on shot as mentioned, without any angle, one possible solution would be to shoot the cue ball firmly, but with a mere touch of follow on it, a stun follow shot some people call it. That may take care of the problem, although others may appear.

Flex
 
As far as I've ever heard, there's nothing you can do about skids other than hoping they happen on the other guy's turn. You can't compensate for them because as Fred said you can't know when they're going to happen. Snooker pros ask the ref to clean the CB if they see much chalk build-up, but in a pool hall this just isn't realistic.

-Andrew
 
You gotta keep 'em clean!

Rarelymisses said:
Here's the situation .... shooting a soft, straight-on follow shot with the expectation that the cueball will travel about 18" forward, but something strange happens at impact. It seems that one or both balls hop a little bit and the cueball only goes about 6" before stopping. There's nothing wrong with my stroke, so don't go there. This only happens occasionally (1 in 200 ?), but it can be devastating to a run. I suspect that this is the equivalent of a "skid" in the vertical plane. That is, I think there might be excessive friction during the contact and much of the rotational velocity of the cueball is transferred to the object ball, effectively killing the cueball. If friction is the cause, then what is the cure ? There will always be chalk imprints on the cueball, and object balls will always be somewhat dirty, so how does one compensate for this while playing ? Or is there something that I am missing to explain this phenomenon ?

You're right, it is vertical skid, and as far as I know, there's no way to compensate for it occuring other than to do everything possible to ensure that the balls are clean. Because of the relative infrequency and unpredictability of occurence, stroking the ball differently will lead you to miss shape much more often than not.

If you play in a decent poolroom the cleanliness of the balls should not be an issue, and if it is, I would advise you to look around at other possible places to play. If, like me, you're from a small place and have limited options, or if you play in a bar, more creative measures will have to be taken. I've played in places where a few of us brought our own ball sets in order to play a proper game. Before doing that, we used to order ball cleaning and polishing solution and we would clean a set of balls and try to negotiate some table time.

During your sessions, though, I strongly suggest a rough field cleaning of the cue ball in between games. As part of your pre-break routine, vigorously roll the ball against the rail a few times before you break the balls. I saw Mika doing it in a U.S. Open match against Jim Rempe and once I adopted the practice, I noticed a reduction in the number of times that a ball would skid on me.

Give it a try, and good luck!
 
I have noticed that when I shoot really hard, the OB barely touches the cloth while travelling to pocket. I am sure shooting all balls like that will eliminate shid.
 
Flex said:
...If you're shooting a straight on shot as mentioned, without any angle, one possible solution would be to shoot the cue ball firmly, but with a mere touch of follow on it, a stun follow shot some people call it...
Absolutely, great suggestion. As it happens, with just a touch of follow, the amount of vertical throw you get (and resulting loss of spin) is independent of any drastic increase in the amount of friction. It doesn't matter if it hits a chalk spot or not. It's not independent of a huge decrease in friction (a slick spot), but this shouldn't matter too much on this kind of shot.

Jim
 
I've had this happen to me, but when the object ball hops, it cuts to the right or the left slightly and I miss the shot.
 
Flex said:
If you're shooting a straight on shot as mentioned, without any angle, one possible solution would be to shoot the cue ball firmly, but with a mere touch of follow on it, a stun follow shot some people call it.

I love this shot. When I can stun-follow with accuracy I know I'm in stroke.

-Roger
 
Jal said:
Absolutely, great suggestion. As it happens, with just a touch of follow, the amount of vertical throw you get (and resulting loss of spin) is independent of any drastic increase in the amount of friction. It doesn't matter if it hits a chalk spot or not. It's not independent of a huge decrease in friction (a slick spot), but this shouldn't matter too much on this kind of shot.

Jim
Would you please say this again in a different way ? I just cannot understand what you said.

I think you guys are on the right track. The problem seems to manifest on soft shots. A person could shoot harder, but maintain the same amount of rotational energy in the cueball. This would result in a shorter contact time (?) when the cueball hits the object ball, and so less chance for the rotational energy to be transferred to the object ball (just a theory). On throw shots in the horizontal plane, there is less throw when the cueball is moving faster, so this should also be true in the vertical plane.
 
The well-advised firmer stroke will reduce the frequency of, but not eliminate, skids.

As others have suggested, the result described in the initial post is, in my view, a vertical skid. Some skid terminology that I've heard over the years:

Vertical skid - the ball "jumped" on me

Horizontal skid - the ball "turned" on me

Clean balls is not enough to get rid of most skids. Clean cloth is vital, as well, as dirt will gradually work its way onto the balls. Those who use powder and handle the balls are also increasing the likelihood of skids, as are those that get chalk on the balls.
 
Rarelymisses said:
Would you please say this again in a different way ? I just cannot understand what you said.

I think you guys are on the right track. The problem seems to manifest on soft shots. A person could shoot harder, but maintain the same amount of rotational energy in the cueball. This would result in a shorter contact time (?) when the cueball hits the object ball, and so less chance for the rotational energy to be transferred to the object ball (just a theory). On throw shots in the horizontal plane, there is less throw when the cueball is moving faster, so this should also be true in the vertical plane.
I think you got his meaning, and I think Jal and Flex are correct. This hop-stop effect in my experience happens a lot more often the closer the cueball is to the object ball. I saw Ginky shooting these shots the way they are describing and he seemed to be getting more follow more easily by hitting lower on the cueball when close to the object ball. The cueball doesn't seem to slow as much on impact, skid or not.

I'm always wary of this happening when the cueball is close and I try and remember not to place the cueball very close with ball in hand on a follow shot.

unknownpro
 
Rarelymisses said:
Would you please say this again in a different way ? I just cannot understand what you said.
Sure.

When the cueball collides with the object ball, on the vast majority of shots the cueball's surface at the point of contact is moving across the object ball's surface, creating friction. So there is a relative surface speed between the balls at the point of contact. Of course, everyone aware of throw knows this. The effect of this friction is to reduce this surface speed during the period of impact. It does this by changing the spin and the speed along the tangent line of both balls (of course the object ball has no spin or speed to begin with so it "changes" them from zero to some value). If the relative surface speed is not too great to begin with, it reduces it to zero and the balls end up rolling across each other. At this point the friction is also reduced to essentially zero. Yes, this all happens in about .0002 seconds.

Now suppose the friction is greatly increased because of chalk or something. In those cases where the balls would end up rolling across each other under normal friction anyway, the only effect of the increased friction is to bring them to a rolling state faster. The result is no change in the amount of throw. The reason this is so is because the friction can do no more than to reduce the surface speed to zero. Once there, it ceases to exist. And whenever the balls end up rolling across each other, the speed imparted to the object ball along the tangent line (throw), whether we're talking about a horizontal or vertical tangent line, is a fixed fraction (1/7) of the initial relative surface speed.

For a medium speed straight-on shot, tip offsets of up to about 1/3 of maximum are within the range where this occurs. For hard shots, it's about 1/4 of maximum, and for soft ones about 1/2. This assumes that the cueball doesn't pick up much additional spin (follow) on the way to the object ball. When the cueball's spin is within this range, the shot is immune to skid effects. And this is pretty much true if the spin is just a little bit outside this range too. I believe you could take sandpaper to the balls, smear chalk over them, and not see any difference in throw.

In the case of pure topspin or draw on a straight-on shot, or pure sidespin on a cut shot, the amount of spin the cueball loses to the friction is also a fixed fraction when the balls end up rolling across each other.

Rarelymisses said:
I think you guys are on the right track. The problem seems to manifest on soft shots. .... On throw shots in the horizontal plane, there is less throw when the cueball is moving faster, so this should also be true in the vertical plane.
I think Flex was on track. I didn't think of it until he brought it up. I agree with your last statement, but speed alone does not give you immunity to skid. The spin has to be within the range(s) discussed above.

Hope that makes some sense. I can't go into the complete theory of throw, but see here if you want more info:

http://www.engr.colostate.edu/~dga/pool/technical_proofs/new/TP_A-14.pdf

The portion of the curves on page 9 (or 10) where the lines are straight are some of the cases where the balls roll across each other.

Jim
 
Last edited:
Back
Top