Transmitted Side

The Final Words

The question of Transmitted Side has raised some lively correspondence and the issue is still able to create controversy with both proponents and opponents equally convinced of the logic of their case. The matter will be closed (At least in the pages of this magazine) and the final words are left to Pete Wide, Phil Davis, Hugo Mulders, and Geza Gazdag.

Billiards Mathematically Treated

Some years ago I managed to get hold of this old book and I photocopied parts of it. Unfortunately, I do not have with me these days the author's name and I am not sure if I have the title exactly right. Some of your readers will correct me if I am wrong. Here is the extract that I found particularly interesting and relevant to the topic under discussion.

"Place a ball 'B' anywhere on the baulk line of a table with a fairly new cloth to avoid the effect of irregular wear from the marking of the baulk line. Play at 'B' from 'A' striking it so as to make 'B' run along the baulk line. This stroke will not always come off quite true, but any trial, when it fails to do so, should be rejected.

When the stroke is true the ball 'B,' if there is any appreciable friction, will return from the cushion in the dotted line instead of along the baulk line, unless 'A' itself is played from the baulk line, in which case 'B' returns from the cushion truly back along the baulk line. This experiment my be easily tried, and it shows that the friction between the balls is enough to put some side on the object ball. This is what players call transmitted side, which, though a reality, is no doubt so small as to exercise only the slightest influence on actual play."

This is by no means proven. The path of the ball shown by the dotted line is almost solely due to the effect of the nap. It is just as likely that the object ball would follow the path of the dotted line if played at from the position marked 'C' as the effect of the nap will always cause a ball to tend to drift towards the head of the table.

Highly Technical

I found the discussion on Transmitted Side very interesting and couldn't resist the temptation to look up some articles in the, "American Journal of Physics," which had been brought to my attention by Ivan Stevenage. (Of the Academy.) I am inclined to share the opinion of Wallace and Schroeder where they say, "Little or no side is imparted to the object ball by the forward spinning cue ball." As regards transmitted side I do not estimate myself good enough a player (or a physicist) to say what is correct and what is not. But I would like to refer to a BBC programme in the series QED. I think that it was in the year that Joe Johnson was the World Champion and it was called, "The Riddles of Ball and Cue." Steve Davis demonstrated how side works, playing up and down the table, the motion of the cue ball when played with side, and etc. It was all very well done with high speed cameras and striped balls. I seem to remember that one conclusion was that side is not transmitted to the object ball. One thing is sure - the last word on the subject has not been spoken yet.

Proof of transmitted side

1. Place the spot-ball on the brown spot with the two spots in line with the baulk line.

2. Place the plain ball 10 inches directly behind the spot ball and play a full-ball shot sending the spot-ball about eighteen inches towards the blue spot. Note that the spots stay in a horizontal plane.

3. Now play the same shot with side on the cue-ball. Note that the spots will come out of the horizontal plane at about 35 degrees.

Transmitted Side Once More

In reply to Peter Wide I start by saying that such a sweeping statement that, "Side from the cue-ball cannot be transferred to the object ball," seems rather hasty when we know that quite a number of professionals and good amateurs maintain that it can. However, if you had said, "In your opinion," for we all only speak from personal experience, that the role of transmitted side in English Billiards is negligible, if any, then I would certainly agree.

As regards the, "Throw," theory, being the worst potter in the universe I don't feel very qualified to comment on the "Commonly known and accepted fact," that potting with side will require different aiming (As shown in Peter's diagram) because the side will throw the object ball. In my time I have waded through all the billiard books I could find in four different languages and none of them have said that the use of side will alter the departure angle of the object ball. With regard to Alan Firth, Riso Levi, and the sheet of glass, Peter explains that the effect described by Alan was due to the, "Extremely low coefficient of friction between balls and glass." I recently repeated this experiment on one of my weekly visits to a friend's house who, in addition to having a full-size table, also has a sheet of glass. Now, I have to report that neither I nor two budding snooker giants had any difficulty pulling the ball back. Indeed, we all had the impression that the cue-ball came back livelier than when on the cloth! So much for the extremely low coefficient of friction, for once the cue-ball transfers its energy to the object ball the imparted backward/forward rotation takes over. And so Alan my old friend. I don't know how he did it but I think that old Riso took you - and others - for something of a ride.