Where is the Friction from the Floor? – Force Transfer on Scale and Mahjong Tile

Intuitive: When someone pushes you (hands in touch), there must exist a horizontal force counteracting the horizontal push. This counteracting force is usually understood to be the friction produced by the feet pressing (often with toes grabbing) against the floor. Such depiction makes a lot of sense particularly when you regard your entire body largely as one piece of rigid object. Action (horizontal push) and reaction (horizontal friction) – straightforward.

Counterintuitive: The Chu-style Wing Chun stance as described in the post Counterintuitive Stance: Stacking vs Rooting; Floating vs Leaning offers a very different alternative. In the “stacking” mode, the stance mechanism enables a force transfer from horizontal to vertical, making it possible for counteracting the “horizontal” force by a “vertical” force, in place of the horizontal friction from the floor.

Grandmaster Chu had demonstrated such ability with two different tools (but in separate occasions): one was a scale, the other was a mahjong (a very popular Chinese game) tile. In demonstration, he stood on the tool (a scale or a mahjong tile) with just one leg while being pushed hard at both hands simultaneously. The major difference lies in the fact that the scale is well big (in area) enough to contain the whole foot palm, while a mahjong tile is so small (one surface) that it is totally covered by and is in contact with just a small portion of the foot palm (probably around the centre).

To be honest, I still doubt if I can give a convincing explanation on how the transfer mechanism works. Anyway, here below I attempt to offer a rudimentary outline in an exploratory manner.

Any force trying to exert on your body will be readily dispersed to be borne by every single part of the body. (How many parts are effective depends on how far your mind can keep them separate.) This is made more possible by the fact that the point-linked structure separates the skeletal layer from the muscular layer, provisioning diverse ways of achieving the dispersion. When dispersed, the pushing force is not only turned into smaller (change in magnitude) ones, but also broken down into varied directions (change in direction) other than the horizontal. At this point the muscular and skeletal layers play their particular functions respectively.

The muscular layer is infiltrated with the intent of soften-melting downward to the floor. This strong intent brings along the already dispersed forces (in reduced magnitudes and altered directions) towards the floor, like a sweeping current realigning everything along its proceeding direction. In this way, the pushing force is transferred from horizontal to vertical.

Concurrently, the skeletal layer, operating with joint-rotating, maintains the converging of body momentum so that the entire structure won’t be broken open by the incoming push. In addition, the multi-directional forces so resulted enact microscopic deflection at the contacts, regulating the amount of force allowed to go into the structure.

The above transfer mechanism can be glimpsed in the two demonstrations: one on a scale, the other on a mahjong tile, each of them showing a different property of the mechanism.

The purpose of the scale demo is to quantify and thus prove that the pushing force (horizontal) has been transferred to become a part of the body weight (vertical) being measured by the scale. The reading of the scale is increasing as the pusher keeps on pressing harder and harder, until a maximum is reached at which the body (mostly the arms being pressed) can’t take in more increase.

In this case, most (if not all) of the initial pushing force and the subsequent increases are allowed to go into the body from the horizontal, and then be transferred to the vertical all the way down to be borne by the foot, the amount of which equals the increase in the scale reading. Such increase is supposed to be significantly great (refer to the footage). Feeling-wise, your foot stands firmer and firmer on the scale.

On the contrary, the focus of the mahjong tile demo is not to display the amount of force transferred. Rather, it further convincingly illustrates the non-reliance on horizontal friction, because the area of the mahjong tile is too small to provide the expected friction; what it relies on instead is the relatively “pure” vertical reactionary force from the floor, and the high-level control of force from the pusher allowed to go into the body. We now turn to elaborate on the latter.

Since the area of the tile is small, a great force acting on it will result in relatively huge pressure, so huge that it penetrates into the foot palm and makes it uncomfortable, if not hurting, and hence weakening the structure.

The point-linked structure adjusts its own shape and the directions of joint rotating to control the amount of force allowed to go into and through it, to be transferred to vertical to reach the foot palm and onto the mahjong tile. How does such control work? I propose that it is by ever-converging and microscopic deflection at the contacts (refer to the posts Illustrations – Project, Converge, Elbow Pin, Multi-directional Forces and What’s Happening at Forearm Contacts? – Microscopic Deflection for details). By doing so, any (intended) increase in the pusher’s force will be expelled at the contacts right away and has no chance to go into your body structure. Feeling-wise, the pusher tries hard to push harder, but he cannot hold on to something concrete to exert an increase in his pushing. In this way, the increase reaching the mahjong tile is minimal.

The scale demo and the mahjong tile demo serve as the two poles of a spectrum of force transfer: maximum for the former, minimum for the latter. In-between are the different degrees of transfer allowed, reflecting the flexibility and capability of the structure, and are often described as force absorption.

2019.08.01

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