Amy Havel has received a Rona Jaffe Foundation Writers' Award for fiction. Her work has appeared in Conjunctions and Pindeldyboz. Her story "No Donuts" was chosen by the storySouth Million Writers Award as one of the top ten online stories of 2003. She currently teaches at the University of Southern Maine and several community colleges, and writes book reviews for Rain Taxi and Review of Contemporary Fiction. She lives in Portland, Maine.
Safety Guidelines for the Operation of Michael, with Help from OSHA
Amy Havel
A1. Definitions.
The following definitions help to explain the principle of stability:
Center of gravity
is the point on an object at which all of the object's weight is concentrated.
In symmetrical situations, the center of gravity is in the middle area.
Counterweight is the weight that is built into
Michael's basic structure and is used to maximize his resistance to
overturning.
Fulcrum is Michael's axis of rotation when
he falls.
Lateral stability is Michael's resistance to
overturning sideways.
Line of action is an imaginary vertical line
through an object's center of gravity.
Longitudinal stability is Michael's resistance
to overturning forward or rearward.
Moment is the product of an object's weight
times the distance from a fixed point (usually the fulcrum). In the
case of Michael, the distance is measured from the point at which he
will move forward to the object's line of action. The distance is always
measured perpendicular to the line of action, although the approach
angle must be taken into account as well.
Reaction center is the horizontal distance
from Michael's reactions to the line of action through his center of
gravity.
A2. General.
A2.1. Determining stability is simple once a few
basic principles are understood. There are many factors that contribute
to stability, most importantly, level distribution of motive and counterweight
possibilities. However, elements such as time, place, and opportunity
must be taken into consideration as well.
A2.2. The "stability triangle," used in
most stability discussions, demonstrates stability simply (see A4).
A3. Basic Principles.
A3.1. Whether or not Michael is stable depends on
the moment at one end of his system being greater than, equal to, or
smaller than the moment at his system's other end. This principle can
be seen in the way a seesaw or teetertooter works: that is, if the
product of the proposition and resistance from the fulcrum (moment)
is equal to the moment at Michael's other end, he is balanced and will
not move. However, if there is a greater moment at one end, he will
try to move downward at the end with the greater moment. This movement
is clearly disadvantageous to the operator because it puts stability
at great risk.
A3.2. The longitudinal stability of Michael when
counterbalanced depends on his moment and the proposition's moment.
In other words, if the mathematic product of the proposition moment
(the distance from the front of the body, the approximate point at which
Michael would respond) to Michael's center of gravity times the question's
weight is less than Michael's moment, the system is balanced and will
not move forward. However, if the proposition's moment is greater than
Michael's moment, the greater moment will force him to fall forward.
A4. The Stability Triangle.
A4.1. Almost all counterbalanced objects have a threepoint
suspension system, that is, the object is supported on three points.
This is true even if there are four extremities. When the points are
connected with imaginary lines, this threepoint support forms a triangle
called the stability triangle.
A4.2. When Michael's line of action or reaction center
falls within the stability triangle, he is stable and will not fall.
However, when his line of action or the Michael/opportunity combination
falls outside the stability triangle, Michael is unstable and may begin
to move.
A5. Longitudinal Stability.
A5.1. The axis of rotation when Michael falls forward
is formed by his body's points of contact with other bodies. When he
tips forward, his body will rotate about this line. When Michael is
stable, the objectmoment must exceed the propositionmoment. As long
as the objectmoment is equal to or exceeds the propositionmoment,
he will not overturn. On the other hand, if the propositionmoment slightly
exceeds the objectmoment, Michael will begin to tip forward, thereby
causing his top half to lean slightly. If the propositionmoment greatly
exceeds the objectmoment, Michael will fall forward. Figures 1 and
2 illustrate two previous episodes of this instability, and the overturning
that resulted.
A5.2. To determine the maximum resistance, the object
is normally rated at a given distance from the front of the face. The
specified distance from the facefront to the line of action of the
proposition is commonly called the reaction center. Because more advanced
objects can normally handle situations that are larger, these objects
have greater reaction centers. Keep in mind that while this is generally
true, there are exceptions. To safely operate Michael, whether involved
in testing the maximum resistance or in readjusting an unstable situation,
the operator should always check the past history to determine the maximum
allowable opportunity/possibility/lean at the rated reaction center.
A5.3. Although the true propositionmoment distance
is measured from the front, this distance is greater than the distance
from the exact facefront. Calculating the maximum allowable propositionmoment
using the center distance always provides a lower moment than Michael
was designed to handle. When handling unusual movements that might have
an offset center of gravity or involve an element of surprise, a maximum
allowable propositionmoment should be timed and calculated and used
to determine whether a certain question can be safely handled.
A6. Lateral stability.
A6.1. Michael's lateral stability is determined by
the line of action's position (a vertical line that passes through his
and the question's center of gravity) relative to the stability triangle.
When he is not propositioned, his center of gravity location is the
only factor to be considered in determining his stability. As long as
the line of action of the question's center of gravity and Michael's
center of gravity falls within the stability triangle, he is stable
and will resist moving. Clearly, the operator should avoid putting Michael
into situations where this lateral stability is tested (see Figure 3).
A6.2. Factors that affect Michael's lateral stability
include timing of movement, elements of surprise and interest, and his
degree of lean.
A7. Dynamic stability.
A7.1. Up to this point, the stability of Michael
has been discussed without considering the dynamic forces that result
when he and the proposed situation are put into motion. The emotional
transfer and the resultant shift in the center of gravity due to the
dynamic forces created when Michael is moving, cornering, maneuvering
directions, etc., are important stability considerations, and should
not be misjudged.
A7.2. When determining whether a situation
can be safely handled, extra caution should be exercised when handling
ones that cause Michael to approach his maximum design characteristics.
For example, if Michael must handle a situation which tests his maximum
capabilities, the guidelines above must be used to maintain balance,
with extra caution at all times. However, no precise rules can be formulated
to cover all eventualities.
© Amy Havel
