Reactionless
drives Vs Stick-Slip drives by JL
Naudin |
All informations in this page are published free and are intended for private/educational purposes and not for commercial applications
WARNING, you may be fooled by some false reactionless drives experiments....
Some of
them use the well known "STICK-SLIP" technique for
moving itself on a surface. This method is commonly used in
nanorobotics....
<< Stick-Slip
Friction : http://entropy.davidson.edu/faculty/dmb/PY430/Friction/stick-slip.html
In any
case where the coefficient of kinetic friction is less than the
coefficient of static friction there will exist a tendency for
the motion to be intermittent rather than smooth. The two
contact surfaces will stick until the sliding force reaches the
value of the static friction. The surfaces will then slip
over one another with a small-valued kinetic friction until the
two surfaces stick again. The most simple model for
explaining this mechanism of friction, known as 'stick-slip,' is
the case of a spring with a mass attached. In this setup there is
a mass attached to a coiled spring being pulled by a tension
force so that the spring moves at a constant velocity. The
surface upon which this setup rests has a coefficient of kinetic
friction that is much less than the coefficient of static
friction. When the spring is pulled one unit of distance, the
tension is enough to overcome the force of static friction, and
the block begins to move.
Because the kinetic friction is far less than the static friction
the block moves at a velocity faster than that of thespring,
rapidly restoring the spring to its unstretched length causing
the block to once again come to rest to start the entire process
over again. The body will again remain at rest until the
tension exceeds the static friction causing the block to move
forward another unit of distance until the mass stops because of
the compression of the spring back to its unstretched length.
By performing this run at numerous spring velocities and making
plots of position versus time, the trend we begin to see is that
the faster the spring velocity,
the motion of the mass becomes less jerky. Also, the motion
of the mass becomes less jerky if the two coefficients of
friction approach the same value.
Now the case of the mass and spring may seem like a very
localized case of 'stick-slip' friction, but the fact is that
even a stiff rod has some amount of elasticity and will stretch
when it is pulled. Although the 'stick-slip' mechanism may
not be as visible to the eye, it will still occur on a reduced
microscopic level.
Furthermore, elastic deformation occurs in all driving
mechanisms, such as the transmission of an automobile, the chain
on a bicycle, or in various cutting tools.
All of these examples are cases wher the static friction is
higher than the kinetic friction and may be prone to intermittent
'stick-slip' motion.
Finally,
what about the velocity dependence of this and other types of
friction? In the case of 'stick-slip' friction the velocity
dependence is easily seen in the case of the mass and spring.
This same type idea applies to kinetic friction in general.
The coefficient of kinetic friction for all materials shows
some dependece on velocity to a marked degree. At very slow
speeds mu for kinetic friction increases with speed until it
reaches some localized maximum, at which point mu begins to
decrease with increasing velocity. In fact very low values
of mu are found for metals moving at very high speeds (several
hundred meters per second). Thus, kinetic friction and
'stick-slip' friction are, for the most part, velocity dependent
forces.
>>
See also some explanations about the Stick-Slip drives technique
at : http://www.linktestlab.com/FEV1.htm
A good "Stick-Slip drive" sample can be found in this
patent from the US Navy :
http://l2.espacenet.com/dips/bnsviewer?CY=ch&LG=fr&DB=EPD&PN=US3916704&ID=US+++3916704A1+I+
<< US3916704:Vibratory
locomotion means
Inventor(s): Gaberson; Howard A.
, Oxnard, CA
Applicant(s): The United States
of America as represented by the Secretary of the Navy,
Washington, DC
Issued/Filed Dates: Nov. 4, 1975 /
April 23, 1973
A vibratory locomotion device which consists
of one or more skids resting the ground supporting a payload, and
a vibrating mass attached to the skid. The mass, operated by a
motor which creates a sinusoidal oscillation, alternatively pulls
and pushes on the skid at a predetermined angle to the ground as
it vibrates. When the mass is at the top of its stroke, it lifts
and pulls forward on the skid and, when it is at the bottom of
its stroke, it pushes downward and backward on the skid. Since
the downward force increases the normal and, hence, the available
friction force, the angle of the mass to the ground can be
adjusted so that no backward slide results. As a result of the
vibration of the mass, the skid incremently shuffles forward
along the ground. >>
See
also some nanorobotics applications at :
ALL THESE KINDS OF
"STICK-SLIP" DRIVES AREN'T ABLE TO WORK WITHOUT A
PRESENCE OF A FLUID OR A FRICTION SURFACE AND THUS THEY DOESN'T
WORK IN DEEP SPACE ( in a FULL VACUUM and in ZERO-G conditions )
....
Some
people have built gizmos that depend on the presence of a fluid
or friction to cause the appearance of a reactionless drive, but
these gizmos only work when sitting on a surface.
These false reactionless devices are very far from some
Electromagnetic Impulse/Reactionless drives currently used for
Stellar Drives researches....
Best Regards,
Jean-Louis Naudin
Email: JNaudin509@aol.com
Web
site : http://go.to/jlnlabs/