TITLE: The dynamical behavior of a rotor on a belt suspension drive
AUTHOR: Ben-Amots, N.
SOURCE: M.Sc. thesis, Technion, Haifa, Israel (1969).
SUPERVISOR: D. Bousso (1933-1971)
ADVISORS: I. Porat (1934-2012),
B. Popper (1927-2012).
SYNOPSIS: The purpose of this research is to investigate the laws that
determine the dynamical behavior of a rotor on a belt suspension-drive,
experimentally and/or theoretically. This drive system was invented by
Bousso, and has not been investigated yet. There are wide research
possibilities because it is new, because there are so many influencing
parameters, and also because of the many possible variations of the system.
The aim was to investigate those factors the control of which is necessary
to enable applications of the system. This is carried out for only one of
the possible variations.
The aim of the research was twofold.
The first was to reach high angular velocities and in particular high
centrifugal accelerations. This aim was achieved, and the laws of dependence
between the accelerations, angular velocities and the main parameters, have
been found. In order to achieve this experiments have been carried out, in
which it has been proved that it is possible to reach high velocities and
accelerations, up to the limit of the strength or the rotor material.
Angular speeds up to 740000 R.P.M. have been reached. The centrifugal
acceleration exceeded 4000000 g's in the rotor having a diameter of 13.5 mm.
The suitable conditions for achieving such high accelerations were found to
be: An angular velocity exceeding 600000 R.P.M.; a rotor diameter of 1-2 cm;
rotor material - steel (yield strength at least 90 kg/mm^2); ambient pressure
1-2 cm Hg abs.
A theoretical model which explains the effects that were investigated
experimentally, and which predicted results for those experiments which were
not carried out, has also been developed. It indicates that at pressure of
1-2 cm Hg abs. the most suitable rotor material is steel. Titanium or
aluminum alloy would be more suitable at lower pressures: 2-3 mm Hg abs.
The second aim was to investigate and learn the factors that determine the
stability of the rotor. It is very important to control the different
vibrations in order to attain as stable a rotation as possible, because the
rotor has no bearings.
The angular stability of the rotor has been investigated. A theory which
explained the observed effects has been developed. This theory pointed out
other predictable effects, observed in the course of additional experiments.
The most important parameter which determined the angular stability was found
to be the tolerance between the belt and the groove in the rotor. A suitable
dimension of the width of the belt and the groove is 1.5 mm. The groove must
be plain, and not conical.
The pendulum vibrations of the rotor was also investigated. A way to control
them has been found experimentally. The pendulum vibrations have a resonance
characteristic. The factor which has the greatest influence on the vibrations
was found to be the humidity. When the surrounding medium consists of water
vapor only, there is no build-up of the pendulum vibrations.
The vertical vibrations have been found to be always damped.
Other effects of instability were discovered.
Non-periodical motions of the rotor have been investigated. An experimental
way to measure the moment that the belt supplied to the rotor has been found.
None of the effects that were investigated, were found to rule out application
of the system. The conclusion is that it is necessary to investigate those
effects not yet investigated, and to continue the research in the direction
of practical application of the centrifugal acceleration achieved.
The set-ups that have been developed for the experiments are described in the
appendices. The last appendix includes suggestions for practical applications
of the high accelerations achieved.
and more 5 references.
Svedberg, T., Pedersen,, G., "The ultracentrifuge," Johnson Reprint, New York (1959).
Popper, J.B. (1927-2012), "Equations of motion of rigid bodies," D.Sc. thesis, Technion, Haifa,
Israel (1960) (In Hebrew) Synopsis in English.
Beams, J.W., "Ultrahigh-speed rotation," Scient. Am., v. 204, No. 4, pp. 124-147 (1961).
Bousso, D. (1933-1971), "A stability criterion for rotating shafts,"
D.Sc. thesis, Technion, Haifa, Israel (1963) (In Hebrew)
Synopsis in English.
Porat, I. (1934-2012), "Optimal damping of flexibly-mounted rotor,"
Israel J. Technol, v. 7, pp. 235-245 (1969)
Abstract in English.
Dedicated to the memory of the author's parents
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