Ben-Amots: The dynamical behavior of a rotor on a belt suspension drive

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 of 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 a 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 that 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 were 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 the 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 the 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.

Hebrew abstract

10 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.

and more 5 references.

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Dedicated to the memory of the author's parents

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