Six links to papers on ball bearing motors, but none of them give you access to free papers. :-(
Some appear to contradict Horace's finding concerning non-ferromagnetic materials. Harry ----------------------------- 1. The electromagnetic torque on axially symmetric rotating metal cylinders and spheres M. P. H. Weenink 1981 Abstract The torque is calculated on an electrically resistive rotating cylinder and sphere through which a current is fed by means of sliding contacts. The torque on a rotating cylinder is proven to vanish identically for arbitrary angular velocity. The torque on the sphere is shown to vanish up to second order in an expansion with the angular velocity as the expansion parameter. The nonzero torque in first order found by Gruenberg is shown to be due to an algebraic error. http://www.springerlink.com/content/g816l5g714564034/ first page is free. ---------------------------- 2. The electrostatic torque on a rotating conducting sphere M. J. C. M. van Doorn1 1983 Abstract The electrostatic torque on a rotating sphere through which a current is fed by means of two diametrically situated sliding contacts is positive in the direction of rotation. However, this torque is too small in practice to keep a ball bearing motor running. http://www.springerlink.com/content/l5618xjmt127xq62/ [First page is free. There he says it works with ferromagnetic as well non-ferromagnetic material?!. Refers to Weenink. See also Watson below] ----------------------- 3. Investigation of small motors operating under the Huber effect Proc. SPIE, Vol. 4236, 306 (2001); doi:10.1117/12.418768 Online Publication Date: 20 May 2003 Conference Date: Wednesday 13 December 2000 ABSTRACT Adam P. Lauterbach, Wen L. Soong, and Derek Abbott Adelaide Univ. (Australia) The Huber effect is an interesting and potential useful means for creating extremely small and simple motors. It is based on the observation that torque is produced when current is passed through a rotating ball bearing. This paper reviews the alternative explanations for its operation and describes the design, construction and characterization of two prototype ball-bearing motors based on high precision miniature ball bearings. A key limitation of earlier work has been difficulties in repeatability due to rapid wear of the motor. This was overcome by using a data acquisition system to record the dynamic acceleration characteristics and hence predict acceleration torque versus speed characteristics. http://dx.doi.org/10.1117/12.418768 --------------------------- 4. Investigations into the roller electrical motor D B Watson, G R Bellam, W Y V Leung and S P Nolan Abstract. The roller electrical motor (REM) consists of non-magnetic stainless steel cylinders rolling on parallel stainless steel rails of the same diameter with an electrical current passing from rail to rail through the rolling cylinders. The REM is found to be capable of carrying heavy loads, the electrical driving force increasing as the current and loading are raised. When the REM carries a 50 kg load the driving force increases at the rate of 80 mN . At 30 A the REM is capable of driving external frictional loads of 1.7 and 2.2 N while carrying loads of 50 and 100 kg respectively. This paper describes the characteristics of the REM and discusses the origin of the driving force. A thermal expansion theory is developed to explain the experimental results. Print publication: Issue 6 (21 March 1999) Received 20 October 1998 http://www.iop.org/EJ/abstract/0022-3727/32/6/021 -------------------------------- 5. Non-ferromagnetic linear ball-bearing motors D B Watson and A M Watson Abstract. The paper describes experiments on a metal ball rolled along parallel metal rails. An electrical force is developed on the ball in the direction of movement by passing current through it from one rail to the other. Contrary to the electromagnetic theory of the ball-bearing motor, the electrical force on a brass ball is of the same order as that on a steel ball. The results are discussed in terms of a torque exerted in the contact region. Print publication: Issue 3 (14 March 1996) Received 7 February 1995, in final form 8 August 1995 http://www.iop.org/EJ/abstract/0022-3727/29/3/007 -------------------------------- 6. Study of electrical characteristics of the ball bearing motor Moyssides, P.G. Hatzikonstantinou, P. This paper appears in: Magnetics, IEEE Transactions on Publication Date: Jul 1990 Abstract The electrical characteristics of the ball bearing electric motor are studied for applied steady currents ranging from 43.5 to 70.15 A. It is found that the ball bearing behaves like a motor when it starts self-rotating meaning that the shaft and inner race of the pair of the ball bearing system start rotating by themselves without the help of any external agent, but with a small efficiency at high currents. During self-rotation the motor's counter electromotive force depends on the angular velocity of the shaft and inner race. The ball bearing's behavior at low currents is also explained when it is not self-rotating, (i.e. rotating with the help of a conventional motor). In the latter case, the motor does not behave like a generator. A theory, based on the electromagnetic interactions developed within each ball, is proposed to explain the action of the ball bearing as a motor. These interactions are caused by the ball's primary currents and magnetic fields and the effects of the induced magnetic field from the current of the motor's shaft http://ieeexplore.ieee.org/xpl/freeabs_all.jsp?arnumber=54012
