Improving running safety in sharp curves, especially in transition curve, reducing lateral force and wheel load variation are very important. In this paper, the newly developed system "a Torsion Equalizer mechanism (T.E.)" for reduction of wheel load variation and the results of on-track tests to evaluate the effect of this system are introduced. It is common that the wheel unloading phenomena are caused by rail twist due to reduction of superelevation in transition section of sharp curves. Because of the reduction of superelevation at a transition curve, rail twist occurs between each position of the front and rear bogies on a car. Because the carbody cannot be transformed to follow a rail twist, large wheel unloading is occurred at outside wheel of leading wheelset in a car. In order to improve the curving performance, the authors installed T.E. that reduces wheel unloading caused by the rail twist due to the reduction of superelevation. The side bearers of bogie bolster on the same lateral sides are joined by the containment hydraulic circuit so as to be coupled. At the exit of a transition curve, the side bearer in the rear bogie on high rail side is forced up. Then the upward force generated in the rear bogie is transferred to the side bearer in the front bogie through the containment hydraulic circuit. Finally the side bearer in the front bogie on high rail side is pushed down and the wheel load in the front bogie on the high rail side is recovered. T.E. was equipped on Tokyo-metro Chiyoda line train, series 16000, and performed on-track tests to investigate the effect of this system. The wheel unloading in transition curves were improved at most 16pt in the tests.
