A comparison of the performances of full and half toroidal traction drives G. Carbone * , L. Mangialardi, G. Mantriota Dipartimento di Ingegneria Meccanica e Gestionale, Politecnico di Bari, V.le Japigia 182, 70126 Bari, Italy Received 5 May 2003; received in revised form 21 January 2004; accepted 10 April 2004 Abstract The eﬃciency of two diﬀerent typologies of the toroidal traction drive, the full-toroidal and the half- toroidal, is estimated in order to point out which of them oﬀers the higher mechanical eﬃciency. A fully ﬂooded isothermal contact model between the discs and rollers, based on the results of EHL theory, is used to evaluate the slip, the spin losses and the mechanical performances of the variators. It is shown that the half-toroidal traction drive oﬀers higher eﬃciency and higher maximum transmissible torque. Ó 2004 Elsevier Ltd. All rights reserved. 1. Introduction The request for a higher energy eﬃciency and CO 2 reduction has pushed several researchers to ﬁnd new technical solutions to improve the emission performance of nowadays IC engine vehicles. While waiting for new and renewable forms of energy to become eﬀective and cost reasonable, new solutions have to be found: among diﬀerent and several technical solutions, new drive train systems are being investigated to accomplish this purpose. The continuously variable transmission (CVT) represents one of the most promising solution since it is able to provide an inﬁnite number of gear ratios between two ﬁnite limits, and, thus, to allow the IC engine to operate closer to its optimal eﬃciency line. Several studies have shown that it is possible to improve the fuel savings and to reduce the vehicle emissions by adopting this kind of transmission [1,2]. It has been shown, for instance, that when the transmission is optimally controlled the mid class vehicles equipped with the CVT and * Corresponding author. Tel.: +39-080-596-2746; fax: +39-080-596-2777. E-mail addresses: carbone@poliba.it (G. Carbone), lmm@poliba.it (L. Mangialardi), mantriota@poliba.it (G. Mantriota). 0094-114X/$ - see front matter Ó 2004 Elsevier Ltd. All rights reserved. doi:10.1016/j.mechmachtheory.2004.04.003 Mechanism and Machine Theory 39 (2004) 921–942 www.elsevier.com/locate/mechmt Mechanism and Machine Theory