In the present work, a new design of magnetorheological (MR) drum brake for two-wheeler is presented, which can be operated in hybrid mode i.e. compression and shear modes, unlike the conventional one, which only operates in single mode. The presented MR brake has a rotating drum (rotor) and stationary concave plates (stator). The MR fluid is filled in between these rotor and concave plates and its gap is maintained 1 mm initially. Other than the stator and rotor, the brake comprises an electromagnet, brake plate, cover plate, screws, sealing, and compression mechanism. The disassembled and assembled view of the presented MR brake is shown in Figs. 1 and 2 respectively. In the present study, side electromagnet is used, while in previous studies, it was placed at centre. In order to pass the magnetic field lines radially in the MR gap of the drum brake, side electromagnet is an alternative solution. A ball bearing is placed on cover plate and at its outer periphery, the side electromagnet is placed. The cover plate, brake plate, and shoes are made of non-magnetic material.

The main objective of the compression mechanism is to compress the MR fluid in the MR zone along the magnetic field direction. To accomplish this purpose and to add compression along with shear mode in drum brake operation, a mechanism of two springs, a cam, a lever and two shoes is utilized which is currently used in conventional drum braking system. For compressing MR fluid between the stator and rotor, the stator (inner drum) has been split into two equal parts which are concave plates. These concave plates are attached to shoes through screws, and the flat end of the shoes is in contact with the flat end of the cam with the help of tension springs. The other end of the shoes is in contact with the brake plate. The cam has two ends; one is a flat face, while the second is a hexagonal cut end. Fig. 2c shows the sectional view of compression mechanism. The hexagonal end of the cam is in contact with the lever. When the load is applied on the lever, it actuates the cam, and this actuation forces the concave plate and shoe assembly to slide towards the inner surface of the rotating drum. Consequently, the gap between concave plates and drum decreases and which creates compression on the MR fluid gap. Fig. 3 compares the braking torque offered by a conventional two-wheeler's friction drum brake (Hero splendor rear wheel drum brake) on the same test and fabricated MR drum brake at 500 RPM. It shows that the range of effective braking torque offered by both brakes for the same speed value is similar.

The size and shape of the presented MR brake has been considered according to working space available for the conventional friction drum brake. Hence, it can be said that the presented MR drum brake operating under compression and shear mode is a better substitute for conventional brakes.