Analysis of Air Brake used in Medium Duty Truck

Abstract

This project work involving modeling and analysis of brake drum of comet vehicle of Ashok Leyland. The work was done using mechanical desktop and Cosmos. The complete brake assembly with about 20 parts was modelled and assembly was created. The assembly is shown below shows the brake shoes, S Cam, cam rod and pneumatic cylinder and slack adjuster. Kinematic analysis was done on the model elements to see interference and limitation of movement. The thrust provided by the shoes on the drum face was computed from the pneumatic pressure under full braking condition and the same was given as a uniform pressure on the brake shoes and the displacement of the drum shell was studied. The maximum deformation of the drum shell was found to be 1.3 X 1o^-5 mm.

The stress induced on the drum due to the force applied by the brake shoe was analysed. The stress plat shows the distribution of Y directional stress in the drum when the shoe applies maximum thrust.

Next thermal analysis was carried out on the drum under single application and multiple application of brake with full force. The vehicle inertia was taken when travelling at 60kmph and the brake absorbed the complete energy proportionately by this drum. This energy was applied as heat on the inner face of the drum for the width the shoe is in contact. The decelerating time was computed using empirical formula given by Rudolph Lumpert was arrived at as 10 sec. for deceleration from 60 – 0kmph. The maximum heat flux is applied at time t = 0 and at time t = 10 heat flux applied is zero as there is no braking action while speed is zero. The variation was assumed as linear. As a second alternative the vehicle was accelerated for 40 seconds and braked for 10 sec. And this acceleration and braking cycle was repeated 10 times and corresponding temperature variation was studied on a node on the outer face of the brake drum where convective cooling is taking place during accelerating phase. The curve above shows the temperature variation with reference to time for a period of 370 sec. As can be seen the temperature has not stabilised but increasing. But the cooling curve doing acceleration phase as the temperature difference between ambient and the node is higher.