ENGME353 Mechanical and Electrical Machines

Slot Car Lab In this lab you will simulate the operation of a slot car in Vissim and select a gear ratio and wheel diameter to complete the track in the fastest time. Description The slot car is 4WD with two brushed DC motors. The DC brushed motors drive the wheels through a gearbox. The gearbox can be compounded, each stage has a gear ratio of 4. The number of teeth on the gears is stamped on the side of the gear. You can assume each gear pair has an efficiency of 90%. Two different wheel diameters are available: 70 and 90 mm. The loaded mass of the car is approximately 835 g. The rolling resistance of the vehicle has been estimated at 0.28 N. The motor has an approximate no-load speed of 13400 RPM, and a stall torque of 31.7g-cm. The first section of the track is flat, and the second section is inclined, as pictured below: Experimental 1. Draw a free body diagram (FBD) of the car. Include all forces acting on the car, e.g. driving force, gravity, rolling resistance 2. Develop a mathematical model of the slot car accelerating from rest along the track. i.e. write down all the equations describing the motion of the vehicle. You do not need to combine the equations. State any assumptions you have made. Helpful equations