A large 10 m diameter tunnel boring machine is driven through a clutch mechanism

Question

A large 10 m diameter tunnel boring machine is driven through a clutch mechanism, as illustrated in Figure 4. The boring machine can be modeled as a solid steel disc of thickness 500 mm with four cylindrical sections of radii 1 m removed, positioned equispaced around the disc at a radius of 3 m. (a) Using a steel density of 7850 kg/m^3, derive the mass moment of inertia of the machine about its rotating axis, ignoring the clutch drive mechanism. (b) The multi-plate uniform pressure clutch mechanism for the boring machine contains six plates with a total of six friction surfaces. Three of the plates have outer diameters of 3 m and three have diameters of 2 m, all with inner diameter of 1 m. Calculate the total avaiTable drive torque for an axial force of 1000 kN. Assume a wet clutch friction coefficient of 0.1. (c) Calculate the total time for the tunnel boring machine to start up from rest to reach an operating speed of 6 rpm, given that there is a frictional resistive torque load of 100 Nm.

Explanation / Answer

The loaded four wheel trailer shown in Figure P8.10 has a total mass of 5t and is pulled along a level road. Average resistance to motion (friction and windage) is 2 per cent of the total weight and acts at the same horizontal level as the applied force P. Determine the normal reaction at each of the front and rear wheels when the trailer moves:

a) at constant velocity

b) with forward acceleration 1.5m/s².

(Average resistance to motion is 2% of total weight is not required.)

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