The SST-1 is a super conducting tokamak, which is in the final phase of assembly and commissioning. The super conducting magnet system of SST1 comprises of Toroidal field (TF) and Poloidal field (PF) coils. The 16 TF coils are nosed and clamped towards the in-board side and are supported toroidally with inter-coil structure at the out-board side, forming a rigid body system. The 9 PF coils are clamped on the TF coils structure. The integrated system of TF coils & PF coils forms the cold mass of @ 50 Ton weight. This cold mass is accommodated inside the cryostat and freely supported on the rigid support ring at 16 locations and support ring in-turn supported on 8 columns of machine support structure. During the operation this cold mass attains a cryogenic temperature of 4.2K in the hostile environment of high vacuum. The thermal excursion of cold mass and its supporting structure during this cool down results into severe frictional forces at the supporting surfaces. There is a design requirement of introducing a thin layer of solid lubricant film of MOS2 having coefficient of friction 0.05 between the sliding surfaces to control the stress contribution due to the friction.To ascertain the compatibility of molybdenum disulphide (MOS2) as a solid lubricant in high vacuum and very low temperature environment, we have carried out qualification tests on various samples and measured the coefficient of friction in both the room temperature conditions and at high vacuum & after thermal shocking to 4.2K temperatures. After successful qualification tests actual components are fabricated and integrated in the cold mass support structure assembly. This paper presents the design requirement, qualification tests performed and details about the integration of thin solid lubricant film of MOS2.
In IC Engines, basically the oil pump is driven either by a drive gear integrated with camshaft or a gear mounted on the crankshaft. In the older engines the oil pumps were mostly camshaft driven with a skew gear arrangement which becomes unique and tailor made for the given engine as part of the engine cylinder block sub-assembly. This arrangement calls for complex machining and the number of parts involved are more compared to a crankshaft driven oil pump as being seen in the modern engines. A crankshaft driven oil pump basically calls for a study of the envelope constraints and boundary conditions and finalising the mounting and maximum envelope possible for accommodating the oil pump. The challenge lies in arriving at a very compact pump with the required delivery for the given engine within the envelope limitations. From the different oil pump types, the external spur gear type was selected for the design as it is the most popular and cost effective with manufacturing friendliness for mass production. The basic design computation was done based on the amount of heat carried away by the lubricating oil and the circulation rate of oil in the system. Through the step by step procedure the gear size and the power required to drive the pump was calculated. Based on the gear size and the some preselected parameters, all the important gear parameters were calculated. The pump discharge was computed and it was verified that the discharge increases in direct proportion with the increase in engine speed, by a plotting a graph of oil pump discharge against engine speed and obtaining a linear trend in it. The design of the relief valve for the pump was also carried out. The physical dimensions of the compression spring were chosen and all the other important parameters were calculated and ensured that the pressure in the lubrication circuit remains within the prescribed limit.
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