A device that supports, guides, and reduces the friction of motion between fixed and moving machine parts Something that supports weight. The part of an arch or beam that rests on a support. Journal bearings The general principle is that a shaft rotates inside a bearing bore slightly larger than the shaft diameter, and a lubricant is supplied to the annular gap The portion of the shaft within the bearing is called the At low speeds, the fluid wedge does not fully develop, and partial contact occurs. The coefficient of friction f is about 0.10. This is called Boundary lubrication As speed increases, contact occurs less frequently, and fdecreases into the range of. 004 <f<0.10. This is Mixed Lubrication Finally, under hydrodynamic lubrication, no contact occurs, and 0.002 f< 0.010. Advantages of Journal Bearings are well suited for high rotating speeds with impact and momentary overloads. The higher the rotating speed, the more effective the hydrodynamic pumping action do not normally generate noise and may dampen noise from other sources. .are less expensive than ball or roller bearings for requiring min imal lubrication provisions. Elements of Bearings These parts include .inner rings: connection to the rotating shaft Outer rings: connection to the stationary housing Rolling elements: such as balls or rollers Cage(retainer or separator): which keeps the ball or rollers evenly spaced and separated Seals: keep grease in the bearing and dirt and debris out of it. Gears Gears, defined as toothed members transmitting rotary motion from one shaft to another, are among the oldest devices and inventions of man A gear is a wheel with teeth along its rim It is used to transmit effort from one shaft to another Terms of Spur Gearset The pinion and gear are regarded as two cylinders that are pressed against one another and smoothly roll together. Speed In Gearset As the pinion rotates, the speed of a point on its pitch circle is vp=rpup LiKewise, that of gear is vg=rgu Because the velocity of points in contact are the same, the velocity ratio is Gear Train Combination of two or more meshed gears Used to change the rate ofA device that supports, guides, and reduces the friction of motion between fixed and moving machine parts. Something that supports weight. The part of an arch or beam that rests on a support. Journal Bearings The general principle is that a shaft rotates inside a bearing bore slightly larger than the shaft diameter, and a lubricant is supplied to the annular gap. The portion of the shaft within the bearing is called the At low speeds, the fluid wedge does not fully develop, and partial contact occurs. The coefficient of friction f is about 0.10. This is called Boundary Lubrication. As speed increases, contact occurs less frequently, and f decreases into the range of .004 < f < 0.10. This is Mixed Lubrication. Finally, under hydrodynamic lubrication, no contact occurs, and 0.002 < f < 0.010. Advantages of Journal Bearings •are well suited for high rotating speeds with impact and momentary overloads. The higher the rotating speed, the more effective the hydrodynamic pumping action. •do not normally generate noise and may dampen noise from other sources. •are less expensive than ball or roller bearings for requiring minimal lubrication provisions. Elements of Bearings These parts include: •inner rings: connection to the rotating shaft •Outer rings: connection to the stationary housing. •Rolling elements: such as balls or rollers •Cage (retainer or separator): which keeps the ball or rollers evenly spaced and separated. •Seals: keep grease in the bearing and dirt and debris out of it. Gears Gears, defined as toothed members transmitting rotary motion from one shaft to another, are among the oldest devices and inventions of man. A gear is a wheel with teeth along its rim. It is used to transmit effort from one shaft to another。 Terms of Spur Gearset The pinion and gear are regarded as two cylinders that are pressed against one another and smoothly roll together. Speed In Gearset As the pinion rotates, the speed of a point on its pitch circle is vp=rpùp. LiKewise, that of gear is vg=rgùg Because the velocity of points in contact are the same, the velocity ratio is: Gear Train Combination of two or more meshed gears. Used to change the rate of