A pulley that is keyed to the machine shaft is called a fast pulley and runs at the same speed as that of the machine shaft.Ī loose pulley runs freely over the machine shaft and is incapable of transmitting any power. This type of belt drive is used when the driven or machine shaft is to be started or stopped whenever desired without interfering with the driving shaft. To avoid this, the shaft must be placed at a maximum distance of 20 B, where B is the width of the belt and the belt speed must be less than 15 m/s. To avoid excessive wear, the shafts should be kept at a maximum distance from each other and operated at very low speeds.Ī little consideration will show that at a point where the belt crosses, it rubs against each other and there will be excessive wear and tear. At the junction where the belt crosses, it rubs against itself and wears off. This type of belt drive employs a belt when two parallel shafts have to rotate in the opposite direction. The lower side belt is known as the tight side belt while the upper side belt is known as the slack side belt. Thus, the tension in the lower side belt will be higher than in the upper side belt. In that case, the driver pulls the belt from one side and delivers it to the other side. The open belt drive is used with shafts arranged parallel and rotating in the same direction. Seven different types of belt drive can be found and those are: Conditions under which belts are used.Arc of contact between the belt and small pulley.The tension under which the belt is applied to the pulleys.The amount of power transmitted depends on the following factors: The belt drive can also be used to change the speed of rotation, either up or down, by using different-sized pulleys. In a two-pulley system, the belt can either drive the pulleys normally in one direction (the same if on parallel shafts), or the belt may be crossed, so that the direction of the driven shaft is reversed (the opposite direction to the driver if on parallel shafts).Īs a source of motion, a conveyor belt is one application where the belt is adapted to carry a load continuously between two points. Belts are looped over pulleys and may have a twist between the pulleys, and the shafts need not be parallel. Belts may be used as a source of motion, to transmit power efficiently, or to track relative movement. A belt is a loop of flexible material used to link two or more rotating shafts mechanically, most often parallel.
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