AutoCAD Mechanical toolset performs calculations for belt or chain lengths based on existing geometry.
AutoCAD Mechanical toolset performs calculations for belt or chain lengths based on existing geometry. A dialog box displays the available representations for chains and belts and for pulleys and sprockets. A library function helps saving and recalling the respective components.
Chain drives are interlocking, wrapping drives, where an endless chain wraps around two or more sprockets. Chain drives, as with spur gear pairs, serve to transfer force and motion between parallel shafts. Chain drives can bridge the distance between axles that typical gearwheels cannot.
Chain drives are not as flexible as belt drives, but can be used when space, power translation, or axis distance make incorporating a belt drive unfavorable. A facet of a chain's length that must be accounted for is the polygon effect at the sprocket. The polygon effect occurs particularly in smaller synchronous belts having relatively low teeth numbers; the turning transmission is not constant, due to the cyclic changes of the chain peaks and valleys. The length of a chain therefore does not correspond to its centerline.
Belt drives can transfer a lot of power with respect to their dimensions and weight; they run quietly without slip, and require relatively little shaft load or support. Belts do not have the polygon effect, therefore the length of the centerline is the length of the belt.
Both calculations essentially follow the same procedures. The chain or belt length calculation routine, used for both calculations requires that you insert at least two circles into your drawing to represent the pitch circle diameter of the pulleys or sprockets. Alternatively, you can insert sprockets or pulleys using AMSPROCKET. The pulleys and chain wheels are displayed as circles. You must select the reference circle to carry out a calculation. The circles establish the tangential conditions required for the chain or belt. We recommend carrying out length calculations on separate layers or in an extra drawing, to view the simplified presentation. To insert a chain or belt, or a sprocket or pulley, you must create and calculate a base arrangement first.
When a chain is drawn, it follows a polyline. This polyline is generated by the length calculation function.
Pulleys are represented as circles. The circles correspond to the pitch radius of the pulley. The tooth profile is calculated from the selected block of the library. The pulley orients itself on the shape of the synchronous belt. The pitch circle corresponds to the length of the pulley at the pitch line.
A sprocket is defined by the number of teeth. The diameter of the roller corresponds to the diameter adjacent to the sprocket.
Note: The teeth of the pulley correspond to the shape of the teeth for the belt of the library. However, in reality these shapes differ slightly.