V-Belt Selection Guide: V-belt Sizes, Types and Safety

V-Belt Selection Guide: V-belt Sizes, Types and Safety - Belts are made of rubber with a cotton cloth core or the like as reinforcing the greatest tensile force. Use as v-belt transmission has the following advantages:

• A portion of the belt is twisted in the pulleys experience a wide arc so that grow large section to provide a large friction.
• The friction force also increases due to the influence of the wedge-shaped which generate a large transmission power of relatively low stress.
• It has a slip to avoid damaging an electric motor.
• It can be used in a large transmission ratio and the distance closest to the shaft.

V-belt is a standard part so easy to find in stores or belt manufacturer's dealers. The machine designer simply chooses the type and size of the belt as required by the machine. V-belt selection is determined by the length and type of the cross section of the belt relative to the power and speed are transmitted. Once selected, the belt also remains to be tested for safety by the power capacity and the speed of the belt.

Determined of v-belt types

V-belt has a trapezoidal section with a variety of sizes, from small to large, ie, type A, type B, type C, type D and type E. The v-belt types sections selected based motor  power and driver shaft speed by the following curve.

Examples:
If the belt driven by a motor with a power of 3 kW at a speed of 2000 rpm pulley, then the graph above corresponding the intersection of the power requirement line (blue line) with the speed of driver pulley (red line) is in the region A means that the type of belt is selected by type A.

Determined of v-belt sizes

Once the type of v-belt is known, the following must be known how long the belt is required. In the trade standard, long belt is expressed by v-belt sizes. The v-belt size is units of inches in circumference around length, not decimals and fractions. Before determining the v-belt sizes, the v-belt must be known mm in length using the following calculation:

Note:
L = V-Belt Length (mm)
C = Center Distance (mm)
d = Diameter of driver pulley (mm)
D = Diameter of driven pulley (mm)The v-belt size is obtained by converting the circumference of belt in inch units. Its results are rounded. For example, if you get 24.45 inches then take a belt number is 25.

V-belt safety by power capacity

Belt has a power capacity that can be transmitted. Power capacity issued for each single belt depending on the v-belt type, pulley diameter, speed of the driver pulley and belt marks. Belt manufacturer usually have the belt capacity catalogue. An example of a table for the power capacity of the v-belt type A shown.

Power capacity of v-belt is main value in table and value added suitable of transmission ratio, example if driver pulley speed is 600 rpm, pulley diameter  is 100 mm and transmission ratio is 1,5 so power capacity of v-belt is 0,77 + 0,06 = 0,83 kW.

V-belt safety is sure if belt capacity in the table is greater than the actual belt capacity. The actual belt capacity can be calculated by the following equation:

Note:
Pr = Actual belt capacity (kW)
P = Power requirement (kW)
N = Number of belt
k = Correction factor

The v-belt correction factor is obtained by following table:

Safety of v-belt speed

V-belt safety can be seen from the ability to withstand the transmitted speed. Generally, the belt speed can be provided for every 10 to 20 m/s and up to 25 m/s with a maximum power which can be transmitted is less than 500 kW. This means that the belt can be considered safe, if its speed is less than 25 m/s (v <25 m/s).

That is a description about how to determine of V-Belt Selection Guide: V-belt Sizes. Types and Safety. If you find misconceptions in the v-belt design, please provide the correction in the comment box.