Belts and Roller Chains

Belts

A flexible power transmission element that seats tightly on a set of pulleys or sheaves.

Flat belt

Used with flat pulleys and allows long distance between shafts.

V-belt

Used with sheaves or groove pulleys and provides stronger grip at short distance between shaft.

Toothed belt

Paired with toothed pulleys and used as timing belt where speed ratio must be maintained.

3.0298 rad

An industrial fan running at 600 rpm is driven by a 25-kW,960 rpm, industrial motor. The pulley mounted on the motor shaft is 270 mm. Center distance is 1.45 meters and f = 0.35. Determine the minimum angle of wrap.

197 mm

From the previous problem, determine the width of belt. Assume t = 5 mm belt thickness and allowable stress of 2.86 MPa for belt material. Neglect the effect of centrifugal force.

4006.7 mm

From the previous problem, determine the length of leather belt.

1. 1.93 kN

2. 1.93kN

3. 261 mm

A pulley 610 mm diameter transmits 37 kW at 600 rpm. The arc of contact between the belt and the pulley is 144 degrees, the coefficient of friction between the belt and pulley is 0.35, and the safe working stress of the belt is 2.1 MPa. Neglect the effect of centrifugal force. Find:

1. The tangential force at the rim of the pulley.

2. The effective belt pull.

3. The width of the belt used if its thickness is 6mm.

1. 13.95m, 3/34 rad=191.4°

2. 2.19 kN, 4.59 kN

A nylon-core flat belt has an elastomeric envelop; is 200 mm wide, and transmits 60 kW at a belt speed of 25 m/s. the belt has a mass of 2 kg/m of belt length. The belt is used in a crossed configuration to connect a 300 mm diameter driving pulley to a 900 mm diameter driven pulley at a shaft spacing of 6m.

1. Calculate the belt length and the angles of wrap.

2. Compute the belt tensions based on a coefficient of friction of 0.38.

Roller chain

Provides a readily available and efficient method for transmitting power between parallel shafts. The roller turns on bushing that are press-fitted to the inner link plate. The pins are prevented from rotating in the outer link plates by the press-fit assembly.

1. 21 teeth

2. 63 teeth

3. 84 pitches

4. 2 strands

A 10 hp engine of 1200 RPM is used to drive a blower with a velocity ratio of 3. The pitch diameter of the driving sprocket is 85 mm and the center distance between the sprockets is 260 mm. The service factor is 1.2 whiile a No. 40 roller chain is used with an equivalent pitch of 13 mm. Find:

1. Number of teeth of driver sprocket.

2. Number of teeth of driven sprocket.

3. Length of power chain in pitches.

4. Number of strands.

2 strands

A no. 80 roller chain is used in a conveyor drive that requires 60 HP. The driver sprocket has 23 teeth and runs at 1200 rpm. Assumning a service factor of 1.2, determine the number of strands required for the chain drive.

69

A certain farm equipment which requires 2200 Newton meter torque at 500 RPM has a diesel engine to operates at 1500 RPM as its prime mover. A No. 60 roller chain with a total length of 60 pitches and a small sprocket with 23 teeth are to be used with an operating temperature to remain constant at 45-degree C. Determine the no. of teeth of the larger sprocket.

RC 60

What is the largest roller chain size that can be used for power transmission at a sprocket speed of 1000 rpm?

291.66 lb and 340 hp

A 4 inches diameter shaft is driven at 3600 rpm by a 400 Hp motor. The shaft drives a 48 inches diameter chain sprocket having an output efficiency of 85%. The output force of the driving sprocket and the output of the driven sprocket are: