Chaindrives
- 1. Chain Drives Overview, Applications and Selection method Presentation On- By- Mukul Wadhokar 16ME115 2018/19 Guided by- Prof. Dr. D Y Dhande Department Of Mechanical
- 2. Overview and Principles • Chain drives consist of an endless series of chain links, which mesh with toothed sprockets. • Chain drives are used to perform three basic functions 1. Transmitting power, 2. Conveying materials, and 3. Timing purposes.
- 4. Chain Drive Principles • Chain drives normally transmit power from one rotating shaft to another. • Chain drives maintain a positive speed ratio between driver and driven sprockets. • The driver and driven sprockets will rotate in the same direction on typical chain drives. • If the chain has an even number of pitches, the sprockets have an odd number of teeth. If the sprockets have an even number of teeth, the chain has an uneven number of pitches. This design feature prevents a single link from contacting the same tooth each time, causing wear and vibration. • Small diameter sprockets cause the chain to bend sharply; therefore, the chain wears more quickly.
- 5. Types of Roller Chain- • Standard Roller Chain • Heavy Series Roller Chain • Multiple-Strand Roller Chain • Double Pitch Roller Chain • Self-Lubricated Roller Chain • Pre-Lubricated Roller Chain Standard Roller Chain
- 6. Advantages- • Chain drives, unlike belt drives, do not slip or creep. • There is no power loss due to slippage; therefore, chain drives are more efficient than belt drives. • Chain drives are more compact than belt drives. A chain drive, for a given capacity, is narrower than a belt, and the sprockets are smaller in diameter than the belt sheaves. • Chain drives are more practical for slow speed drives. • Chains can operate effectively at high temperatures. • Chains are usually easier to install than belts on power transmission drives. • Chains do not deteriorate due to oil, grease, sunlight, or age. • Chains withstand chemicals and abrasive conditions. • Chains can operate in wet conditions. • Chains are effective when several shafts are to be driven from a single shaft, as positive timing between the driven shafts is usually required. • Chain stretch due to normal wear is a slow process. • Chains require less take-up adjustment than belts. • Chains can be used with varying shaft center distances, whereas gears usually cannot. • Chain drives are simpler and less costly than gear drives. • Chains can be used on reversing drives.
- 7. Disadvantages- • Chain drives cannot be used where the drive must slip. • Chain drives cannot accept much misalignment. • Chain drives usually require frequent lubrication. • Chain drives are noisy and can cause vibration within the machine. • Chain drives do not have load capacities or service life characteristics equal to those of gear drives.
- 9. Applications of Chain Drive- 1. Transmitting Power Chain drives are used to transmit power from one component to another. Chain drives are well suited for this task because the sprocket teeth and chain setup results in a positive speed ratio and the ability to transfer a large amount of torque within a compact space. • Rigging and moving heavy materials • Hydraulic lift truck fork operation • Increasing or decreasing a driver’s output speed by altering gear ratios between the driver and the sprocket being driven • Overhead hoists • Operating conveyer belts
- 10. 2. Conveying Materials • Chain drives are used in many types of industries to move, slide, carry, push and pull a variety of materials. • These drives can be used to move objects directly by attaching pockets, buckets, frames, or meshes to the chains. • They can also be used indirectly, such as turning rollers, which, in turn, move a conveyor belt. 3. Timing Purposes • Chain drives can also be used to synchronize or time movements. For example, industrial combustion engines use chain drives to control valve timing.
- 12. Conveying
- 13. Selection of chain drives • Determine the designed power from the motor power P and application factors, f1, f2 and f3 if applicable. Pd = P* f1* f2 *f3 f1 = Service Factor f2 = Sprocket Size Factor f3 = Temperature Factor Selection of ‘f1’
- 14. • The sprocket sizes are determined by the drive ratio required. • Having selected the number of teeth of the sprockets factor f2 can be determined from the chart aside. • By relating the design Power Pd with the rotational speed of the small sprocket n1 on the Capacity Chart the correct size of chain can be selected.
- 17. • The preferred centre distance ranges between 30 and 50 times the chain pitch, • There should always be a minimum arc of contact of the chain on the small sprocket of 120˚; or for sprockets with low numbers of teeth a minimum of 5 teeth in contact. • The following are preferred centre distances against chain pitch-
- 18. British System Simplex Roller Chains Specifications
- 19. American Standard Chain Specifications
- 20. Case Study •Problem- Select a chain drive for driving an apron conveyor head shaft operating at 25 RPM and requiring 30 HP. Operation is an average of 18 hours per day and power will be supplied by an electric motor with output speed of 60 RPM.
- 21. STEP 1- Determination of Service factors • Moderate shock load, electric motor = 1.3 • Moderately dirty = 1.2 • 18-hour service = 1.2 • Combined service factor = 1.3 X 1.2 x 1.2 x 1.2 = 1.87
- 22. Step 2 – Designed Horsepower • Design HP = Given HP * Combined Service factor = 30 * 1.87 = 56.1 HP
- 23. Step 3- Quick Selector Chart • The intersection of the 56.1 HP and 60 RPM falls with the parameters of 3514 chain, which will be the tentative chain selection.
- 24. Step 4 - Horsepower table for 3514 chain • At 60 RPM, a 10- tooth sprocket will transmit 58.7 HP. Since 58.7 exceeds the design HP, the 3514 chain and 10- tooth sprocket satisfy the requirements.
- 25. Step 5: Drive ratio • Drive ratio = 60 / 25 = 2.4 • Number of teeth of driven sprocket: 2.4 x 10 = 24 teeth
- 26. Step 7: Chain length • Since the recommended center distance for an average application would be 30 to 50 pitches, for this example 40 pitches will be used. 𝐿 = 2𝑐 + 𝑁 + 𝑛 2 + (𝑁 − 𝑛)2 39.5𝐶 = (2*40)+(24+10)/2+142/39.5*40 = 97.124 Since a fractional link cannot be used, 98 links of chain are required for the drive.