Chains and Belt Drives Flashcards
Difference between a belt drive and a chain drive
Belt drives are for high speed, low torque applications, while chain drives are for low speed, high torque applications.
Purpose of belt and chain drives
Used to transmit power between parallel shafts.
Characteristics of Flat Belts
Quieter than VeeBelts, higher efficiency, run in barrel-shaped pulleys to prevent slipping.
Two main types of belts
VeeBelts and Flat Belts.
Characteristics of VeeBelts
Common type, Vee shape enhances friction with pulley, lower efficiency due to heat generation.
Toothed Belt Drives
Engage in pulley grooves to prevent slipping, ensuring constant speed ratios.
Key points about Roller Chains
Made of steel, suitable for high torque, and achieve constant speed ratios with no slip.
Comparison of Belt and Chain Drive in terms of lubrication
Chain drives need frequent lubrication, while belt drives do not require lubrication.
Lifespan comparison between Belt and Chain Drives
Belt drives have a higher life expectancy (~60k mi) compared to chain drives (~30k mi).
Power loss in Belt vs Chain Drives
Belt drives have higher power loss (~11%) compared to chain drives (~3%).
Belt Geometry analysis - Angle of Contact for Small Pulley
Calculated using the formula involving the radius of pulleys and center distance.
Belt Length Calculation
Depends on the diameters of the pulleys and the distance between them.
Importance of Friction in Belt Drives
Required to transmit force between belt and pulley; essential to avoid belt slip.
Centrifugal Force in Belt Drives
Acts to pull the belt from the pulley, affecting tension and slip.
Pre-Tension in Belts
Belts are installed with an initial pre-tension to take out slack and maintain tension balance when rotating.
Belt Drive Analysis - Centrifugal Force Effect
Requires compensation in the tension calculation to prevent slip.
Additional Friction in Vee Belts
Vee belts provide additional frictional grip along the sides of the pulley.
Equation for Belt Pre-Tension
Calculated based on the tensions on the tight and slack sides of the belt.
Maximum Power Transmission in Belt Drives
Depends on the strength of the belt and the tension on the tight side.
Key Summary Points for Belt and Chain Drives
Belt drives are suitable for high speed/low torque; chain drives for low speed/high torque. Calculations for both are similar.
Linked Belts
- Small sections of vee belts joined by pins
- Used where shafts would have to be dismantled to
fit continuous belt.
