Belts Flashcards
3 types of belts
Flat, v or wedge, and toothed
Flat belts
Low torque/horsepower. Drums and pulley. Flexibility to go around corners. Operate under tension and a tensioner tightens belt. Relies on high tension (disadvantage)
V or wedge belts
Medium torque/horsepower. Sheaves and pulley. Operate under friction. Belt doesn’t touch the bottom of the sheave. Sidewalls provide the friction.
Toothed belts
High torque/horsepower. Sprockets and pulley. Works from positive tooth engagement. Very little to no deflection is how you tension.
Advantages of belt drives
Act as a clutch, cheap, need no lub, easily installed, and simple to design. Disadvantage: slippage between driving and driven shaft
2 designs of v belts
Raw edge and envelope
Raw edge
Used for none hazardous areas.
Envelope
Used for hazardous areas. Protect from oil, grease, dirt, water, and chemicals
Parts of a belt
Cushion rubber- working surface and cord support
Tensile cord- gives strength
Insulation rubber- protects cords
Backing fabric- protects insulation
Cogged
Notches removed from the belt that gives it flexibility
Classical v belts
Load range from -1 to 500 HP. Good for poor operating conditions.
A=1/2, B=5/8, C=7/8, D=1 1/4 (uses inside length)
Wedge v belts
Provides more support, better contact, and higher hp.
3=3/8, 5=5/8, 8=1”, 10= 1 1/4 (uses outside length)
Fractional horsepower v belts
Used to operate drives of less than one horsepower. 2L= 1/4, 3L= 3/8, 4L= 1/2, 5L= 5/8 uses outside length
Banded belts
Multiple belts together that all travel at the same speed to eliminate rollover tendency.
How to tension v belts
1/4 deflection per foot of span
