Mechanics Quiz Belts Flashcards
What are the 3 basic classifications of belts?
Flat
V
Synchronous(Toothed)
Which component is driven by the belt?
Pulley
What is the driving “pulley” for flat belts?
Drum
What is the driving “pulley” for V belts?
Sheave
What is the driving “pulley” for Synchronous belts?
Sprocket
What are the advantages to belt drives?
•Inexpensive to install/maintain
•Reliable
•Simple design
•Easy to install
•No lubrication
•Wide variety of applications
•Adjusted for nearly any speed
•Pulleys are less expensive than chain sprockets
•Long pulley life
•Act as a clutch
What is the primary benefit to flat belts?
Have the flexibility to go around corners for special drive configurations.
How do flat belts drive?
Tension
How do V belts drive?
Friction
How do Synchronous belts drive?
Positive Tooth Engagement (and tension)
Which belt is ideal for low speed?
Flat
Which belt is ideal for medium speed?
V
Which belt is ideal for high speed?
Synchronous
What part of a V belt should be your contact/friction point?
Sides
How tight should a V belt be tensioned?
1/4in per foot of span (contact to contact)
Which side of a V belt is the tension side?
The side in which the sheave is pulling
Which side of a V belt is the slack side?
The side in which the sheave is “pushing”(paying off)
What are the two base construction categories for V belts?
Envelope and Raw Edge
What is the difference between Envelope and Raw Edge V belts?
Envelope V belts are enclosed in a rubber/fabric coating which protects from contamination and elements, Raw Edge belts are not.
Where would we use Envelope V belts?
Outdoors/Harsh conditions
When would we use Raw Edge V belts?
Interior/clean conditions
How can you tell the difference between Envelope and Raw Edge V belts?
Raw Edge V belts have visible cords
What is the bottom of a V belt and what does it do?
Cusion Rubber - Provides cord support.
What part of a V belt is above the Cushion Rubber and what does it do?
Tensile Cords - Carry the load.
Which part of a V belt is above the Tensile Cords and what does it do?
Insulation Rubber - Protect/Adhere to cord.
Which part of a V belt is above the Insulation Rubber and what does it do?
Backing Fabric - Resist Abrasion
How are classic V belts identified?
Letter Designation (A,B,C,D)
Identify this V belt.
C65
C - 7/8in(Classical V) 65- 65in inside length
What is the speed range for classical V belts?
Fractional to 500HP
What do double V belts look like?
Hexagonal
What does X denote on a V belt?
The belt is cogged.
What does a cogged belt refer to?
Belt with notches removed from the Cushion Rubber with the intent to increase flexibility.
What is the difference between Classical V and Wedge V belts?
Wedge V belts fit deeper into the sheave and provide better contact and strength.
How are Wedge V belts identified?
A number (denoting x/8in), the letter V (denoting Wedge V), and a number ending in 0 (denoting outside length with the first number(s)) The 0 at the end stands for outside.
Identify this belt.
7VX400
7 - 7/8in
V - Wedge Belt
X - Cogged
400 - 40in outside length.
How are Fractional Belts identified?
A number (x/8in denoting belt width), the letter L (denoting Fractional HP belt), and a number ending in 0 (Denoting length in inches for the outside of the belt, using the 1st number(s)) Last 0 stands for outside
What are Fractional Belts used for?
Drives with 1 or less HP.
What are banded belts?
V belts (either Classical or Wedge) banded together using insulation rubber and backing fabric for use in multi channel sheaves.
Why do we use banded belts?
Prevent uneven slipping from using multiple single belts. Eliminating rollover tendency.
How are banded belts identified?
Same as other V belts, but starting with a number and slash (x/) which denotes the amount of belts banded together.
What is the disadvantage of Synchronous belts?
No slippage due to positive
tooth engagement which leads to possible damage to clutch (if applicable) or other components.
