= Operating V belts drives are subject to two ‘slipping’ phenomena
Creep
= A V-belt under proper tension creeps ahead about .5% due to its elasticity and changes in cross section and length as the belt moves from the tight side of the drive to the looser side and back.
= The heat created by creep is of a magnitude which can be dissipated by the sheaves
= therefore, V belt drives cannot be used for synchronous or timing applications
Slip
Excessive slip is caused by poorly designed or maintained drives where:
1. driving pulley is too small
2. load is too great
3. belt is running too loose
4. belt is not being properly cleaned (glazing)and maintained
Slip can be controlled by?
using smaller sheave ratios (angle of contact)
ensuring the sheaves are aligned correctly
ensuring adequate take-up is available (motorbrackets, idlers) to allow correct belt tension.
ensuring the sheaves aren’t worn to the point of bottom V belt contact
Belt Tensioning Techniques
slotted motor mounts
use of an idler sheave
Note the belt guard: protective yet ventilated
Idler Sheaves 2 Main Purpose?
1. increase arc of contact
2. act as a belt tensioner for belt drives without a moveable unit.
Measuring Belt Tension?
Run-in period?
Note: A new belt should have a 12 to 24 hourrun-in period. It should then be retensioned to the manufacturer’sspecifications.
The two most common causes of misalignment?
V-Belt Types, Sizes and Codes
There is an industry standard for belt section sizes and angles so that belts from different suppliers can be used on the same sheaves.
V Belt Types
Cog type
PowerBand® Belt
Serpentine Belt
Synchronous Belt Drive BENEFITS...
Attaching a Sheave to a Shaft
Common Problems of Belts?
cracking – heat and/or age related
glazing - worn belt grooves
Maintaining Healthy Belt Drives
Belt & Sheave Groove Gauges
V-Belt Bill of Material as solutions to probems...