| Angular Misalignment |
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| Angular misalignment is where the driver and driven shafts are not parallel. Resulting in uneven loading of the tensile cords. The tensile cords on the high tension side are often overloaded which may cause edge cord failure which would be transmitted across the width of the belt. This misalignment also results in high belt tracking forces which causes excessive belt edge wear. |
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Aramid – Tensile Cord
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Aramid fibers (most commonly known as 'Kevlar' or 'Twaron'), which have been commercially available since the 1960s, have found a wide field of applications.
Aramid fibers offer the following properties:
- Low density
- High tensile modulus
- High tensile strength
- Good vibration damping
- High energy absorption
- High impact resistance
- Low material fatigue
- Good temperature resistance
- Good chemical resistance
- Low thermal conductivity
- Low compression strength
- Moderate adhesive properties
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| Axial Run Out |
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| The total deviation of the axial reference surface noted during one revolution of the work piece. It is expressed as TIR (Total Indicator Reading). |
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| BackLash |
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| Backlash can be defined as free play between two mating parts. A prime example of backlash is sloppy steering in a car, where the steering wheel can be turned left or right a small amount with no change in the direction of the car. Backlash in a synchronous belt results from clearance between belt teeth and pulley grooves. This clearance is needed to allow the belt teeth to enter and exit the grooves smoothly with a minimum of interference; the amount of clearance necessary depends upon the belt tooth profile. Too much clearance creates positional inaccuracy, while too little can generate excessive noise, vibration and wear. |
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| Belt Pitch Length |
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| Belt pitch length is the total length (circumference) in millimeters as measured along the pitch line |
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| Belt Pitch Line |
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| Belt pitch line in theory lies within the tensile member of the belt |
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| Belt Pitch |
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Belt pitch is the distance in millimeters between two adjacent tooth centers as measured on the pitch line of the belt
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| Clearance Values |
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| The clearance between the synchronous belt teeth and the matching synchronous pulley teeth is the principal indication of backlash in a drive. Proper clearance between a belt tooth and a pulley groove lets the tooth enter and exit smoothly. |
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| CTD Profile |
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| (CTD: Conti Torque Drive) is the symbiosis of the HTD and the STD profile and combines both profile advantages in a single profile. The arch-shaped pulley-entry geometry, on the one hand, and the higher tooth, on the other, makes for ideal conditions for use on dynamic drives with simultaneously high tension load. |
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| Elongation |
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| Elongation of a belt or stretch occurs naturally when a belt is placed under tension. The total tension exerted within a belt results from installation, as well as working loads. The amount of belt elongation is a function of the belt tensile modulus, which is influenced by the type of tensile cord and the belt construction.
A belt with a high tensile modulus stretches less and improves positional accuracy, however in order to maintain the belts life the tensile cord must also exhibit flexibility. |
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| Flanges |
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Timing belts typically track to one side of a pulley during operation, and would slide off the pulley if it was not flanged.
FLANGING GUIDELINES:
Two Pulley Drives - On simple two pulley drives, either one pulley should be flanged on both sides, or each pulley should be flanged on opposite sides
Multi Pulley Drives - On multiple pulley drives (i.e. more than two pulleys, serpentine), either every other pulley should be flanged on both sides, or every pulley should be flanged on alternating sides around the system
Vertical Shaft Drives - On vertical shaft drives, at least one pulley should be flanged on both sides, and the remaining pulleys should be flanged on at least the bottom side
Long Span Drives - Belts on drives with long spans, typically (8x) times the diameter of the smaller pulley require both pulleys to be flanged |
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| Flank (Pulley Tooth Flank) |
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The surface area of a pulley tooth between the pitch circle and the bottom land along the length of the tooth, including the fillet. |
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| Fiberglass - Tensile Cord |
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Fiberglass tensile cords are the most common reinforcement in synchronous belts.
Fiberglass fibers offer the following properties:
- Low tensile modulus
- High bending flexibility
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| HTD Profile |
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