BELT DRIVE IN POWER TRANSMISSION SYSTEM

Power transmitted between a belt and a pulley is expressed as the product of difference of tension and belt velocity

A mechanical system consisting of a flexible belt and at least two fixed pulleys that is used to transmit motion. Belt drive systems are low maintenance and do not require lubrication.

Application of Belt Drive

 a conveyor belt is one application where the belt is adapted to continuously carry a load between two points.

Types of Belt Drives

Open Belt Drive

Open Belt Drive

In open belt drive the two shafts rotates in the same direction the angle of lap.

Crossed Belt Drive

Crossed Belt Drive

in the cross belt drives the two shaft rotates in opposite direction.

Flat Belt

Flat Belt

Used in line shafting to transmit power in factories.

can deliver high power at high speeds (500 hp at 10,000 ft/min)

the drives are bulky, requiring high tension leading to high loads, and are poorly suited to close-centers applications.

flat belts tend to climb towards the higher side of the pulley, so the pulleys were made with a slightly convex or "crowned" surface (rather than flat) to allow the belt to self-center as it runs.

V Belt

V Belt

V-belts (also known as V-belt or wedge rope) solved the slippage and alignment problem. It is now the basic belt for power transmission.

provide the best combination of traction, speed of movement, load of the bearings, and long service life.

generally endless, and their general cross-section shape is trapezoidal (hence the name "V").

improving torque transmission

Timing Belt

Timing Belt

A positive transfer belt and can track relative movement.

These belts have teeth that fit into a matching toothed pulley

 When correctly tensioned, they have no slippage and run at constant speed.

often used to transfer direct motion for indexing or timing purposes

often used in lieu of chains or gears, so there is less noise and a lubrication bath is not necessary.

Belt Tension and Misalignment of Belt Drives

A condition in a belt drive system when pulleys or their shafts are not arranged properly. Both shaft and pulley misalignment can damage belt drives. misalignment

will reduce belt life by increasing wear and increase the probability of belt turnover by decreasing stability.

If too little tension is applied, the belts may slip. Too much tension can reduce belt and bearing life.

Applying the proper tension is very important. The correct tension is the lowest tension at which belts will run and not slip when the drive is under a full load.

Belt Maintenance/Symptoms/Record Observation for Preventive Maintenance

Premature Belt Failure

SYMPTOMS CAUSE CORRECTIVE ACTION

Broken belt Under-designed drive

Redesign, using Gates manual.

Belts fail to carry load, no visiblereason

Damaged tensile member

Follow correct installation procedure.

• Edge cord failure

Pulley misalignment

Check alignment and correct.

• Belt de-lamination or undercordseparation

Too small sheaves

Check drive design, replace withlarger sheaves

Severe / Abnormal Belt Wear

SYMPTOMS CAUSE CORRECTIVE ACTION

Wear on top surface of belt

Rubbing against guard

Replace or repair guard.

Wear on top corner of belt

Belt-to-sheave fit incorrect (belttoo small for groove)

Use correct belt-to-sheavecombination.

Wear on belt sidewalls

Belt slip Retention until slipping stops

Banded (Joined) Belt ProblemsSYMPTOMS CAUSE CORRECTIVE

ACTION

Tie band separation 1. Worn sheaves2. Improper groove spacing

1. Replace sheaves.2. Use standard groove sheaves

Top of tie band frayed or worn

1. Interference with guard2. Backside idler malfunction ordamaged

1. Check guard.2. Replace or repair backside idler

PowerBand® belt comes off driverepeatedly

1. Debris in sheaves2. Misalignment

1. Clean grooves. Use single beltsto prevent debris from beingtrapped in grooves.2. Realign drive.

Belt Noise & Unusual VibrationSYMPTOMS CAUSE CORRECTIVE

ACTION

• Belt squeals or chirps

1. Belt slip2. Contamination

1. Retension.2. Clean belts and sheaves.

Slapping Sound 1. Loose belts2. Mismatched set3. Misalignment

1. Retension.2. Install matched belt set.3. Realign pulleys so all belts shareload equally.

• Unusual or excessive vibration

1. Incorrect belt2. Poor machine or equipmentdesign3. Pulley out of round4. Loose drive components

1. Use correct belt cross section inpulley. Use correct tooth profileand pitch in sprocket.2. Check structure and brackets foradequate strength.3. Replace with non-defective pulley.4. Check machine components

Sheaves, Belt Stretches Beyond Take Up Problems

SYMPTOMS CAUSE CORRECTIVE ACTION

Multiple belts stretch unequally

1. Misaligned drive2. Debris in sheaves3. Broken tensile member or corddamaged4. Mismatched belt set

1. Realign and retension drive.2. Clean sheaves.3. Replace all belts, install properly.4. Install matched belt set

Single belt, or where all beltsstretch evenly

1. Insufficient take-up allowance2. Grossly overloaded or underdesigned drive3. Broken tensile members

1. Check take-up. Use allowancespecified in Gates design manuals.2. Redesign drive.3. Replace belt, install properly.

V-Belt Turn Over / Jump of Sheaves

SYMPTOMS CAUSE CORRECTIVE ACTION

Involves single or multiple belts

1. Shock loading or vibration2. Foreign material in grooves3. Misaligned sheaves4. Worn sheave grooves

1. Check drive design. Use GatesPowerBand® belts or PowerCable® belts.2. Shield grooves and drive.3. Realign the sheaves.4. Replace sheaves.

Belt Drive Maintenance ProcedurePROCEDURE DETAILS

Safety First -Use OSHA approved guards-Keep the drive completely enclosed-Use accessible inspection doors or panels-Maintain good ventilation-Allow for easy removal and replacement

Regular Inspections -Critical nature of the equipment-Drive operating cycle-Accessibility of the equipment-Drive operating speeds-Environmental factors-Temperature extremes-Drive history

Belt Inspection Remove the belt drive guard and mark a point on the belt. Work around the belt and look for cracks, frayed spots, cuts, missing teeth (if it’s a synchronous belt) or unusual wear.

Belt Alignment Methods:-Straight edge-String-Laser alignment tool

Belt Drive Installation Remove the old belt and inspect it for unusual wear. This process can provide clues to a problem with the drive. Also, inspect the sheaves or sprockets for signs of unusual wear.

Storage and Handling – - Store belts in a cool, dry place protected from direct sunlight.

– Do not store belts near equipment that generates ozone, such as transformers or electric motors, and keep them away from areas where they might be exposed to solvents or chemicals in the atmosphere.

– -Belts should be stored on shelves or in boxes or containers.