Belts are mechanical elements used for power transmission without phase shift. They are loops of flexible materials used to mechanically connect several rotating shafts, most often parallel. Belts can be used as a transmission element, to efficiently transmit power or movement.
In order to make the right choice, you will need to know the type of section and the belt dimensions. In this guide you will find the different sections available on the market, with their advantages and disadvantages.
The type of belt you should use depends on the type of application:
torque to be transmitted
temperature and lubrication conditions
Why choose an flat belt?
As in any transmission belt system, the flat belt allows a mechanical force to be transmitted from one pulley to another. Flat belts offer an optimal efficiency of 98%; however, they are only suitable for low loads. Once the drive system is aligned, flat belts can be self-centered by curved pulleys. This type of belt is used in many power transmission applications.
In the case of large pulleys, wide flat belts can be used to provide high power at high speeds (up to 373 kW at 51 m/s).
Better efficiency than V-belts, over 98%.
Longer service life than V-belts.
Very quiet operation.
Large center distance possible.
Risk of pulley displacement.
Requires high voltage maintenance.
Tendency to slide on the face of the pulley when heavy loads are applied.
Most flat belts are made of rubber or synthetic polymer. Generally, they are strips with both ends joined by stapling or welding. There are also so-called endless or seamless belts that are manufactured in one piece.
Why choose a V-belt?
These are the most commonly used belts for power transmission. At the same level of tension, they transmit higher power than flat belts. They are used, for example, in variable-speed drives. They offer the best combinations of traction, speed, bearing load and service life.
The V-shaped section of the belt follows a groove in the pulley, which prevents the belt from slipping and improves torque transmission.
It is less wide than a flat belt and therefore takes up less space.
It doesn’t need to be as taut.
The optimal speed range is between 300 and 2,130 m/min.
For high power requirements, two or more V-belts can be assembled side by side in an arrangement called a “multiple belt drive.”
V-belts, also called trapezoidal belts, can be made of rubber or polymer without reinforcement, or they can have fibers incorporated into the rubber or polymer to increase strength. These fibres can be made of textile material (such as cotton), polyamide (such as nylon), polyester or, for greater strength, steel or aramid (such as Kevlar).
When a seamless belt does not meet the requirements of the application, articulated V-belts can be used. Most models offer the same power and speed as endless belts of the same size and do not require special pulleys to operate. They are easy to install and have a higher environmental resistance than rubber belts. They are also adjustable in length if you choose to remove the links.
Why choose a ribbed belt?
As its name suggests, this kind of belt is ribbed lengthwise, which greatly increases the contact surface between the pulley and the belt. It works by adhering the ridge part of the belt to the pulley. Its one-piece structure allows for homogeneous distribution of the belt tension on the pulley’s contact surface.
Wide power range (from 0 to 600 kW).
Long service life and reliability.
Large transmission ratio possible.
Ribbed belts are used as drive belts on automobiles. They are also used for large electrical appliances (i.e. washing machines, dryers) and on concrete mixers, compressors, lawnmowers, etc.
Why choose a synchronous slotted belt?
Synchronous belts are slotted. They are used, for example, to drive camshafts or for the secondary transmission of some motorcycles. They are also used on many industrial or agricultural machines. Synchronous belts are essential for avoiding any phase shifts. A belt that isn’t slotted will always shift due to its elasticity, even if it is very taut.
Polyurethane belts are more resistant to oil, ozone, vibrations and low temperatures than neoprene belts. Polyurethane belts also make it possible to transmit higher power and torque than neoprene ones.
They guarantee the synchronization of the system and the transmission of movement without slipping.
Since power transmission is accomplished through gear meshing, unlike other belts, these belts are able to withstand low speeds and require a lower initial tension.
What are the advantages of a belt drive?
Compared to other transmission systems (gears, chains, etc.), belts offer many advantages:
Don’t require lubricant
Don’t require parallel shaft
The clutch action can be activated by releasing the belt tension
Protection against overload and obstruction
Efficiency from 95 to 98%
Easier to install and maintain
Machine service life is increased because load fluctuations are absorbed
Lower total installation cost
Low maintenance costs
When the distance between the shafts is very large, belt drives are the most economical option
What are the disadvantages of a belt drive?
Compared to other transmission systems, belts have some disadvantages:
Can’t be repaired If they break or stop working, they must be replaced
Deterioration due to exposure to lubricants or chemicals
Typically, operating temperatures are limited from -35 to 85°C
The speed ratio varies due to belt slippage
Limited speed, about 35 m/s
The angular velocity of belt drives is not constant
The power transmission of belts is limited to 370 kW, which increases heat accumulation
Belt drives usually place a heavy load on shafts and bearings
To compensate for wear and stretching, belts also require a deflection pulley or an adjustment of the center distance.
What can a transmission belt be used for?
One of the best known applications for belts is the automotive industry: cars have a ribbed belt to synchronize the movements of the main engine components (valve, pistons) during the various operating phases. A ribbed belt drives a number of peripheral components: alternator, power steering pump, water pump, etc. For the transport industry, we could also mention bicycles and motorcycles. Belts are also used in a wide range of industrial applications requiring motion or power transmission, particularly in conveyors.