What Are Transmission Belts?
Transmission belts are a continuous loop belt, set between two ‘pulleys’ to transmit power through the transmission belting into the machinery the belting is situated.
Transmission belting is used across an array of industries from automotive manufacturing and performance through to industrial belting production and manufacturing as well as a source of motion
Positive Drive vs Friction Drive Transmission
Fundamentally there are two forms of transmission belting for power transmission. These are either friction drive or positive drive. Friction drive belts utilize the friction between the belt and pulley to transmit power. The friction drive belting requires balanced tension to maintain the right levels of friction. These are traditionally flat belts.
Positive drive belts will rely on the engagement of what is referred to as ‘teeth’ on the belt within the grooves on the pulley(s). There is no slippage with this transmission belt unless the teeth between the grooves ‘jump’.
Different Types of Friction Drive Transmission Belting
Depending on the requirement for power transmission, the type of belt will be fundamental to either friction or positive drive belts.
Outside of plastic or rubber drive belts, woven transmission belting is used specifically for friction drive belts. The types of friction drive belts are typically drop stamp, flat nylon belts or hair belting.
Drop Stamp Belts
Used specifically in the forging industry, drop stamp belts (also referred to as ‘hammer belts’), are a type of heavy duty lifting transmission belt.
The belt drop hammer one is of many drop forging machine tools used within the industry. How the drop stamp belt is used, is by rollers that grip the belt connecting it to the ‘ram’. The rollers allow the belt to raise the hammer which causes the belt to slack. The next stage of the process is the pulling apart of the rollers which releases the belt – this allows the hammer to fall using gravitated force to hammer the metal sheet in place.
The drop stamp belt is made from polyester multi-filament and ply yarn, covered by play layers of cotton on both the top and bottom of they polyester core layer.
To increase durability, and avoidance of abrasion during lifting, the drop stamp belt is treated with a temperature resistant coating. By treating the media this way, this gives the drop stamp belt an increased friction property.
The key components of a drop stamp belt are:
Due to the multi-filament yarn, weave construction and temperature resistance coating, a drop stamp belt is extremely durable with high-levels of strength. This makes for a longer living belt solution perfect for the lifting and forging industries.
The temperature resistance impregnation of the polyester filament layer means that the drop stamp belt can perform in much tougher temperature than other transmission belting.
High Friction Coefficient
The frictional force derived from the drop stamp belt is greater than that of say rubber or PVC transmission belts. This allows for no sticking and smoother transition between the rollers of the drop stamp machine.
Unlike drop stamp belts, hair transmission belts are used within power transmission. Made from a combination of nylon and wool hair woven into the ‘wrap’ ply of the belt before cotton is added to the loom and is then treated with bitumen impregnated into the cotton for additional strength, power and a the prevention of fungus properties.
These transmission belts are woven using the traditional ‘warp and weft’ technique which ensures a robust and highly durable power transmission belt. Hair belting uses a ‘twisted cord’ edge to avoid any fraying from the belt which provides a longer lifespan to the belt.
Hair belting is used across all industries powering the drive shaft and is preferred to other belting due to the belts ability to bite on the pulley which avoids slippage and losses of power. In hotter climates, hair belting performs at a much higher capacity to its compatriot transmission belts.
Flat Nylon Belting
Flat transmission belts are a form of friction drive belt relying on the friction between the belt and pulley to transmit power across the machinery. These belts are particularly used in high performance areas with smaller pulleys in central areas.
The belt comes in both endless and connected forms depending on the requirements of the pulley and powers transmission required. Flat belts use tension to maintain the correct level of friction across the belting – this allows for a balanced friction coefficient and transmission of power from the drive shaft through to the pulley.
Flat belts are traditionally manufactured using nylon material for both short and high ratio drives; performing better when crowning one pulley that is larger than the other.
The flat transmission belt relies heavily on alignment and when aligned correctly, the belts lifespan increases ten fold. Due to the belting’s lack of grooves, energy loss and wear and tear is at a minimum.
Flat Belt Drive vs V-Belt Drive
Often, there is a common misconception between flat belt drives and v-belt drives. While both belts are used in friction transmission, ultimately, there are substantial differences in how the belts are executed and perform within the pulley.
|Flat Belt Drive||V-Belt Drive|
|Flat belts only maintain surface contact on one side with the pulley||V-belts maintain contact surface with the pulley on both sides|
|Flat belts are preferred for long distance transmission||V-belt drives are preferred for short-medium distance transmission|
|The rectangular cross-section allows for a thicker belt width||The trapezoidal cross-section allows for balanced belt width|
|Cheaper in construction and easier to configure||Costlier to construct and more complex to configure|
|Can be utilized and configured for stepped pulley system||Cannot be utilized, nor configured for stepped pulley system|
|Power transmission is lower, making flat belts more efficient (3% more than v-belts)||More power transmission, but less efficient|
|Can be used in dirty environments||Must be treated and cased before being used in dirty environment|
Woven Transmission Belts vs Other Transmission Belting
Across transmission belting there are multiple materials used in the execution of friction transmission. These range from woven materials such as nylon, cotton etc. and thermoplastic such as PVC, or rubber belting materials.
A true transmission belt manufacturer needs to understand the nuances and differences in performance between both positive drive and friction drive transmission belting while also understanding the material best suited to the machinery, drive solution and pulleys.