Power transmission belts link two or more rotating shafts so that a driver, such as a motor, can turn a driven machine. This page compares the main belt types, shows what to check before you choose one, and links to the industrial belt range.
Settle the type first: flat, V-belt, banded, poly-V or timing belt. Section and length only make sense once the type is clear.
Key Takeaways
- A power transmission belt links rotating shafts; a conveyor belt carries a load between two points instead.
- V-belts wedge into the pulley groove; timing belts do not slip when correctly tensioned but need toothed pulleys.
- Choose on speed ratio, shaft distance, drive unit, environment, load and pulley layout, and check the pulley diameter.
Table of Contents
- What power transmission belts do
- Belt drive types compared
- How to choose a belt for your drive
- Belt materials and reinforcement
- Tension, wear and belt life
- Industrial belts from LYBELT
- FAQ
- About Longyi Rubber Products Factory
What power transmission belts do
A belt is a loop of flexible material used to link two or more rotating shafts mechanically (Belt (mechanical) on Wikipedia). The driver is usually a motor or an engine, and the driven side can be a fan, pump, compressor or gearbox. A conveyor belt is a different product: it carries a load continuously between two points, while a transmission belt only links shafts.
Belt drives run smoothly and with little noise, absorb shock, and help protect machinery from overload and jam. Their efficiency is 90–98%, usually 95%. The drawback is that they transmit less power than gears or chain drives, so compare those when the power demand is high. Working temperatures range from −35 to 85 °C (−31 to 185 °F) (Belt (mechanical) on Wikipedia).
For a hot drive, check the rubber compound separately.
In a two-pulley system the belt can drive the pulleys normally in one direction, or it can be crossed so that the driven shaft turns the opposite way. Using pulleys of different sizes changes the speed of rotation up or down, and stepped or tapered pulleys give different speeds. A belt can even act as a clutch, by shifting it onto a free-turning pulley or by releasing its tension (Belt (mechanical) on Wikipedia).
A belt grips by friction in a groove, by lengthwise ribs, or by teeth. That choice decides the family: a friction belt can slip if tension or load is wrong, while a correctly tensioned timing belt does not slip.
Belt drive types compared
The table compares the belt drive types you meet on machinery, from the older flat belt to the toothed timing belt.
| Belt type | How it transmits power | Worth knowing |
|---|---|---|
| Flat belt | Friction on a flat pulley face | V-belts have mainly replaced flat belts for short-distance power transmission. |
| V-belt (classical, narrow, cogged) | Wedges into a matching pulley groove as the load rises | Needs less width and tension than a flat belt. |
| Banded (multiple-V) belt | Two or more V-belts joined side by side | Runs in matching multi-groove sheaves. |
| Multi-groove (poly-V, V-ribbed) belt | Lengthwise ribs sit in matching pulley grooves | Usually 3 to 24 V-shaped sections; thinner and more flexible than a V-belt; can run over pulleys on its back. |
| Timing (synchronous) belt | Teeth engage a toothed pulley | No slippage when correctly tensioned; needs toothed pulleys and gives less overload protection. |
Source: Belt (mechanical) on Wikipedia.
Flat and round belts
Flat belts are still used today, although not nearly as much as in the line-shaft era. Round belts have a circular cross-section and run in a pulley with a 60 degree V-groove; they are for relatively low torque situations only (Belt (mechanical) on Wikipedia).
V-belts
A V-belt has a roughly trapezoidal cross-section and tracks in a mating pulley groove, so it cannot ride out of the pulley. It wedges into the groove as the load increases, needs less width and tension than a flat belt, and has mainly replaced flat belts for short-distance power transmission (Belt (mechanical) on Wikipedia). Classical, narrow and cogged forms share that principle. The V belt guide covers the profiles, and classic V-belts are the usual starting point in the industrial range.
Banded and multiple V-belts
Two or more V-belts side by side form a multiple-V-belt drive that runs on matching multi-groove sheaves (Belt (mechanical) on Wikipedia). A banded belt is the same multiple-V arrangement supplied as one joined belt.
Multi-groove and poly-V belts
A multi-groove belt, also called a V-ribbed or poly-V belt, usually has between 3 and 24 V-shaped sections. It is a thinner belt for the same drive surface, so it is more flexible, and it can run over pulleys on its ungrooved back. The PK section, with a rib pitch of 3.56 mm, is commonly used in automotive applications (Belt (mechanical) on Wikipedia).
Ribbed belts are fitted to compressors, agricultural machinery, food mixers, washing machines and lawn mowers (Belt (mechanical) on Wikipedia). The multi-groove and serpentine belt page explains the names.
Timing belts
Timing belts, also known as toothed, notch, cog or synchronous belts, are a positive drive. Their teeth fit a matching toothed pulley, and when correctly tensioned they have no slippage. The trade-offs are the need for specially made toothed pulleys and less protection from overloading (Belt (mechanical) on Wikipedia). Choose a timing belt when slip is unacceptable, and a V-belt when overload protection matters more.
Other industrial belt types
Other industrial types include cogged V, hexagonal, variable speed, light duty and raw-edge cutting belts.
How to choose a belt for your drive
Work through these factors in order, and write each answer down before you name a length.
- Speed ratio and power: the driver speed, the driven speed and the power the belt must pass.
- Shaft distance: the center distance between the shafts.
- Type of drive unit: an electric motor or an internal combustion engine loads a belt differently.
- Service environment: oily, wet or dusty conditions, plus heat and weather.
- Driven-unit load: steady, jerky, shock or reversed.
- Pulley-belt arrangement: open, crossed or turned, and whether any pulley touches the back of the belt.
These are the selection factors listed on Belt (mechanical) on Wikipedia. Then check the minimum pulley diameter listed for the section.
For V-belts, the preferred center distance is larger than the diameter of the bigger pulley but less than three times the sum of both pulley diameters, and the optimal speed range is 1,000–7,000 ft/min (300–2,130 m/min) (Belt (mechanical) on Wikipedia). Where one large belt would otherwise be needed, two or more V-belts side by side are often more economical.
Once the type is chosen, read the section and length on the V belt size chart, or work the length out from the pulleys with the V-belt length calculator.
Belt materials and reinforcement
A V-belt may be one material throughout, or it may carry reinforcing fibers: cotton, polyamide (such as nylon) or polyester or, for greatest strength, steel or aramid (Belt (mechanical) on Wikipedia). If a drawing already names the fiber, keep it.
The rubber around the fiber is a second decision. Heat, oil and weather call for different compounds, so a hot drive, an oily gearbox and an outdoor drive should not share one default. The factory works from 130+ rubber compounds; state the temperature, the oil exposure and the weather in the inquiry and the compound is chosen from that set.
Tension, wear and belt life
The ideal belt runs at the lowest tension that does not slip under high load. Fatigue, more than abrasion, is behind most belt problems, and high tension, excessive slippage, adverse environments and overloads all add to it (Belt (mechanical) on Wikipedia).
Small pulleys greatly reduce belt life. If a belt still slips at the lowest tension that holds, change the pulley or the section and set the tension again. The belt tension guide shows how to check a V-belt by deflection.
Industrial belts from LYBELT
The industrial range covers classic V, narrow V, cogged V, banded V, banded cogged narrow, hexagonal, variable speed, light duty and raw-edge cutting belts, industrial multi-ribbed (poly-V) belts and timing belts. Browse it in the industrial belt range.
OEM and ODM belts are made to the customer’s part number, drawing or size, with private label and packaging; see the OEM and ODM page. Use the buttons below to send the belt code, a drawing or a photo.
FAQ
What is the difference between a power transmission belt and a conveyor belt?
A power transmission belt links rotating shafts. A conveyor belt carries a load continuously between two points.
How efficient are belt drives?
High: 90–98%, usually 95%. They still transmit less power than a gear or chain drive (Belt (mechanical) on Wikipedia).
Can a poly-V belt run on V-belt pulleys?
No. A poly-V belt needs pulleys with matching multi-groove ribs. Check the pulley before you change the belt type.
When should I use a timing belt instead of a V-belt?
When the two shafts must stay in step. Expect toothed pulleys and less protection from overloading (Belt (mechanical) on Wikipedia).
How do I read the code on a worn belt?
Measure the top width and height and compare them with the V belt size chart, then check which length the code refers to. If the print is gone, send the belt or a photo.
Do you make belts for OEM or private label?
Yes. OEM and ODM belts are made to the customer’s part number, drawing or size, and private label and packaging are available.
Sources
Source names appear here only as references. LYBELT is not affiliated with them.
About Longyi Rubber Products Factory
LYBELT is the brand of Longyao County Longyi Rubber Products Factory (General Partnership), based in Longyao County, Xingtai, Hebei, China, and making rubber belts since 1999. The factory holds IATF 16949 and ISO 9001 certification and works from 130+ rubber compounds.
The range covers automotive, industrial, agricultural, ATV/UTV and motorcycle belts. For OEM and ODM orders, belts are made to the customer’s part number, drawing or size, with private label and packaging. Email: luxin@lybelt.com.