Belts are the cheapest and easiest way to take power from any driving device to a recipient piece of apparatus. This is done by mechanically linking two (or more) rotating shafts to each other via a belt. They transmit the power efficiently. Although belts are usually used in this way they have also been adapted to transport products. These are commonly known as conveyor belts. There have been various designs of belts over the years and it is wise to take advice on what type of belt you require when in the design stages, or to make sure you continue using the correct type of belt that is already existing on your machinery. The belt fitted is often fitted for a reason! The common belt types are listed below.
- Wedge belts
Wedge belts are a brilliant design and are now the most commonly used style of belt for power transmission. They can be found everywhere from your lawn mower to the auxiliary belt on your car.
The next design progression from the classical V Belt the wedge belt is designed in such a way that the belt makes full contact with the sides and bottom of the pulley instead of the inner side of a flat belt. It produces more power transfer than that of a flat belt.
One belt is sometimes not enough to take the load necessary for the job. When this occurs multiple belts can be fitted together to eliminate the breaking strain of the said belt. Please be aware that when buying belts for this instance you must state that you need a matching batch number for the belts supplied. If you fit non matching belts then you may find that the belt lengths are not equal. If this happens the smallest belt will take the full load and the other belts will run loose.
The pulleys for these belts come as two types, Pilot bore, meaning that the pulley has a factory machined nominal hole through the centre. These pulleys will have to be reworked to suit the size of shaft and any keyway and grub screws required. The other type of pulley is the taper lock version. Once the diameter of the pulley is ascertained a matching taper lock bush will need to be purchased to suit the diameter of the shaft. Standard keyways are factory machined to suit and this is fitted to the shaft prior to the pulley. The pulley is then fitted onto the bush and locked into place with grub screws supplied with the bush. The taper lock version is superior in the fact that once the bush is fitted any pulley can be changed with ease when needed instead of having to wait for it to be reworked thus cutting out the down time.
There are different sizes of belt/pulley section and styles of wedge belt.
They are as follows:
- Classical wrapped belts.
These are the basic core product of V belts. They are wrapped with a synthetic material to allow an amount of slippage sometimes needed in an operation. There are two types of classical wrapped belt, the basic Z,A,B,C,D or E section listed below, these sections were then followed by the later designed Wedge belts or the SP sections known as SPZ,SPA etc. The SP style has a deeper wall side thus giving full contact with the pulley sides and bottom allowing for slightly more power transfer.
- Raw edge cogged belts.
The raw edge cogged belts do not have a material wrapping over them. They are indeed raw edged faced with a rubber that allows full grip onto the sides of the pulley. This in turn gives some 25-35% more power transfer than that of the SP styles and 40-50% of that of the standard section. The belt is notched on the underside to give it that cogged view. The notches not only allow the belt to loop easily over a small pulley, they also trap air which in turn helps to cool the belt and pulley.
The table below may help you determine what belt you require.
|BELT SECTION||BELT TYPE||BELT WIDTH MM||BELT DEPTH MM||COGGED|
|· SPZ||CLASSICAL WRAPPED||10||8|
- Cogged manufactured as standard
- Cogged available to order
Please note that the standard section belts can be supplied as a cogged style too although still a wrapped belt offering the same power transfer but giving the user the option of looping around a smaller pulley and helping with cooling issues. They are usually not in popular demand. These belts have an “X” as the suffix to the base number e.g. AX, BX etc.
There are more variants to the v belt selections. Also available are muscle belts, hexagonal (double sided) V belts, narrow v belts and banded belts.
- Lawn and garden belts
These belts are basically a V belt but have a Kevlar based chord in its design make up. Kevlar is stronger than the standard aramid or polyester cord that you would find in other belts. As well as the Kevlar cord these belts will also have a “Dry Cover” where the wrapping of the belt is impregnated with cotton – this allows the belt to slip and act like a clutch. With their Kevlar construction these belts are ideal for “back tension idlers” and able to withstand extreme bend and flexing making them the ideal drive belt for mowers and garden machinery. They are often brightly coloured. They use the same pulleys as the above mentioned.
- Variable speed belts and pulleys
The unique design of a variable or vari speed pulley enables a user to change the speed of the running gear to the user’s choice. A simple operation involving moving the pulleys closer or further apart is all that’s needed to change the speed (or the gearing) of the driven shaft relative to that of the driver unit. This mechanical action is achieved quite simply by changing the tension. As the pulley’s are opposing each other the vari speed belt is pulled further into the pulley, the pulley has a spring tension to allow this to happen and keeping the tension on the belt for frictional grip. As the belt moves further into the pulley the speed of the driven shaft increases. The opposite happens when the pulleys are moved closer together.
- Timing belts and pulleys
A timing belt or synchronous belt is a non-slipping mechanical drive belt. It is made as a flexible belt with teeth moulded onto its inner surface. It works in conjunction with the toothed pulley to help keep time of mechanical devices. When correctly tensioned, they have no slippage and are often used to transfer motion for indexing or timing purposes (hence their name). They are often used in lieu of chains or gears, so there is less noise and lubrication is not necessary. They come in both metric and imperial sizes, can be in rubber or polyurethane and have a range of tooth profiles. The pulleys have to match the belt and tooth profile. They come in aluminium, steel or even plastic and can be taper lock or pilot bore.
- Multi ribbed belts
Multi Ribbed belts, often referred to as Ploy V or serpentine belts are a continuous grooved belt designed to drive many devices from one drive source. They are commonly used in automotive and industrial applications. Modern day “fan belts” or axillary drive belts are usually a multi ribbed belt. The beauty of these belts is that they can be subject to high tension and high loads.
- Conveyor belts
Conveyor belts are usually a long wide section of belt that rotates between 2 rollers. Often having some interim rollers along the way to bear the loads. They carry any given pay load to a destination. They can be produced in a number of styles and materials depending on their load. Sometimes a conveyor belt may have attachments fitted. These are available from order. Kettering bearings will help design or replace a conveyor belt and may be able to arrange fitment too. The rollers that compliment a conveyor belt can be obtained. Please ask about our engineering service for rollers.
It does not matter what type of belt you have fitted, be it a V belt or any other, it is imperative that all belts are aligned properly and that the tension is set to the correct levels. Failure to do so will lead to your belt wearing quickly and in turn can damage the pulleys, shafts and bearings connected to it. Aligning and tension tools are available to order. Please see diagram below for correct alignment: