General Description

Timing-belt drives enable a quiet operation and synchronous transmission of power. As they are maintenance free, these drives are very cost efficient. Due to varying requirements and consideration of the latest developments, there are a large number of different profiles, belt types and pulleys on the market. When non-positive drives (e.g. v-belt systems) are replaced, it is worth considering whether a conversion to a positive power transmission could be allowed from a safety point of view (some drives require slip at overload).

Selection and Dimensioning

The belt material and type of timing belt must be selected considering the specific situation (e.g. required features regarding machine or surroundings). There are performance tables and a user-friendly calculation programme on the internet to help you select the correct size. Small pulley diameters reduce the service life. And at least 6 teeth should be engaged at any time. When consulting the performance tables, several application-specific operating factors must be considered.

Mounting and Maintenance

At least one pulley must be equipped with flanges. The axes must be parallel (deviation no more than +0.5°). The belt must not be overstretched during mounting. For mounting and adjustment of the ideal belt there have to be sufficient possibilities for adjustment incorporated into the system.

Belt Tension

Each belt needs a certain pre-tension, depending on the type of belt, pulley diameter, center distance and the tangential force to be transmitted. The overall sum of tensioning and peripheral force must not exceed the permitted tensile force of the belt. The belt tension is best adjusted by altering the center distance. Otherwise a smooth tensioning pulley mounted on the outside or a toothed one on the inside of the belt may be used for adjustment.

Degree of degree of efficiency de

Depending on the type of belt (flexibility) and the number of teeth on the pulley (bending) the degree of efficiency can reach 98 %. Belts with tensile members of glass fibre cords (HTD and Inch) are particularly flexible.

Tensioning rollers are used for tensioning on the outside of the belt (back of belt). The tensioning rollers can either be mounted rigidly or be combined with tensioning elements to make up an elastic belt tensioner.

When used properly, high quality roller chains are powerful and reliable drive systems. They can serve to bridge large centre distances. Various transmission ratios can be realized, independently of the centre distance. In Europe mainly roller chains according to DIN ISO 606 (ex DIN 8187) are used.

Note Regarding the Breaking Load
The DIN ISO 606 (ex DIN 8187) specifies the minimum breaking
load for each chain size. When this breaking load is exceeded, the
chain is destroyed. Roller chains should be loaded with no more
than one sixth of the stated breaking load, to avoid an early plastic
deformation (permanent elongation).

Mounting and Maintenance
The shafts must be set in parallel. The sprockets must be aligned. The slack span should amount to approx 1% to max 2% of the centre distance. For this purpose we recommend mounting a chain tensioner. Large centre distances require a support (guide rail) to be used. Chain drives must always be well lubricated. Lubricants and lubrication
methods depend on the specific application.

Determining the Chain Length
The chain length can be stated in meter or mm, or by stating the number of links. In the latter case, inner and outer links are counted. The chains are usually delivered open. The last link on both ends is an inner link. This leads to an uneven number of links. If a straight connecting ling is used, the closed chain strand has an even number of links.