ConCar Variable Speed Belts 29.5x7 - 817 Li

ConCar Variable Speed Belts 29.5x7 – 817 mm inner length – DIN 7719 / ISO 1604

The ConCar Variable Speed Belts 29.5x7 x 817 Li is a flank-driven variator belt according to DIN 7719 and ISO 1604 with a molded toothed underside. The transversely molded teeth are not a tooth profile in the sense of a toothed belt; they do not engage with the pulley. Their purpose is to reduce bending stiffness so that the belt can be bent even on small running diameters without the flanks tearing or the belt heating up due to internal flexing.

This length in the drive

With an inner length of 817 mm, this belt falls within the mid-range of the 29.5x7 profile and thus offers the most favorable ratio of bending to tensile stress. For two identical pulleys with an effective diameter of 160 mm, this results in a center-to-center distance of approximately 175 mm. This is the range in which variator drives are typically designed, as the tension travel, wrap, and belt mass are well-matched.

For design and comparison with an existing belt, the three length specifications are important because manufacturers use different reference dimensions. The inner length (Li) is 817 mm; it is measured at the inner circumference of the belt and is the standard ordering dimension in Germany. The effective length (Ld) of 852 mm refers to the neutral axis and is the dimension used in many catalogs and drive calculations. The outer length (La) of 861 mm is measured at the back of the belt. With a profile height of 7 mm, the difference between the inner and outer lengths is 44 mm, which corresponds to twice the difference in circumference across the belt height. When replacing an old belt, always compare using the same reference dimension; otherwise, you can easily be off by several centimeters.

Dimensions and specifications

• Internal length (Li): 817 mm

• Effective length (Ld): 852 mm

• External length (La): 861 mm

• Profile: 29.5x7 according to DIN 7719 / ISO 1604

• Top width: 30 mm

• Height: 7 mm

• Flank angle: 28°

• Construction: open-sided, toothed

• Mixture: Chloroprene (CR)

• Tensioning material: Polyester cord

• Antistatic: yes, according to ISO 9563

• Temperature range: -30 °C to +80 °C

• Belt speed: up to 30 m/s

• Weight: 0.2 kg

• Article number: G429070817

• EAN: 4059213021957

• Manufacturer: ConCar

Structure and materials

The belt consists of a chloroprene rubber core with a longitudinally inserted polyester cord as a tensile member. The flanks are open, meaning they are not covered with fabric. This noticeably increases the coefficient of friction on the pulley and thus improves the transmissible torque, but in return requires clean, unworn pulley flanks. The compound is antistatically conductive according to ISO 9563, which allows the belt to be used in dusty areas and in ATEX-relevant environments.

The 28° flank angle is the crucial difference compared to a conventional V-belt, which operates at 34 to 40 degrees. The shallower angle generates less wedging effect per millimeter of radial travel, ensuring smooth belt operation across the entire pulley adjustment range and preventing binding at the end positions. Simultaneously, the large 30 mm upper width provides the necessary contact area to transmit torque solely through friction. The toothed underside reduces bending stiffness to such an extent that the belt can operate even on small effective diameters without the flanks overheating due to internal flexing.

Typical areas of application

Belts of this size cover the classic field of industrial variators: feed and grinding belt control in woodworking machines, demand-controlled piston and screw compressors, spinning and drawing units in textile machines, industrial mixers and kneaders with soft start, take-off and screw drives on plastic extruders, as well as boring mills and lathes with stepless control.

What these applications have in common is that the rotational speed must be adjusted during operation to suit the material, batch, or demand. A Variable Speed Belts solves this problem purely mechanically, without any electronics in the drive train. This is advantageous wherever dust, moisture, vibration, or temperature would damage a frequency converter, and it remains the only economical solution for existing machines because the variator is an integral part of the machine's design.

Assembly and tension

Before ordering, check the adjustment range of your drive. The belt must be able to be fitted without force, whether the pulleys are fully closed or open. After fitting, tension the belt to the tension specified by the machine manufacturer and check again after the break-in period. If several belts run in parallel in one drive, they must always be replaced as a complete set, as a new belt, in addition to worn ones, bears the entire load.

Transverse cracks on the underside indicate an insufficient bearing diameter or cold brittleness, while longitudinal cracks and frayed edges point to misalignment between the pulleys. It's worthwhile checking the alignment with a ruler or laser when changing the belt, as even a few millimeters of misalignment over a one-meter center-to-center distance can halve the belt's lifespan.

Similar names for other brands

Variable Speed Belts are standardized according to DIN 7719 and ISO 1604. A belt with a 29.5x7 profile and an 817 mm inner length is therefore dimensionally identical regardless of the manufacturer; no modification of the pulleys is required for replacement. This ConCar belt replaces, among others:

• OPTIBELT: VB 29.5x7 / VARIO POWER 29.5x7

• GATES: Multi-Speed ​​29.5x7 / Predator V Variable Speed

• CONTITECH: VARIO Speed ​​29.5x7 / CONTI-V VARISPEED

• MEGADYNE: VARISECT 29.5x7

• MITSUBOSHI: VARI-SPEED 29.5x7

• BANDO: Variable Speed ​​29.5x7

• PIX: Variable Speed ​​29.5x7

Delivery

The belt is supplied as a single, endless belt. Standard lengths and common profiles are available from stock; custom lengths and widths are available upon request. If you are unsure which length your drive requires, please send us the part number of your old belt or the dimensions of your pulleys, and we will check the compatibility.