ConCar Variable Speed Belts 29.5x7 - 1057 Li

ConCar Variable Speed Belts 29.5x7 – 1057 mm inner length – DIN 7719 / ISO 1604

The ConCar Variable Speed Belts with a profile of 29.5x7 and an inner length of 1,057 mm, is an open-flanked, molded-tooth variator belt conforming to DIN 7719 and ISO 1604. It transmits drive power exclusively via its two flanks, moving radially on the conical, axially displaceable pulley halves during operation. This movement is precisely the principle of a mechanical speed converter: when one pulley closes, it pushes the belt outwards to a larger effective diameter, while on the opposite side it slides inwards. This allows the transmission ratio to change continuously without the need for shifting, clutching, or electronic control.

This length in the drive

With an inner length of 1,057 mm, this belt is one of the longer versions of the 29.5x7 profile. For two equally sized pulleys with a 250 mm effective diameter, this corresponds to a center distance of approximately 155 mm. Long belts are less prone to bending stress; at 20 m/s, they rotate only about 18.3 times per second. However, they require more attention to tension: the slack side tends to flutter with large center distances, and the belt's own mass generates additional centrifugal force during operation, which reduces the contact pressure on the pulley.

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 1,057 mm; it is measured at the inner circumference of the belt and is the standard ordering dimension in Germany. The effective length (Ld) of 1,092 mm refers to the neutral axis and is the dimension used in many catalogs and drive calculations. The outer length (La) of 1,101 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): 1,057 mm

• Effective length (Ld): 1,092 mm

• External length (La): 1,101 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: 0.26 kg

• Article number: G429071057

• EAN: 4059213021971

• 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

Variable Speed Belts are supplied as continuous, single belts and cannot be shortened or joined. Before installation, the tapered pulleys must be fully opened so that the belt can be positioned at its smallest effective diameter. Tensioning is then achieved via the pulley's adjustment range or the motor rocker arm. Prying the belt open by the pulley edge is particularly damaging with Variable Speed Belts , as this can damage the exposed flanks and the tension member without any visible external damage.

A typical wear pattern in the variator is glassy, ​​shiny edges. This is not a sign of aging, but rather slippage: the belt slips under load and polishes the edge. The cause is almost always insufficient tension or a worn pulley with an enlarged groove width. If only the belt is replaced and the pulley remains the same, the damage usually recurs within a few weeks.

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 inner length of 1,057 mm 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.