Motor (gearboxes)

In order to meet with each question and to be able to offer the most appropriate gearbox, “Bierens Machinefabrieken BV” and “Defawes ’96” have standardized a number of gearbox types. For certain applications it is not possible to use these standard types and therefore these gearboxes are thus custom made calculated and designed, in order to choose for a solution as ideal and economically possible.


Housings (gear housings)

All our gearboxes possess a solid housing of cast or nodular cast iron or cast steel or welded steel. The form and proportions are conceived in such a way that besides a maximum stability, they also ensure an easy maintenance of the various components and a good heat emission to the environment, as it partly determines the accurate functioning of the gearboxes. By processing on precise machine tools, bores and centre distances of the housings are manufactured with high precision. Holes with watch covers provide a simple possibility to inspect the gears.


The oildensity at the partition surface between the two housing parts and to the covers is obtained by a precision work of the contact areas and by applying an elastic seal between these areas during assembly. Seals are mounted in centered covers. The seal to vertical (hollow) shafts is ensured by an inside fixed flange bush or double packing ring in the housing. The sealing at the in- and output shafts is obtained through the use of elastic oil seals of rubber or synthetic material.
See also “Seals”.


The angled, straight and helical teeth of cylindrical gears and the straight and spiral teeth of bevel gear sets are produced in such a way that a good balance is achieved between the tooth root strength, resistance to surface pressure and wear, noise level and efficiency. This is the result of:

  • the choice of high quality material and thermic treatment
  • the scientific defining of dimensions and tolerances, pressure angle, module, helix angle, tooth form corrections
  • a safe method of calculation
  • a manufacturing on machine tools with high precision and corresponding control

The pinions and gears are manufactured from the best materials, mainly of high-alloy steels and alloyed cementation steels. The thermic treatment is performed according to modern methods and the obtained properties are checked. The teeth are hobbed and or grinded according to the hobbing system at modern toothing machines or on our 5-axis freeform milling machines. The choice of the tooth profiles and the necessary profile shifts are calculated to obtain an improved resistance to wear, a high efficiency and an operation as silent as possible. All bevel gears with “Gleason” and “Klinglenberg” spiral teeth are manufactured from alloy carborizing steel, hardened after milling and then lapped. See below “Material types”.

Shafts and bearings

An adept dimensioning, the studied form, the grinding, the use of chromium-molybdenum steel are all factors through which very rigid shafts are obtained with high resistance to fatigue and shocks. Depending on the type of gearbox conical or self-aligning roller bearings are applied for the bearing. They guarantee a long lifetime, even at major radial or axial outer force at the shaft ends. For certain models that should operate silently or at high rotational speeds, bronze or white-metallic bushings are used. See below “Bearings”.



Standard fans or cooling tubes can be applied in cases where the natural heat dissipation through the housing is insufficient.

The large number of mounting surfaces of the housing offers various possibilities for mounting an engine on top of the gearbox.


  • Generalities 
    The lubrication of the gears is done mostly by dip lubrication, where sometimes oil dispensers are used to lubricate teeth and bearings that run above the oil level. In other cases, e.g. at very high and very low rotational speeds (see below), spray lubrication with a pump is necessary. The gear housing offers a spacious reservoir, which ensures a long lifetime of the oil. In most cases the bearings are lubricated by the oil bath; in other cases, grease lubrication is applied, including in the versions with vertical shafts.
  • Choice of lubricant 
    The lubrication is carried out by means of the usual “mineral oils”, which contain the so called “extreme pressure” additions which limit the oil aging and corrosion. The required viscosity depends on the lubrication system and the application. This viscosity is indicated on the identification plate that is mounted on the gearbox. Below 300 tr/min at the high-speed shaft and at very low temperature (-10°C) or very high surrounding temperatures (> 40°C) sometimes there must be chosen for other oil types or viscosities. Please consult us if appropriate.
    For the bearings lithium grease is recommended with a consistency NLGI kl. 3.6.
    It is necessary to check the amount of oil using the oil gauge stick or oil gauge glass. At the oil gauge stick there are two marks that indicate respectively the maximum and the minimum oil level. The average quantity, expressed in litres, is indicated on the identification plate.
  • Oil change
    The first oil used with putting the gearbox into service, should be replaced after 500 effective operating hours. The second oil bath can be maintained during 2000 operating hours. From the third fill it is sufficient to replace the oil after a maximum of 8000 operating hours.

Delivery condition of the gearboxes

Before shipment, each gearbox trialed and it was checked on the basis of the specification of the order.

  • Preservation 
    The outside of the gearbox: satin gloss synthetic varnish, in the colour of choice, in accordance with the RAL-color classification with a corrosion resistance of about 5 years in indoor environment the conservation is resistant to oil, weak acids and bases. The interior of the housing is painted with an oil-resistant paint and sprayed with corrosion resistant oil; protection granted during one year after delivery at storage in a closed space; also suitable for overseas transport. For a longer storage period, please consult us. All gearboxes are supplied without oil for security reasons during transport. The grease nipples are filled with grease before shipment.
  • The shaft ends
    The shaft ends are protected with a paint layer or oiled paper.

The following is a summary of our standard series that can be modified according to powers and ratios of the customer. Further data are available on request. For any price quotations please use one of the dimensional sketches of the gearbox type. We can offer any type in various designs. Don’t forget to mention the following: power, maximum input torque, input rotational speed, gear ratio, operating conditions, type of engine.

Reduction gearbox type AA

1 Reduction gearbox with one pair gears and parallel shafts – type AA

Reduction gearbox type ab

2 Reduction gearbox with two pair gears and parallel shafts – in– and outgoing shaft are in line – type AB

3 Reductiekast met twee stel tandwielen en evenwijdige assen – type AC

3 Reduction gearbox with two pair gears and parallel shafts – type AC

4 Reduction gearbox type AC

4 Reduction gearbox with three pair gears and parallel shafts – type AE

5 Reduction gearbox type BB or BD

5 Reduction gearbox with two or three pair gears and parallel shafts – type BB or BD also available as coupling gearbox

Angular gearbox – type KLS or KLD

6 Angular gearbox with two or three standing out shafts – type KLS or KLD

Reduction gearbox - type KAA

7 Reduction gearbox with one pair bevel gears and one gear set- type KAA

Reduction gearbox - type KAC

8 Reduction gearbox one pair bevel gears and two gear sets – type KAC

9 Reduction gearboxes – type VF - VG - VIB - VIH - VJ

9 Reduction gearboxes with worm and wormwheel – type VF – VG – VIB – VIH – VJ