FlexoGear® – our flexible special gear unit

Special gear box for the drying group in a paper machine

The FlexoGear® gear series from AS has been specially developed for use on drying cylinders of a paper or board machine. On the market since 1996, the FlexoGear® gear unit has been installed more than 600 times and has established itself ever since.

Flexible gearbox

The hollow shaft on the FlexoGear® enables it to be mounted directly on the dryer cylinder journal. The FlexoGear® is installed directly on the cylinder journal with shrink discs. Through the use of adapter sleeves, the FlexoGear® can fit almost any cylinder journal. If the existing cylinder journal is too short, it is usually possible to work with journal extensions. This makes the FlexoGear® ideal for modernising the drives on paper-making machines.
The steam needed for the drying process and the condensate that occurs can be directed effortlessly through the hollow shaft.
To assure optimum supply to gear meshing points and bearing locations, oil distributor blocks are installed on every FlexoGear®. From there, oil is directed through pipework to the corresponding locations, supplying them with lubrication and/or cooling oil.
Since all FlexoGear® units are identical in terms of external dimensions, and due to their flexible installation position, it is never any problem to exchange these gearboxes against one another. As a result, only a small number of replacement gearboxes is needed in order to response flexibly, e.g. as a result of maintenance work on the gearbox such as the replacement of wearing parts.

With FlexoGear®, the tendency to break can be significantly reduced and productivity can be greatly improved by reducing downtime. The FlexoGear® can easily reach speeds of up to 1400 metres per minute – of course depending on cylinder circumference and the installed engine power.

The patented torque support

AS Drives recognised at an early stage that rigid torque supports can cause torsional stresses in the system, and it therefore developed a flexible torque support.
Ideally, there are always two FlexoGear® that can provide each other with this support. This dispenses with the need to have a connection to the machine framing. Possible movements of the gearboxes, for example as a result of uneven journal movement, are absorbed by the torque support. In overall terms, the torque support provides three-dimensional compensation for movement.
If only a single gearboxes are used, torque support is provided through a connection to the machine framing. These flexible properties and compensation for movement are retained.

Always combined perfectly

The FlexoGear® KS 295 series can be connected to a system with 2 gearboxes; the series KS 340 and KS 400 can be connected even up to 4 gearboxes. For each group of gearboxes, it is therefore possible to drive two, three or four dryer cylinders using one motor and one frequency inverter. Torque is transmitted between the individual gearboxes by a zero-maintenance solid steel coupling or by a universal shaft. Therefore, no additional intermediate or transfer gearboxes are required.

Single drive

FlexoGear single drive

Duo drive

FlexoGear duo drive

Triple drive

FlexoGear triple system

Quattro drive

FlexoGear quattro system

Special solution

FlexoGear Special Solutions


When selecting an appropriate gearbox range, due account is taken of the distinctive properties of each dryer group structure. This includes definition of the required level of drive power, the number of cylinders to be driven, and the axial forces imposed by the steam & condensate system. The guide values listed above apply to each gearbox at a defined speed, not including axial forces and gearbox coupling connections. Details of other ratios and power ratings are available on request.

FlexoGear® KS 295

FlexoGear® KS 340

FlexoGear® KS 400

FlexoGear® SZ 300

The advantages at a glance


  • Mounting directly on the cylinder journal
  • Connection via shrink disc
  • Coupling of several gears possible => only one motor per gear group
  • Steam and condensate passage

FlexoGear® System

  • Only one motor and one frequency converter per system
  • Connection via special torque support with three-dimensional movement compensation = no destruction of the torque support
  • No connection to the machine frame
  • Flexible mounting position and arrangement of the gearboxes
  • Direct connection of the gearboxes with maintenance-free all-steel coupling = no intermediate or transfer gearbox

Gearboxes, made to drive your machine reliably

Here you will find suitable services and products

Drive services


Flow controller

Lubrication units