Auxiliary shaft gearboxes: distributing drive through EA, ZA and DA arrangements

Many machines require a single drive to supply several driven components. The challenge is to distribute that drive within the available space while maintaining the required shaft speeds, directions of rotation and load capacity.

Auxiliary shaft gearboxes provide additional mechanical drive connections within a common gearbox assembly. They can help simplify the transmission layout where several parts of a machine need to operate together, particularly when drive must be distributed in different directions.

TANDLER’s modular spiral bevel gearbox range includes EA, ZA and DA auxiliary shaft arrangements, providing different options for the number and position of the additional shaft extensions. These allow the gearbox configuration to be selected around the machine layout and the required transmission relationships.

In a suitable installation, taking additional drives directly from the gearbox can reduce the need for separate transmission stages, intermediate shafts and associated supports. This can make better use of the available installation space and reduce the number of components requiring alignment.

The benefit is particularly relevant where several driven elements require a fixed speed relationship. A mechanical connection establishes that relationship through the gearbox arrangement, allowing the connected branches to operate together from a common input.

The additional shafts do not necessarily run at the same speed as the main output. Understanding the differences between EA, ZA and DA is therefore an essential part of selection.

EA arrangements provide one additional shaft extension in line with the input shaft. This auxiliary shaft runs at the same speed as the input, maintaining a 1:1 relationship regardless of the main gearbox ratio.

ZA arrangements provide one or two additional shaft extensions on a further axis. In a speed-reducing configuration, these auxiliary shafts run at input speed. In a speed-increasing configuration, they run at the same speed as the main output. The required shaft speeds and directions of rotation therefore need to be established when selecting the arrangement.

DA arrangements combine the in-line extension of an EA arrangement with the two additional extensions of a ZA arrangement, providing three auxiliary shaft extensions. The in-line extension runs at input speed. The other two auxiliary extensions run at input speed in a speed-reducing configuration, or at main output speed in a speed-increasing configuration.For these standard spiral bevel configurations, ZA and DA arrangements are not available with a 1:1 main input-to-output ratio. Rotation directions must also be confirmed for the selected gear arrangement.

As an illustration, a speed-reducing ZA arrangement operating at an input speed of 1,500 r/min with a 2:1 main ratio would provide a main output speed of 750 r/min, while its auxiliary shaft extensions would run at 1,500 r/min. This follows the catalogue’s specified speed relationships.

Capacity must be assessed against the complete operating duty. Each driven branch places a demand on the transmission, and the gearbox must accommodate the combinations of load that occur in service. Continuous torque, starting torque, acceleration, reversals and occasional peak loads can all influence the specification.

The distribution of those loads matters as much as the total demand. The torque transmitted through each shaft and gear mesh must be understood, together with any external radial or axial forces introduced by the connected equipment.

Precision requirements also need to be considered across the complete drivetrain. Mechanically linked shafts provide defined speed relationships, while backlash and torsional deflection influence angular behaviour under changing loads. Where accurate positioning or frequent reversals are involved, the gearbox, connecting shafts and couplings should be assessed together.

For an initial selection, the most useful information is a simple layout showing the proposed input and driven connections, supported by the required speed, direction of rotation and torque at each shaft. Duty cycle, mounting position, installation space and operating environment complete the application picture.

At Tandler Precision, we help customers select gearbox arrangements around these requirements. EA, ZA and DA configurations provide different ways to distribute drive, with the most suitable arrangement determined by how the machine needs to operate.

To discuss an auxiliary shaft gearbox application, send your proposed layout and operating requirements to sales@tandler.co.uk or call 01604 588056.