Special Models covers individual blade types built for specific duties: the R4Z bi-directional aluminium blade, which reverses airflow with motor rotation, and the Emax4 PAG blade for special applications.
Some duties do not need a pitch mechanism at all. The R4Z is the clearest example: a die-cast aluminium blade that runs in both directions, so the airflow is reversed by turning the motor around instead of changing the blade angle. The actuator, the hydraulic or pneumatic circuit and the pitch setting all disappear from the fan.
Special Models collects these individual blade types. They are used where the machine already has a reversible drive, where no actuator can be fitted into the available space, or where the temperature close to the impeller is beyond what a standard moulded blade is comfortable with.
| Model | Blade type | Reversing method | Diameter range | Material | Hub | Product page |
|---|---|---|---|---|---|---|
| R4Z | Special profile | Motor rotation (bi-directional) | 299-1011 mm | ALU (ADC12) | Z-3 | R4Z axial fan |
| Emax4 | Special profile | Fixed | Quoted per project | PAG | Quoted per project | Quoted on request |
Because the R4Z reverses with the drive, nothing has to be adjusted in service; the reversing capability depends on the motor or gearbox being able to run in both directions.
Blade material is selected from the working temperature and from the atmosphere around the impeller:
| Material | Composition | Temperature range | Typical duty |
|---|---|---|---|
| PAG | PA6 with 30% glass fibre | -40 °C to 110 °C | Heavy-load cooling, anti-aging, general engine cooling |
| ALU | Die-cast aluminium ADC12 | -40 °C to 150 °C, short-term 300 °C for 2 h | High-temperature and fire-resistance zones |
Blades are supplied with matched hub sets. The hub carries the blade loads and sets the shaft interface, so it is selected together with the blade count:
| Hub type | Weight | Hub diameter |
|---|---|---|
| HUB Z-3 | 0.74 kg / set | 190 mm |
| HUB Z-5 | 0.86 kg / set | 157 mm |
| HUB Z-7 | 0.86 kg / set | 194 mm |
| HUB Z-12 | 2.045 kg / set | 285 mm |
| HUB Z-16 | 3.64 kg / set | 385 mm |
This series is normally specified for the following duties:
Cooling packs with a reversible drive and no actuator space
Simple forward and reverse cleaning cycles
High-temperature zones close to engine components
Retrofit projects where a pitch mechanism cannot be fitted
When a fan is being specified or replaced, the following points are confirmed before a blade set is released. They are the same checks used for OEM programs and for retrofit projects.
Duty point: airflow and static pressure required at the working speed, taken from the cooling pack or ventilation requirement
Installation: available diameter, shroud clearance, mounting pattern and the shaft interface of the existing hub
Environment: maximum air temperature, dust or gas atmosphere, and whether static discharge has to be avoided
Drive: available power, belt or direct drive, and whether the fan has to reverse in service
Service: blade weight for handling during maintenance and spare-part availability across the machine fleet
Blade count, profile and material are then matched to those conditions in a fixed order: material first, then blade count, then hub family, with diameter confirmed against the shroud. Working in that sequence keeps the mechanical interface stable when the duty requirement changes later in the project, and it is why the same blade family can often stay in production while the cooling pack is revised.
Special-model impellers are assembled as a matched blade and hub set and balanced on a hand laser balancing machine before shipment, which keeps vibration low in both directions of rotation.
Blade count, blade profile, hub family and material can be customized for OEM programs, and existing fans can be reviewed when airflow, noise or durability has to be improved on a running machine. Where continuous pitch control or cleaning under load is needed, the pneumatic and hydraulic reversible fans provide dedicated reversing mechanisms instead.
Related ranges: R4Z Series overview · 4XR Series aluminium blades · P Series axial fan · PMAX Series high pressure fans.
