Oct 9, 2020


Multi-wheel carriers or self-propelled modular transporters (SMPT) are rather unique vehicles designed to carry heavy loads. They can propel independently and/or be used on-road as semi-trailers and trailers. Self-propelled transporters operate in relatively controlled areas such as shipyards, nuclear power plants or automotive plants. Their versatility has given rise to their popularity, and the need for efficient, smooth motion of large and heavy loads of critical or expensive equipment spans a number of industries.


Developing a self-propelled multi-wheel carrier presents a number of challenges:

  • designing an efficient system architecture to drive a large number of wheel motors together in a closed loop
  • the space constraints for each component
  • meeting turning radius needs
  • enabling synchronized movement with multiple platforms either side by side or front to back

The type of facility in which the machine will work and whether or not it will need to be used on-road ultimately drives the decisions for its power transmission system.

Self-Propelled Transporters:

In a parallel circuit, oil will take the path of least resistance. When there are many wheels on the same circuit, the flow to the wheels can be irregular. As flow affects speed, this presents a challenge for the OEM especially when moving laterally. All wheels need to work together to move the machine at the right rate to provide smooth and even mobility.  An antiskid system adapted to the multi-wheel carrier can help mitigate irregular flow by ensuring that each wheel receives the precise amount of oil needed at any moment.

Achieving smooth and precise motion at low speeds is one of the biggest requirements for multi-wheel carriers. Poclain Hydraulics’ cam-lobe radial piston technology can run at speeds as low as 1kph—without cogging—delivering the smooth motion needed for transporting fragile or sensitive but large material.

Another challenge is fitting the right amount of torque, speed and safety functions such as braking into the buggie’s envelope. The buggie’s envelopes are not adapted to fit a gearbox. Each buggie is comprised of two wheels, which means it must fit two motors.


Poclain Hydraulics Solutions for self-propelled multi-wheel carriers:

In this case, Poclain Hydraulics’ MHP motors with combined brakes fit the wheel motor needs well. The MHP boasts three speeds. Aided by a directional control valve, the MHP’s fluid transitions from one speed to another deliver the smooth drive needed in this application. The MHP’s compact design makes it possible to fit two motors in the buggie’s small envelope, whereas a motor and gearbox combination would not be possible.

The combined brake option available with the MHP motor consists of a service and parking brake inside the bearing support. It allows for the necessary safety features without taking up additional space.

A solution for wheel orientation – a vertical MSE motor on a circular track – helps the multi-wheel carrier achieve the steering and the crab motion necessary for precise movement.

An electro-proportional control pump, an electronic control unit and software to pilot the system complete the Poclain Hydraulics offering, which integrates easily into the machine’s electronic controls.

Gonzalo de Sebastián, Sales and Marketing Director for DTA a designer and manufacturer of industrial vehicles for in-plant transportation including multi wheel carriers on the Poclain Hydraulics wheel motors:

The high efficiency of the new MHP motors together with the capability of having three or four different displacements with the Poclain automatic transmission, make this solution able to compete successfully against variable displacement motors.

An advantage over variable displacement motors is the possibility of having the motor, the gearbox and the dynamic and parking brakes in a single compact unit.


To learn more about power transmission solutions for multi wheel carriers as well as other applications, visit Poclain Hydraulics at Bauma China in booth N4. 821. Contact us to set up a meeting at the show to learn more about this and other solutions. 

Bauma China 2020 

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Poclain Hydraulics multi-wheel carrier contact: Paola IPSA