In-Wheel Motors

Printed Motor Works pioneered the development of the in-wheel electric motor and have delivered many samples and prototypes to a wide variety of customers in the marine, aerospace & defence, heavy industrial and commercial automotive markets.

Printed Motor Works have a wide range of hub motors available for highly specialised applications. The in-wheel XR series (XR stands for eXternal Rotor) offers a glimpse into the future of powered wheel technology. We are happy to work with customers to develop, manufacture and supply wheel motors for these specialist applications.

In-Wheel XR Series Motors

Direct Drive In-Wheel Electric Motors

Side by side view of direct drive in-wheel electric motors: XR15-05 in-wheel motor for autonomous robot, XR15-05 in-wheel motor for hoist/winch system, XR20-12 in-wheel motor for automatic guided vehicle and XR32-11 in-wheel motor for car.

The in-wheel XR series is a permanent magnet brushless motor with an external rotor. Permanent magnet brushless motors are generally the most efficient and highest torque density motors available today. The XR series gains from two distinct additional advantages: the magnets are positioned on an externally running rotor which gives the motor the fundamental geometric advantage that torque is being delivered on the outer-most point of the motor. Finally, the torque density of the XR series is maximised by a high degree of slot fill. The high slot fill is achieved by winding each of the stator teeth individually before assembling them together into a stator.

The stator teeth of the XR series are modular and interlock in such a way that we can vary the diameter and length of the stator more or less infinitely to fit both the packaging and the power requirements of the application.  The in-wheel XR series can be liquid cooled or even oil filled for subsea applications that require underwater pressure compensation.

Applications for the XR Series in-motors include substitution of large high torque hydraulic actuation systems with a compact efficient motor, industrial and marine winch systems, propulsion of bomb disposal robots and other specialised military electric vehicles and trailers, traction for commercial electric vehicles for example in mining, direct drive radar systems, direct drive railway vehicles, compact generators for auxiliary power units, and general hybridisation of vehicle propulsion systems.

Below are some examples from the XR Series in-wheel motor range:

XR Series In-wheel Motors Table
-click part number to open drawing
Performance SpecificationsWater cooledWater cooled
Peak TorqueT PNm14--2.9160400577-
Rated Continuous Torque @ 50°CT25Nm825311.1360250300753
Rated SpeedNRPM480450450300750150187600
Rated Output PowerPkW0.4021.21.535.54.73.935.8747
Maximum Recommended SpeedNmaxRPM---350104020002000-
Peak Output PowerPkW0.96010623.137.655.0
Electrical Specifications
Nominal Operating VoltageEVolts48363640066100100300
Typical Operating Voltage RangeEVolts12-19624-14424-1440-70066-11450-65050-65050-650
Rated Continuous CurrentIAmps (RMS)10.2560600.141472213322250
Peak CurrentI PAmps (RMS)20--0.2350376550-
Motor Constants
Line-Line Resistance R L-LOhms0.490.074
Back EMF ConstantK EV/kRPM6147.747.7503.3648.23110110276
Torque Constant K TNm/Amp0.580.440.445.790.
Armature Inductance (Line-Line)LmH0.540.54451.60.14241111-
Mechanical Specifications
Rotor Diametermm134200200209360324.5324.5-
Length (mounting face to face)mm49898952.5112130130-
Permitted Radial Load (50% safety factor)kg5018015001500-
Permitted Axial Load (50% safety factor)kg4512001200-
Magnet TechnologyNdFeBNdFeBNdFeBFerriteNdFeBNdFeBNdFeBNdFeB
Cooling Specifications
Water FlowLitres/min--7--7-
Water pressureBar--1.4--1.4-
Air Speed @ 150 RPMm/s2.752.75-2.752.75-2.75

The following data sheets are available for the XR Series brushless DC in-wheel motors:

XR32-13 In-Wheel Motor


Printed Motor Works XR32-11 direct drive in-wheel electric motor with disc brake mounting points

Front side view of XR 32-11 direct drive in-wheel motor for car (disc brake mounting points on rear face).


PMW XR32-11 In-Wheel Motors featured on Riversimple Rasa car

PMW XR32-11 In-Wheel Motors featured on Riversimple Rasa car



XR32-13 in-wheel motor

Rear side view of XR32-13 direct drive in-wheel motor next to its wheel rim.


Photograph of XR 32-13 hub motor inside wheel of military electric vehicle.