We have experience in the design of a new frameless brushless DC torque motor series using the outer rotor concept. Certain models have already been designed and are commercially available.
In many direct drive applications the outer rotor principle is better suited than conventional inner rotor designs. If the rotor inertia is not the most important criterion, the bigger air gap area of the outer rotor design with identical OD leads to about 40% increase of torque. In many machine designs the outer rotor principle can avoid the use of sliprings.
We can also deliver outer rotor motors with an inner water cooling jacket to increase the continuous torque capability.