MAC GT5 Sprag Clutch
The sprag is not a new idea in aircraft soft-start and free-wheel clutches. Pretty much every helicopter flying today uses them so that in the event of an engine-out, the pilot can auto-rotate the helicopter to a safe landing, in much the same way a that gyrocopter always operates. Arrow started using them in their gearboxes to soft start their 2-cycle engines in1980. They have found their way onto many gyrocopter pusher prop hubs since, and more recently MAC started using them as a soft-start shaft coupling for their Yamaha conversion kits for customers demanding to use smaller Rotax C gearboxes which required even greater space economy. Since the GT5's rely on a "clutch bearing", a clutch element that is shipped with an integral ball bearing set, the clutch can be made much smaller, and has no need for grease seals since the element is self-sealed. The result is a very narrow, lightweight clutch that can be a direct swap out for the RK400 and weighs less than half of it.