Ballscrews and ball drive actuators are normally associated with machine tools. Every so often though, engineers get the chance to go pit their knowledge about these components in unusual applications, such as a motorcycle built be beat land speed records. When engineer Mike Akatiff and the rest of the team behind the Top 1 Ack Attack Streamliner Motorcycle set out to defend their land speed record title, everything had to be precise. Since the Ack Attack team first broke the motorcycle land speed record in 2006, they have been planning to be the first bike to blast through the 400 mph speed barrier. Attempting to top your own record of 376.363 mph offers little room for error. Records are meant to be broken, not bike parts and spirits.
That’s why the safety features needed for the bike were crucial. The “training wheels” for the start and end of the runs and rear stabilizing flaps during the coast down period at the end of the run were critical safety considerations. To handle the specific mechanics involved for these safety components, Akatiff and his team chose Motion Systems Corporation’s 1,000-lb-rated Model 85199 ball drive actuator. Ball drive type actuators have better efficiency compared to acme screw type units and require less energy to move the same amount of load. This helps reduce the power supply size and weight making the device far more user and environment friendly. This type of actuator also has better speed and a custom stroke.
The actuator has a diameter of 0.979 in. and integral freewheeling at stroke ends to eliminate limit switches. This freewheeling feature prevents over travel at the end of stroke. A ball cage within the nut ID cams up against stop pins at each end of travel to initiate freewheeling and linear advance stops. The stop pins are mounted in the screw thread and are factory installed for the specified stroke. This design generally eliminates the need for externally mounted limit switches. All elements (screw, nut and ball cage) are heat treated alloy steel with bearing surfaces for long wear characteristics. The nut is provided with a 19⁄16 thread for attachment of the translating tube on the 85199 actuator.
With the demands of the motorcycle’s parts being so rigorous, some elements of the 85199 actuator had to be modified. There are a number of design considerations when building components for projects as unique as the Ack Attack Streamliner. Unlike actuators used in normal conditions, the G-forces in both acceleration and deceleration are extreme. Additional means of ensuring the actuators remain functional and intact under these loads was a challenge for the design team. Every mechanical design element was directly responsible for keeping a person safe. “The human element regarding safety is paramount. Our ability to modify base line actuators into custom one-off units makes Motion Systems the choice of world class competitors,” said Erik Wolf, president, Motion Systems Corporation.
Motion Systems Corporation