Drivetrain components have not all evolved at the same rate. Batteries and motors have changed dramatically in search of higher efficiency and longer battery life but low-ratio drivetrains remain fundamentally unchanged since the inception of the Planetary drive. Parametric changes such as tooth geometry, lubrication, material and manufacturing techniques account for the main differences between a modern and old-fashioned drivetrain. The Orbitless drive is a fundamentally new alternative to a Planetary or Spur drive that delivers ground-breaking efficiency in an economical package. Its simple layout uses standard components that leverages past innovations found in conventional gear-trains and enables the use of new materials such as plastics to reduce both weight and cost.
ANATOMY OF AN ORBITLESS DRIVE
An Orbitless drive resembles a Planetary drive with its Orbit (ring) gear replaced by a second carrier. Like a Planetary drive, the load is distributed among multiple planets for high load capacity and smooth operation, and the output shaft is co-axial and rotates in the same direction as the input shaft.
Unlike a Planetary drive, the cost and complexity of integrating a ring gear into the case are avoided. There are half as many planet meshes which provides substantial efficiency gains, avoids reverse bending, and makes the Orbitless drive a prime candidate for alternative materials such as injection molded plastics, sintered metals, and 3D printing. The single planet mesh allows backlash to be managed without sacrificing stiffness by optimizing the distance between the planets and sun. This design flexibility is lost when planets simultaneously engage both a sun and a ring gear.
Orbitless planets do not rotate. They circulate the sun at a fixed orientation, as a consequence of being supported by two non-coaxial carriers. The result is a low pitch velocity combined with low bearing speeds which translates into a high input speed rating and low NVH. An Orbitless drive has half the reduction ratio of a Planetary drive with similar pinions. For example, equal sun and planet pinions results in a 2:1 reduction ratio, a ratio which is theoretically impossible with a Planetary drive.
LEADING INNOVATORS GO ORBITLESS
High efficiency Orbitless drives are currently being developed by two leaders in the small format precision motion control industry, MICROMO – Faulhaber, and Maxon Motor. The high efficiency and low noise characteristics are expected to deliver meaningful improvements in battery life in the wearable medical device industry and other applications where high efficiency, small size, and low noise are of primary importance.
The Advanced Engineering group at MICROMO pioneered the first study to measure the load capacity and efficiency of an Orbitless drive. Orbitless prototypes were constructed and compared to an OTS Planetary drive. The result was a drive that withstood the same input speed and torque, but consumed as little as half the power of the commercial unit, using identical components and lubrication. In addition, motor losses were reduced by up to 44% due to the reduced current draw, and total system losses (includes drive electronics) were reduced by up to 47%.
An Orbitless drive may be reconfigured to trade-off simplicity, load capacity, cost, and ratio. Different configurations have been constructed in the R&D labs at MICROMO and Maxon Motor to identify relative benefits and suitability for specific applications. These trade-offs will be discussed at ICG 2017.
FUTURE APPLICATIONS THAT MAY BENEFIT FROM ORBITLESS DRIVES
While this article focuses on small format drives, the long-term vision is far reaching. The lab-tested efficiency gains coupled with the theoretically predicted low noise levels and high speed ratings (to be proven in future tests) promises to impact a wide range of frame sizes and applications.
A primary obstacle faced by EVs (electric vehicles) is battery range. With a 44% reduction in total system losses already demonstrated, the potential benefit of an Orbitless drive coupled with a high-speed motor is clear. In addition, seats, steering wheels, mirrors, sunroofs, and door locks are actuated by geared motors. Any energy spared by cabin actuators translates into additional miles of EV travel range.
In commercial and military aviation, weight is the biggest enemy, reducing payload and increasing operating costs. A single-stage, plastic, Coupled Orbitless drive provides a light, high-ratio solution that can be mated with a small high-speed motor to deliver high energy density in a simple and cost-effective package.
Factories run around the clock and use countless gear-heads to actuate everything from robot joints to conveyor belts. Large format Orbitless drives may be used to lower the electricity bill of automated facilities.
Wind turbine gears are over-driven which is the least efficient mode of operation. Over-driving amplifies the potential energy savings of an Orbitless drive which has the added benefit of reduced noise to lessen the impact of wind power on wildlife habitats and the Environment.
Innovative companies are invited to contact Robert Eisses (roberteorbitlesscom) to discuss how an Orbitless drive can be used to provide a competitive advantage in their own Marketplace.
- L. Stocco, 2016, The Orbitless Drive, ASME International Mechanical Engineering Congress & Exposition, Nov. 2016.
- L. Stocco, 2016, The Coupled Orbitless Drive, ASME International Mechanical Engineering Congress & Exposition, Nov. 2016.
Leo Stocco, PhD, PEng, Director of R&D at Orbitless Drives Inc.