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VariDrive Transmission May Be Boon for Single-Engine Sweepers

December 29, 2005

VariDrive, Inc. is developing a new line of continuously variable transmissions (CVT) for accessory systems that offer unprecedented design flexibility, optimal control and reduced cost. The product could be used in street sweeping vehicles to drive sweeping components off of a PTO from the main engine as opposed to using a second engine or hydraulic system. It has a higher power capacity and efficiency than current hydraulic systems and much lower costs, emissions, noise and power loss than any option currently available.

An example of using an alternative CVT for accessory drives is depicted in the figure below, where the CVT was driven off the of the front end accessory system to control a generator that powers a cooling unit on a refrigeration truck. The vehicle was driven through a common city driving cycle, accelerating and decelerating the engine. The figure shows the generator speed in tests both with and without the CVT.

Obviously, the CVT enables constant control of the accessory component, independent of the main engine. This could be an enormous benefit to street sweepers, enabling independent control at lower costs, especially in the higher powered vehicles where hydraulic systems have yet to really take off.

CVT Graph PTO Drive Optimization with CVT

Continuously Variable Transmission Technology

VariDrive will license the NuVinci CVT from Fallbrook Technologies and offer a range of product lines to several industries. It is a very simple design that offers smooth continuous speed ratio change without the use of any gears or clutches. The system incorporates an array of rotating balls and input and output discs that operate in “rolling traction contact” to transmit power.

Ratio variation is achieved by tilting the balls to change the distance from the axis of the ball to the contact point and thus change the surface speed at the contact points. It has a modular, low cost design with stable control and minimal space requirements.

CVT Cross-section
NuVinci Generic Cross Section

The NuVinci is a perfect solution to the problems facing large utility trucks like street sweepers, construction equipment, or tractors. The product would enable optimal control of all accessory components over their unique range of peak efficiency, especially in difficult operating ranges such as sweeping downhill.

Several prototypes of the NuVinci for lower power applications have already been built and tested. The ratio range and power/speed requirements for sweeper applications are well within the NuVinci's capabilities and VariDrive is in the process of looking for partners to work on beta version development. Two of the prototypes are shown below.

NuVinci Prototypes

For more information on VariDrive and the CVT sweeper project, contact Jeremy Carter at or Erik Azulay at Erik can also be reached at (512) 990-5846.

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