Tangent's drive

The key to shrinking the size of the engine and control electronics is a proper reduction. Tangent's drive puts a near indestructible 20:1 reduction gearbox in less than 2 inches of length on the end of the highest quality components available. The results are undeniable. 

Nested bearings keep the unit narrow

Nested bearings keep the unit narrow

Tangent's drive isn't just any cycloidal design. High speeds and high shock loads must be accounted for in a minimum volume while retaining outstanding efficiency. Our patented eccentric cage effectively creates a 60mm diameter shaft mounted between enormous 3000lb capable bearings- a very rigid environment for the eccentric gears to operate.

Quality bearings by SKF are used throughout. A large loading of NLGI grade 00 grease is now sealed inside and flows to all important locations through the patented channels in the eccentric and ring gears. Spinning a Tangent gearbox unloaded at our full 12,500RPM requires less than 200W. 

Our second generation drive brings big changes to a proven design- every part has been redesigned from scratch. The unit uses gear teeth twice as large as previous while a special ring gear lowers pumping losses while improving lubrication flow by pushing fluid past the teeth and into channels surrounding the ring gear. The profile of the ring gear has been chosen to minimize sliding and maintain lubricant within the tooth's dedendum. 

ecc_assembly split.jpg

Shown on the right is Tangent's 'upgrade' drive unit intended for customers with an existing Astro Flight engine. We surround the motor with a thin jacket of fluid, allowing efficient and effective heat transfer between our source and sink. More cooling means more power. All 2nd generation units (including batch #1) will bond the Astro Flight winding directly to the heat sink, allowing maximum cooling. The engine bay is completely sealed from the environment with a high temp o-ring. 

Each housing of our drive unit starts life as a 3.6kg billet of aluminum; the finished piece weighs under 400g. Cooling fins extend the full length of the motor and gearbox. 

Starting with 8lbs of aluminum billet, almost 90% of the material is removed to create our drive housing. One piece is more robust than separate motor/gearbox and creates a no-flex mounting system, even while laying down 100ft-lbs of torque. 


A freewheel adapter allows for easy changes of the motor freewheel to facilitate maintenance or alterations for specific setups. 14t, 16t, 18t and 20t freewheels are available. 

Intelligent design minimizes the number of pieces needed to fit virtually any frame. Different width BB's are accomodated with simple spacers and the appropriate BB spindle. Contact with your expensive frame is limited to the BB faces and downtube strap. The drive unit hardware can be installed and removed again in less than 10 minutes. The gold anodized heat sink covers our Castle Creations TalonHV and uses a layer of Chomerics T766 phase change material as the thermal interface. 


Silicone o-rings retain 10mL of fluid, filling any gaps between heat source and sink. 


Simple tension. Spring loaded and bearing mounted helps prolong chainline components.