The NerraTrac continuously variable transmission (CVT) utilizes a traction drive in a traction fluid (high viscosity lubricant) that ‘solidifies’ momentarily between two hardened metal surfaces under high contact pressure, thus providing a traction force. It employs the same elasto-hydrodynamic lubrication principle used by all current automotive CVT transmissions.
The NerraTrac CVT uses a commercially available traction fluid, such as Santotrac, from Santolubes. Refer: https://www.santolubes.com/products/santotrac/
A 1985 NASA paper on the Design of Traction Drives provides a credible reference on the technology principles. Refer to: https://ntrs.nasa.gov/api/citations/19860004265/downloads/19860004265.pdf. Well established and proven technology principles.
The NerraTrac CVT enables features such as:
- Automated ratio control
- Geared regeneration
- Full CVT capability under all load conditions
- 91-94% efficiency (MATLAB Simscape simulation, 374% ratio)
- Shaft driven, fully enclosed system; practically zero maintenance
- Simple, durable, lightweight design (2.3kg or 5.0lbs without external casing)
- 370% ratio range (198mm diameter disk)
- 510% ratio range (248mm diameter disk)
Benefits include:
- multiplication of motor torque
- motor down-sizing (optimization)
- maximising motor efficiency
- maximum current reduction
- high speed capability
- extended range
- limited to zero maintenance
- no cooling issues
- silent operation
Scalability:
- 9.2 kW (current ebike CVT design):
If the input power is 25 Nm, it will be suitable for an 9.2 kW ICE or an electric motor at 3,500 rpm.
Power (Watt) = 0.105 x Nm x rpm, therefore, this will result in Hertz contact stresses of around 1.35 GPa, thus, it can be manufactured using relatively low cost EN36B steel (case hardened to 60 HRC). - 15.8 kW:
As per above example but at 6,000 rpm input, will result in 15.8kW - 34.6 kW:
As per the first example, but using special steel* for the disk and rollers that can handle 2.7 GPa (55 Nm) at a high duty cycle. * Note: an example of suitable steel is KUJ7 manufactured by Koyo.
This will result in 20.2 kW at 3,500 rpm and 34.6 kW at 6,000 rpm. - Further scaling (bespoke):
The NerraTrac CVT can be further scaled by increasing input rpm above 6,000 ≤ 21,000rpm.
Secondly, by applying the variations on the design space & relationships e.g. larger rollers, a larger disk etc, according to the requirements of specific applications.
The NerraTrac CVT represents an adaptable platform technology
Suitable a transmission for light electric vehicles and ICE vehicles such as:
- motorcycle scooters, mopeds, three wheelers
- ‘pod’, microcars, LEVs, autonomous delivery vehicles (ADVs)
- UTVs & ATVs
- ebikes, ecargo bikes
- golf carts, lawnmowers etc
- and all rubber belt CVT applications
Also suitable be for industrial applications including:
- Pumps
- Compressors
- HVAC
- Geared motor drives
- Conveyors
- Appliances such as washing machines
- As a Variable Speed Drive (VSD) alternative
- Artificial lift (oil & gas)
CVT vs VSD advantages include:
- multiplication of motor torque
- speed control
- motor optimization
- motor size reduction
- system start-up control
- energy/electricity optimization and start-up current spike reduction
Voting
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ABOUT THE ENTRANT
- Name:Bruce Thompson
- Type of entry:individual
- Software used for this entry:MATLAB Simscape
- Patent status:pending