Further Development of the Limestone Engineering Continuously Variable Transmission (CVT)

James Kalkstein, PE, Chief Engineering Officer and Principal, Limestone Engineering Services, LLC
Limestone Engineering Services, LLC (LES)

Limestone Engineering Services, LLC (LES) has continued development of our unique and patented CVT under patent #11,371,592. The development has moved from the Research Proof-of-Concept Prototype as shown in the patent disclosure to an engineered Development Prototype (DP#1) shown in the figure below (Figure#1).

*Figure #1: Development Prototype #1 (DP#1) on Test Bench Setup

The DP#1 is constructed from 3D-Printed Hyper-PLA material. This material is rated at a tensile strength that is approximately 20 % of the strength of typical aluminum. Therefore DP#1 has a limited torque capacity when compared to a full-production metallic unit. However, the belt is a production-ready 5Mx15mm cog-type timing belt with a torque capacity of approximately 95 N-M (70 lb-ft). The gear-ratio span for the DP#1 unit is setup to be from approximately 1.2:1 to 0.8:1.

The ratio-change actuator in the DP#1 uses a threaded rod to actuate the devices that changes the ratio. However, the patent includes actuation devices of any kind, including but not limited to; 1) electromechanical; 2) hydraulic, or 3) pneumatic.

Please note that:

1. Virtually any timing belt width and pitch is possible allowing for virtually any torque capacity and;
2. Ratio spans are a function of the physical size of the unit and can be increased or reduced by design.

Several design iterations have been made for the idler pulley arrangements. All proved to be satisfactory, and the final choice should be based on the final design chosen.

Testing:

This DP#1 has been tested on a test bench using a simple Prony-Brake absorber system. The test-applied torque/speed capacity is approximately 20 N-M (15 lb-ft) maximum at approximately 1,000 rpm. Please note that this is using non-metallic Hyper-PLA material and not aluminum or other metallic material components. Additionally, the input drive device was limited to these values (20 N-M (15 lb-ft) @ 1,000 rpm). We believe that this testing level was very close to the ultimate-strength of the component design using this Hyper-PLA material. However, a material change (e.g … to aluminum or steel) should bring the capability to the level of the belt ultimate-strength without any additional design changes.

Cost and Supply Chain:

The supply chain for the DP#1 requires no special components for belts, fasteners, or bearings (rotational, thrust and linear). They are all Commercial Off-The-Shelf (COTS) items. However, the main operating components are specially designed for this application. We have investigated small batch fabrication for a small number (~ 5 units) of DP#1 for full-power test-bench testing. We estimate that these units would cost approximately $500 − $750 per unit to produce, not including assembly labor and special assembly fixtures. We estimate that in series-production, the cost would fall by, at a minimum, one order of magnitude , but could have even greater reductions in larger volumes.

Revolutionizing Electric Mobility with Emil Motors’ SAM Technology

Maximilian Guettinger, CEO & Co-Founder, Emil Motors

The electric vehicle (EV) industry is experiencing unprecedented growth, driven by global demand for sustainable transportation. Yet, this momentum faces hurdles: the reliance on rare-earth magnets − primarily sourced from China − introduces supply chain risks, compounded by potential tariffs that could disrupt production and escalate costs. Amid these challenges, Emil Motors emerges as a game-changer with its Segmented Axial Flux Asynchronous Motor (SAM) technology. This magnet-free innovation not only sidesteps geopolitical and environmental concerns but also delivers superior performance, efficiency, and scalability, positioning it as a cornerstone for the future of electric mobility.

The standard induction motor and its shortcomings

Induction Motors (or asynchronous motors) are well known work horses in industrial applications and even in automotive drivetrains. They work well and do not rely on magnets. In principle an induction motor replaces the magnets inside the rotor with conductive bars. In operation the stator field rotates faster than the rotor, which induces currents in the rotor conductors. These currents then create the rotor field which interacts with the stator to produce torque. Sounds easy enough, so why are we not using them everywhere?

The issue is low power density coupled with high manufacturing expenses for high efficiency induction motors. Torque density in induction motors is much lower compared to permanent magnet designs and if you want to build them cheaply you will sacrifice efficiency. The difficult bit is the manufacturing of the rotor conductor. For a standard radial flux machine, it must be cast or assembled in a complicated welding or brazing process. The cheapest way is cast aluminum, which has lower conductivity compared to copper and results in higher losses and lower efficiency. Achieving high efficiency in a conventional induction motor requires copper rotor conductors. These can be cast with expensive molds, or they can be assembled using a costly brazing process. When going through this complicated process you will still end up with a machine that will be much heavier or less powerful than a permanent magnet motor, making it undesirable.

Emil’s mission was clear. Make induction motors more powerful with low weight and low manufacturing cost. Achieving Performance without magnets.

Unveiling the SAM Architecture

SAM’s brilliance lies in its axial flux design, a departure from the conventional radial flux motors dominating the market. Unlike radial designs, where magnetic flux flows perpendicular to the rotor shaft, the Emil’s disc-shaped configuration directs flux parallel to the shaft. This allows for a larger rotor radius within a compact footprint, boosting torque density and power output without increasing the motor’s size. The result is a lightweight, high-performance motor that punches above its weight class.

The stator is a core component towards achieving extraordinary performance. Segmented into precise sections, it achieves a slot fill factor exceeding 65 % which describes how much of the available space is filled with copper wire, maximizing space efficiency for enhanced performance.

Our fully automated winding process is exceptionally well suited for mass production – a critical advantage for scaling EV manufacturing. Conventional round wire windings achieve slot fill factors around 40 %. State of the art hairpin designs may reach 60 % but require very difficult laser welding processes or huge machines for a continuous wave winding.

Compared to this we can easily wind a coil segment by segment and use reliable well known welding processes. A similar approach was pioneered in the world of smaller electric motors in hybrid vehicles, where it has already proven itself to be cost efficient.

Meanwhile, SAM’s integrated oil cooling system sets it apart. Oil flows through channels in direct contact with the copper windings, minimizing thermal resistance and maintaining optimal performance even under high loads.

Cooling the rotor conductors is equally important in an induction motor. SAM achieves this feat by integrating cooling channels near the rotor conductors, keeping continuous power up and losses down.

Both of these revolutionary technologies, winding and integrated oil cooling are made possible using advanced plastics. Injection molding is much more manageable on small stator segments and creates advanced geometric features without increasing cost at all.

Together with our manufacturing partner Schlaeger we have developed an advanced injection molded segment design including very thin walls for slot insulation. No need for slot liners. Oil cooling channels, structural support and winding ixation all taken care of with a simple and cheap injection molding process. The best part is no part, the best process is no process.

The rotor construction is equally impressive, diverging from conventional manufacturing technology. Emil’s axial flux topology allows for major changes and innovation inside the rotor. For example, we can incorporate significant structural reinforcements on the outside of the rotor for high rotor speeds, which is much harder to achieve in a standard radial flux machine.

Manufacturing and assembly of the rotor conductor is simplified, no casting or welding is necessary. This enables the usage of higher performance alloys and a simplified manufacturing process.

As previously explained a conventional induction motor requires copper conductors in the rotor to achieve great efficiency numbers. This is not the case for SAM. The axial flux topology enables big rotor slots with a high cross section. This decreases losses, even when using a material with lower conductivity like aluminum. Additionally, the usage of different alloys makes it possible to achieve higher conductivity compared to cast alloys.

The SAM-M240 showcases these innovations:

• Peak Shaft Power: 330 kW
• Peak Torque: 450 Nm
• Max Speed: 16,000 RPM
• Efficiency: >97 %
• Active Weight: 35 kg (electromagnetic components only)

At just 35 kg of active weight, the SAM-M240 achieves a power-to-weight ratio that rivals permanent magnet motors, proving that magnet-free designs can lead the pack.

These performance claims have been validated through hours of testing data on a test bench. Talk to us directly to get more information on testing and validation of this groundbreaking technology.

A Competitive Edge Over EESM

To appreciate Emil’s significance, consider its magnet-free competitors, such as the Externally Excited Synchronous Machines (EESM) from BMW, ZF and Mahle. EESM technology replaces rare-earth Magnets with an electrically energized rotor, using current to generate the magnetic field. While effective, this approach requires additional power electronics to manage rotor excitation, increasing complexity, weight, and cost. These extra components can also introduce reliability concerns over time, a drawback in high-stakes EV applications.

In contrast, SAM relies on induction motor principles, eliminating the need for rotor excitation systems. By inducing a magnetic field through the stator’s interaction with aluminum conductors in a dual rotor setup, Emil achieves simplicity without sacrificing performance. Its axial flux design delivers torque density on par with permanent magnet motors, while its lightweight construction − just 35 kg of active mass − outshines EESM’s bulkier profile. The motor’s ability to hit 16,000 RPM enables high power capability and low motor weight.

In addition to the increased power density, Emil brings down cost by using an aluminum conductor in the rotor compared to expensive copper windings in EESM technology.

Efficiency is another win. With over 97% efficiency, SAM minimizes energy losses, extending vehicle range − a priority for manufacturers and consumers alike. Compared to EESM, SAM offers a streamlined design, higher power density, and lower production costs, making it a standout choice among magnetfree solutions. It strikes an unrivaled balance of performance, efficiency, and affordability, ready to meet the demands of mass-market EV production.

Strategic Resilience and Sustainability

Emil’s advantages extend beyond the technical. By using widely available materials like copper and aluminum, it eliminates dependence on rare-earth magnets, shielding manufacturers from supply chain volatility. To this day 90% of rare earth magnet production is controlled by China and magnet motors rely on that 100%.

Getting rid of these critical materials in your motor design is the fastest and easiest way to protect against these risks.

We have seen how quickly tariffs can get out of hand and the rare earth supply chain will take a very long time to build up in other countries than China.

For EV manufacturers, this translates to a competitive edge. Emil enables the production of high-efficiency, cost-effective vehicles without the risks tied to magnet-based motors. Its readiness for automated, large-scale manufacturing will accelerate adoption, empowering the industry to meet rising demand without compromise.

Driving the Future Forward

Emil Motors’ SAM technology is more than an engineering breakthrough − it’s a vision for a resilient, sustainable EV ecosystem. With its lightweight design, exceptional efficiency, and magnet-free architecture, SAM redefines what’s possible in electric propulsion. It challenges the status quo, proving that innovation can overcome the limitations of traditional motor technologies.

We invite industry leaders, engineers, and visionaries to experience this revolution firsthand. Visit Emil Motors to explore how we can power your next EV project, enhance your competitive edge, and contribute to a cleaner, more sustainable future. Together, let’s drive electric mobility into a bold new era.

Multi-Speed Transmission with Uninterrupted Shifting for EV & IVT for HEV

Raja Rajendran MSME, President, EcoNovaTech LLC
Prashanth Rajendran MSME, PhD Candidate, CEO, EcoNovaTech LLC

• Breakthrough innovation using Geneva mechanism for transmissions
• Multi-speed uninterrupted shifting for EV
• IVT with uniform input-to-output ratio, NOT dependent on friction for HEV

For the last several years, EcoNovaTech has been developing multiple innovative technologies to solve problems that are in the forefront of the automotive industry. With its latest developments, EcoNovaTech provides a paradigm shift in transmission technology with uninterrupted shifting and ALL gear-based transmission.

Multi-Speed Transmission with Uninterrupted Shifting (MSTUS) for EV:

OEMs are continually striving to increase the range per charge for EVs. Some OEMs now recommend not depleting the battery below 25 % capacity, to extend its life. Battery charges relatively fast for the first 80 % but the last 20 % takes about as much time. Therefore, charging the battery up to 100 % could take overnight. However, there are concerns that the battery can catch fire making it difficult for consumers to use the full capacity. Moreover, battery degrades depending on the frequency and number of times it is charged and discharged. A transmission that can improve the range will reduce this frequency thereby extending battery life. So, OEMs are actively looking for a multi-speed transmission in place of a single speed Transmission to increase the range.

OEMs currently use two stage reduction for EVs. They are also actively looking into two speed transmissions with two stage reduction. Ideally, shifting occurs at around 40 − 45 miles per hour at which the wheel spins at about 650 − 750 RPM and the motor spins at about 6,500 − 7,500 RPM, since two stage reduction results in about one tenth the RPM of the electric motor. Current technology takes about 150 milliseconds of interruption for synchronizing and shifting, which causes a delay in achieving 0 − 60. So, a Multi-Speed Transmission with Uninterrupted Shifting (MSTUS) is desirable since it further increases the range, without affecting the time needed for 0 − 60. For electric motors spinning at 7,000 RPM the first reduction results in about 2,200 − 2300 RPM. This allows about 25 − 30 milliseconds for the transmission to shift over a full revolution, during the second reduction.

Smooth shifting occurs when the vehicle speed remains constant during shifting. Since vehicle speed is a product of motor RPM and angular velocity ratio, the change in this ratio should be inversely proportional to the change in motor RPM. Since the rotor of an electric motor has very low inertia when compared to IC engines, the RPM can be rapidly changed without changing the vehicle speed during shifting. As a result, occupants will not experience a jolt during shifting.

Experimental study using chain and sprocket mechanism for uninterrupted shifting shows that when shifting in about 19 milliseconds, most occupants may not experience the abrupt change in vehicle speed. However, use of chain and sprocket mechanism in transmissions is still in developmental stage. Noise and durability issues must be overcome. Chain and sprocket mechanism is not commonly used in transmissions in the industry.

Founded in 2014, EcoNovaTech has been dedicated to its mission of designing custom eco-friendly products through simple, effective engineering solutions and being a leader in Automotive Engineering.

In 2021, EcoNovaTech came up with a break through invention for Multi-Speed Transmission with Uninterrupted Shifting where the motor is continuously powering the wheels, even during shifting. It replaces the synchronizer with custom Geneva mechanism where the Geneva pin wheel has multiple pins and the Geneva slot wheel has multiple custom slots, along with dog clutch. The force required to operate a dog clutch is negligible.

With its latest innovation, EcoNovaTech now has two MSTUS solutions (one using non-circular gears and the other using Geneva mechanism) for EVs that are patent pending in multiple countries.

To briefly explain the operating principles of this innovation, both EcoNovaTech solutions use a transition module for uninterrupted shifting. The transition module transmits power parallel to the transmission gears in the transmission. The transition module can be engaged or disengaged using a dog clutch. The transition module has non-circular gears or Geneva pin and slot wheels cycling smoothly through all the constant angular velocity ratios used in the transmission, ramping up and down as needed. In a two-speed transmission, the transition module has 4 zones, a constant low speed zone, ramp up zone, constant high-speed zone, and a ramp down zone. Thus, it alternates between two constant speed zones sandwiched by a ramp up zone and a ramp down zone.

Use of partial gears for the constant zone makes it economical and less complex, and the number of pins can be reduced to 1 pin for up-shift and 1 pin for down-shift.

Use of helical gears reduces the space required when compared to chain and sprocket with tensioner. Also, helical gears provide a smoother and quieter ride at higher efficiency, when compared to chain and sprocket systems. A pair of Geneva wheels without partial gears and a pair of Geneva wheels with partial gears are shown in the figure.

Unlike in DCT the need for a high-pressure hydraulic system is eliminated resulting in significant savings. Also, the DCT only decreases the duration of interruption while EcoNovaTech innovation COMPLETELY eliminates the interruption. The lower ratio driven gear is placed on a one-way bearing on its shaft eliminating the need for linking it through a dog clutch. During reversing or regenerative breaking this must be connected through a dog clutch.

EcoNovaTech’s first solution is best suited for luxury passenger vehicles. For such vehicles, it is recommended that duration of uninterrupted shifting is extended when compared to current emerging technology, for a perfectly smooth ride. This solution uses a Duration Extender Module (DEM) that extends the duration of uninterrupted shifting to an optimal value of 30 − 50 ms (multiple revolutions) with zero interruption. DEM uses additionally a pair of overdrive gears., however is highly suitable for luxury passenger vehicles.

EcoNovaTech’s second and latest solution uses a DEM and eliminates the shortcomings of the chain and sprocket solution that is currently being developed in the industry. In 2019, EcoNovaTech developed a solution for uninterrupted shifting without a DEM using non-circular gears (patent pending). EcoNovaTech now has a less expensive innovative design (patent pending) that uses Geneva pin and slot mechanism with a customized slot, in lieu of non-circular gears, to transition from one angular velocity ratio to another. Geneva wheels can be mass produced at a lower cost when compared to non-circular gears.

Since the original design, EcoNovaTech has come up with a significant improvement where the Geneva wheel has only one pin for upshift and one pin for downshift, with the addition of two pairs of partial gears.

For EV, since the electric motor has a low inertia and can change the RPM instantaneously, shifting can occur within one revolution of the input from the electric motor. Since EV uses two stage reduction, it is advantageous to have the uninterrupted shifting happen in the second stage so that it spans a longer duration.

Non-friction dependent IVT for HEV:

In a hybrid vehicle, since we have a combination of IC engine and electric motor, a smaller IC engine can be used. An IVT can get maximum power out of a small engine for a quick acceleration.

EcoNovaTech has two innovative IVT solutions, one using non-circular gears (patented in US, China and Japan, and patent pending in Canada and India) and its latest using Geneva wheel mechanism (patent pending), along with other COTS components.

The operating principle involves converting

• uniform rotation from the engine to non-uniform rotation using non-circular gears or Geneva mechanism
• non-uniform rotation from above to linear oscillation (a portion being uniform) of a rack using a Scotch yoke mechanism
• linear oscillation of the rack to rocking motion of a pinion
• rocking motion of the pinion to a unidirectional uniform rotation of the output using a one-way bearing

The location of the pin in the scotch yoke mechanism dictates the angular velocity ratio. With as low as 3 scotch yoke modules, a continuous and steady output can be achieved.

The ratio changing mechanism in EcoNovaTech’s solution uses a unique and simple feature enabling the relocation of the crank pin in a rotating coordinate system from a fixed coordinate system. This is used to change the input-to-Output ratio for the transmission. The crank pin location can be changed purely mechanically at high RPMs so that it can be operated with a lever or cable. Planetary gears, computer controlled clutch or reversible one-way bearing can be used to achieve reverse gear. Use of reversible one-way bearing eliminates torque recirculation thereby reducing the peak load on the one-way bearing. This results in overall size reduction, since the size of the one-way bearing increases with the torque that is transmitted via the one way bearing.

Use of elliptical gears produce close results as non-circular gears, allowing ease of mass production since the driving and driven non-circular gears can be identical. EcoNovaTech’s latest IVT solution using Geneva wheel mechanism instead of non-circular gears will significantly reduce the manufacturing cost associated with non-circular gears.

EcoNovaTech’s eco-friendly innovative technical solutions can help OEMs progress towards the goal of Net-Zero Emissions by 2050 to help stop climate change.