Flywheel Mechanics & Low-ImpactA Kinetic Study on Elliptical Machines
Elliptical machines utilize a flywheel mechanism to overcomes the pedaling "dead spot" issue and deliver a low-impact exercise experience.
Page Content Index
- Dead Spot
- Flywheel Mechanism
- Kinetic Energy Storage
- Flywheel Size vs. Speed
- Constraints of Conventional Elliptical Machines
- LB007 Overcoming Conventional Constraints
- Summary
Dead Spot
Dead spot is a crank position at which the user's pedaling force produces no rotational torque. On an elliptical machine, it occurs when the crank reaches its upright or straight-down position during each pedal cycle.
Surrounding the dead spot is a low-torque zone, where the pedaling force produces less torque on the crank.
Dead spot is an inherent characteristic of elliptical machines. If not addressed, it causes jarring resistance and abrupt mechanical impacts on the joints.
Our musculoskeletal system is naturally adapted for stepping against gravity. On an elliptical machine, users instinctively step downward rather than deliberately pushing the pedals forward or backward to overcome the dead spot.
Flywheel Mechanism
To provide motion continuity and a natural exercise experience, elliptical machines utilize a flywheel mechanism to overcome the dead spot issue.
Why bicycles do not require a flywheel?
The "flywheel" in a bicycle primarily functions as a pulley.
Although the rotation system (pulleys and wheels) of a bicycle stores some rotational kinetic energy, the bicycle mainly rely on its forward motion to store and transfer linear kinetic energy to help pass the pedaling dead spot.
However, stationary bikes do need a flywheel.
Stationary bikes and ellipticals are stationary machines and do not produce linear kinetic energy. They rely primarily on the rotational kinetic energy stored in the flywheel and transfers it back to the drivetrain to maintain movement continuity and pass the dead spot.
Kinetic Energy Storage
A certain level of kinetic energy storage needs to be maintained in the flywheel to achieve motion smoothness for a natural, low-impact exercise experience.
The higher the kinetic energy storage, the easier the drivetrain can bridge the torque gap, the smoother the resistance.
Flywheel Size vs. Speed
The kinetic energy storage of a flywheel is determined by its size, shape, weight and the rotation speed.
Higher kinetic energy storage can be achieved by increasing the flywheel size or speed.
Size Approach
Conventional elliptical machines mainly rely on a large flywheel to achieve a certain kinetic energy storage. That is because their flywheel rotates at a slow speed.
In their bar-linkage motion system, the flywheel rotates at the same rate as the pedal stroke — a relatively slow speed.
Speed Approach
LB007 Vertical Elliptical adopts the speed approach. LB007 uses a small flywheel rotating at a high speed to achieve asignificantly higher kinetic energy storage.
In LB007, a two-stage transmission drivetrain is incorporated into a conventional four-bar linkage to multiply the flywheel speed by 15 times.
Constraints of Conventional Elliptical Machines
Large Flywheel, Low Speed
Conventional elliptical machines use a bar linkage to drive a large flywheel. The flywheel rotates at the same rate as the pedal stroke.
Because the flywheel rotates relatively slow, the elliptical machine relies primarily on flywheel size to achieve the kinetic energy storage required for the machine to carry through the dead spot.
This is why conventional elliptical machines are typically designed with a large flywheel.
Limited Kinetic Energy Storage
Low flywheel speed limits the kinetic energy storage capacity of conventional elliptical machines, because it is not practical to make the flywheel overly large.
Limited Applicable Resistance Range
Limited kinetic energy storage also limits the applicable resistance range.
Higher resistance design would require higher kinetic energy storage to help smoothly pass through the dead spot.
To assure motion smoothness, conventional elliptical machines are typically designed for low resistance applications, more suited for cardio or aerobic exercises.
LB007 Overcoming Conventional Constraints
Small Flywheel, High Speed
LB007 Vertical Elliptical achieves high kinetic energy storage using a small flywheel rotating a very high speed.
By incorporating a two-stage transmission to a conventional four-bar linkage, LB007 multiplies the flywheel speed by 15 times.
High KE Storage
KE Storage is the quantitative indicator of resistance smoothness.
With 15x flywheel speed, LB007 achieves 111 Joules KE storage at pedal stroke rate of 1 stroke per second.
Broad Resistance Range
The upgraded kinetic energy storage capability allows LB007 to smoothly pass the pedal dead spot at higher resistance level. LB007 is designed with a broad resistance range - pedal torque range 5 - 43N·m.
The broad resistance range extends LB007's application from low-resistance cardio / aerobic exercise to mid-resistance calorie burn and high-resistance muscle strength training.
Responsiveness & Engagement
The 15× flywheel speed also significantly increases acceleration resistance, as a result, the machine responds to pedaling cadence change quickly, creating a more engaging and natural exercise experience.
KE Comparison
Conventional Ellipticals vs LB007
The table below compares a typical mid-range commercial elliptical, NordicTrack AirGlide 14i Elliptical with LB007 Vertical Elliptical.
| Typical Commercial Elliptical | NordicTrack AirGlide 14i | LB007 Vertical Elliptical | |
| Mechanics | Four-bar linkage | Glide linkage | Four-bar linkage + Two-stage transmission |
| Transmission Ratio | 1:1 No Transmission | 1:1 No Transmission | 1:15 |
| Flywheel Diameter | 18" | Undisclosed Estimated ⌀20" |
⌀9.4" |
| Flywheel Weight | 25 lb | 32 lb | 5.5 lb |
| Flywheel Velocity @ 1 Pedal Stroke/sec |
60 RPM | 60 RPM | 900 RPM |
| KErot | 8 Joules | Undisclosed Estimated 16 Joules |
111 Joules |
Summary
Dead spot is an inherent characteristic of crank-driven elliptical machines. Without an effective means of overcoming it, resistance becomes jerky and mechanical impact on the joints increases.
The flywheel mechanism solves this problem by continuously storing and transferring rotational kinetic energy, allowing the drivetrain to pass smoothly through the low-torque zone and the dead spot. This kinetic energy transfer provides movement continuity, smooth resistance, and a low-impact exercise experience.
The amount of kinetic energy available depends primarily on flywheel size and rotational speed. Conventional elliptical machines rely mainly on larger flywheels because their flywheels rotate at the same rate as the pedal stroke. In contrast, LB007 adopts a two-stage transmission that increases flywheel speed by 15 times, achieving substantially higher kinetic energy storage with a compact flywheel. The result is smoother resistance, a broader applicable resistance range, and a more responsive exercise experience.