Kinematics & Geometry in Ellipticals Advantages of Vertical Elliptical 11x5 TM
How LB007 Vertical Elliptical Trainer different to traditional elliptial machines? This article discuss the differences from kinematics and geometry perspective, and introduce the proprietary Vertical Elliptical 11x5TM movment profile.
Kinematic Comparison
Traditional Ellipticals
A typical elliptical machine is essentially two planar four-bar linkage devices connected side by side. The two devices share one crank bar which also serves as the flywheel of the elliptical machine.
Roles of the Four Bars in the System
| Coupler Bar | Foot Pedal (one on each side of the machine |
| Crank Bar | Flywheel (both linkage devices drive the same flywheel |
| Rocker Bar | Also serve as the swing handlebar |
| Ground Link Bar | Machine Frame |
In traditional elliptical machines, the four-bar linkage system serves a dual purpose: (1) converting reciprocal movement into rotation and (2) retaining kinetic energy through the rotation of a flywheel.
LB007 Vertical Elliptical Trainer
LB007 Vertical Elliptical Trainer adds a 2-stage transmission drivetrain is between the four-bar devices and the flywheel.
In this architecture, the crank bar and the flywheel are separated. Therefore, the four-bar linkage system only converts the reciprocal movement to rotation; and the 2-stage transimission system drives the flywheel and retains the system kinetic energy. Each device does its best job, and allow each function to be refined and optimized.
With a much smaller flywheel and the 2-stage transmission, LB007, besides achieving optimized kinetics, overcomes the geometry contraints inherent to traditional elliptical machines, allowing better geometry design for refined biomechanical design.
Geometry Design Comparison
Geometry Constraints of Traditional Ellipticals
Traditional elliptical machines, due to their large flywheels and the lack of kinetic energy retention (or momentum), are large-n-heavy and only provide horizontal elliptical movement.
Long crank bar constraint ...
Due to the lack of momentum, its crank bar moving joint needs to be positioned towards the outer ring of the flywheel. This way the crank bar (the effort arm of the lever) is long enough so that the foot pedal can move pass the dead spot in its rotation by a reasonable push force. The long crank bar makes the foot pedal on the coupler bar to move more in horizontal direction and less in vertical direction (a horizontal elliptial trajertory).
Foot pedal tilt ...
Large flywheel also makes the coupler to tilt high in motion, which means a high tilting range for the foot pedal. Therefore, traditional elliptical machines are usually designed with a very long coupler bar to keep the pedal tilt in a comfortable range. This design gives the classical image of a tradition elliptical machine — two long foot pedal bars and a huge flywheel on the back.
A certain pedal tilt range is essential for natural ankle movement throughout the stride. Over-tilt can place excessive stress on the plantar and ankle joints.
Gliding coupler bar, a compromized design ...
Some elliptical machines are designed in short length by using a gliding coupler mechanism to solve too much pedal tiling issue. In this design, the coupler bar does not directly connects to the rocker bar, instead, it glides on a rail, and through another bar that is hinged on it to connect to the rocker bar. The foot pedal sits on the hinged bar and gets leveled.
However, allowing the coupler bar to glide on a rail and adding a hinged bar decrease the stability of the system. The hings are often not adequately designed for reliability and durability. It is a compromized design just to make elliptical machines smaller for home-use.
Also this design does not reduce the need of a large and heavy flywheel.
LB007 — A Paradigm Shift
| Model | NordicTrack AirGlide 14i | LB007 |
| Max User Weight | 300lb | 250lb ASTM‑Based Testing |
| Transmission | 1:1 (No Transmission) |
1:16 (2-Stage Transmission) |
| Flywheel Weight | 32lb | 5.5lb |
| Flywheel Diameter | Undisclosed | ⌀9.4" |
| Machine Footpring | 71"x25" | 42"x23" |
| Machine Weight | 225lb | 84lb |
| Movement Trajerctory | Horizontal Elliptical | Vertical Eliiptical |
| Movement Range | Horizontal: 18" Vertical: Undisclosed |
Horizontal: 4" Vertical: 11" |
| Pedal Tilt Range | 20° (-5° to 20°) | 21° (-3° to 18° |
| Resistance Levels | 24 Levels (in low resistance range) | 8 Levels (full-spectrum resistance range) |
| Kintic Energy Retention | Not albe to calculate without flywheel diameter | Approx. 127 Joules @ 1 pedal-stroke/seccond |
The crank also acts as the flywheel. Therefore for traditional ellipticals, the four-bar linkage system serves two roles:
- transfer reciprical movement to rotation
- retain the kinetics energy (flywheel momentum)
The flywheel rotation is tied to the padal cadence, very low velocity. For each pedal stroke, the flywheel rotates a complete cycle.
Due to its low velocity, the flywheel needs to be large and heavy to retain a certain rotation kinetic energy (KErot) for a smooth resistance.
The large flywheel and its direct connection to pedals also constrains the geometry design of the machine, especially the trajertory of the pedals. Traditional ellipticals are more horizontal stride bias.
| Four-Bar Coupler | Pedals(one on each side of the machine |
| Four-Bar Crank | Also the crank of the 2-stage drivetrain |
| Four-Bar Rocker | Fixed with the swing Handlebar |
| Four-Bar Ground | Machine Frame |
| 2-Stage Drivetrain | Connect the four-bar system to the flywheel. |
In this architecture, two devices each take their own best role:
- The four-bar linkage transfers reciprical movement to rotation
- The 2-stage drivetrain boost up the flywheel velocity for high kinetic energy storage.