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Working Model® Helps Life Fitness Work Out Designs of Exercise
Just as health-conscious individuals use Life Fitness exercise equipment
to work out muscles and build cardiovascular endurance, Life Fitness
engineers use Working Model® motion simulation software for exercising
equipment on a computer, eliminating the need for physical prototypes.
By working out designs in this way, Life Fitness is reducing the costs of
physical prototyping, shortening design cycles and bringing high quality
exercise equipment to market more quickly.
Life Fitness, a Brunswick Company, has been the world leader in
commercial fitness equipment for nearly 20 years. In 1978, the company
introduced the world's first computerized exercise bike, the Lifecycle®
Its current product line includes the Life Fitness 9500 HR Cross-Trainer
- Total Body System, Exertainment® interactive fitness system, along with
traditional equipment such as treadmills, stairclimbers, rowers, and
computerized and weightstack strength training systems. Life Fitness is
registered to ISO 9001 international quality standards.
Life Fitness employs nearly 800 people worldwide, with headquarters in
Franklin Park, Illinois. It sells its products primarily to large health
and fitness clubs, and to consumers through retail stores and specialty
Please click here to navigate around the Life Fitness virtual prototype working under VRML 2.0 technology (futher details in http://www.lista.it)
Exercise Machine Mechanics
The company's 35-member mechanical engineering department is responsible
for design and analysis of its unique exercise equipment. Chuck Rosenow,
a mechanical engineer, uses Working Model motion simulation
software to design equipment without building physical prototypes.
Recently, Rosenow and his team completed development of the
Cross-Trainer, a piece of exercise equipment that gives a total
cardiovascular body workout through simultaneous movement of the arms and
legs. According to Rosenow, Life Fitness unveiled the Cross-Trainer at
two tradeshows on both coasts of the United States, and received rave
"I use Working Model to experiment with large numbers of simulations
without building physical prototypes," he says. "Actually, analysis of
the Cross-Trainer mechanism is complex so I wouldn't have been able to
design it without Working Model." In the past, it had taken over a year
to finish a series of costly physical prototypes. Now, with Working
Model, he can visualize and analyze dozens of different variations of
mechanisms in two weeks.
Beginnings of the Cross-Trainer
As Rosenow began designing the Cross-Trainer, he focused on two elements
an exerciser manipulates, the handlebars and the pedals. Rosenow first
used Working Model to generate rough shapes for the major parts of the
Cross-Trainer. Then, he produced linkages for these parts by connecting
them with the Pin Joints tool in Working Model. Next, he used the Rigid
Joint tool to establish bolted and welded joints. Last, he applied the
Motor tool to the linkage and applied forces to simulate the exerciser.
He also input the density for each of the links.
Up and Running
Once the model took shape, Rosenow used his CAD software to draw the
actual parts and create a detailed 2D drawing. He then exported his CAD
file into Working Model for simulation. While running the simulation of
the model, Rosenow used the Tracing tool to trace the motion of the
handlebars and pedals. The Grid Function tool allowed Rosenow to quickly
see if the motions of the handlebars and pedals were within the
appropriate dimensions to provide effective, comfortable exercise.
While in Working Model, Rosenow chose the Measuring feature to show
forces acting on any chosen pin joint at any particular moment during a
simulation. For rigid joints, such as those that are bolted or welded,
he analyzed them for torque and force. He also used the Slot tool to
simulate a roller moving along a fixed path.
Rosenow appreciates the ability to click on "run" at any point while
using Working Model to activate the simulation. Working Model's graphics
show the motion of the mechanism while the simulation runs. If there are
errors in the model, such as an undefined pin joint, the simulation will
quickly show the error.
Rosenow easily changed dimensions of the Cross-Trainer simulation model,
such as length and location of links, to quickly run more simulations.
He experimented with over 100 simulations to optimize the design.
Finite Element Analysis
To analyze stresses at the joints, Rosenow took force data from the
simulation model, combined it with his CAD geometry, and imported the
information into his finite element analysis software.
Then, he ran an analysis to ensure that the links could indeed handle the
stresses placed on them by the exerciser. Once the overall design gained
departmental approval, Rosenow generated detailed engineering drawings
Pre-production Cross-Trainers underwent grueling 24-hour endurance
testing to ensure that all parts of the machine met Life Fitness's high
standards for durability and reliability.
Working Model Essential to Cross-Trainer Design
"We couldn't have achieved the design for the Cross-Trainer without
Working Model," remarks Rosenow. "It enabled me to look quickly at over
100 linkage simulations without needing to build physical prototypes,
greatly increasing our speed to market.
"Working Model is also a tremendous communications tool that I use for
presentations to audiences who may not be familiar with technical aspects
of exercise equipment," notes Rosenow. "I could show written equations
to explain what I am calculating, but Working Model let's me tell a
better story with pictures. It's been extremely useful for communicating
to everyone - including staff in marketing, management, engineering, and
"Working Model's intuitive object-oriented user interface makes it very
easy to use. I can easily measure forces, torques and movements which is
critical to my work. Also, the software is essential for the iterative
work required in the design of exercise equipment.
"There's no doubt that Working Model software has helped us to design the
most durable, safe and effective Cross-Trainer for our customers, and
will continue to help us with future products."