Mechanized Legless “Classic Rocker”

Team #7

Tom Dabrowski

Sarah Philo

Adam Rauwerdink

Outline

• Specifications• Physical challenges• Mechanics of rocking• Potential mechanisms• Competitor products• Project constraints• Design summary• Budget• Marketing• Conclusion

Specifications Rocking mechanism

Comfortable speed Does not surpass tipping angle (varying user weight) Does not require permanent attachment to floor

Control Simple power switch for user Control of audio by user Caretaker has master control for all power and for music track and

volume All easily accessible and with high ease of use

Audio Internal speakers Input from CD player accessible to caretaker

Physical Challenges

Users have wide array of physical and mental limitations

Cerebral palsy, Multiple sclerosis, varying levels of paralysis Coordination Muscle control Mental abilities and attentiveness Seizures of varying intensity (some CP)

Mechanics of Rocking

mg

mg

Equilibrium, all in lineCenter of curvature of rocker

Center of gravity of chair and occupant

Point of contact with ground

No moment

Mechanics of Rocking (con’d)

R

h

mg

mg(R-h)sin(θ)

Chair rotatedRestoring moment from force of gravity

Moment taken about point of contact with ground

M=IαMoment = (Moment of Inertia) x (Angular Acceleration)

-mg(R-h)sin(θ)=mh2α

Frequency of rockingDependent on radius of curvature and occupant center of gravity

Mechanics of Rocking (cond’d)

www.exoticoutdoors.com/swing.pdf

Potential MechanismsRack-and-pinion styled

Motor turns stationary small gear over a long, linear piece attached to chair back

Counterweights Like an elevator system

Linear Actuator Rod extends, pushes up on

chair back Rod returns, pulls down

chair back

Competitor Products/Previous Projects

• Electronic and Mechanical Assistant Technologies – Motorized Rocking Chair

•NSF Project – Rensselaer Polytechnic Institute – 1989 – “The Mechanical Rocking System”

• Various non-mechanized legless rockers, available at many major retailers (Wal-Mart, Target, etc)

• Numerous patents granted for mechanized rocking systems

• Single instances (web forums)

Competitor Products/Previous Projects (con’d)

Project Constraints Safety

If 120V power is being used, must be completely isolated from possible shock and from chair fabric

Angle and speed of rocking must not cause tipping Environmental

Must be durable and capable of surviving moderate abuse

Should be able to withstand spilling of liquids and be easily cleaned

Economic Pre-built chair must be purchased

Project Constraints (con’d)

Control Caretaker must be capable of having master

control of the rocking Audio volume, track, and master power are

also to be under caretaker control

Construction Internal frame of chair will vary with models Ability to build off of frame will be dependent

on this

Design Summary

Budget $750 from National Science Foundation Chair prices ($30-$100)

Quality (frame, fabric) Accessories (speakers, audio input)

Motor ($16-$50) Power, RPM

Actuator ($100-$150) Power, length

Speakers ($40-$100’s) Wattage, size, quality

Accessories Amplifier ($100+) – probably excessive Subwoofer Linkage bars, brackets, mounts Frame material

Maximum Total: $500 (rest for error analysis)

Marketing

Target: special needs consumers who wish to enjoy a relaxing experience No physical input needed to rock Music enhances overall experience

• “Classic-Rocker”

Simplicity Basic controls Simple controls for caretakers

Conclusion

Will provide self-rocking motion for those with physical disabilities

Reliable, easy to use, and safe rocking mechanism

Final product will include implanted audio system to enhance the “experience”

Caretaker will have master control over all parts of the chair

Complete product will be sturdy self-contained unit that is easy to maneuver