OTHER DATA
ON THIS PAGE YOU CAN FIND SOURCED DATA, RESEARCH AND PROTOTYPING.
LEG STRENGTH
In order to establish a range for leg strengths of the users I consulted online studies, journals and books.
• Maximal Unilateral force (no arm load): 822 Nm – Maximum voluntary force of bilateral and
unilateral leg extension
• Estimated percentage off untrained (15%): 699 Nm
• Elderly have 50% less leg strength: 350 Nm
• Will be less in the majority of cases
Results from mixed subjects – physical education students and trained ballet performers.
SPRING SELECTION
Using the data from studies and ergonomics a datum spring rate value of 150 n/mm was reached. This spring rate will not require the user to produce a maximal out put several times during a song, but is strong enough to ensure that the users leg muscles are being worked.
The free length of the spring should be 80mm ± 5mm and have an outer diameter of 50mm -5mm.
SPRING PERSONALISATION
Though this product is aimed at users roughly in the same age group, ability level will range dramatically. Many of the users will have very weak legs, and a large number will have very strong legs, and then there is everything between.
In order to cater to the individual needs of each user it is a suitable/sensible idea to have each users Foot Pedals adjustable in difficulty (how hard it is to push down each pedal).
After looking at varying ways to approach this, the best way was to make it possible for users to decrease the distance from the pedal to the base of the spring. This will increase the potential energy of the spring whilst also making it harder for the user to push down on the spring as the same spring rate is being forced into a smaller area.
SPRING PERSONALISATION MECHANISM
In order to compress the spring some type of mechanical or electrical component will be needed. Looking into Actuators proved that this would not be suitable as an Actuator small enough to fit into the space provided would not be strong enough to overcome the force (N) of the users legs.
Research was also done into hydraulic components but they were either too big or much to expensive to be considered a viable option.
This left the only option of using a mechanical system to reduce the spring size. This meant looking at various gear configuration to see which would be most appropriate. After researching different type of mechanisms, the Rack and Pinion system was the most appropriate.
RACK & PINION
After creating CAD and physical models of the rack and pinion mechanism it became apparent that the length of the rack that would be able to fit inside the product would in fact be so small that it would not be justifiable.
However, the users still needed a customised spring difficulty.
The simple and effective soultion to this was as follows. Since a set there would be 6 Foot Pedal it meant that each pedal set could have a different spring rate, allowing users to pick the appropriate pedal with their desired difficulty level.
This system allowed the users to have that customisation, but also kept costs low from a manufacturing point of view.
COMPONENT LIST & ELECTRONICS FLOW DIAGRAM
This flow diagram shows how the various components that would be used in the product would work in sequence with each other to produce the desired outcome.
A component list and brief Arduin system sheets is also located below.
REFERENCES
Arduino.cc,. 'Arduino - Tone'. N.p., 2015. Web. 22 Mar. 2015.
Electronicsclub.info,. '555 And 556 Timer Circuits'. N.p., 2015. Web. 22 Mar. 2015.Google.co.uk,. 'Travel Measure Sensor -
Google Search'. N.p., 2015. Web. 22 Mar. 2015.
Häkkinen, K. et al. 'Changes In Electromyographic Activity, Muscle Fibre And Force Production Characteristics During Heavy Resistance/Power Strength Training In Middle-Aged And Older Men And Women'.
Acta Physiologica Scandinavica 171.1 (2001): 51-62. Web.
Instructables.com,. 'How To Make Leds Flash To Music With An Arduino'. N.p., 2015. Web. 22 Mar. 2015.
Roymech.co.uk,. 'Ergonomics'. N.p., 2015. Web. 22 Mar. 2015.
Talkingelectronics.com,. 'Touch Switch'. N.p., 2015. Web. 22 Mar. 2015.