The Vibro-Twist

How It Works: Isokinetic Dynamometry

Designing Safer Cleats

Identify:

The earliest use of cleats has been reported since 1525 when King Henry VIII had a pair of soccer cleats. Since then, their design has changed drastically in order to accommodate changes in sports and technology. Today in sports there are many varieties of cleats that each provides their own advantages and disadvantages. However, as safety becomes a priority in modern sports regulation, certain cleat materials are beginning to become banned from use. Metal spikes present a hazard to players who may be stepped on or kicked. So there is a need for new cleats to be made from less hazardous materials that still provide the facilitation of rapid acceleration and deceleration in athletes.

Figure 1: A low-cut cleat with metal studs.

When athletes accelerate or change direction there is a great deal of force that is placed between the shoe and the ground. In order to prevent slips, studs on the bottom of shoes are necessary so that greater amounts of force can be reached. These studs can be replaceable or permanently attached to the sole of the shoe. Depending on the amount of force, the studs must be designed with a large enough surface area of attachment to withstand the shear stress. By understanding how much shear force each cleat stud will experience, it is possible to design a shoe with large enough studs that will not break off of the shoe when the user is accelerating.

Formulate:

In order to design a cleat able to withstand the forces of athletes there are several factors to consider. The material that is being used in the design of this cleat is rubber which provides stability and strength without the dangers of metal studs. The force applied to the studs will be greater if there are fewer studs and smaller if there are more studs. The weight and speed of the user must also be considered for the design. Heavier and faster users will generate more force when they accelerate or decelerate. It is also important to consider which sport the shoe is being designed for as different sports deal with different sized athletes and different speeds. For this design the cleat is being made for soccer players. The heaviest soccer player currently in the league weighs in at 227 pounds. With regard to slowing down and speeding up, Usain Bolt can accelerate from 0 mph to 12 mph in 1.85 seconds. So with this known weight and acceleration data, assumptions and simplifications can be made in the calculations.

 
Figure 2: Depicts the force of the ground acting on the shoe in order to accelerate the athlete in the +X direction.

 

Figure 3: Fground is translated into each stud separately.

Assumptions, Simplifications, Estimations, and known values

Weight: 250 pounds (more than max soccer player weight)

Acceleration: 10mph in one direction to 10mph in opposite direction in 2 seconds (faster than Usain Bolt.

10 studs on the cleat (number used in many designs)

Force in Y-direction negligible

Shear modulus of rubber is 300kPa

Equivalent force applied to each stud

 

Equations used:

Force = mass * acceleration

Acceleration = change in velocity / time

Area of circle = pi * r2

 

Solve:

Solving for force applied on each stud:

20mph = 8.94 m/s

250lbs = 113.4kg

a= (8.94m/s)/(2s) = 4.47m/s2

F= (113.4kg)*(4.47m/s2) = 506.9N

F/stud = 506.9N/10 = 50.69N = 11.4 pounds of force per stud

Solving for radius required per circular stud

300kPa = 43.51psi

SA = (11.4lbs)/(43.51lbs/in2) = 0.262 in2

0.262 in2 = (3.1415)*(r2)

r = .288 in

 

Each circular stud will need to have a radius of at least 0.288 inches in order to withstand the applied shear force and not be torn off of the rest of the shoe. If a heavier weight, a larger change in velocity, a shorter time period, or fewer studs were used in the calculations, the required radius would be larger than the calculated value. This value is reasonable as it would easily allow for 10 studs to be configured onto the bottom of a shoe without the need for a larger shoe sole.

However, these calculations are limited in that the forces in the y-direction were left out. The force of gravity would compress the studs into the shoe in addition to a shear force. This may result in an increase or decrease in required radius of the studs. Additionally, this assumes that only one foot is involved in the process. If both feet are being used then more studs are being applied and therefore the equivalent force each stud experiences will be decreased. Knowing the required radius though will allow for the design of a rubber cleat that can be used in a similar way to metal cleats without losing any functionality.

 

For more information, visit:

http://www.goldenshoesmovie.com/the-history-of-soccer-cleats-part-1/

http://footballstopten.com/top-10-heaviest-footballers/10/

http://datagenetics.com/blog/july32013/index.html

http://www.engineeringtoolbox.com/modulus-rigidity-d_946.html

 

 

 

 

An Ocean Without Sharks

Patent title: Protective Swimsuit Incorporating an Electrical Wiring System

Patent number: US 20030233694 A1

Patent filing date: June 25, 2002

Patent issue date: December 25, 2003

How long it took for this patent to issue: 1.5 years

Inventor(s): Wescombe-Down, Michael

Assignee (if applicable): Wescombe-Down, Michael

U.S. classification: 2/2.15, 405/185, 405/186

How many claims: 10

 

Have you ever wanted to learn how to surf? What is the biggest thing that stops you from going out and getting a lesson? For most people, it is the fear of what animals might be lurking in the water below. Surfing can be one of the most beneficial exercises and unlike most workouts, its actually incredibly fun. Constantly paddling and swimming provides a great cardio workout, as well as strengthens your back and shoulder muscles. Standing up and balancing on the board then strengthens leg and core muscles as you get to enjoy riding the wave. This constant fear of sharks and other animals prevents so many people from gaining the benefits from this extraordinary exercise. However, this fear no longer needs to exist. Michael Wescombe-Down has patented a unique swimsuit that incorporates two electrodes connected to an electromagnetic field generator that allows for an electromagnetic field to be created around the user. This field in turn will prevent any aquatic creatures from entering close proximity to the wearer.

The suit’s power is supplied by a releasable electromagnetic field generator that is located near the waist region and has a status indicator visible to the user. This generator is connected to the two electrodes via two electrically conductive wires that run through the material of the suit. The wires are also releasable from the generator so that in case of emergency, the generator can be fully removed. Due to the conductivity of the sea water and the ions within, an electromagnetic current is able to be established between the electrodes. This current is then able to spread outward into a field through the conductive salt water. This electromagnetic field then works to repel sharks because of a special organ that sharks possess, Ampullae of Lorenzini. These are electroreceptors that are found in sharks and rays and so their sensors will be overstimulated and will deter them away from the source.

 

Figure 1: Depiction of the design of the suit (10) with the location of the generator (18) connected to the electrodes at each ankle (12, 14) by conductive wires (16).

Prior to this electromagnetic repellent technology there were two major strategies for avoiding sharks. One incorporated using stickers that slowly released a repellent substance as the water moved against the surface of it. The trouble with these was that the repellent was limited and a new sticker is required for every new trip into the water. The other strategy was using swim suits made of metal chain. These were more often only used for diving though rather than surfing so that the weight of the metal could be countered with the diving equipment. However, this technology is not really a repellent and more of just a protection against teeth if the sharks do bite. This was the first technology that was able to incorporate an electromagnetic repellent system into an average wetsuit that could be used for surfing as well as diving.

This swimsuit is perfect for people who have always been interested in surfing but have never tried because of their fears. It is also great for professional surfers who travel the world for great surfing locations that can be notorious for their shark populations. Even those who surf regularly for leisure would benefit from this device as it would just provide an extra piece of mind for anyone sitting out on their board with their legs dangling below the surface.

Personally, as a surfer, this suit has gripped me full attention. I have always been interested in shark repellent technologies and now there is one that is so attainable. When I surf with friends and I am able to converse the thought of animals below me completely escapes my mind. However, when I go alone or if I drift out farther than anyone and then realize I immediately get terrified and lift my limbs out of the water while paddling as fast as I can back to shore. Sitting on a board in the waves can be one of the most relaxing and peaceful experiences, but once the thought of sharks enters my mind it’s ruined. A wetsuit like this would be amazing for me as it would just allow me to sit out in the water alone, relax, and not have any fears tumbling through my mind.

 

To learn more about this patent click here.