Design challenge 2

Introduction

This report will focus on the modification of a mechanism that was created in a previous design challenge project. The challenge was to build a model for a machine that could grab, lift and move objects from one place to another. The challenge was successfully done by drawing sketches and then constructing the model by using pieces of LEGO. The modification for this challenge was to improve the mechanism and then discuss how the mechanism would work in real-life and what types of recently discovered materials that could be used to build it at a real-life scale.

The first model that was created had a lot of factors that require a lot of consideration as the machine would be created in real-life and the safety of people would be crucial. Most of these factors face the mechanism because of its huge size in real-life; two of these forces are friction and air resistance.

To start with, friction would affect the mechanism in real-life as it consists of many gears and levers; and air resistance would affect the movement of the machine especially at windy days. Hence, proper materials should be used to counter those forces and allow the mechanism to operate.

Later in this blog, a section containing the conditions where the mechanism would be useful will be discussed. In the section that follows, the problem about outside forces will be presented, followed by the ways how these problems could be countered and the materials that are required to do so. This section will also include details about the properties of these materials and how effective they would be to the mechanism. In the final section includes a few paragraphs that summarize the main points in this report, along with a general statement about the importance of new materials and ideas in the field of engineering.

The original mechanism

The original mechanism contained an inclined plane that was fixed to the bottom of the device. This inclined plane was designed to lift the object needed to be transported from ground level. The gripping part was constructed by using two claws that open automatically and close manually. This was achieved by using two levers connected to an elastic band used to close them automatically. A pulley connected to a fishing line and attached to the levers was used to close the claws. Finally, an adjustable lock was connected to the levers and road wheels were used to move the device. 

The in which this mechanism works is that the wheels were used to move the device to the designated position in order to lift the load. Then the inclined plane was used to slide under the load and then lifts it off the ground. The claws were then closed by using the pulley, and the grip was locked after adjusting the lock. After that, the device was moved to the desired destination and the lock was manually unlocked in order to release the load.(For a picture of the design made, see appendix A, figure 1)

The real-life application

The imagined real-life application of this device was designed to be used in constructions, as it would seem fit to do so. The reason for this is that the device would be built to be highly stable and able to lift very heavy loads. The device would be used to transport loads from one place to another quickly and efficiently. In order that this could be achieved more effectively, the gripping part would be made to rotate horizontally and vertically, hence the inclined plane would not be needed to lift the loads off the ground. Moreover, the gripping part would be made in a way that it could be changed from claws to other grips in order to make it work on specific circumstances.(See appendix B, figure 2 for the sketch of the device and appendix C, figure 3 for the sketch of the road wheels)

The most important thing needed to make the device work properly is to determine its size in real-life. The size imagined for the device was that it would be most efficient at four meters length, three meters width and two meters height. The way in which this size was determined was by thinking of how it would be best to make the device stable and able to lift loads from ground level.

The forces affecting the mechanism

There are several forces that could affect a mechanism, some of them are gravity, friction and air resistance. However, in this case friction and air resistance are the forces that should be dealt with as those are the two forces that could affect this kind of mechanism the most.

To start with, friction would be the greatest problem at all situations because the device would include many gears and pulleys. Due to friction, more power is needed to be supplied to the device due to massive amounts of energy loss. Moreover, friction would cause the inner parts of the device to become extremely hot, and therefore making gears or any type of metal expand and this would result in jams, making the device non-functional.

Moving forward, air resistance could cause several problems especially on a windy day. At those times, if the device was used to lift large loads with a high surface area, wind could cause the device to turn upside down.

Necessary material properties for this mechanism

To begin with, this device is considered to be heavy-duty, so it is compulsory for the device to have an overall high yield strength especially for its claws and body. Yield strength is the amount of stress which a material can handle without going through a permanent deformation. When any part of this device deforms, huge problems could occur which could lead to turning the device into scrap. The two parts of the device that will be discussed are its gears and claws.

The gears in this device are to be handled carefully, as they can suffer from stress and heat due to friction. So an alloy that does not expand greatly, highly resistant to rust and has high yield strength is needed. The device’s claws require an alloy that does not rust along with a high yield strength property.

New material research findings

This section focuses on researches about two materials that are efficient and just recently discovered and used.  Those materials are carbon fiber and metal foam. These two materials' properties will be presented and discussed in detail.

To start with, carbon fiber belongs to the family of polymers and was found in the late 1800's by Thomas Edison, but it had no tensile strength and it was only possible to use it to resist heat. Carbon fiber had an increasingly high demand when it was developed to be of high tensile strength in the 1950's by Rayon.("The history of carbon fiber," n.d.)

Carbon fiber is a polymer with very complicated and different molecular structures, where each has slightly different properties than the other. But mainly the structure is built up of a layer of carbon fabric which is coated with fiberglass.

The main properties of this material that make it unique are its density, strength and stiffness. In relation to steel, carbon fiber is much stiffer than steel, five times harder than steel and it weighs a lot less than steel. This makes carbon fiber extremely safe, reliable and heavy duty.(Daeton, 2008)

Moving on to metal foam, which can be made up of almost any metal, but mainly aluminium and its alloys due to its low density. Metal foam was discovered in the late 1940's and was only used by a few patents, who did not gain much use of it. However, after discovering new ways of its production, it became of a high demand due to its several properties.(Banhart, 2006)

Metal foam has several properties that make it unique. One of them is that it can act as a shock absorber and hence can be used to protect other materials. Moreover, metal foam has a high coefficient of stiffness, does not catch fire and has a low thermal conductivity.("Metal foam," n.d.)

Metal foam is produced by injecting gas into a metal that is at liquid state with the aim of creating gas filled pores in the molten metal. The, the metal is cooled until it retains its solid state and hence creating metal foam (Thomas, 2013). This way in which metal foam is created makes up its properties. For instance, the gas filled pores allow the metal foam to act as a shock absorber, reducing damage that could be dealt to an object. Its ability of not conducting heat and reducing damage would make it perfect to be placed on the body of the device, knowing that the construction environment is very insecure.

Recommendations for use

One of the biggest problems in construction sites is the danger of loads falling on devices. This section will focus on the materials that could make the device able to suffer more damage whether it was from a falling object or a crash.

To start with, it is recommended to use carbon fiber as the body of the device. Due to its high yield strength, the device's body would last longer and would be able to bear more damage. Its density would allow the device to move faster and this would help in faster deliveries of objects. These factors would make carbon fiber perfect to be used at construction sites.

To improve the overall protection, coating the device's body with metal foam would make a significant difference. The metal foam would absorb a large amount of any impact that lands on the device, giving it more survivability without increasing the mass of the device as it has a very low density. Moreover, in some circumstances where a fire would happen, metal foam will not catch fire and would conduct a small amount of thermal energy. ("Super strong metal," 2010)

It can be deduced that applying these two methods will increase the chance of the device to survive at extreme conditions, and would offer much more protection to the driver than using materials like steel.

Conclusion

All in all, a lot of things require consideration before building a device in real-life such as: the device’s size, materials that are required for its construction, factors that limit its functionality and if it could be applied in real life. Before choosing any material for building the device, outside forces that could act on the device should be noted in order to deal with them. Therefore, the properties of the materials should be listed, followed by choosing the most typical material needed for the job.

The device was designed after considering the safety of the driver. This was done by presenting the situation that the device would be in. A construction site would have a dangerous environment, so the device’s body was designed to become as strong as possible. Moreover, the device would experience friction and air resistance and this was countered by choosing a material that does not expand easily, the surface area of the bottom of the design was made large enough to prevent the vehicle from flipping and road wheels would be used to pass through uneven surfaces.

Nowadays, the field of engineering is growing larger and larger, providing new ideas and ways for better achievements. More new materials are being discovered day by day in order to make life easier and provide safer living. New ideas bring much more advanced materials, which can be of high yield strength, low density, high elasticity and more properties that would make a material unique.

References

The history of carbon fiber. (n.d.). Retrieved from http://www.hj3.com/company/history-of-carbon-fiber

Daeton, J. P. (2008, May 27). Can carbon fiber solve the oil crisis?. Retrieved from http://www.howstuffworks.com/fuel-efficiency/fuel-economy/carbon-fiber-oil-crisis1.htm

Banhart, J. (2006). Metal foams: Production and stability. Retrieved from http://www.researchgate.net/ publication/40829868_Metal_foams_Production_and_stability/file/9fcfd50fe8714a59a0.pdf

Metal foam. (n.d.). Retrieved from http://en.wikipedia.org/wiki/Metal_foam

Super strong metal foam discovered. (2010, February 1). Retrieved from http://science.slashdot.org/ story/10/02/01/1722252/super-strong-metal-foam-discovered

The history of carbon fiber. (n.d.). Retrieved from http://www.hj3.com/company/                              history-of-carbon-fiber

Thomas, G. (2013, January 29). Metal foams – properties, production and applications. Retrieved from http://www.azom.com/article.aspx?ArticleID=8097

Appendix

Appendix A

 Figure 1: the device's model

Appendix B

Figure 2: sketch of the new shape of the device (seen from above)

Appendix C

Figure 3: sketch of the device’s road wheels