MEGR 2156 Portfolio

Assignment Five- Gear #2

Solid Model of Component

Gear 2

Gear #2 is the "output" gear of the design it is press fitted to the base in order to allow the base to rotate. The gear is controlled by the transmission gear, where the larger gear ratio produces a larger torque at the cost of a lower angular velocity. The gear will connect to the rest of the design through an extrusion at the bottom of the gear.

FRDPARRC

Calculations

Gear 2 Calculations

Materials

From the above calculations we find that the maximum normal stress allowed before failure is 11.72 ksi and the maximum shear stress allowed before failure is 7.65 ksi. Some of the materials that fit the description and can be easily casted (the process that would be used to make gears) are down below. Other factors that I took into account when making the decision are the density of the material, the average cost of the material, and other properties of the material.

* Density is a good factor to recognize because it will determine the weight of the component. The stress of elements depend on the elements above them in this module, with the shaft and transmission gear supporting almost all of the pressure of the moment caused by the water coming from the hose plus the weight of the previous elements. This means that a lighter material is more valuable to this design because it will put less stress on the gear.

* Cost is another important factor because in the real world, the material must be purchase in order to make the design. The cost of the material plays a huge part in the cost of the product. The more expensive the material is per cubic inch, the higher the price of the product would be in order to make a profit in the material.

* Properties of the Material is another factor in choosing a material, if the material does not have the correct properties for this module, then it will not be a good idea to choose the material.

Material	Min Ultimate Normal Stress (ksi)	Min Ultimate Shear Stress (ksi)	Yield Strength	Density (lb/in^3)	Cost of Material ($/lb)	Hardness (Brinell Hardness Number)	Pros	Cons	Resources
Cast Iron Class 25	at least 72 ksi	at least 32 ksi	About 30 ksi	0.25	$0.75	187	* Wear Resistant; Resistant to Galling (wear by materials sliding on top of each other); Good vibration damping	* Difficult to machine at thin thicknesses * Higher modulus of elasticity in compression *Properties depends on thickness of material	Machinery's Handbook, pg. 365 and pg.420; https://www.foundry-source.com/Iron_Castings_Properties.html (Properties) *http://www.iron-foundry.com/cast-iron-price-lb.html (Cost);
Cast Aluminum A380	47 ksi	27 ksi	23 ksi	0.098	$0.89	75	* Better in machining than cast iron; * Does not solder to the die easily * Lower melting range *Good surface finish	* Harder to machine than other Al alloys; *Not very corrosion resistant	https://destindiecasting.com/wp-content/uploads/2014/09/Sect3.pdf (Properties); http://www.infomine.com/investment/metal-prices/aluminum/ (Cost)
Cast Aluminum Alloy A360	46 ksi	26 ksi	25 ksi	0.095	$0.89	80	* Better in machining than cast iron; * Good Yield Strength; *Good Corrosion Resistance	* Harder to machine than other Aluminum alloys * Mediocre at filling the die; * Lower Hardness than Al A380;	https://destindiecasting.com/wp-content/uploads/2014/09/Sect3.pdf (Properties); http://www.infomine.com/investment/metal-prices/aluminum/ (Cost)
SAE Steel 1141	120 ksi	70 ksi	100 ksi	0.284	$0.36	220	* Better resilience than Aluminum alloys; * Lower Thermal Expansion; *High Fatigue Strength	* Worse strength to weight ratio than Aluminum alloys; * High melting point; * Low Stiffness to Weight than other materials;	https://www.makeitfrom.com/material-properties/Cold-Drawn-1141-Carbon-Steel (Properties); https://agmetalminer.com/metal-prices/carbon-steel/(Cost)

After an analysis, I had decided that the best material for the Gear is Steel 1141. It has a high fatigue strength, which means it will take more cycles in order to fail than the other materials. It has a low cost/lb, which means I can make the part fairly cheap. Finally, it has a high hardness score which means the weight of the base will not indent the part as much as it would with other materials.

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