Assignment 5

Problem Statement

To design an automatic dog door security cover that can be used to open and close doors mechanically with an electronic motor. This device will be able to be set on a timer so that anyone can schedule when the security door raises and lowers. The device will be able to accommodate any sized dog door from small to large. The device will be powered by a Acetal plastic gear used on the side that turns and opens the door via teeth on the security shield. It will be easy to install for the customer and will include all necessary components.

Assumptions

This device should work for any size animal except for in some extreme cases of animal sizes under the condition that the homeowner has the space by their dog door to accommodate for the space needed to house the shield when it is open. There is also the assumption that the owner will know how to set operate the timer or use a potential app to control the shield

Assumptions regarding the calculations are the assumpion that the security door will be made of polyeurethane which is the material used for the density as well as the coefficient of friction. Another assumption is that all motors will turn at 60 rpm

Pugh Decision Matrix

Pugh Decision Matrix

The criteria was weighted in order of what i believe to be the most importance. Cost being the most important with 5 points. This is because the price of this component will effect the overall price of creating the product. Strength being the second most important because of the need to have a high enough material strength to support the weight of the security shield door, However with most of the materials having high enough yield strengths to be able to support the weight the strength gets less imporatant since they all meet the requirements by multiple magnitudes. The safety is an extension of the strength and is mostly concerned with chance of failure which is why it increases with strength. Size is the size of the actual gear used from the McMaster-Carr site this was created because of the effect of the size of the gear on the torque on tooth and the otrque of the gear. The larger gear, being the steel gear got the most points while the pother two got the same since they were the same size. Last is the maintenance score, this was weighted on the lower side due to the fact all the gears will have a similar maintenace requiremnts however in the case of a replacement the acetal gear takes the lead simply due to the price.

Through the decision matrix I was able to determine that the best material to use for my gear component was an Acetal plastic Gear this was determined because of the strength being able to support the bending stress of the doors weight and the cheap cost. The carbon steel gear came in second place due to its high yield strength however with it being almost 10x the price of the Acetal gear and both gears exceeding the stress capacity by a few multiples the higher strength was not worth the extra cost. The cast Iron came in last place since the strength wasn't exceptional but the price was quite a bit more expensive being 14x more expensive the the Acetal gear. A model of the module and the component calculations are shown below.

Model and Sketch

Sketch of Movement

Components

The first component is the Acetal Plastic Gear. Below is the link to the product page and a link to my calculations based on this gear material and size. The bending stress for the tooth was calculated to be 28.968 Psi with the Modulus of elasticity of the material being 1000 Ksi. The price of this gear would be $5.66 and the corresponding gear rack would be $3.86/foot

Acetal Plastic Gear

Calculations Acetal

The second component is the Carbon Steel Gear. Below is the link to the product page and a link to my calculations based on this gear material and size. The bending stress for the teeth was calculated to be 7.337432189 Psi with the Modulus of elasticity of the material being 27557 Ksi. The price of this gear would be $51.02

Carbon Steel Gear

Calculations Steel

The third component is the Cast Iron Gear. Below is the link to the product page and a link to my calculations based on this gear material and size. The bending stress for the teeth were calculated to be 16.2947 Psi with the Modulus of elasticity of the material being 9000 Ksi. The price of this gear would be $71.84

Cast Iron Gear

Calculations Cast Iron

Gantt Chart

Gantt Chart

FRDPARRC Tables

FRDPARRC

Lessons Learned

1. I learned that I defintiely need to brush up on my CAD skills because I heavily struggled with modeling these again.

2. Learned more about Coding in HTML.

3. I learned how to determine the bending stress on gears as well as what the Lewis Factor is.

4. I learned how to navigate through a parts page and determine which parts are what I would like to use in my design

Activites Date and Time

Began determing what material gears I would like to consider - 12/2/2020 - 5:00pm

Began Calculations for different materials - 12/2/2020 - 6:30pm - 7:30 pm

Created FRDPARRC table - 12/2/2020 10:30pm - 11:30pm

Created Decision matrix - 12/3/2020 12:00am - 12:30am

Transferred everything to website - 12/3/2020 12:30am - 1:00am

Checked advisee's webpages and made comments - 10/22/2020 - 1:00am - 1:30am

Comments for Advisees

Anna Devereaux

As of 1:09am your link for assignment 4 did not work

Ethan Fredheim

As of 1:10am there was no link for your assignment 4

Sources

Gear Tooth Strength Analysis

Lewis Factor Table

Acetal Properties

1117 Carbon Steel Properties

Assignment 5A

Assignment 5a