Miss Professor

1. A customer submits the drawing below as a design for you to you to manufacture. What’s wrong with it? Draw it correctly, showing the appropriate level of views and detail, on a separate sheet. The hole diameter is 1″ and it goes all the way through; the hole is also counterbored on the backside, 1.5″ in diameter, 0.25 deep.

2. How many seconds old do you need to be in order to purchase alcohol (legally) in Massachusetts? Show how you got this.

 

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The legal drinking age is 21

            There are 60 sec in a min

            60 min in an hour

            24 hours in a day

            365 days in a year

             Therefore:

            60 × 60 × 24 = 86400 sec in a day

            86400 × 365 = 1536000 sec in a year

            1536000 × 21 = 662256000 sec in 21 years

 

 

3. An engineer submits a design for coupling two steel plates together with three 7/16-14 UNC bolts (ref. chart, http://www.enqineersedqe.com/screw threads chart.htm for the specifications). The coupling must sustain an axial force of 2,600 pounds. You think that the design is insufficient.

A.If the maximum allowable sheer stress on the bolt material is 8,800 psi, how many
bolts are required? How many rivets?

B.List at least two reasons for choosing one type of fastener over another.

 

A] 7/16-14 = pitch Ø= 0.3876 in I assume min diameter used for margin of error

e = P/A

            P = 2600 lb

            A = π × 0.38762 /4 = 0.11799 sq. ln

            τ design = 8800 psi

            τ 2600/0.11799 = 22035 psi

            τ/τdesign

  = 22035/8800 = 2.56 = 3 bolts required

            If rivets are used of diameter 13/32, 3 rivets will be required

B]

1. Fastener function:   Clearly specify what the fastener will do when ordering. Be aware of fastener limitations.

2. Material:   Match the grade of steel to the application. Be particularly aware of gauge thickness.

 

 

 

 

 

4. Describe the steps you would take to solve a complex problem. Use an example if it makes the explanation more clear.

 

 

Step 1: Pin the Problem

Step 2: identify the Issues

Step 3: Generate Hypotheses and Prioritize Proving Them

Step 4: Conduct your Analysis   

Step 5: Advance your Answer

 

 

 

 

 

 

 

 

 

 

 

5. You are given the following data and clearly there is a range of values. What would you consider (as a starting point) to be the range of “good” values? What do you base this on? Show your work/calculations.

 

Ø  15

Ø  23

Ø  17

Ø  15

Ø  19

Ø  15

Ø  17

Ø  27

Ø  24

Ø  32

Ø  19

Ø  30

Ø  16

Ø  18

Ø  19

Ø  20

Ø  22

Ø  31

Ø  19

Ø  21

Ø  19

Ø  25

Ø  20

 

Range of values

15-19

20-24

25-29

30-34

 

 

6. You go in to buy tires for your car and the tire salesman tells you that he would give you a great deal on a set of tires which could safely run at 5,000 radians per minute. The outer diameter of these tires is 32 inches. Would you buy these tires? Why or why not?

 

1 radian = 57.296 degrees

5000 radian per min = 286480 degrees per min

1 revolution = 360º

                     = 286480º

            795.778 revolution per min

1 revolution = perimeter of wheel

1 inch = 2.54 cm

            = 2.54 × 32

            = 81.28 cm

            = 0.813 cm

P = π D = 22/7 × 0.813

Perimeter = 2.5545 m

Distance covered in a min

            = 2.5545 × 795.778

            = 2032.88 m

            = 33.88 m/s

I wouldn’t buy the tires…

Too slow

Top speed not achieved