Kinematics - Spur Gears

 Spur gears or straight-cut gears are the simplest type of gear. Sometimes, many spur gears are used at once to create very large gear reductions.They consist of a cylinder or disk, and with the teeth projecting radially, and although they are not straight-sided in form, the edge of each tooth thus is straight and aligned parallel to the axis of rotation. These gears can be meshed together correctly only if they are fitted to parallel axles. 

Retrieved from Wikipedia.org

Two meshing gears transmitting rotational motion. Note that the smaller gear is rotating faster. Although the larger gear is rotating less quickly, its torque is proportionally greater.

Kinematics - Plate Cam CAD (Plate #5)

 Design a cam, turning counterclockwise, to give a reciprocating follower, slide 4, following motion: rise 4.25 inches with simple harmonic motion during 135 degrees rotation of the cam; rest for 45 degrees; drop 1.25 inches instantly; drop 3 inches with harmonic motion during 120 degrees; remain still for 60 degrees. Oscillating arm AC is 14 inches long and carries a roller .75 inch in diameter running on a journal B, 8 inches from A and on the center line of AC. This roller is actuated by the cam. A connecting link CD, 6 inches in length, joins C to the slide 4 at D. D is below AC. The fixed axis A, of AC, is 6.5 inches to the left and 3 5/8 inches above the axis of rotation of the cam. The center line of travel of D is vertical and 6 inches to the right of the axis of rotation of the cam. AC is to travel equal angular distances above and below the horizontal.


The problem was retrieved from Elements of Mechanism by Doughtie and James, p.480 - L-39.


Download the figure HERE.

Kinematics - Instantaneous Axis (Plate #3)

 Here's my third plate. Like my second plate, it's about Velocity Analysis. I made this plate right after drawing the second one. It took me 2.5 hours to completely finish the plate. I had a hard time drawing it because the instantaneous axis of the links are too far, so I have to use a big compass. Here's the compass used by my classmate while making this plate.

Drawing after the cut.

Kinematics - Resolution and Composition (Plate #2)

 My second plate is about Velocity Analysis using the resolution and composition method. Velocity analysis is a graphical technique used for the determination of the velocities of the parts of a mechanical device, specially those of a plane mechanism with rigid component links. It was the first lesson on my Kinematics class and my third plate is also about velocity analysis using the instantaneous axis method.

The drawing itself is not that hard but you need to be very careful in executing the steps. Analyzing the problem is much more difficult. The more complex the linkage are the harder it will be. My second plate isn't that complicated but it took me about 3 hours just to finish this plate and I hope I will get a high grade on it. 

Drawing after the cut.

Kinematics - Instantaneous Axis CAD (Plate #3)

Given the linkage Q2BCQ4EFH. Q2 and Q4 are fixed centers lying horizontally 6 in. apart with Q2 to left of Q4. Q2B is a crank 3 in. long and CQ4E is a lever 8 in. long pivoted at its mid point Q4, with C oscillating above the center line Q2Q4. BC is a connecting rod 7 in. long. EF is a link 8.5 in long driving a sliding block 8 and pinned to 8 at F, which moves along a horizontal line through Q2Q4 and to the right of Q4. MH and NH are links 2 in. long pinned to links EQ4 and EF, respectively, 2 in. from E. These link are pinned at H within the acute angle Q4EF. Q2B rotates counterclockwise at 30 rpm.

Figure after the cut.

The Drawing Scale

 The whole idea behind creating scale drawings it to allow the drafter to create  a drawing which is proportionately the same as the artifact it represents. Using a measuring device called a scale, we can create accurate drawings of both very large objects or very small objects and fit either on a standard size piece of paper.

2:1

Pronounced "Two is to One"

DOUBLE SIZE :2 millimeters on paper =1 millimeter on the artifact

The drawing is twice as large as the artifact.

Kinematics - Displacement (Plate #1)

 After three failures on my first plate, I've finished a decent one. The first try was acceptable since I made a mistake on the first steps in drawing the figure. The problem on the second try was in terms of the scale so it's not pain in the ass. And the last one was a failure of my ruler. The ruler that I'm using that time has a different dimension, an inch in my ruler is smaller than the real "inch", and thanks to my friend because he's the one noticed the glitch on my plate but I hope he saw it earlier before I'm totally finished drawing my plate. Maybe my ruler was fake. So beware of fake rulers, it will waste your precious time.

Photo courtesy of wikipedia.org

My first drawing plate for this sem is about four-bar linkage. A four-bar linkage is the simplest movable linkage. It consists of four rigid bodies called cranks and links, each attached to two others by single joints or pivots to form a closed loop. Four-bars are simple mechanisms common in Mechanical Engineering machine design and fall under Kinematics. 

First few lines were drawn.

Finishing the oscillating crank.

Final plate.

I've traced the ellipse like curve and the semi-circular curve using my FRENCH CURVE. I've spent a full 5 hours in finishing this first *take note, FIRST* plate. So join me on the upcoming head-aches. Just kidding. 


Seriously, I'm having a hard time on my Kinematics. And I'm expecting a lot of trouble in the near future *fingers crossed* but I'm allotting more time in studying the course. Wish me a good luck.

Kinematics - Velocity Analysis

Velocity Analysis

 Topics included in the hand-out:

1. Velocities and Acceleration of Mechanisms
    a. Resolution and Composition
    b. Instantaneous Axis of  Velocity
    c. Centro
    d. Velocity Polygon or Relative Velocity

2. Short review of Vectors

3. Scales
    a. Space Scale, Ks
    b. Velocity Scale, Kv
    c. Acceleration Scale, Ka


 Our professor also gave the presentation for the course, Kinematics. Download it now.


Kinematics Presentation