Mech Sys 1 Midterm

A structure is a linkage with a mobility equal to ______.

0

How many degrees of freedom does a full joint have?

1

Given four links (one of them being ground) in a system with 3 full joints and 1 half joint. How many degrees of freedom exist in this system?

2

In a class 3 fourbar mechanism how many change points exist per revolution?

2

How many classes are discussed in the kinematic chain?

3

The example of a book on a table represents a system with how many degrees of freedom?

3

Which is preferred if we have predefined constraints on O2 and O4.

3-Pos with specified fixed pivots.

A fourbar linkage has how many inversions?

4

How many kinds Synthesis were there?

4

How many ways do we have to classify joints?

4

What is the ideal transmission angle (in degrees) for force transmission?

90

Order the steps for 2-Pos Synthesis Rocker Output w/ Complex Displacement.

Correct1. Draw link CD in two desired positions. Label ends of lines C1D1 and C2D2. Correct2. Draw constructions lines from C1 to C2 and from D1 to D2. Correct3. Bisect both construction lines and extend perpendicular lines so that they intersect. Label as rotopole. Correct4. Select a conveinant radius and draw a circle with rotopole as center and label intersections with C1 O4 as B1 and label intersection with C2 O4 as B2. Correct5. Complete by repeating steps 2-8 of the two-position rocker output with angular displacement.

As we arrange links to create isomers we must be careful not to do which of the following

Create a structural subchain. Isolate motion to one side/part of the mechanism.

Which of the following joints has 2 degrees of freedom?

Cylindric (C) joint.

What is the triangular shaped link called?

Ternary Link

In the position synthesis examples, link CD referred to which link?

The Coupler

Which of the following are characteristics of the Design Process?

The design process open us to new paradigms The design process helps us make qualitative choices The deisgn process reveals and helps prevent duplication and paten infringement

Which of the following would represent a performance specification for a new stapling device?

The device must be able to staple a 0.25in stack of paper.

As explained in the quick return mechanism video, if the time ratio goes beyond 1:1.5 then it is necessary to use a _____ bar quick return. Hint: Type the number using letters.

six

What Class of Grashof do we normally consider a typical double rocker mechanism to be?

Class I

When suspicious of a paradox, a key thing to look for is parallel links.

Agree

What is another name for Quantitative Synthesis?

Analytical Synthesis

Which type of application was used as an example of a revolute joint?

Door hinge.

In the example using Specified Fixed Pivots, which link ultimately became the ground position O2O4 after applying inversion?

EF Response Feedback: After proceeding with three position synthesis using link EF, in order to complete the procedure, you need to apply inversion, making E1F1 ground (O2O4) and GH a moving link.

There are generally more equations than solutions in what type of Synthesis?

Quantitative

All inversions are distinct.

False

Alpha is always larger than the angle beta.

False

Analysis of something can be done without Synthesis.

False

Finding the transmission angle for a linkage often takes a lot of time and analysis.

False

For 4-Position synthesis a similar design plan to the examples in sect 3.4 is followed on paper.

False

If a group of people are using analogies and synonyms they are likely performing design selection.

False

In order for a fourbar mechanism to be Grashof, the shortest plus the longest link lengths must be greater than or equal to the sum of the other two link lengths.

False

In two-position coupler output with complex displacement, O2 must be placed on the perpendicular bisector of line D1 D2 (Be careful...look carefully at where O2 was placed and where it is stated that it can be instead).

False

One of the moving pivots is generally named O4.

False

S+P>L+Q is the equation to test whether a four-bar linkage is Class I Grashof.

False

The process for finding all the valid isomers for an n-link mechanism is no longer an open research question.

False

The quick return stroke is known as the load stroke.

False

The saw mechanism is an example of when a faster work stroke is necessary.

False

There is only one toggle position in a Grashof crank-rocker mechanism.

False

You generally have more than one choice in rotopole location when doing 2-position rocker output with complex displacement.

False

In the example of the 4-bar linkage, shown in the figure, switching links 2 and 3 would produce an isomer. 4 Bar Linkage.png

False Response Feedback: The Gruebler criterion is only a function of linkage nodes, not shapes or lengths.

An important assumption made in the roller example was that continuous slipping was occurring.

False Response Feedback: A no-slip condition was assumed.

Another word for performance specifications is design specifications.

False Response Feedback: Another way to think of performance specifications is task specifications.

Identification of need something that is often very detailed and structured.

False Response Feedback: Identification of need often comes from your manager or client is usually brief and lacking in detail and structure.

The addition of a driver dyad to a double or triple rocker effectively creates a Watt's 4 bar linkage.

False Response Feedback: The addition of a driver dyad to a double or triple rocker effectively creates a Watt's 6 bar linkage.

You should always avoid branching off from your main idea.

False Response Feedback: This is sometimes helpful during background research.

Toggle should always be avoided when designing a mechanism.

False Response Feedback: Toggle can sometimes prove useful, such as the case of designing a mechanism with a self-locking feature.

Which of the following mechanisms would be most suitable for usage in a conveyor belt mechanism?

Geneva Mechanism Response Feedback: The Geneva Mechanism allows for the conveyor belt to move for a period of time, then pause so certain tasks can be carried out.

In Dimensional Synthesis our focus is on ________ Dimensional Synthesis.

Graphical

Which choice best describes the application where a rachet and pawl would be used.

Hand wench on jeep.

Select of all the following characteristics which apply to both Link Against Plane and Pin In Slot joints.

Higher pair 2 DOF

Match the design process step with its characteristic or definiton.

Identification of Need Normally done for you perhaps by a manager Background Research Often most neglected step Goal Statement Recast problem statement of identification of need Performance Specifications What your product should do Ideation and Invention Children excel at this step Analysis Uses engineering to compare and contrast ideas Selection Decision matrix is often used Detailed Design Likely involves CAD drawings Prototyping and Testing Realize the design and test it perhaps using a model

Which are true regarding constructions arcs?

They are triangles in that they have three required sides. When the construction arcs are moved the points that were initially the specified fixed pivots become the new coupler joint positions. The final design based on the new coupler joint positions must be inverted. One point of the construction arc should be on one of the specified fixed pivots O2 or O4.

In the first example of 3 position synthesis with Specified Moving Pivots, which link needed to be driven in order to achieve the desired motion?

L4 Response Feedback: In this example, L4 needed to be the driven link in order to ensure that point D moved downward as desired. Driving L2 would have caused it to move upward.

Which of the following were selection factors for the Plazma Car.

Max support weight Cost Complexity

Which statement best describes the definition of a mechanism isomer.

Mechanism isomers contain the same number of links connected in different ways to produce the same DOF.

In this lecture, the notation used for the links when calculating the Grashof condition is "s" for the shortest link, "L" for the longest link, and what for the other two?

P and Q - the remaining links

Based on what you learned about detecting a paradox, the following mechanism will be a Gruebler paradox

While there are 5 links as in the paradox example, the links are not parallel. Indeed this linkage is 0 DOF as predicted by Gruebler.

All class 2 fourbar linkages are _____ rockers.

Triple

A crank-rocker mechanism assumes 2 toggle positions when the shortest link is collinear with the coupler

True

An inversion is considered distinct if it produces unique motion

True

Another name for degree of freedom is mobility.

True

At the conculsion of the specified fixed pivot synthesis we will likely need to extend the coupler to include the original line of concern.

True

Class 3 is considered the special case

True

Collapsing a quaternary into a ternary link should not change the DOF.

True

Dimensional Synthesis is the determination of proportions of links necessary to accomplish desired motions.

True

During Ideation and Invention it is ok to come up with an idea that would require additional Background Research.

True

Gruebler's Equation and Kutzbach's Equation can both be used for planar systems.

True

If a pin connects 5 links together then the joint order would be 4.

True

In most cases, it is often easier to design for Specified Moving Pivots than Specified Fixed Pivots.

True

In some situations, it is important to analyze how long the motion of a mechanism takes.

True

One difference between lower pair and higher pair joint contact is that lower pair joints have surface contact; whereas, higher pair joints have point or line contact.

True

Qualitative Synthesis is the creation of potential solutions in absence of algorithms that predict solutions.

True

Qualitative Synthesis often requires iteration between synthesis and analysis

True

Removing a link will reduce the dof by 1.

True

Revolute and prismatic joints are examples of form closed joints.

True

Revolute, prismatic, and cylindric are all examples of lower pair joints with 1 degree of freedom.

True

The Grashof condition is used to better understand how the links in a linkage rotate.

True

The first paradox example was a traditional 4-bar that was changed to a five bar.

True

The most commonly seen mechanism which uses a rocker output is the crank-rocker.

True

The number of links in a linkage is equal to the number of inversions that exist in that linkage.

True

The rotopole is not necessarily used in 2-position coupler output with complex displacment.

True

The transmission angle is used to determine the quality of force and velocity transmission at the joint.

True

When determining how to place the driver dyad, whether the linkage assumes a toggle position should be considered.

True

Where the radius of a cam is getting larger the follower will be rising.

True

All of the inversions for the 4-bar slider-crank are distinct.

True Response Feedback: All of the inversions for the 4-bar slider-crank are distinct.

In the first example of the 4-bar crank-rocker, if the Grashof condition was not satisfied, you can change the position of O2 until it is.

True Response Feedback: During the design process, you choose where along the line to place O2, so, if the link lengths need to be adjusted, you can move this point to a different point along the same line.

Replacing a revolute joint with a prismatic joint will not change the system's DOF.

True Response Feedback: Replacing a revolute joint with a prismatic joint will not change the system's DOF.

For this class's purposes, the systems observed are assumed to be made up of rigid bodies.

True. It is assumed that no deformation occurs

As described in the Design Process, bench-marking is the process of:

assessing competitor's products Response Feedback: Bench-marking is part of Background Research and involves assessing competitor's products.

The two types of position synthesis discussed in this section were rocker output and [x] output.

coupler

Which of the following mechanisms were said to have moving pivots.

coupler output with complex displacement

The initial mechanism created on force effect motion is called the four bar slider ____.

crank

Quantitative Synthesis is the generation of only one solution of a particular type known to be suitable and for which there is a synthesis algorithm.

false

The definition of dimensional synthesis is the determination of types of links to accomplish a desired motion.

false

The link on a plane is an example of a [x] joint.

half

Degrees of Freedom is generally defined as the minimum number of independent parameters needed to uniquely define a body's position and [x] in space.

orientation

Limiting Conditions are used to help evaluate the [x] of a proposed solution.

quality

Joints allow [x] [y] between links.

relative motion