TDJ3M_Mechanical_Design

include component="page" wikiName="jmcintyre" page="course_tabs_header" include component="page" wikiName="jmcintyre" page="menu_TDJ3M_crumbs" Mechanical Design | Rapid Prototyping | Sketchup | Sketchup Challenge | Trebutacular Design Challenge =Mechanical Design= While often referred to as mechanical engineering, mechanical design is the discipline of engineering that applies the principles of physics and materials science for analysis, design, manufacturing, and maintenance of mechanical systems. It is one of the oldest and broadest engineering disciplines. [|[source]] Simply put - mechanical engineering is the study, design and maintenance of mechanical things. While modern mechanical engineering was birthed during the industrial revolution in a variety of ways mech.eng. has been around for a LONG time. Some of the earliest written references to mechanical engineering include the [|MANY works of Archimedes]in c. 287-212 BC). Archimedes lived in Syracuse (a Greek city-state) and was under the constant threat of invasion by Rome. As such, many of Archimedes' inventions are machines of war - including the ship [|claw] ship trebuchet [|(2)], and [|the scorpion], but Archimedes also invented other mechanical engineering marvels that transformed civilization such as the water [|screw](to move water), and the water organ.

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Other notable early historical mechanical engineers include Da Vinci, Zhang Heng, Ibn Ishaq Al-Kindi, Al-Fraganus, Al-Jazari (and many other Islamic visionaries from the 'golden age of Islam' [500AD-1500AD]. Newton, then afterwards industrial revolution era engineers quickly filled the world with marvelous machines of varying designs. Once the industrial revolution started, the 'civilized world' was transformed quickly ([|a list of major historical engineering advances]).

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media type="youtube" key="emK-qIbuJ-k?version=3" height="315" width="560" align="right" Engineering in general is the study and design of systems, materials, machines and processes to solve a problem. In many ways engineering is what humans do best. Think creatively about a problem, then come up with a solution. This solution is often a way of automating, or interacting with the world around us in a way that makes our lives easier or better. Arguably many aspects of architecture, industrial design, and other such disciplines fall under engineering. Likewise most physical disciplines in the world have aspects of engineering built into them.



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Rapid Prototyping
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media type="youtube" key="MkOEPLXwbx0?version=3" height="315" width="560" align="left"Critical to Mechanical Design is the use of both CAD software (we use AutoCAD here at SC) as well as 3D programs such as Inventor. To that end, in the past decades fast replicators (though technically it's rapid prototyping) known collectively as 3D printers, bring the 3D drawings to life. In rapid prototyping typically a resin or polymer (though it can be sand or metal) is subjected to a binder which can either be chemical or light (either for heat, or for converting a chemical structure). The 'scribe head' passes over the material in an X,Y plane, but then passes in consecutive Z layers until the product is manufactured. While not useful for large runs, rapid prototyping is very useful to get a good idea of how a mechanical engineer's design will work out on a small scale. If there are no further design alterations, then the design is sent to be manufactured writ large. To date, cheap rapid prototyping machines (known collectively as 3D printers) cost roughly $1,500 to $20,000 whereas high-end RP's are easily higher than $60,000 (filling the vat on a high-end photopolymer machine can cost $50,000 alone!!!).

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== =Sketchup! Our cheap and easy 3D modeling software=

3D modeling is the process of developing a mathematical representation of any three-dimensional surface of object (either inanimate or living) via specialized software. The product is called a 3D model. It can be displayed as a two-dimensional image through a process called 3D rendering or used in a computer simulation of physical phenomena. The 3D model allows designers to problem-solve, share their ideas in a more tangible way with other people, and lastly, to export to 3D printers - if the materials allow it.

All 3D programs share the same basic components in that they have to represent 3D space in 2 dimensions. The solution is to use projective geometry which transforms shape vectors (lines, curves, spheres, boxes etc...) into a 2D line which can be displayed on the screen. These lines are often colour-coded, or displayed with alpha-dissolves (same colour, but made more faintly) to make it easier to see the dimensions on the screen for the designer.

Some 3D modeling programs include Sketchup, form-Z, Maya, 3DS Max, Blender, Lightwave, Modo, solidThinking, SolidWorks and many more.

We will be using [|Sketchup]for our 3D modeling. Not only is it free, but it has quite a powerful set of tools available to us that are fairly intuitive.

Please visit my Sketchup tutorial page for detail basics on how to use Sketchup software.

Some tricks to using Sketchup

 * Always ensure that you're using lines that follow the x, y, and z axes. The lines will flash green, red or blue if you're drawing correctly down one of these axes.
 * When possible, draw a guide before drawing a line/shape. It will ensure you get the correct distance. You can draw a guide by using the tape measure tool (toggled with control to get the 'plus' symbol), or the protractor tool for an angle (toggled with control once you've decided the angle reference).
 * Middle-mouse (MMB) click orbits your project, while holding shift+MMB allows you to pan your sheet in the current view (slide it around).
 * Spacebar is the universal 'get out of here' shortcut (much like the Esc. key is in AutoCAD). It allows you to select lines or deselct lines.
 * While selecting, holding Shift down allows for multiple selections.
 * Dragging a marquee box to the right functions just like in AutoCAD (makes a selection if the selection is completely within the marquee). Dragging a marquee box to the left selects anything that falls even a little bit within the marquee (again, just like in AutoCAD).
 * In complex objects - ensure your layers are open and you're putting each new element on a new layer. E.g. - in a house drawing, the walls may be in one layer, while the floor is on another, and the roof on yet another.
 * When push/pulling an object - toggle a new face by hitting Control before starting your push/pull. This creates a new face and doesn't leave a mess later on.
 * Work in the extended toolbar mode and learn your shortcuts!!!!

==

Assignment #6 - Sketchup Challenge
Once done previewing the videos - complete the Sketchup challenge (picture seen here at right). Download this to your school account and use it to measure angles/lengths so as to get a perfect replica as exact as you can make it. Once done submit both a picture at the exact same angle (gotten by exporting a 2D graphic), and the sketchup file itself.

__Evaluation__
To submit:
 * Sketchup file
 * An Exported 2D graphic picture (png) of the same angle as my picture above
 * **CATEGORY** || **4** || **3** || **2** || **1** ||
 * **Sketchup File** || Logical steps are followed and resulting design is exemplary. || Generally all steps are followed, there are small errors in lines. || Generally the product is as it should be, though there are enough errors in replication that final product is flawed. || Large errors in generation of the design. ||
 * **Picture File** || Logical steps are followed and resulting design is exemplary. || Generally all steps are followed, there are small errors in orientation. || Generally the product is similar, but either the angle, or material/colour choices are poor. || There are large discrepancies in either shape, textures, or 2D angle. ||
 * **Use of Time** || Used time well during each class period (as shown by observation by teacher, and documentation of progress in journal) with no reminders. || Used time well during most class periods (as shown by observation by teacher, and documentation of progress in journal) with no reminders. || Used time well (as shown by observation by teacher and documentation of progress in journal), but required reminders on one or more occasions to do so. || Used time poorly (as shown by observation by teacher and/or documentation of progress in journal) in spite of several reminders to do so. ||
 * **Product** || Final product is exemplary || Final product is superior, with some minor flaws || Final product is presentable, but contains some flaws || Final product is inferior ||

 [not this year] =Assignment #xx - Trebu-tacular!=

You are to create, in miniature, a fully functional trebuchet that is capable of launching a 100g weight no less than 1m distance. The goal is two part:


 * 1) See who can propel the 100g weight the furthest
 * 2) See who can be most accurate in hitting a target

Description:
The counterweight trebuchet appeared in both Christian and Muslim lands around the Mediterranean in the twelfth century (though was likely developed some 700 years earlier in China). It could fling projectiles of up to three hundred and fifty pounds (140 kg) at high speeds into enemy fortifications. This created a far more formidable siege engine than the catapult which was limited in both range and durability.

General Rules:
The trebuchet can be no taller from ground to the pivot point where the arm passes through of 30 cm. The arm itself can be no longer than 70 cm.The goals are to make both a robust design that is capable of launching a 100g mass as far as possible, but also to be able to be accurate for the second portion of the competition (given a couple of tries). In order to qualify for competition points, the 100g mass must launch no less than 1m from the trebuchet's arm's pivot point.

All contestants are expected to follow the engineering rule of ethics (no cheating). Failure to comply will result in forfeiture of a grade.

Materials:
Any wood materials are acceptable for the structure for this competition. Any other pieces must be supplied from home, but be subject beforehand to approval by me. No part of the trebuchet may be bought from parts especially designed for such activity. Wood glue will be the adhesive used to glue members of wood to each other. Allow a 24h cure time between the last stages of construction and the test date.

Testing:
__**1) Distance**__

You will attempt to launch a 100g mass as far as possible using your trebuchet. No interaction may be made with the device after you trigger it to release. The mass will only be able to be launched from the inertia given to it by the falling counterweight.

__**2) Accuracy**__

You will attempt to launch a 100g mass exactly 1.3 m away from the pivot arm of the trebuchet. You will get 3 attempts to do so. The average of the distance away from the 1.3 m mark will be taken as the competition entry.

Helpful Calculations
A very simple model found online just uses the mass of the projectile (m2), the mass of the counter weight (m1), and the height the counter weight falls (h):

Range (max) = 2 * (m1/m2) * h

Now the efficiency of the trebuchet will cause this model to be off by quite a bit. But once you have a working trebuchet, we find this model works well when we vary m1, m2, or h. We assume we have a take off angle of 45 degrees above the horizon. This solution is based on the classic max range ballistics problem - 45 degree take off angle. It also assumes converting all the potential energy of the counter weight to kinetic energy of the projectile. That is why the efficiency issue comes up as a lot of energy is lost due to friction in the moving trebuchet. If the projectile spins a lot then it will travel a shorter distance as the potential energy is split into kinetic and rotational energy. Projectile shape and wind will also vary the results.

Evaluation:

 * Before construction begins - paper sketches, and a 3D Sketchup model must be submitted for assessment. After completion, sketches, a final CAD file and a 3D model will be submitted with the design report. The Sketchup model will include all relevant details as pullouts.
 * From the isometric sketch, you are to create front and side views as well as top view of your trebuchet in AutoCAD. You will use these in guiding your construction.
 * Trebuchet construction - overall design of the finished product will be evaluated including: dimensions, style and adherence to the working drawings.
 * Distance results
 * Accuracy results
 * Self-Evaluation/ write-up.

General value of various components of the project:
 * Component || Value ||
 * 1 - sketches and 3D model || 4 ||
 * 2 - AutoCAD files || 4 ||
 * 3 - Trebuchet construction || 8 ||
 * 4 - Trebuchet distance result || % of 10 ||
 * 5- Trebuchet accuracy result || % of 10 ||
 * 6 -Technical Report || 6 ||

//6-(5)4-(3)2-1// || All aspects of the report are present and exemplary || All aspects of the report are present, though may require some work || There are aspects missing and work is required || There are many flaws in the report ||
 * **CATEGORY** || **4** || **3** || **2** || **1** ||
 * **sketches and 3D model** || Dawings and model are flawless - pullouts (notes) include relevant design details || Drawings and model are good, pullouts are included. Mostly all details are addressed. || Generally the drawing and model conveys design plans. There are several design elements missing. || Many design elements are missing from the drawing or the model, but overall the design can be understood. ||
 * **AutoCAD File** || Relevant views of the there are clear || All views are present, though there may be confusion in the drawings || Generally the drawings can lead towards a final product, but there are flaws in which construction details may be obscured || There are large errors in the object views - such that construction will be difficult based on the schematics. ||
 * **Trebuchet construction**
 * (double value)** || Construction of the product is superior. All joints and cuts are careful and deliberate. Product is stylistically superior. || Construction is sound. Cuts and joints may not all be perfect. Product is generally pleasant to look at. || Generally the construction is solid. Cuts and joints as well as style all leave something to be desired. || The construction is weak. Joints and or cuts are mismatched which results in a stylistically inferior product. ||
 * **Technical Report**
 * **Use of Time** || Used time well during each class period (as shown by observation by teacher, and documentation of progress in journal) with no reminders. || Used time well during most class periods (as shown by observation by teacher, and documentation of progress in journal) with no reminders. || Used time well (as shown by observation by teacher and documentation of progress in journal), but required reminders on one or more occasions to do so. || Used time poorly (as shown by observation by teacher and/or documentation of progress in journal) in spite of several reminders to do so. ||