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McGill Racing Team
Design Standards 2
Change History
1st August 2008 First Issue
10th September 2008 Second Revision – Added Part numbering system
6th November 2008 Third Revision – Reviewed part numbering system to comply with new cost report requirements. Added Mapkeys section
13th January 2009 Fourth Revision – Updated Mapkeys and shortcuts and split them into different sections
24th March 2009 Fifth Revision – Part numbering system updated to reflect changes in FSAE cost report
21st July 2009 Sixth Revision – Added Manufacturing Methods, Technical director guide, Design documents for SAE and Analysis and FEA sections. Reviewed and modified Import and Export, Mapkeys and added tables for easier reading (Title changed to Member Handbook, Design Standards)
10th August 2009 Seventh Revision – Updated “The V drive” section with a recent layout of the folders. Note added about the section on the MRT’s “Hardware CAD Library”. Updated ANSYS analysis of welded structures. 3D annotation feature preview
McGill Racing Team
Design Standards 3
Table of Contents
Change History .................................................................................................................................................... 2
Introduction ........................................................................................................................................................ 5
Starting Up .......................................................................................................................................................... 6
Working Directories ........................................................................................................................................ 7
Options file ...................................................................................................................................................... 7
Configurations ................................................................................................................................................. 8
EDU_COM Converter ...................................................................................................................................... 8
Message bar .................................................................................................................................................... 8
Mouse commands ........................................................................................................................................... 9
Keyboard Commands ...................................................................................................................................... 9
Mapkeys (user defined shortcuts) ................................................................................................................. 10
Part/Assembly Basics ........................................................................................................................................ 11
Constraining and Dimensioning ..................................................................................................................... 11
3D Annotation Feature .............................................................................................................................. 11
Units ............................................................................................................................................................. 11
Materials ....................................................................................................................................................... 11
Application Modules ..................................................................................................................................... 11
Colours and Textures .................................................................................................................................... 11
Formatting and Drawings .................................................................................................................................. 12
Drawing Procedure ....................................................................................................................................... 12
Part Names and Part Numbers ...................................................................................................................... 12
Multiple Sheet Drawings ............................................................................................................................... 14
Dimensioning and Annotating ....................................................................................................................... 14
Bill of Materials ............................................................................................................................................. 14
Printing and Plotting ..................................................................................................................................... 15
Import & Export ................................................................................................................................................ 16
File Transfer Formats .................................................................................................................................... 16
ProE to Mastercam ....................................................................................................................................... 16
Manufacturing Methods within Design ............................................................................................................. 17
Tolerancing ................................................................................................................................................... 17
Tolerances with Bearings ........................................................................................................................... 17
Anodization ............................................................................................................................................... 17
CNC Milling and Lathing ................................................................................................................................ 17
Frame Design ................................................................................................................................................ 17
Laser, Plasma and Water jet cutting .............................................................................................................. 18
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Design Standards 4
Creating the Laser cutting Toolpath File .................................................................................................... 18
Tolerancing and Final Changes .................................................................................................................. 18
Design for welding ........................................................................................................................................ 18
Sheet and solid design ............................................................................................................................... 18
Welding of Thick Walled Structures ........................................................................................................... 18
Analysis and FEA ............................................................................................................................................... 19
Structural Idealisation ................................................................................................................................... 19
Welds ........................................................................................................................................................ 19
Composites & Glued Structures ................................................................................................................. 19
Cyclic Loading and Fatigue Failure ................................................................................................................. 20
Pointers for FEA ............................................................................................................................................ 20
Meshing .................................................................................................................................................... 20
Result Plots ............................................................................................................................................... 20
Technical Director & Designers Guide ............................................................................................................... 21
Responsibilities of Technical Director ............................................................................................................ 21
The V drive .................................................................................................................................................... 21
CAD setup for new prototypes ...................................................................................................................... 22
Modelling Guidelines & CAD Maintenance .................................................................................................... 23
Detailing Frame and Suspension ............................................................................................................... 23
Suspension Representation ....................................................................................................................... 23
Hydraulics, Pneumatics & Electrical Routing .............................................................................................. 23
Design Documents for SAE ................................................................................................................................ 24
Design Report and Specification Sheet .......................................................................................................... 24
Guidelines for writing Design report .......................................................................................................... 24
Design Report Drawings ............................................................................................................................ 24
Structural Equivalency ................................................................................................................................... 25
Impact attenuator ......................................................................................................................................... 25
Design Presentation ...................................................................................................................................... 25
References ........................................................................................................................................................ 26
McGill Racing Team
Design Standards 5
Introduction
This document was made to keep a record of design practices on the team. Many people have contributed over the years and much of this useful information was never documented until now. The second role of this document is; as in any engineering company, to have standards by which designing and manufacturing is done. We are not a high budget team and many design decisions included in this document have aided us in actually having a completed, competitive car.
Professors and classes don’t teach much of the physical engineering. When you are part of a design team, you will be learning beyond what is done in class. You would not learn many of the topics that could be used on the car until your last year. Even then you would have only touched the surface of the subject. New members should immerse themselves and try to absorb as much knowledge from the senior members in their first year. This document should help new members in getting involved in the design process within less than a year.
Personally, every member should have a copy of this document either in print or on their desktop and consult it throughout every design step. This is why I’ve named it the Member Handbook.
The McGill Racing Team’s primary CAD software is ProEngineer. We also use AutoCAD for editing of drawing files and ANSYS for structural analysis.
ProE as is a very powerful tool which helps us make the car. From experience, learning ProE isn’t at all easy but once you cross the turbulence it goes like clockwork and you even get addicted. You never stop learning something new on MRT.
Philippe Picchiottino
Body Sub‐Team 2005‐2007 Technical Director 2007‐2010 Special Thanks to the following people for their input over the years; helping compile this document Bobby Lumia Jean‐Pierre Bahous William Kerley Philippe Pinard Pierre Yves Lacroix Maxime Romano Gabriel Dessureault Amrit Richardson Matthieu Gignac Jonathan Dubé Jonathan Laliberté
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Design Standards 6
Starting Up
Here is the procedure for opening and creating files in ProEngineer for McGill Racing Team. Descriptions of these procedures are on the next page. Please read all sections carefully.
Open ProEngineer Wildfire
Set your Working directory
Activate the Options file
Activate the EDU/COM converter (if required) 1. Go in Tools on the top tool bar 2. Floating Modules 3. Check the option “EDU/COM Converter”
NOTE: if the option is already checked and you are unable to check the option, it means that someone else is using the license. Check often and register as soon as it is available. You can check who is using it and on which computer by clicking INFO at the bottom of the Floating modules window.
Input the design Parameters (A mapkey is defined for this operation) 1. Go in Tools on the top tool bar
2. Edit Parameters
3. Enter your full name for the value in MODELED_BY
4. Enter the part or assembly description in DESCRIPTION (e.g. rear top a‐arm)
5. Enter the part number in PART_NO according to “Part Names and Part Numbers” found on
p.13 6. Enter the state of the model under IN_PROGRESS. This is a Yes/No field with No meaning that
the model is finished and ready to be reviewed by the Technical Director.
If you are starting a part (ie ProEngineer Part), set the material. If the material is not in the database, add it. (A mapkey is available for this operation). 1. Go in Edit on the top toolbar 2. Setup 3. Material
NOTE: There should only be one material in the right column
Before saving your work, make sure that you are under the correct Working Directory.
If the Edu/Com Convert has not been checked, try to register again
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Design Standards 7
Working Directories
You must always set your working directory before you start anything. Go to FILE>Set Working Directory> then you select the path. The path should be the root directory for that years’ car (e.g. V:/2010). This indicates to ProEngineer where to save any files you create. ProE keeps a log of your work for that session in the working directory. You must set this every time you start a new session.
NOTE: Never open CAD files from the Windows Explorer; this can lead to not opening the correct version and erasing more up‐to‐date versions when you save. This can also lead to crashes of your assemblies and a lot of frustration in troubleshooting.
Options file
Go to TOOLS>Options and open it, APPLY then OK. The options file contains all your preferences for display, opening, setting up, formatting etc of your models and drawings. You can add more options to the list and edit others but be careful to press Add/Change after modifying each one and save the file before closing the window.
Figure 1: ProE Options Window
A common entry in the options is search_path. ProEngineer needs to know where you have stored models for your assemblies if they do not exist in the Working Directory or the folder in which the assembly is located. When you set a path, ProE looks in that directory for any parts that are required when you are opening the assembly.
For a list of all the options available see ProE Configuration Options.pdf found in V:/ProE Documents
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Design Standards 8
Configurations
There are many configuration files that are lying behind the scenes. These are set in the Options File and are called in when you apply it. These are located in the “ProE Config & Drawing Formats” folder on the V drive. THESE FILES SHOULD NOT BE ALTERED, MOVED NOR THE FOLDER RENAMED
ANSI drawing format.dtl: Configuration file containing proper font and dimension formats for drawings
mrt_color_palette.dmt: The set of standard colours which the team uses: This needs to be opened in the colour and appearance console when assigning colours to parts.
mrt_mdl_tree.cfg: The configurations file containing preferences for displaying the model tree
printer_settings.pcf: The configurations file containing default printer settings
mrt_inlbs_part_solid: Part template
mrt_inlbs_asm_design: Assembly template
syscol.scl: GUI colour scheme (the background colour is easier on the eyes)
EDU_COM Converter
The EDU_COM converter can be found under TOOLS>Floating Modules and once applied to the session allows you to save files created in the educational version of ProE in the commercial format. Files created in the commercial format however, can be used by the educational version.
Message bar
The message bar at the bottom of the screen is your best friend. It tells you everything that is going on. If you forgot something, performed an illegal operation, what you have to select for a certain feature, why it cannot create the geometry and so on. Often, you are prompted to type something or click yes/no so pay attention to it. Most times if you feel like the program is frozen, you haven’t completed your task and it will say so in this box. The little traffic light to the bottom right tells you the status of the model.
Geometry selection filterHistory, Instructions, Feedback is given here
Status (traffic light)
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Design Standards 9
Mouse commands
The commands on the mouse are simple.
Left button: selecting, dragging, panning and usual stuff
Right button: (click and/or hold) shows drop‐down menu for component selected
Scroll wheel: (forward/back) zoom in/out, (click) validating or cancelling commands, (click, hold and move mouse) 3D orientation
Keyboard Commands
CTRL+A: Activate/deactivate when switching windows
CTRL+G: Global regeneration
CTRL+TAB: Toggles ProE windows
SHIFT+middle mouse: Pan
CTRL+middle mouse: In plane rotation/centre point fine zooming/window zoom
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Design Standards 10
Mapkeys (user defined shortcuts)
Mapkeys are macros (commands) that you record when you create one and they key sequence you assign them runs the macro.. Some of the Actions below require going into drop down menus whereas just typing the key sequence in the active window does the same. This list was implemented and updated during the 2008‐2009 year.
Key ActionF1 Set Parameters (opens parameters)F2 Set Material (Opens material selection window)F3 Opens reference selection and list in sketcherF4 Delete Old (Deletes old versions of the active model; model must be in the working directory)F5 Clear memory (aka Erase Not Displayed)F6 Set Colour (Opens and loads MRT colour palette)F7 Render Window F8 Add model (opens the dialog box for adding models to the current drawing) F9 Open View Manager F10 Select highlight ON (turns preselect highlight on)F11 Select highlight OFF (turns preselect highlight off)vi Isometric view (the standard isometric)vr Right view vl Left view vt Top view vu Bottom view (under) vf Front view vb Back viewvs View Sketch (replaces view normal to the sketching plane and centres the sketch) we Show model with edges highlightedmrt Opens full assembly of vehicle
metric Converts model units to metricinch Converts model units to inchesxx Closes active window mp Mass properties wd Set working directory (by default it sets the main working directory for the year)
Table 1: Mapkeys and functions
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Design Standards 11
Part/Assembly Basics
Constraining and Dimensioning
White dimensions indicate that they are strong, grey dimensions are weak and orange ones are locked. It is good practice to have your sketches fully defined. To lock a dimension, left click the dimension, then right click and select “locked”. Once a dimension is locked you can drag sketch entities without modifying these dimensions.
3D Annotation Feature The 3D annotation feature is quite useful. The dimensions and tolerances are placed in the environment of the part/assembly. The dimensions rotate with the part/assembly, are imported into drawing views and update with the part. This makes for faster drawings without having to redimension the part in every drawing made. In the preview before opening a file the dimensions are also visible, so no need to open the file to query values. Adding Notes and Datum Tags will greatly help with manufacturing, cost reports and documentation for years to come.
Units
By default, the units are set to Imperial (Pounds, inches and seconds). If you need to convert units or model in Metric go to EDIT>Setup>Units and select the appropriate one from the list. A mapkey is defined for this operation. ProE will prompt you to either convert inches to millimetres (1in=25.4mm) or the same, scaling by a factor of 25.4 (1in=1mm).
Materials
Go to EDIT>Setup>Material and select the appropriate material for the part. If the material doesn’t exist in the library, define a new material. A mapkey is defined for this operation. We have a library of all materials we use. For material properties you can get almost any at www.matweb.com. They provide property sheets for materials with various treatments.
Application Modules
Application modules are an array of different toolbars and environments which allow different features/operations to be executed. The most common ones used are Standard, Sheetmetal, Welding, Piping and Mechanism.
Colours and Textures
This is where the fun begins. Go to EDIT>Colour and Appearance, from here you can alter the colour of your parts to suit their material or their surface finish. If you can match the colours to the actual components you can then make a very nice rendering. At the top of the colour and appearance window open the mrt_color_palette.dmt and select Override All to set our colour choices.
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Design Standards 12
Formatting and Drawings
Drawing Procedure
When creating a drawing for Cost Report or machining purposes
Under the “New Drawing” window:
1. Set the default model (important if you have many parts/assemblies open)
2. Empty with Format under “Specify Template”
Choose the format from the drop‐down menu. If it is not present browse and activate it.
mrt_format_ansi‐a.frm This is the format that will be used for all Cost Report drawings and drawings for Sponsors or any outsourced work
ProE will then ask for your Drawing information:
DRAWN_BY : Put your Full Name here (e.g. Felix Lacroix)
PART_FINISH : type “na” for assemblies EXCEPT if the assembly is assembled to the car as one piece
Machined Painted/clear coat As Cast Polished Powder coat Anodised (with treatment information indicated on the drawing) Any other special surface or heat treatment should be stated (e.g. Nitridization, Case hardened C40)
Part Names and Part Numbers
The following must be adhered to when issuing numbers to components/assemblies/drawings. Names of models should be short and give a good description of the model (e.g. pedal‐tray‐bracket)
All in CAPITAL letters (makes all documents standardised) Part numbers are in the form XX‐BBYZZ‐AA Drawing files carry a _dwg suffix on the filename for easy identification For bought parts, Part#, Assembly# and Drawing# are that of the manufacturer/supplier.
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Design Standards 13
XX‐BBYZZ‐AA
System Designation
Type Designation
A1 : System Asm 1
A2 : System Asm 2
A3 : System Asm 3
Etc. A0 : Sub‐Assemblies
00 : Parts
SubAsm/Part Category No
Counter
For parts and sub assemblies
00 : System Asm
Change History
BR Brakes system
1 DISCS
2 HYDRAULICS
0 HARDWARE
EL Electronics, controls & wiring
1 ECU/DASH
2 CONTROL BOXES/BATTERY
3 CONNECTORS/HARNESS
4 DATA ACQUISITION SYSTEM
MS Misc finish
& assembly
1 SEAT
2 FIREWALL/SHIELDS
3 MISCELLANEOUS
FR Frame and
Body
1 TUBE STRUCTURE
2 UNDERTRAY
3 BODY PANELS
4 BRACKETS
5 SHIFTER
6 MACHINED PARTS
EN Engine and Drivetrain
1 INTAKE
2 EXHAUST
3 FUEL SYSTEM
4 COOLING SYSTEM
5 DIFFERENTIAL
6 MOUNTING FLANGES
7 SHAFTS/CV JOINTS
0 HARDWARE
ST Steering system
1 STEERING WHEEL
2 STEERING SHAFT
3 STEERING RACK
4 STEERING LINKS
0 HARDWARE
SU Suspension system
1 UPRIGHTS
2 A‐ARMS
3 PULL/PUSH/TIE RODS
4 BELLCRANKS
5 ANTI‐ROLL BARS
6 DAMPERS & SPRINGS
0 HARDWARE
WT Wheels & Tyres
1 WHEELS
2 SPINDLES
0 HARDWARE
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Design Standards 14
Multiple Sheet Drawings
You can add many models to your drawing in the same sheet or in different sheets
1. Go to File>Properties>Drawing Models>Add Model
2. Add those models that will be used in that set of drawings.
3. Set the model/assembly that you will use in the first sheet.
BEFORE ADDING A NEW SHEET, SET THE MODEL THAT WILL BE USED IN THAT SHEET OTHERWISE PROE WILL FILL THE TEMPLATE WITH DETAILS FROM THE PREVIOUS SHEET’S MODEL
Dimensioning and Annotating
Drawings should contain all dimensions and tolerances required for fabrication. Someone reading the drawing should be able to make the part without asking for any additional information. Pay particular attention to hole and thread definitions and tolerances. Keep all dimensions and notes neatly laid out (See Figure 2).
DRAWINGS SHOULD NOT BE A NOVEL. EXCESSIVE TEXT IS UNNECESSARY.
Bill of Materials
For assemblies, the BOM is generated automatically in the proper format. When making part drawings remove the BOM column on the right
Figure 2: Example of Assembly Drawing
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Design Standards 15
Figure 3: Example of Part Drawing
Printing and Plotting
Once the options file has been activated the print settings for “A” size format is set for printing directly to the printer.
Print all drawings for the cost report and official drawings in PDF format using High Quality Print preferences. Save the files to the “Cost Report” folder.
Shop drawings only need to be printed directly for distribution (saving the dwg file of course)
*PROENGINEER PRINTING BUG
If the PDF converted drawing is off centre, the offset values for X and Y should be filled in +0.235 in the Printer configuration shown above. This is a bug in ProE that we haven’t been able to resolve and comes up when printing to a PDF. One way to get by this is to use the SaveAs PDF however the max resolution is much less than the printed drawing.
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Design Standards 16
Import & Export
File Transfer Formats
There are several file formats with which we transfer data to other programs which do not support ProE files. These two are most common to us.
STEP (STandardised Exchange of Product) *.stp , *.step IGES (Initial Graphics Exchange Specification) *.igs , *.iges DWG (AutoCAD DraWinG file) *.dwg
We have used the IGES format extensively in the past however I have found that some crucial data is lost during conversion to this format. As of 2009‐2010, we will be using the STEP format for data transfer since the models’ integrity is conserved. DWG is exclusively for transfers to AutoCAD.
ProE to Mastercam
When importing ProE files to be used in Mastercam there are some settings you need to select. You will need to specify the coordinate system for your piece. Placement and orientation of the axes should be done to correspond to those of the milling machine.
SAVE A COPY in IGES format. If another format is required for the export you may choose it from the drop down list. When you say OK you will be prompted to make certain choices. For importing to Mastercam you select:
Wireframe Edges Datum Curves and Points Surfaces The coordinate system that you placed above
ALWAYS PAY ATTENTION TO WHERE THE FILE IS BEING SAVED AND IF NECESSARY, SET A DIFFERENT WORKING DIRECTORY BEFORE SAVING TO RECOVER THE FILE.
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Design Standards 17
Manufacturing Methods within Design
Tolerancing
Tolerancing is very important in mechanical design and manufacturing. In ProE, we design using NOMINAL dimensions unless you incorporate tolerances in your modelling. We run into unnecessary problems if parts to be machined are not made to the proper tolerance. Tolerancing is a whole subject on its own and I will only discuss the aspects relating to our vehicle design
Tolerances with Bearings In making fits for bearings, pay special attention to where the bearing is being used, the bearing size and if interference is necessary and account for this in machining.
On the spindles, the bearing should be a slip fit on the spindle bearing surface and be a slight press fit (one which could be removed without damage to the part) into the upright. If it were press fit both inside and outside the bearing would be seized. Too much of a press fit increases rolling resistance. The press fit on the uprights should be in the order of 0.0005”‐0.0015“on the diameter.
When machining, have one of the bearings to check the bearing dimensions since they differ slightly from one to the next. With the bearing you can also check the fit physically.
NOTE: Pay attention to which side requires the negative or the positive material condition.
Anodization Anodization Verdun uses Sulphuric acid to produce anodized coatings. The regular coating; usually coloured, adds a moderate thickness between 0.0007" to 0.001".
Coatings thicker than 0.001" are known as hard anodizing. Hard anodizing can be made between 0.001" to 0.006" thick. Anodizing thickness increases wear resistance, corrosion resistance, ability to retain lubricants and PTFE coatings, electrical and thermal insulation
NOTE: Due to the extra material added by the anodising (especially the hard one) we need to mask all threaded holes, press fit holes and shaft surfaces that have been made to very high tolerance.
CNC Milling and Lathing
Cnc work should be kept solely to what is absolutely necessary. These parts include uprights, spindle profiling, steering housings, differential casing milling alone, differential flanges, and other intricate parts. What could be completed with some time on the manual milling/lathe machines should be done to not backlog the machines.
Frame Design
Always remember that the frame’s role is both aesthetic and structural. Must be visually appealing Remember to check load paths, where are loads going to be applied and the least amount of tubes to
brace it properly. Rule of thumb: no more than 3 tubes coming to a node (3 DOF makes sense?). Always parameterise the frame skeleton. Yields easy design changes. Keep dimensions in increments of 0.25” or 0.5”. These values are easier to check when jigging
ALL NODES ON THE FRAME MUST BE NON‐INTERSECTING. MANUFACTURING IS GREATLY SIMPLIFIED WITH THIS METHOD
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Design Standards 18
Laser, Plasma and Water jet cutting
Creating the Laser cutting Toolpath File When making the file for giving to the laser cutting company the steps to follow are:
Make a drawing in ProE without the title block and to the rough dimensions of the stock material which will be used.
Place one of each component which is of that thickness into the drawing area Save the file then SAVE AS an AutoCAD drawing. The file name will be in the form:
material_grade_thickness_sheet number.dwg (e.g. steel_1020_0375_1.dwg or aluminium_3003_0049_1.dwg)
Tolerancing and Final Changes Within AutoCAD add the corner radius of 0.02” on all sharp direction changes as a relief so the part doesn’t develop undesirable melted corners
NOTE for precise holes that are laser cut: The laser cutting machine cuts tapered holes especially as material gets thicker than 0.049”. For precision holes, make the inner bore 0.2” smaller in diameter. The holes will then be post machined to the required size and fit.
Design for welding
Sheet and solid design Welded sheet metal should be designed to have T joints EVERYWHERE.
Advantages of T jointsThe T joint offers better strength of parts since the weld is made to be in pure shear Jigging will be included into the parts being joined ‐ the parts to be welded are self supporting like Lego The final weld looks uniform and is less prone to leaks – good for fuel, oil tank applications Better finish on final partsThe sheet metal model is easily altered to produce the analysis model
NOTE: The leg of the weld needs to be taken into account when leaving extra material. If there is too little material the end becomes melted and is not aesthetic. If there is too much material it looks out of proportion and adds unnecessary weight.
Sheet Material Extra for overlap Material Grades Weld Leg Aluminium 0.375” ‐ 0.5” AL3003, AL5052 0.15”
Steel 0.1875” – 0.25” All mild steel (e.g. 1020) 0.08” Table 2: Weld design parameters
Welding of Thick Walled Structures For parts having thicknesses exceeding 0.095”, a relief on either one or both of the parts should be made. The example of shown to the left with one of the parts bevelled. This allows for better weld penetration. The weld will have to fill from the bottom to the top of the crevice.
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Design Standards 19
Analysis and FEA
On Formula SAE we use ANSYS Workbench to do our finite element analysis. In the rare case you might be obliged to use ANSYS Classic but these cases can be simplified to something doable in Workbench. In many cases, the good old paper and pencil calculations are much better than the most elaborate or simplest FEA. Good Excel documents are the best way to keep design calculation records (graph and compare)
Structural Idealisation
Welds Simulating welds requires a great deal of time preparing and conditioning the model. Here are the steps to follow in preparing the model for analysis in ANSYS Workbench.
Create a backup of the model of the assembly to be analysed. Save the backup under a different name and place it into an analysis folder for subsequent modifications.
In the new assembly, suppress parts and geometry that do not concern the analysis and mend parts for good interaction/connections.
Convert the assembly to a single solid part. Protrude parts into others if necessary. Define the welds as chamfers with the specific leg length. This is a bit time consuming but it takes into account the stress concentrations at the welds. Some iteration might be needed to get a model that meshes correctly but it’s worth it.
Open the Simulation module; importing the model, add material properties then mesh, define loads and run the analysis. It will take a long time to solve.
NOTE: Measure the actual thicknesses of parts and use them when defining the analysis model. You will probably fall right in sync with the physical testing data doing the above.
Composites & Glued Structures The one aspect that we have to look at is the attachment and the adhesive. The adhesive bonding the sheets together affects the deformation, hence the behaviour of the loaded panels.
In the analysis, the facing sheets should not be in direct contact with the core material. In reality the core material is attached through the resin/film adhesive. When adding the film adhesive to the analysis we have to give it a reasonable thickness (0.01” should suffice). The glue’s behaviour may be non linear however the thin coat can be assumed linear.
Using a composite laminate program or Classical Laminate Theory, calculate the in and out of plane engineering constants for the facing skins. Since the sandwich panel is a form of I beam, you can then make some assumptions and obtain near accurate results by hand (Parallel axis theorem)
With the engineering constants, define an ORTHOTROPIC material in ANSYS with the corresponding engineering constants. Pay attention to the coordinate system in the model.
Figure 4: Weld idealisation
Figure 5: Sandwich panel idealisation
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Design Standards 20
Cyclic Loading and Fatigue Failure
50‐90% of structural failure is due to fatigue. The more we optimise parts, fatigue plays an important role. With any part of the car that is being analysed, a fatigue analysis is indispensable. Fatigue is usually covered in Machine Element Design. As this course is taken in 3rd year, I urge everyone to read the chapter on Fatigue from the course textbook or online.
Alternating Stress Curves: This has to be input in the ENGINEERING DATA section in order to obtain a result from the fatigue analysis. These curves can be found from material test data in books or online.
Fatigue Strength Factor (Kf): this is a correction factor for the fatigue strength of the specimen. Standard material test data represents a polished specimen under ideal loading. Use the correction factor found in Machine Element Design books. It is between 0 and 1 (e.g. 0.8 for a cast steel part). This really influences the life of your part so if you don’t have access to the data make an appropriate (conservative) assumption…0.5 is conservative enough.
Mean Stress Theory: This again can be found in Machine Element Design books. The Goodman Theory is more suited for brittle material whereas the Gerber is generally a better approximation for ductile materials
Design life: 1‐1.5 Million Cycles: We assume that we would never reach 1 million cycles however just to be safe and to show that the car was made to be more than a prototype.
Pointers for FEA
Meshing The following settings are good for generating a mesh if you are inexperienced and need a near good result.
Always keep Element Midside Nodes unless all your elements are quadrilaterals. Even then it is good to keep them. Relevance Centre depends on the model size but for us it will always be Fine.
After meshing a model, check to see if all the elements are of regular shape.
Good tetrahedral mesh
Mesh too stiff compared to reality
Good transition in element size
Result Plots The Contour Legend, showing the stress distribution needs to be redefined to show more meaningful contour values. This will depend whether you are close to the yield strength or away from it.
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Design Standards 21
Technical Director & Designers Guide
Responsibilities of Technical Director
CAD maintenance Sub‐team coordination in terms of design. Design final say – it means if we are stuck between a few choices for something, the tech director
decides what will be chosen after weighing pros, cons etc. Design Report (submitted prior to competition) Design Posters (With help from members) Ensuring every participating member has the documentation he/she needs and is up to date with the
why’s and How’s (Coordinating only)
The V drive
The Folders in the V drive are ordered in an efficient manner to simplify accessing, classifying and editing of documents. Each folder should be named appropriately (ie NOT Mattyfuckingaround_1)
In the team’s existence many documents have been lost from year to year and these have had an adverse effect on the teams’ performance when it comes to design.
The V:\ is shown on the left. The contents of each folder are the fruit of many persons dedicated work on the team. The files numbered 1‐10 contain a great deal of useful and interesting information so if anyone has questions they should browse these, they probably will find the answer.
The files marked with the year contain the models and all documentation for that year.
ProE Config & Drawing Formats should never be renamed nor its contents altered besides the drawing template.
Hardware CAD Library contains all the solid models of fasteners, Fittings and Connectors used from year to year. Having them in this library makes it easier to manage bought parts by keeping them separate from the rest of files. At the start of the year, no need to copy these files over into the new folders. All that is required is the addition of these search paths in the year’s options file.
ProE Material Data contains all the material
data for materials used on the car. Materials may be added and modified but the folder again shouldn’t be renamed or deleted.
McGill Racing Team
Design Standards 22
CAD setup for new prototypes
1. Create a folder for the new competition year. Create the sub folders for each sub system and Documents. The hierarchy below should be reproduced since it has been proven to work extremely well in the past couple years. 1 Documents found in each folder should only contain…well documents; all other folders should only contain CAD files.
2. Setup the ProE Options File for the new directories. Make sure the options and Mapkeys are working properly for different persons. The Options file should have the same basic configuration except for the Search Path entries.
3. Transfer backup copies of files and models/assemblies that will be reused/modified slightly from the previous year.
4. Ensure that the assemblies follow the cost report scheme (how it is assembled) to ease the cost report work. Make sure that the part/asm numbers are coherent and not duplicated.
5. Update the drawing template to reflect the new Application year, baseline tolerance changes or possible newer ProE version.
McGill Racing Team
Design Standards 23
Modelling Guidelines & CAD Maintenance
Make regular back‐ups of the full assembly on an independent drive in the educational version during the design phases
You should start the year by reverse engineering last minute parts; good ones of course, which were not modelled. Failure to do this result in many good ideas lost over subsequent years. As of 2009, I would like the following to be implemented. These tips can potentially save us time and get people involved from the start in September. These are some good practice for new members in modelling and understanding the car while doing so.
Detailing Frame and Suspension Using the Welding module in ProE, define all welds on the frame and other welded components. When the time comes to calculate total weld lengths it’s just one click away. This will make it easier for cost reports and everyone would know where gets welded and push the designs further.
Here are the steps:
1. Go to Applications>Welding. The welding module will activate. 2. Setup Welding Rod. Go to Tools>Weld>Rod and input the parameters for Cronatron 315T (steel filler
rod) 3. This symbol above, found on the right toolbar defines the welds. Choose Fillet and the Leg value then
proceed following the instructions in the message bar.
Suspension Representation Since the suspension/steering components are the same left and right of the car (mirrored for some) One side of the car should be modelled in the static condition to get the appropriate arm lengths and static suspension geometry. On the opposite side, assemble showing two positions: droop and bounce. This can even be made in mechanism mode so clearance checks and geometry change can be quickly simulated. Let’s use ProE fully!
Hydraulics, Pneumatics & Electrical Routing All piping should be routed to a certain extent using ProE Piping module. This gives a rough idea of the lengths to order and saves the hassle later on of attaching it to the frame. You can inquire lengths and bends for use in the cost report. Piping includes engine cooling, lubrication and fuel systems as well as brake lines and/or pneumatic lines. Below is a colour code to identify different piping systems.
The Electrical harness should also be modelled. A simplified model to show positioning and routing is sufficient. The ProE Cabling module is a bit more involved and not that straightforward.
NOTE: These colours already exist in the MRT COLOR PALETTE under their respective names
PIPING COLOUR CODING STANDARD System Colour
Lubrication Bronze Fuel Orange
Cooling Blue Brakes Green
Pneumatic Purple CABLING COLOUR CODING STANDARDHarness Red
McGill Racing Team
Design Standards 24
Design Documents for SAE
Design Report and Specification Sheet
Guidelines for writing Design report The report is comprised of 8 pages total. Out of these 4 pages are restricted to text alone, 3 pages for drawings and 1 optional page. I have prepared a DESIGN REPORT TEMPLATE found in 1 MRT Standards. Its format is similar to one of our reports done in 2009 which got good remarks from the design judges.
As for any report, the first page is the cover page. The text should not exceed 3 pages. Any more then you’re using too many words or being repetitive. This is where we need someone proficient in English to proofread and give their opinion on the structure.
Introduction You need to give a brief history of the team followed by defining the problem or aspect of the car that required attention. Secondly, you clearly state the team’s objectives in terms of design. There are goals such as “reduce weight” which should not be stated – we always strive to reduce weight, it’s more of a perpetual consideration.
Text Here you talk briefly about what is new/innovative/modified on the car relating it to the year objectives outlined in the introductory paragraph.
Optional Page This page should be somewhat an appendix. You can fill it with interesting pictures of production, design, graphs and they should be captioned. You should always refer to them in the text pages
Design Report Drawings Here is the guideline to compiling PERFECT drawings for the design report. This is written taking the judges’ comments on our drawings over the years into consideration.
TECHNICAL DRAWINGSPage Drawing View and Description Dimensions to show 1 Side view with bodywork on this side
removed to be able to see behind the firewall
wheelbase, total length
2 Top view with wheels on one side of the car removed to show the inner wheel assembly, again with bodywork removed
front and rear tracks
3 Front view with wheels on one side removed
height, total width
IMPORTANT NOTES
Title block must be properly filled Scale of views should be chosen to use more than 80% of the drawing space dimensions and dimension lines should not encroach upon the drawing of the car Make the engine skeleton model visible since skeleton models are hidden by default Loose or non coherent parts should be hidden (eg. an incomplete model of a part/asm). The judges
want to see your car for the first time. Ideally the CAD should be complete at this stage however they do not penalize you if it’s incomplete.
McGill Racing Team
Design Standards 25
Structural Equivalency
Start preparing the structural equivalency early in the design stages. You need to get the SEF to the SAE committee as soon as possible so that extra information is needed you have enough time to do the tests or calculations. If you have to do give additional information after the due date of the report then you will receive a deadline in the order of 1‐2 weeks.
The basic step to having a good report:
Show a calculation of the structure as specified by the FSAE Rules Show calculations of the proposed deviation from the rules Perform and show a pertinent physical test
The format of the Structural Equivalency document is outlined in the rules but it is nice to format it using the Design Report Template.
Impact attenuator
The impact attenuator report is as equally important for the competition. This report is easy design points that we can obtain. This report and the testing involved should also be done in the early design stages to allow for unforeseen setbacks.
A Physical test is mandatory for this report. Setup of the test rig and making of sample attenuators may take some time especially due to lab hours so this should be considered early on.
Design Presentation
The design presentation is held at the competition. It entails us presenting the design characteristics of the car to design judges. These judges come from different companies and are specialised in various aspects of vehicle design, testing and performance. You can be best prepared to answer certain questions however you must be knowledgeable about all aspects of the car. If you are unable to answer certain questions tell them so. They do not appreciate being baffled by bull. Each presenter should be familiar with all of these in order to direct or present the information effectively.
Each presenter should have a ½” binder with documents relating to his/her subsystem. The binder should contain graphs, calculations, spec sheets of bought assemblies, sketches of concepts or brainstorming.
Mech Eng Project design reports of systems that are still being used Components from the previous car for comparison Test pieces from impact attenuator tests, new mfg process or iterations of a part.
McGill Racing Team
Design Standards 26
References
KXCAD http://www.kxcad.net/ A resource containing Help for all CAD and CAE programs
RoyMech Engineering Library
http://www.roymech.co.uk This site provides useful information, tables, schedules and formula related to mechanical engineering and engineering materials. It provides convenient access to data for design engineers and engineering draughtsmen. The site also lists useful engineering standards.
MatWeb Material Database http://www.matweb.com Data sheets for over 69,000 metals, plastics, ceramics, and composites
Mechanical Engineering Design By Joseph Edward Shigley, Charles R. Mischke, Richard Gordon Budynas
Machine Element Design textbook
Gear Design Simplified By Franklin Day Jones, Henry H. Ryffel
Good resource for gear design and characterisation
PTC http://www.ptc.com ProEngineer resource
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