mechanical engineering applications. when planning construction an understanding of materials has to...
TRANSCRIPT
Mechanical EngineeringApplications
When planning construction an understanding of materials has to
be your starting point
As you design each part - ask yourselves
A) What is the parts function?
B) Which direction will forces be exerted?
C) How much force will be applied?
A-Arm Example
Types of Materials
Steel A lum inum Titanium
Metals
Fiberglass Lam inates Carbon fiber
Com posites
Plastics Cloth Foam
Other
SteelA) Mild - Easy to formB) Tool - Wear resistantC) Stainless - Stiff, wear and
rust resistantD) Chromoly- Strong but not
brittleE) ETC.
All are weldable
Tie Rod
AluminumA) Cast - Hard, wear resistantB) 4043 - Soft, workableC) 6063 T-6 - Aircraft grade,hard,
weldableD) 7075 T-6 - Aircraft grade,
very hard, can bemachined but notwelded
E) ETC.
Aluminum Parts
Titanium
Titanium comes in different degrees of hardness and brittleness. It tends to crackin the corners then rip.
Examples
Fiberglass This material takes advanced
thought. You can make changes to it after construction. However, changes not in the original plan often create a reduction in strength or a significant increase in weight. We have found it difficult to use fiberglass and prevent the resign from creating more weight than We would like. There are also dangers in working with and breathing the components used in this process.
LaminatesThere are a number of possibilities in
this area. We have used corrugated plastic, corrugated fiberglass (flooring from passenger planes), and Reynolite (an aluminum and plastic laminate used for signs). Another laminate construction is wood. Boats, canoes and home built aircraft use wood laminate as a method of construction.
Carbon fiberWe have researched this possibility and shied away from it. We feel:
A) It is excessively expensiveB) To design a structure you must
learn at a completely different level the material and process
C) You must think through EVERY detail in advance
D) A mold is time consuming
PlasticsWe have used .035 Lexan for a number
of applications. One of those being our wind shield. We have also used it in our battery box. It insulates the box while providing a visible check of the batteries without removing the the seal from the box. Lexan is pliable and easy to work with. Canopy is another application. Plastic has also been formed to produce our lenses for our lights. This has been done by having a laser harden resign in layers.
Stretch and shrink wrap is another option.
ClothIn some locations spandex is useful.
This might be done where you want to hinder air flow but allow movement.
Airplane cloth on the other hand can provide reduced weight and allowenough strength to with stand a mansweight.
Airplane Cloth
FoamHouston Mississippi is a great
example. The outer airfoil of their carhas been foam insulation for homes. It is light weight and cuts the air well.
We have used foam to laminate,providing a shape between layers to create strength.
Construction Joining MethodsA) Bolt D) FiberglassB) Rivet E) SolderC) Weld F) Glue
1) Rosette2) Spot3) Seam
Fastening MethodsA) VelcroB) Roll pinsC) Cotter pinsD) Hitch pinE) Push pinF) Zip tiesG) HaspsH) ZeusI) CaulkJ) Spirolox
Zeus
Chassis
Chassis DesignsA) MonocoqueB) I – Beam / C - ChannelC) Tubular
1) Round2) Square3) Rectangular4) Extruded
SS I
SS I Rolling
SS II
SS III
Chassis ConsiderationsA) Design each member to
perform its functionB) A triangle is the strongest
structureC) Use struts or corner braces
to spread out stress and loads
Suspension
SuspensionSuspensions can very greatly. If
you are racing only at the track event you can save the weight of suspension PROVIDED your car has a low stable center of gravity. On the road races that is not true. For those races no suspension will make the car hard to control, fatigue the driver, and tend to shake the car apart.
Types of suspension might include the following:
A) Double A-ArmB) Go-KartC) Radius link solid axelD) Trailing arm (motorcycle)E) RockerF) Shocked fork
How can you provide shock absorption? I think the ways are limitless. Let you minds think outside the box. Here are but a few suggestions:
A) Car, snowmobile, motorcycle, bicycle4-wheeler, or airplane shocks
B) ElastimersC) SpringsD) Budgie cordsE) A Piece of a tireF) Use your imagination
Shocks
Steering
To do this properly you need an autosteering development program. We use A-Arm Pro.
(use last years breaking mishap as the example)
A-Arm Pro
Aerobody
A) How important is it?B) What considerations might I need
to take a look at?C) What shape is the best?
How important is it?
This, in my opinion, differs for different teams.If you plan to play the role of the tortes it is notreal important to your racing ability. If you plan to maintain a speed below 25 mph it will not make a great difference. On the other handIf you plan to run at faster speeds it is very important. An additional consideration mightbe sponsorships. I think the more sleek and professional the car looks the more you car is noticed and the better the exposure for your sponsors. Which translates to easier fund raising
What considerations might I need to take a look at? (in no particular order)
A) Frontal areaB) Shape (tear drop, wedge, etc.)C) Stability (other vehicles, weather)D) Planned speedE) Height off of the groundF) High / Low pressure areas
(computer program)G) Safety if impacted ( review later)
C) What shape is the best?
You will need to decide. If no other factors existed a tear drop is consideredthe most aerodynamic by most. You do not want lift nor do you want downforce. The car should be as neutral as possible.
Solar Body ShellHandout
Look at your design with Discriminating eyes
Consider the following. If an impact or mechanical failure occurred how would it affect the driver, car and others?
Examples:If a car impacted your design from theside at 90 degrees would the driver besafe?
Considering the height of car and truckbumpers, what would be the results to your driver if the breaks failed and theyrear ended a vehicle?
If your car were driving at 45 mph and the left front tire and rim separated from the car what might be the result?
If the front of your car impacts something solid would it cause parts ofthe car to shear of and pose a danger tothe driver?
If an impact occurred would it cause the driver exit to become jammed to hinderthe driver from reaching safety?
Join halves
Added roll bar
SS VI
Crush Zones
Car designs of others