Mechanical Engineering Applications When planning construction an understanding

Mechanical Engineering Applications

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

Steel A) Mild - Easy to form B) Tool - Wear resistant C) Stainless - Stiff, wear and rust resistant D) Chromoly- Strong but not brittle E) ETC. All are weldable

Tie Rod

Aluminum A) Cast - Hard, wear resistant B) 4043 - Soft, workable C) 6063 T-6 - Aircraft grade, hard, weldable D) 7075 T-6 - Aircraft grade, very hard, can be machined but not welded E) ETC.

Aluminum Parts

Titanium comes in different degrees of hardness and brittleness. It tends to crack in 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 tha We would like. There also dangers in working with and breathing the components used in this process.

Laminates There 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 fiber We have researched this possibility and shied away from it. We feel: A) It is excessively expensive B) 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

Plastics We 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 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.

Cloth In 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 allow enough strength to with stand a mans weight.

Airplane Cloth

Foam Houston Mississippi is a great example. The outer airfoil of their car has 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 Methods A) B) C) Bolt Rivet Weld 1) Rosette 2) Spot 3) Seam D) Fiberglass E) Solder F) Glue

Fastening Methods A) B) C) D) E) F) G) H) I) J) Velcro Roll pins Cotter pins Hitch pin Push pin Zip ties Hasps Zeus Caulk Spirolox

Zeus

Chassis

Chassis Designs A) B) C) Monocoque I – Beam / C - Channel Tubular 1) Round 2) Square 3) Rectangular 4) Extruded

SS I

SS I Rolling

SS II

SS III

Chassis Considerations A) Design each member to perform its function B) A triangle is the strongest structure C) Use struts or corner braces to spread out stress and loads

Suspension

Suspensions 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-Arm B) Go-Kart C) Radius link solid axel D) Trailing arm (motorcycle) E) Rocker F) 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, bicycle 4 -wheeler, or airplane shocks B) Elastimers C) Springs D) Budgie cords E) A Piece of a tire F) Use your imagination

Shocks

Steering To do this properly you need an auto steering 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 not real 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 hand If you plan to run at faster speeds it is very important. An additional consideration might be 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) B) C) D) E) F) Frontal area Shape (tear drop, wedge, etc. ) Stability (other vehicles, weather) Planned speed Height off of the ground High / Low pressure areas G) (computer program) 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 considered the most aerodynamic by most. You do not want lift nor do you want down force. The car should be as neutral as possible.

Solar Body Shell Handout

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 the side at 90 degrees would the driver be safe? Considering the height of car and truck bumpers, what would be the results to your driver if the breaks failed and they rear 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 of the car to shear of and pose a danger to the driver? If an impact occurred would it cause the driver exit to become jammed to hinder the driver from reaching safety?

Join halves

Added roll bar

SS VI Crush Zones

Car designs of others