CO2 Dragster: The Science Of Speed

Panayotis ManganarisKent Johnson

Understanding

● Create a racing vehical propelled by a canister of compressed CO2 gas.

– Minimize all restraining factors● Friction● Drag● Weight

● Explore best design possibilities – Sketch

● Prototype best idea using Autodesk Inventor● Manufacture out of wooden blank.

Explore

● Use a Shell car or a Rail Car?– Rail cars could be made

lighter, much thinner

– Shell Cars would have superior Aerodynamics

● How short can the car be?– TSA Criteria limit the car at a minimum of 20cm

● Do we want Speed or Style?– We will try to develope the most aerodynamic car

with speed as the goal, looks should be nice.

Exploring Possibilities

● A number of quick brainstorming ideas

Define: What designs are most aerodynamic?

● Using a hybrid of Shell and Rail

design

– Allows for thin mid section● using a broad-head arrow tip.

– Best Aerodynamics● Introduce a body-length channel

– reduces weight

– allows for less air resistence

Ideate: Final Sketch

● Pictoral and Profile view

Ideate: Prototyping in Inventor

● Developing Preliminary shape out of blank– Using extrusions

– No further refining needed

● Initial shape is not adjusted any great amount

Prototype

● Testing aerodynamics with Inventor– Environmental analysis

● FlowDesign Software

Prototype: Testing in Flowdesign

● Average Drag Force at 10m/s: 0.06 Newtons● Average Drag Force at 25m/s: 0.4 Newtons

– Some apparent oddities, apparently very little change in dragforce from blank to finished car.

Prototype: Readying for Construction

● Final Blueprints in preparation for crafting

● Materials Needed

Refine

Refine: Manufacturing

● Drawing design to scale on graph paper– Attach sketch to blank

– Trace using band saw

● Use drill-press to make clean and straight axel hole● Use Drum-sander to clean up edges.

– Edges not accounted for in inventor prototype.

– Should reduce weight and better aerodynamics

Solution: Weight and Drag Force

● Mass: 115 grams– 7th lightest out of 20 in class

● Weight: 1.12776475 Newtons● Drag force (newtons): 0.139

– 6th most Aerodynamic of 20 in class

Solution: Race Results and Testing

Trial Time (s) Speed (m/s) Speed (km/hr) Speed (miles/hr)

1 2.16 10.46 37.66 23.4

2 2.21 10.22 36.79 22.86

3 2.32 9.74 35.06 21.79

Average 2.23 10.13 36.47 22.66

Times for dragster racing on 22.6 meter track5th place out of 20 CO2 Dragsters

Solution: Wheel Allignment and Spin

Wheel Alignment:

If the wheel alignment of a dragster causes it to veer sideways, it will create friction between the tires and the track, and friction between the string and the guiding eyelets. Friction will cause the dragster to slow. We can measure the wheel alignment of dragsters by rolling them down a short ramp, and measuring how far it veers to the side on a one meter run.

#1: 5mm right drift

#2: 7mm right drift

#3: 3mm right drift

Average: 5mm drift per meter implys possibly as much as 10cm of drift over the cource of the whole 22 meter track.

Wheel spin:

If the wheels on a dragster are wobbly or if they stick, it will slow the dragster down. To measure the wheel spin of a dragster, turn it over and spin each wheel in turn with your finger. Try to be as consistent as possible in the force used to spin the wheel Time how long each wheel spins using a stop watch.

Left Front Wheel #1: 1.25 #2: 0.96 #3: 1.09 average 1.1 seconds

Right Front Wheel #1: 1.13 #2: 1.00 #3: 1.48 average 1.203 seconds

Left Back Wheel #1: 2.86 #2: 1.87 #3: 1.85 average 2.193 seconds

Right Back Wheel #1: 2.08 #2: 1.60 #3: 2.28 average 1.986 seconds