Alternative Fuels Group- Meeting 09/14/05

ASSIGNMENT 1 RESPONSES

Alternative Fuels Group Assignment 1:The design of our MULE must be conceptualized from a list of vehicle performance specifications (i.e. vehicle packaging, vehicle mobility, etc) defined by FCS. These specifications were included in the PowerPoint presentation at the 8/31/05 AFG meeting.The goal of this assignment is to use the performance specifications to bracket the vehicle requirements. Consider the MULE to be a black box with dimensions X, Y, and Z. The MULE has a weight and center of gravity (CG). The MULE will have a particular drive mechanism (tracks, wheels, legs, etc), propelled by a certain amount of horsepower.

In a 1-2 page PowerPoint slide, bracket the ranges of the following vehicle parameters necessary to achieve the performance specifications defined by FCS:

1. X, Y, Z2. Vehicle Weight/Payload Weight3. CG Location4. Vehicle HP5. Drive Mechanism6. Ground Clearance7. Tractive Coefficient8. Vehicle Mass Density9. Payload Mass Density

Try to justify your brackets by identifying which performance specifications are the limiting factors for the above vehicle parameters. For example, the MULE cannot be 22 feet long, since 3 of them could not be transported by a C-130 aircraft. On the other hand, a 3 foot long MULE is probably not capable of crossing a 40” gap.

Alternative Fuels Group- Meeting 09/14/05

ASSIGNMENT 1 RESPONSES

Payload weight / Vehicle weight

Spec.: 5,000 lb Gross Vehicle Weight + 1,900 – 2,400 lb payload

Payload / Vehicle Ratio: 63% – 92 % HMMWV designed for 89% - Achievable Goal

Do not exceed specified GVW, lighter is desirable but difficult to achieve

Vehicle Mass Density

16 -71 lb/ft3 (HMMWV empty [11,500 lb, 110”L x 85”W x 69” H} – M1 combat weight)

KRC’s UGV = 13 lb/ft3 but designed to float

Design goal of 30-40 lb ft3 (would result in 75 ft3 vehicle: 3.5 ft x 4 ft x 5+ ft)

Payload Mass Density

Hay bales 20 lb/ft3 Lumber 38 - 42 lb/ft3

Diesel 50 – 54 lb/ft3 Water 62.4 lb/ft3

Gravel 111 lb/ft3 Steel 489 lb/ft3

260 gallons of water and/or fuel weighs about 2,000 lb and requires 3 ft x 3 ft x 4 ft

Alternative Fuels Group- Meeting 09/14/05

ASSIGNMENT 1 RESPONSES

Vehicle Horsepower

20 - 40 HP/ton = 50 - 100 HP

Assumptions on rolling resistance (wheels or tracks), aero drag, mechanical efficiency

Need to prioritize maximum speed versus speed up maximum grade

Drive Mechanism

Tracks – Good mobility, speed limited

Wheels – Good speed, gap limited

Need to prioritize specifications and compromise

Tractive Coefficient

0.07 (ice) – 1.0 (soft rubber on asphalt)

Need 0.5 to climb 60% slope

Difficult for wheeled vehicle to exceed 0.4 on dirt, without chains or lugs

Alternative Fuels Group- Meeting 09/14/05

ASSIGNMENT 1 RESPONSES

XYZ

Length: 56 – 110 inches (min. driven by gap crossing and payload capacity)

Width : 42 – 85 inches (min. driven by stability, max. by other vehicles)

Height: 18 – 48 inches (min. driven by payload, max driven by stability and visibility)

Based on density assumptions will need 111 ft3. These dimensions result in 24 – 259 ft3

Ground Clearance

8 – 18 inches

ATV’s = 7.5 – 9.5 in. HMMWV = 15 – 24 in. M1 = 17 – 19 in.

Need to prioritize Ground Clearance vs Stability vs Payload capacity

CG Location

Fore and Aft: Center of vehicle ± 2 inches (for gap crossing and traction)

Side to Side: Center of vehicle ± 2 inches (for traction, stability and component life)

Vertical: Low as possible, Max = .67x Width (min. is trade-off with ground clearance)