Proposed Dewbot V Chassis

Clem McKownTeam 1640

December 21, 2008

Why 6wd? This summer’s prototyping and follow-

up analysis demonstrated that 6 wheel drive robots have a significant advantage in maneuvering vis-à-vis a 4wd robot

Omni-wheels facilitate 4wd turning, but make a robot easier to push around

6wd middle wheels are key for turning performance

Also a plus for ramps

Good practices 6wd has no advantage in traction or

stability, but… For traction,

all wheels should be driven; robot should be at maximum weight;

and traction tread material should be used

For stability, Maximize wheelbase Keep center of mass low and central

The Specs

(6) 6” AndyMark Plactron Wheels (4) CIM Motors (2) modified 2-speed AndyMark

Shiftboxes 9.4:1 & 24:1 Overall Gear Ratios 14.8 & 8 ft/s maximum speed 24.26 x 30” wheelbase

Isometric View“Grease Guard”1/16” PC partitionto keep electronicscompartment clean

cRIO Controller

Battery

Isometric View (showing Jags)

Jaguar (PWM)motor controllersmounted onfront panel

Front / Rear Elevations

Right / Left Elevations

Plan View

Plan View (Showing Jaguars)

Direct drive to Middle Wheels

Middle wheels are direct, gear-driven from the gearbox

Front & Rear wheels are slave-driven via chains & sprockets from the middle wheel

Benefits Reliability Keeps motor & gearbox (and

center of mass) low Weight savings

Customized (Team 1640) Direct-Drive AndyMark Shiftbox

New front & back platesSprockets replaced w/ 20 tooth gear

Additional axle = wheel axlew/ 45 tooth drive gear

Spacer bolts (now¼-20) also serveas mounting bolts

Identical left & right drive units

We could build & bring a spare

Design Performance Acceleration

curves are with wheels slipping

High gear provides adequate power for turning (enough to make wheels slip)

velocity versus time

0

2

4

6

8

10

12

14

16

18

0 1 2 3 4 5

time (s)

v (f

t/s)

High Gear

Low Gear

Weight Current Mass is 68.9 lbm, which includes

Chassis w/ Drivetrain Pneumatic System up to & including Regulator Panel mounts for electronics Battery Mount cRIO controller with:

cRIO w/ 5 modules Alalog bumper Pneumatics bumper Digital side-car & cable Distribution Block Radio

Does not include: Jaguar (PWM) Motor Controllers Battery Bumpers (not the electronic bumpers) Oh, yeah, whatever we actually need to play the game

Center of Mass

4.4 in above grade

4.5 in aft of chassis center (w/ battery)

1 in left of chassis center (w/ battery)

A reminder

This is a still work in progress

Any suggestions or critique will be appreciated