RC08Shell

Making up the RoboCup 2008 Mechanical System, the shell protects the insides from a fast moving ball and should look cool.

A developement rendering of the 2008 RoboCup robot shell

Composite Layup Info

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Parts & Components

Kevlar Fiber Roll

Vendor - US composites

Part No. - FG-KEV538

Cost - $16.50 per yard

Description - 0.01" thick 38" wide. Probably using 2 layers for the shell.

Wood for mold

Vendor -

Part No. -

Cost -

Description - 3/4" particle board. Used left over pieces from making cabinets.

Resin and Hardener

Vendor - US composites

Part No. - EPOX-635315

Cost - $104

Description - Epoxy and hardener with medium setting time. 2 gallons of epoxy and 85 fl oz. hardener.

Vacuum bag

Vendor - US composites

Part No. - VB-VF0272

Cost - $3

Description - Nylon bagging to hold vacuum. 72" wide, price is per yard.

Vacuum tape

Vendor - US composites

Part No. - VB-BT25

Cost - $6

Description - 25' length

Black pigment

Vendor - US composites

Part No. - AC-BL016

Cost - $10.50

Description - 1 pint

Bleeder cloth

Vendor - US composites

Part No. - VB-BLE60

Cost - $4

Description - Allows air flow and absorbs excess epoxy. 60" wide, price is per yard.

Shell design

Dimensions

The total height of the shell is 5.8 inches. The outer diameter is 7.04 inches with a shell thickness of 1/16 inch. The angle on top allows the vision system to better see the ball in front of the robot compared to last year. The angle starts 3 inches from the bottom of the shell at an angle 15.5 degrees from the vertical. This allows significant room for electrical components while maintaining room on top for the dots to locate the robot. The flat in the front is 3.664 inches wide. The cutout in front allows room for the dribbler and kicking system. It is 2.8 inches wide and 2.5 inches tall.

Manufacturing

Mold

The shell is being manufactures using a layup of kevlar and epoxy inside vacuum bags. A negative mold for the shell is made using particle board cut out on the CNC mill. Particle board was chosen since it is cheap and has fairly consistent isotropic properties in comparison to standard wood. The dimensions on it also tend to be more accurate. Cross sections of the shell are cut out of particle board starting from the bottom and moving to the top. Once all of the cross sections are cut, they are glued together to form a complete mold.

Action Log

1. 04/18/2008 - Fiber glass wet layup complete and ineffective.

   Note - Will try preimpregnated strips.

2. 04/20/2008 - Second wet layup stronger, but dimensionally not acceptable.

   Note - Will now proceeded on to vacuum bagging.

3. 04/30/2008 - First vacuum bag test done.

   Note - Smaller strips needed, cap with single patch on top and sides.

4. 05/02/2008 - Shell with pigment completed and impact testing successful.

   Note - Creases are apparent all critical dimensions are acceptable.

5. 05/28/2008 - More vacuum tape arrives and Kevlar testing can now proceed.