RC08-Chipper

This page contains the information and documentation of the 2008 chipper system

Robocup 2008 Mechanical

Assembly Structure

PART NAME	PART NUMBER	QUANTITY
Chipper Plate	RC-2008-06-01	2
Left Arm	RC-2008-06-02	2
Right Arm	RC-2008-06-03	1
Chipper Hinge Shaft	RC-2008-06-04	2
8-32 Lock Nut	RC-2008-06-05	2
4-40 x 1/4 Screw	RC-2008-06-06	2
8-32 Socket Cap Set Screw	RC-2008-06-07	2
8-32 x 3/8 Hex Standoff	RC-2008-06-08	2
8-32 Connecting Rod	RC-2008-06-09	1

Parts & Components

Motor

Vendor: MicroMo

• Motor: 12V DC brushless servo motor #E-1628B
  • $147.10 each
• Planetary gearhead: #E-167 gear reduction: 14
• Complete assembly 1628-V-0003

Cost: $200.40 each

• MicroMo
• Motor Data Sheet
• Gearhead Data Sheet

• Electrical specification
  • 12 Volts
  • must have position or speed encoders
  • brushless DC

Gears

Motor gear

Vendor: SDP/SI

Part No.: A 1B 2MYK05030H

Description: 3mm bore, 30 teeth, 15mm pitch diameter, brass gear with set screw

Cost: $6.72

Drawing:Motor Gear Spec Sheet

• Connects directly to output of motor and powers dribbler roller

Roller gear

Vendor: SDP/SI

Part No.: A 1B 2MYK08020

Description: 4mm bore, 20 teeth, 16mm pitch diameter, brass gear with set screw

Cost: $9.12

Drawing:Dribbler Gear Spec Sheet

• Roller gear needs be turned down from 7mm face to 2mm face width
• Powers the dribbler roller - is recessed into the roller itself

Plates

Swing

Vendor: McMaster-Carr

Part No.: 8885K13

Description: Alloy 7075 Aluminum Sheet .063" Thick, 12" X 12"

Cost: $21.73

• Contains the roller shaft, the motor mounts, spacers, and hinge shafts
• Material is same and shared with Omniwheel plates
• Left and right swings are identical

Motor plate

Vendor: McMaster-Carr

Part No.: 8885K13

Description: Alloy 7075 Aluminum Sheet .063" Thick, 12" X 12"

Cost: $21.73

• Supports motor and connects to the 2 spacers in assembly
• Material is same and shared with Omniwheel plates

Cross Plate

Vendor: McMaster-Carr

Part No.: 8885K13

Description: Alloy 7075 Aluminum Sheet .063" Thick, 12" X 12"

Cost: $21.73

• Connects both mounting blocks and provides mechanical limitation for swing and torsion springs
• Material is same and shared with Omniwheel plates

Standoffs

Standoff

Vendor: McMaster-Carr

Part No.: 9062K271

Description: Alloy 6061 Aluminum Precision-Ground Rod 5/16" Diameter, 1' Length

Cost: $9.10

• Standoff between swing and motor plate

2" Hex Standoff

Vendor: McMaster-Carr

Part No.: 91780A339

Description: Aluminum Female Threaded Hex Standoff 1/4" Hex, 2" Length, 6-32 Screw Size

Cost: $.88

• Hex standoff between motor plate and swing
• Both torsion springs anchor into the standoff

Fasteners

6-32 x 1/4" socket cap screw

Vendor: McMaster-Carr

Part No.: 92220A141

Description: 6-32 x 1/4" steel, low profile, socket cap screw

Cost: $7.22 for 25

• Connects the swing and hex standoff

6-32 x 3/4" socket cap screw

Vendor: McMaster-Carr

Part No.: 93615A217

Description: 6-32 x 3/4" 18-8 stainless steel, low profile, socket cap screw

Cost: $12.72 for 25

• Connects the swing, motor plate, and hex standoff

8-32 Lock Nut

Vendor: McMaster-Carr

Part No.: 90633A009

Description: Steel Hex Nylon-Insert Locknut, 8-32 Screw Size, 11/32" W, 11/64" H

Cost: $2.21 each - STOCK

• Constrains the dribbler and hinge shafts

4-40 Set Screw

Vendor: McMaster-Carr

Part No.: 91375A105

Description: Alloy Steel Cup Point Socket Set Screw 4-40 Thread, 3/16" Length

Cost: $7.99 for pack of 100

• Pins dribbler roller to the dribbler shaft

Shaft

Hinge shaft

Vendor: McMaster-Carr

Part No.: 8116K3

Description: A2 Tool Steel Tight-Tolerance Metric Rod 4 mm Diameter, 3' Length

Cost: $6.10

• Joint between swings and mounting blocks

Dribbler shaft

Vendor: McMaster-Carr

Part No.: 8116K3

Description: A2 Tool Steel Tight-Tolerance Metric Rod 4 mm Diameter, 3' Length

Cost: $6.10

• Roller and dribbler gear spin on dribbler shaft
• Material is shared with the hinge shaft

Springs

Left Torsion Spring

Vendor: McMaster-Carr

Part No.: 9271K35

Description: 1.375 lbf-in of torque. Music Wire Torsion Spring 90 Deg Angle, .309" Coil OD, .040" Wire, Cw/Lh, Packs of 6

Cost: $6.56 for 6

• Left hand wound torsion spring
• Rests on hinge shaft and provides cushioning for ball impact

Right Torsion Spring

Vendor: McMaster-Carr

Part No.: 9271K33

Description: 1.375 lbf-in of torque. Music Wire Torsion Spring 90 Deg Angle, .309" Coil OD, .040" Wire, Cw/Rh, Packs of 6

Cost: $6.56 for 6

• Right hand wound torsion spring
• Rests on hinge shaft and provides cushioning for ball impact

Other

Mounting block

Vendor: McMaster-Carr

Part No.: 3511T11

Description: Alloy 6061 Aluminum Ground Flat Stock .250" Thick, 6" X 6" Size

Cost: $45.44 each - STOCK

• Connects entire dribbler assembly to the robot

4mm snap thrust bearing

Vendor: McMaster-Carr

Part No.: 7817K33

Description: Metric Nylon Snap-in Thrust Bearing for 4mm Shaft Dia, 1.45-2.34 mm Sheet Metal Thick

Cost: $1.32 each

• supports dribbler shaft in the swing

3/8" Washer

Vendor: McMaster-Carr

Part No.: 93286A009

Description: Aluminum washer 3/8" OD,.175" ID, 1/32" thick

Cost: $3.52 for 100

• Washer between the swing and hex standoff

Neoprene Rubber Tube

Vendor: McMaster-Carr

Part No.: 7505K86

Description: Ultra-Flex Neoprene Rubber Heat-Shrink Tubing 3/4" Expanded ID, 3/8" Shrunken ID,

Cost: $8.97

• Roller and dribbler gear spin on dribbler shaft
• Material is shared with the hinge shaft

Calculations

Torsion Spring

• Analysis was done using the Work-Energy Principle with the assumption that the only work done is from the torsion spring and gravity. Because the dribbler assembly swings and has zero velocity at both positions, only the kinetic energy of the ball was used, at its maximum value of 10 m/s

Roller Speed

• Gears were selected for a gear ratio lower than 2007. The 2008 ratio is 1.5. This was with the hope of having more torque available for the roller to grip the ball.

Notes

• 4mm steel shaft chosen to increase strength to prevent bending of dribbler shaft when hit with a ball
• roller diameter - .5"
• dribbler shaft still slides free in between two snap-in thrust bearings and can be removed to allow the roller to be changed out