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4.2b: Functional Prototype

4.2b: Functional Prototype

May 01, 2024

The team's first functional prototype is shown in the images below.

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Movement

In the two videos, the full revolution of the mechanism is shown. When the crank is rotated, there is a distinct "flicking" motion as estimated by our kinematic analysis. The flicking motion occurs at the bottom of the revolution of the joint 6.

 

Manufacturing and Materials

The materials used and their specific manufacturing methods are included in the following table.

Part Name

Quantity

Method

Material

File Name / Note

Standoff

4

3D Print

PLA

Standoff.3MF

Link - Green

1

Laser Cut

1/4in Acrylic

TestLinkGreen.DXF

Link - Cyan

1

Laser Cut

1/4in Acrylic

TestLinkCyan.DXF

Ternary Link

2

Laser Cut

1/4in Acrylic

TestLinkNavy.DXF

Link - Pink

1

Laser Cut

1/4in Acrylic

TestLinkPink.DXF

Link - Red

1

Laser Cut

1/4in Acrylic

TestLinkRed.DXF

Ground

2

3D Print

PLA

Ground V2.3MF

Ternary Ground

1

3D Print

PLA

Ternary GroundV2.3MF

Base

1

Laser Cut

1/4in Wood

TestBase_Top.DXF

M6 Spacer - 15mm

2

3D Print

PLA

M6_Spacer_15mm.3MF

M3 Spacer - 10mm

2

3D Print

PLA

M3_Spacer_10mm.3MF

M3 Spacer - 5mm

2

3D Print

PLA

M3_Spacer_5mm.3MF

Crank Handle

1

3D Print

PLA

Crank Handle.3MF

Shaft - 57.7mm

1

ME Machine Shop

 

Joint 1

Shaft - 70mm

1

ME Machine Shop

 

Joint 4

M3x20

14

Inventory

 

Standoffs and Grounds

M3x30 Screw

2

Inventory

 

Joints 2 and 6

M3x35 Screw

2

Inventory

 

Joints 3 and 5

M3 Washers

16

Inventory

 

Joints

M3 Nuts

36

Inventory

 

Joints, Standoffs, and Ground

M6x45 Screw

1

Inventory

 

Joint 7

M6 Nuts

3

Inventory

 

Joint 7

 

Notes for Final Prototype

  1. The spacers and washers utilized in this design were not as expected in the CAD. Currently additional M3 nuts are acting as spacers in order to provide smooth motion.

  2. The ternary link short end is not the correct dimension, and we are noticing the angle between links 2 and 3 is not changing as much as anticipated in the Python analysis. 

  3. The ground position of the ternary link is not in the correct place. This may also be contributing to the angle issues noted in (3).

  4. The ternary link may need to be keyed in the future in order to mitigate slip on the shaft. Currently, the M6 holes were down sized to 5.80 in order to create a snug, press-fit.

  5. The team will need to replace the crank handle with a 12V DC motor, H-Bridge, and Arduino. Appropriate calculations may be required to ensure the motor can supply enough torque.