4.2b: Functional Prototype

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

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 NameQuantityMethodMaterialFile Name / Note
Standoff43D PrintPLAStandoff.3MF
Link - Green1Laser Cut1/4in AcrylicTestLinkGreen.DXF
Link - Cyan1Laser Cut1/4in AcrylicTestLinkCyan.DXF
Ternary Link2Laser Cut1/4in AcrylicTestLinkNavy.DXF
Link - Pink1Laser Cut1/4in AcrylicTestLinkPink.DXF
Link - Red1Laser Cut1/4in AcrylicTestLinkRed.DXF
Ground23D PrintPLAGround V2.3MF
Ternary Ground13D PrintPLATernary GroundV2.3MF
Base1Laser Cut1/4in WoodTestBase_Top.DXF
M6 Spacer - 15mm23D PrintPLAM6_Spacer_15mm.3MF
M3 Spacer - 10mm23D PrintPLAM3_Spacer_10mm.3MF
M3 Spacer - 5mm23D PrintPLAM3_Spacer_5mm.3MF
Crank Handle13D PrintPLA

Crank Handle.3MF

Shaft - 57.7mm1ME Machine Shop
Joint 1
Shaft - 70mm1ME Machine Shop
Joint 4
M3x2014Inventory
Standoffs and Grounds
M3x30 Screw2Inventory
Joints 2 and 6
M3x35 Screw2Inventory
Joints 3 and 5
M3 Washers16Inventory
Joints
M3 Nuts36Inventory
Joints, Standoffs, and Ground
M6x45 Screw1Inventory
Joint 7
M6 Nuts3Inventory

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.