Introduction: How to Make a Scissor-type Extension Arm

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Scissor-type extension arm is a common extension device which has relatively short stroke and can extend proportionally, as showed in the picture above.

The displacement of B =the displacement of A x the number of the segments

For instance, the above picture2 shows a 4-segment extension arm, hence the displacement of B can be calculated by using the formula, that is by multiplying A (the stroke change of the slide) by 4.

All these parts are from: www.makeblock.com

Next is the constructing steps:

Step 1: Build the Drive Part 1

Part List:

1 x Servo

1 x Plate 3x6

3 x Screw M4x8

Step 2: Build the Drive Part 2

Part List:

1 x Beam0824-080

1 x Beam0824-024

2 x Nylon Lock Nut 4mm

2 x Screw M4x22

Step 3: Build the Drive Part 3

Part List:

1 x Plate 45°

1 x Plastic Rivet R4100

Step 4: Build the Drive Part 4

Part List:

1 x Beam0824-080

1 x Screw M4x40

2 x Plastic Spacer 4*7*10

This extension structure
needs to drive thru linear motion, hence we used plate l1 as a guide rail and used plate 45°to transform the circular motion of the servo into linear motion.

Step 5: Build the Drive Part 6

Part List:

2 x Plate I1

4 x Screw M4

4 x Screw M4x14

Note: As showed in the picture 3 in this step, we need to drill a 4mm hole at the end of plate l1

Following the steps, we finished building the drive part.

Step 6: Build Extension Arm 1

Part List:

10 x Plastic Rivet R4100

8 x Beam0808-076

Step 7: Build Extension Arm 2

Part List:

3 x Plastic Rivet R4100

2 x Beam0808-044

Step 8: Repeat Above Building Steps, Then We Got the Structure Below:

Part List:

2 x Beam0808-044

2 x Plastic Rivet R4100

1 x Plastic Spacer 4*7*2

Step 9: Connect the Extension Arm and the Drive Part.

Part List:

2 x Screw M4x30

2 x Nylon Lock Nut 4mm

Several Plastic Spacer 4*7*2

Step 10: Fix Screw Number 1 and Screw Number 2 Separately Into the Hole and Groove of Plate L1, As Showed in Picture Below:

Step 11: Note: the Plastic Spacer Here Is to Parallel Two Plates. the Quantity of Plastic Spacer Used Here Depends on Actual Situation.

Following above building

steps, we finished building the scissor-type extension arm.

This extension arm can be mounted onto Starter, Ultimate, mBot or other Makeblock robots.

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