# Hydraulic Judo Bot in an Hour! STEM Project

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This instructables is about a kids project with simple and cheap materials and the opportunity for further analysis and deepening if needed.

For the "How to" the video presented is very helpful.

The construction is consisted from three parts: the base, the fighting arm and the vertical axis support.

What makes this project a STEM project is the evaluation and the corresponding remake, that comes with some measurements.

These are shown at the end of the video.

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## Step 1: Materials Needed

The materials that were used are:

1. 30 - 40 wooden sticks like these of lollipops
2. hot glue
3. cylindrical wooden sticks (I've used two pieces of 50cm in total, with a diameter of 6mm)
4. 2 syringes for single use 10ml (the needles should be thrown away immediately!)
5. 2 syringes for single use 12ml (the needles should be thrown away immediately!)
6. Two elastic tubes for making a connection between two syringes (one of 10ml with one of 12ml)
7. some tyre ups
8. 7 wooden cubes 2cmX2cmX2cm that should be drilled a hole of 6mm diameter
9. 1 wooden cube 2cmX2cmX2cm that needs no hole

## Step 2: Base Construction

The base is consisted from two trapezoids and one rectangle. It takes the area of a A3 sheet like the cutting pad I've used. The distance and direction of the syringe in relation to the drilled cube (2 as seen on the pictures) determines the measure of the rotation around the vertical axis.

## Step 3: Fighting Arm Construction

Looking carefully at the back side of the fighting arm you could see a triangle shaped part, which serves as a counter-weight holder. There could also be some exploring, to which is the right weight.

## Step 4: Vertical Axis Support

This part has four of the drilled wooden cubes. One couple of these is used for the vertical axis and the other for the horizontal axis.

It is very important to have a a wooden stick through the wooden cubes while you glue them. This ensures the frictionless(as less as possible) rotation of both axis horizontal and vertical.

## Step 5: A Few Tips...about the Pneumatics of the Project

For every couple of syringes choose the smaller (in my project these of 10ml) to be on the judobot and the bigger on your hands.You can either use air or water to fill in the couple of syringes and the tube inbetween. The air provides smoother moves than water.One couple of syringes turns the bot around the vertical axis and the other turns the fighting arm around an horizontal axis. So if you want some deepening, find the limits of these rotations and explore solutions for improving such performance. At the end of the video are providided some ways of measuring roughly the rotation limits.

Have fun!

## Step 6: STEM

Wenn somebody wants to use the project for educational reasons there are some educational questions to be asked and corresponding measurements and observations to be done. Some ideas are presented consequently.

For example:

1. What are the rotation limitations of this device?
2. What are the reasons for these limitations?
3. How is it posible to extend the movements mechanicaly?
4. What are the limitations set by the pneumatics?

There are two measurements shown in the video and these are related to the rotation range around the vertical and horizontal axis.

Any comments or suggestions are welcomed!

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