Welcome to the rero Lego Dinosaur Instructable! If you've stumbled upon this Instructable, you're either looking for a good project to build with your rero set, you love playing with Lego, or maybe you just adore our ancient reptilian overlords!

Part Requirements:

For this model, 1 rero Standard Set and 1 rero Expansion Set by Cytron Technologies is used, so you won't need to worry about not having enough rero parts as long as you have those two sets. As for the Lego parts, I can't say for certain which Lego set you can get that has all the required parts in it, so you will have to look for them or work around them yourself. You'll also need the rero Animator software to program the robot, so install that too.

How to use this Instructable:

Due to the sheer amount of things I have to cover in this Instructable, I've broken them down into several major 'Steps' where we will complete the robot one section at a time.

Assembly instructions and notes are included in the pictures, so make sure you read them so that you don't get lost.

For those who intend to "freestyle" the build:

Now, I know that there would be plenty of people among you who would take the assembly instructions I provide as a reference only and come up with your own designs based off them (I am referring to the mechanical aspects, not aesthetics). If you are among them...... go ahead! I will be in no way offended, and instead be glad that you could come up with your own designs. Sincerely.

However, please do give the written materials a quick read through, as I have taken care to include things that you need to take note of when building your Dinosaur, such as places where you need to reinforce, the weight distribution and the walking mechanism etc.

Last but not least, happy building!

Step 1: List of Parts (For One Leg Only)

In the event where you can't find some Lego parts listed here, it's fine! You can always utilize what you do have and work around things. That's what Lego is all about anyways.

A quick note on the 8 Length 13 Beams used (Second pic.):

The beams make up the main structure of the legs, meaning that they do most of the supporting, together with the rero Cube Servos.
By the end of the build, the Dinosaur may experience problems standing up, especially if the amount of "cosmetics" you add are too heavy.
To fix this, you may use shorter Beams (minimum should be Length 9, before it gets too short) as replacements so that the torque from the Cube Servo transfers over more efficiently to the legs (as in a lever system).

Since these are for one leg only, you need to prepare one more set of these for the other leg.

Step 2: Assembling Leg Components

We will assemble individual components first, and put them together in the next Step.

Step 3: Putting the Components Together

A note on using the stopped axles and bushes for the joints:

The joints connected by the axles are vital mechanical hinges that support the Dinosaur's movements (Thanks, Captain Obvious!).
It is not rare that the joints will loosen when the Dinosaur moves if the connections are weak, especially with the weight the joints need to endure.
If you don't have enough stopped Axles (you will need 12 in total), feel free to use your own methods, or else remember to check them periodically if you use a more "unstable" build.
I utilize the '1x stopped axle, 3x 1/2 bush' setup because it is the tightest/ stablest setup I can think of, where I've never seen the connections loosen yet.

Step 4: Assembling the Main Body

After completing, remember to connect the wires and set the limits for the Cube Servos using the rero Controller.

Step 5: Tying Up Loose Ends

I'd like to talk about some details that you should tend to to make sure that your Dinosaur functions properly.

Enforcement

The body is going to be heavy. There's no going around this, and it causes the Lego connections to give-in to the weight, loosening them or breaking them apart.
Thus, it is important enforce the legs' structure, especially at several key points (as shown in the pictures above).

Wire Clips

Wire clips are provided in the rero Standard and Expansion sets.
You should always use them to keep the wires in place so that it will not entangle or get in the way of Dinosaur's motion.

Foot Plate Protection

It is wise to add a layer of protection to prevent the foot plates from being worn out.
Try to use materials that won't add friction. It is preferable for the Dinosaur to walk smoothly.
Recommended material: Paper Tape

Step 6: Walking Mechanism

**Warning! Elementary Physics Stuff Ahead!**

Kinetic and Static Friction

Friction is the force resisting the relative motion of surfaces. However, there are two types of friction between solid surfaces: StaticFriction and KineticFriction.

The three main points are:

Staticfriction applies when an object is stationary.
Kineticfriction applies when an object is moving.
In terms of force, staticfriction is greater than kineticfriction.

For example, notice how when you try to push a heavy object, you only really struggle when the object is stationary (static friction). Once you apply enough force, the object 'spurts' forward (overcomingstatic friction). After the initial 'spurt', it becomes easier to push (kinetic friction kicks in, lesser force is needed) until it stops again.

Applying this, the walking mechanism is as follows:

Leg starts at a forward position.
Leg shifts backwards slowly (static friction), so there is 'grip' on the floor, pushing the Dinosaur forward.
Leg shifts forward quickly (kinetic friction), so there is no 'grip', as if the leg is lifted back to the forward position.
Motion alternates between both legs.

To Summarize:

The Dinosaur walks by shifting it's legs backwards (slow motion) and forwards (fast motion), producing a forward shuffling motion.

This form of locomotion is used to compliment the mechanism used, and also to work around the fact that it can't really lift it's legs due to the body's weight.

**The angles and duration used in the video are for reference purposes only.

The angle greatly depends on the orientation of the Cube Servo.
You should experiment with the duration to find the ones that suit your robot, as it may be affected by the weight and material used to protect the footplates.

Step 7: Building the Rest of the Body

Remember to connect and clip the wires. Also, set the limit for the Cube Servos.

You may use Beam Joints and Lego parts to form the head and arms of the Dinosaur.

The design is completely up to you, and I won't be covering how to build mine either. For one, the design shown here is the first one I came up with, effectively making it the prototype. You may mimic it, of course.

And don't forget, customization isn't limited to these sections only!

Explore to see what you can do with the rest of the body!

Mass

It's important to remember to minimize the mass of aesthetic parts you add onto the Dinosaur if you don't want to sacrifice it's functionality.
The Cube Servos may overheat after walking (or even standing, in extreme cases) if the body is too heavy. If this happens you should turn them off to decrease the strain and prevent damage.
Parts where you can devote a lot of designing to (like the head) may cause too much weight to shift to the front. You may increase the length of the tail (add segments) to counter the weight.