I just ordered the 4DOF T-HEX during the anniversary sale. (Thank you Lynxmotion.) I have been trying to pass on to my 12 year old grandson my love of technology by building things with him. We did a BRAT together. So I sent him the video youtube.com/watch?v=-dUPNYIs … r_embedded with the question, “Should we build this?”
He replied: “Yes and it looks like a walking tank maybe you could take off the legs and put some treads on it.”
What follows is my response to him. WARNING it is perhaps long-winded. At my age I avoid anything short-winded. 
Yes we could do that.
But then we would have to throw away:
24 high quality servos (There are six 4DOF legs.)
Six sets of leg hardware
The special servo controller board and all the special programming
If you watch the video carefully you will see that every part of every leg is doing something very different all at the same time. Sometimes all legs are raising or lowering the body of the robot, but some legs are also raising themselves higher to clear the ground. Some are moving forward or backward to move the robot in a straight line, or make it turn in an arc, or spin around in place.
Imagine if you want to do a complex move. With your PS-2 controller, you tell the robot to:
Start standing up very slowly
While still rising up, move forward one foot quickly
Then move diagonally to the left while rotating to the right a quarter turn
Then stay facing right but move forward in an ‘S’ turn first right then left for two feet
Stop with the body now raised to full height
You could do that very easily with your PS-2 controller. But look how many words it took me to describe the whole series of moves. Now imagine breaking that series into individual commands for what each leg should be doing. Got that figured out?
Now imagine breaking each of the six leg processes into the four parts for each leg for each move. Does the thigh go up or down? Does the knee go forward or back? How fast? How far? All of these questions have to be answered 24 times for every time interval (1000th of a second) of every move the robot makes. Then the right amount of electricity must be sent to each servo, in the right direction, for the right amount of time, to make the move happen.
Did you see how many more words it took me just to describe the questions? And I still don’t have any answers yet! There is an enormous amount of difficult math involved for every one of those 24 parts. (You haven’t even studied that kind of math yet.) And it all has to happen over and over again every 1000th of a second.
And yet you can guide the whole thing very easily with your PS-2 controller!
That’s the beauty of the special servo control board. The BRAT didn’t have one. It only had the microcontroller board. This T-HEX has both. The microcontroller (BBII) sends the basic commands to the servo controller (SC-32) and the SC-32 does all the math work and sends the electricity to the servos. This frees up the BBII to accept more commands from you or inputs from sensors.
With the T-HEX , you can understand much more about how humans can use their own minds to set goals and directions while using computers to do the grunt work for them; and higher levels of computers, BBII, can do the same with lower computers, SC-32. The future of your whole life will depend more and more on understanding these connections and on getting them right.
Tanks aren’t easy, but they are much easier to make and control than all this.
And you want me to throw away all those parts and that wonderful servo controller.
You horrible little boy, you!
Grandpa
We Should Build These Things because, my friends, it is The Meaning Of Life! 
Perhaps I will just send you thousands of questions instead. 
