Limited Slip Gear Differential

I went to the new exploratorium in San Francisco where I saw a working model of the limited slip differential system used in cars.  I'm still learning about it, but I think the gearing mechanism is used to allow one wheel to move faster than the other to prevent skidding on a turn.  Basically, when one wheel has friction and slows down, the other wheel speeds up to compensate for the lack of energy.  Differentials are important because on a turn, when the outer wheel travels more distance then the inner one.  If they both rotate the same amount of times, then the outer wheel will be dragged, ruining the tire.
Here is my firs differential:

More lego guns- and now a working one!

After ordering some new pieces, I made a new lego gun.  This one holds eight bullets and fires them all within a few seconds.  It just uses the basic lego "rocket launchers" that fire when the trigger is pressed.  Because of the circular rotating design, all of the triggers are pressed after a complete circle.  Unfortunately, in this video, the shots are staggered because the triggers weren't pulled all the way.  It's not perfect, but its an improvement from my earlier designs.

My Excavator

I haven't posted in a while, but here is a video of my fully built excavator with my custom additions.  I added two motors to power the treads, a motor to shift between arm functions, and I made the whole thing remote control.  Also, when the arm moves, lights on it turn on to illuminate the way (sorry, they aren't easy to see here).  It's super fun to drive.  Here is the video of it just moving a roll of wrapping paper:

1st place in our FLL tournament!

We had a great tournament this weekend at the Nasa Ames Research Center.  We came in 2nd place in the robot game, but 1st overall (and received the champion's award.)  It has been a great season and I can't wait to continue.  Our team name is REX.

4WD Buggy

I saw a video on youtube of a four wheel drive buggy, and I like the design.  I tried to build my own version, using 2 medium motors in the back and two large motors in the front.  Unfortunately, I had no great off-road wheels, so I used other ones that aren't as good as I would have liked.  Here is the video I watched: http://www.youtube.com/watch?v=uff7vZ-Pcds

Here is the robot, with the "protection" I added to it:

This is the robot without the outer layer.  If you look carefully, there is a turntable gear in behind the front motors; this is to allow the front wheels to rotate from the back wheels, so when it goes over an object only one wheel will go into the air and the rest will remain pushing on the ground:

Here is the robot in action:

Fencing Robots

A few days ago, I decided I wanted to make fencing robots.  Instead, I ended up with a robot that can spin and jab out at you.

I put it on a base with four support legs, and played with it for a little while.  It can spin 360º, but can't move, so it isn't that fun to play with.

The next day my uncle came over, and challenged me to put wheels on it.  So I did.  Since it was pretty heavy, I used my XL motors, the strongest power functions motors.

Building Lego "Guns"

Last night I was up trying to build a crossbow, or gun, or whatever I could to project a object.  I had limited success.  In my first design, I compressed a shock absorber and then released it to hit and fire an object.  It only shot pieces about one foot.

 Next, I tried to use rubber bands to launch a piece down a track.  It could fire about four feet, but didn't work every time.

Happy Halloween!

It's a little late, but Happy Halloween everyone!

Treads as a conveyer belt?

I am in the process of building lego model #8294, an excavator:

It is super fun to build and I can't wait to finish it. In the progress of constructing, I realized that treads could be used as a conveyor belt to transport objects, such as balls.  The video below is a quick demonstration of a ball moving upwards.  In the future, I would attach a motor, but for this I just used my hand to move the belt.

Why Half Robot?

I've always liked to build things.  My favorite toy when I was really young was rope.  I loved to tie knots and I would tie things up all over the house.  My dad told me that one day I tied the vacuum cleaner up so well it took 20 minutes to free it.  I would often string ropes across my bedroom and tie them together into a giant web-like net, then hang toys off the various ropes.

Around when I was seven, I got a Robosapien toy robot for Christmas.  It was two feet tall, and it could walk, move, dance and fart, which seemed really funny.  Right away I thought robots were cool.

After that, I discovered the Lego Mindstorms robot platform and started asking for one.  When I was eight I got one as a gift and soon after that I started a First Lego League team with some friends.  FLL was challenging, but we made it past the local qualifier and won a judges choice award against fifty other teams at the regional championships.  Through participating in FLL I started to realize that I was decent at building things, or what my dad calls mechanical engineering.

Now I'm thirteen and my interest in robots has really taken off.  I still do FLL every year, and now robot-building has become my biggest hobby.  Since I'm more interested in design and mechanics, I mainly use the Lego Power Functions and Lego Technics platforms for my experiments.  When I'm not doing homework or playing soccer I tend to build bots, and on a good day I might build several different designs.  One of my favorite things is to battle robots against each other.  Basically I think robots are awesome, and my dad jokes that I am half robot, so that's what I decided to name my blog.

I am going to use this blog to keep track of some of my creations and the thoughts that occur to me as I'm building and experimenting.  Hopefully I can help others with some of my ideas.