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.