Go Back to Weird Richard|
I have always been fascinated by LEGO® pneumatics! Air pumps are cool to begin with
and the ability to transfer power without building oddball gear trains is just too good to be
true. For example, I built a robot arm with a pneumatic end effector that
allowed me to shave weight off the arm. But let's take it one more step...can it be possible to
use LEGO® pneumatics to displace water and thus create a submarine? ( For an good
discussion of how a submarine works, read David Macaulay's The Way Things Work )
Time to find out.
My first problem was a gear train that would run the pump. Being a political scientist, building a gear train is an accomplishment from go! On the Martian Probe Robot Arm Project my air pump gear train was a monster that was almost as large as the turntable for the arm itself! What's an inquiring mind to do? The problem was the offset. I could never find the right distance...either the turning gear or pulley was a a little too far or a little too close and threatened to jam the works. My savior came in LEGO® BRICKS' addition of an offset axle that is exactly the right distance for the large pneumatic pump. With that piece in place, I was assured of pressure! ( What was it that Archimedes said? Oh yeah, "Any body completely or partially submerged in a fluid is buoyed up by a force equal to the weight of the fluid displaced by the body." Of course he probably said it in Greek though...) The next question was what should I use for the body of my sub? In my first experiment, I built a simple bathysphere using a Megabloks sampler box and a surgical glove. As air was pumped into the glove,it expanded displacing the water in the box and creating buoyancy! I could bob the sampler box up and down in my bathtub at will! Next, I chose a 20 oz bottle of Diet Coke® ( convenient, cheap and I was drinking one when I thought of this ) and glued a small rubber stopper into a hole I carved into the lid. ( I wanted to be able to open and close the bottle at will, and the threads on the cap would help hold the works into place. I glued both sides of the stopper with a hot glue gun and put radiator sealer on the inside of the cap to prevent leaks ). With a LEGO® pneumatic switch I was able to control the output. ( In other words, I could pressurize the sub and get forward propulsion ). With this system, I can float on command and maneuver! YES, a genuine WORKING LEGO® submarine! The next question was how can I sink on command? Buoyancy is one thing, achieving a controlled sink or negative buoyancy is another. Merely taking off the cap and allowing the bottle to flood smacks of cheating. I decided to utilize the "old" LEGO® pneumatics with the diaphragm valve and build a water pump. Would there be a solution to this using the new LEGO® pneumatics I wonder. In any case, I challenge you folk in webland to build LEGO® subs and see if you can improve my design! |
Go Back to Weird Richard