This series of magnificent machines and balmy bodgers has culminated to this cacophany of wild welding and great grinding. The NERDS have built a submarine and a steam-powered car to get them into the final. The Brothers In Arms created a bridging machine and a giant mower for their berth in the finals. It all comes down to this, the rare "double machine"...a fireboat. The machine they build must be sailed across a lake, pump water onto a fire, run and grab a flag then sail to the finish line.
 

We've seen boats before, so I won't go into detail about bouyancy and how things float. What is interesting in this challenge is the water pumping systems. The Brothers in Arms will be building a jet-pump. It works by filling up a tube with water then using a piston to push it out of the nozzle. The concept is similar to a Super Soaker water gun.

The NERDS will be building a much more sophisticated pump using impellers. A centrifugal pump operates like a washing machine's spin cycle. Water is flung against the wall of a cynlinder that has a spinning disc with impellers (basically, fan blades). The water is flung around the wall and out of a nozzle.
 
 
 

The Brothers' expert is Ian McCrae	Helping out the NERDS is Steven Riley
This diagram shows better how the NERDS centrifugal pump works	Ooh! That was almost nasty.
This van roof will be the Brothers' boat	This Rover, which crashed into the set wall, will float the NERDS dreams
The judge this week is Jerry Lennents	Uh guys? Your Rover, stripped down weighs a metric ton and a half
Col. Dick makes a precision adjustment to that engine with a sledge hammer	This is the rear half of an "abbreviated" Range Rover
The inner workings of an engine	Robert lends his expertise
Jeff, you're a cut above the rest	The floats get attached to 'Major Leak'