It's the final semi-final before the final. Got that? One of the two teams competing, The X-tinguishers or The Cat-alysts, will be in the grand final. This mission involves building a machine to break our teams out of prison. They must build a machine capable of boring a hole atleast 2 feet in diameter through two different type of concrete. The first is regular cement. However, the second wall is made of cement and large aggregrate stones mixed in for extra toughness. The first team to bore through wall number one, get their teammates through the hole, bore through wall number two, get the teammates through the wall, dash across the yard and climb through a fence into their build area is the winner.

The Cat-aylsts want to use a 4-wheel drive for their Tunnel Boring Machine (TBM). The plan is to disengage the rear axle and use that drive shaft for their drill bit. The front wheels will provide the propulsion. It's a very simple idea but, will it be too much strain on one engine?

The X-tinguishers plan on putting an engine onto the back of a truck. The 2nd engine will power a hydraulic ram that will provide torque and will allow them to pus their drill into the walls. Hydraulics work by forcing fluid into one end of a cylinder that pushes a piston forward and tremendous pressure. However, can the X-tinguishers find two working engines on the scrapheap? What about the misearble success rate of hydraulic machines?

Four hydraulic machines have been built and none of them have won. I know what you're thinking but the Miami Gearheads' hydraulic wall basher didn't work...they just ran their truck into the wall to knock it down. Their hydraulics failed them.

The X-tinguishers Expert
Bill Lloyd
The Cat-alysts Expert
Andy Weatherall
The Cats want to build a simple
driller using the rear drive of a four
wheel drive truck
The X-tinguishers are building a
complex hydraulic TBM
This is the real deal, used to tunnel
a portion of the Chunnel
The Cats hope this Austin Gypsy
will power their TBM
The X-tinguishers hope to ride
a Ford F150 to victory
Unable to use the Gypsy to provide
torque to the TBM, they weld a
second truck to the front
The judge this week is
Trevor John
Can the X-tinguishers use this
massive hydraulic system?
It will but they need this beam, part
of the set, to support it
Look out! I hope there wasn't
anyone back there
Those hydraulics have a leaky radiator
Are they serious?!
This coupling between driveshaft
and driller is crucial...
...as is the strength and position of
those hardened steel teeth
The X-tinguishers are using a 2-stage
cutting head. The first will act as a sort
of pilot hole
Gotta hate the daily grind...
One hour teams. One hour remaining
The business end of the Cat's TBM
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