THE WAR WHEEL
Ultra-Heavy Rolling Tank
ARMOR CLASS 3 
HIT POINTS 120 (HD 20)
MOVEMENT 18 (L150 x W150)
ATTACK x2 Heavy Tank Gun (F), x2 Heavy Tank Gun (R), x5 Heavy Tank Gun (L), x5 Heavy Tank Gun (R)
MODIFICATIONS Communications, Firing Port x3 (14 Heavy Tank Guns), Reinforced Hull (x6, 0 damage from Heavy Weapons due to mass and armor), Supercharged Engine
The War Wheel's spiked exterior is made to crush and roll over enemies. It does x6 damage to objects it is rolling over and with it's Reinforced Hull x6 it takes no damage from anything less than another ultra-heavy vehicle or objects (at the War Master's discretion.) It's crew take no damage in a collision unless the War Wheel is actually damaged in a collision.
Vehicle Mishap (OWB Tactical Combat, pg 33)
Due to its gyroscopic design and size the War Wheel ignores the Roll Over result. Roll again.
If a raiding party manages to destroy the gyroscopic mechanism from within the War Wheel may fall on its side if the Roll Over result comes up.
A massive Nazi super weapon crewed by 22 men: fourteen gunners, two drivers, four technicians, a Sgt, and a Captain (Commander.)
The dreadnaught is 150' in diameter and covered in massive spikes. It is incredibly armored and can survive artillery fire. It is vulnerable to bogging down in wetlands.
The first Wheel also had another flaw: electricity. If coming into contact with power lines or other major electrical source the crew will suffer 4d6 damage, Save for half. Later Wheels were insulated against this.
If a squad can get on the Wheel and inside they can shoot their way through several levels of the goliath machine.
Another adventure would be the Allies creating an ultra-damage weapon to do full damage and the squad having to bring it, position it, attack, etc.