this is my latest truck, a DAF XF 105. I liked my black one so much I had to build a bigger one. The tractor is fully remote controlled and has working lights. The truck and trailer both have full suspension. The trailer has steering that works with a push bar that couples to the fifth wheel to steer the axle and the sides of the trailer also fold down. The crane was a challenge to build as well, I basically had to take all the features of the 8292 cherry picker and fit it in a space about the size of two battery boxes. The gearbox the motor and selector switch. the crane slides on rails in the trailer bed and has full power functions. The boom goes up and down and can traverse 360 degrees. the boom also extends, but not with power functions. The drive train and steering had to be over built because the whole truck weighs about 8 pounds, five for the trailer and three for the tractor. I had to use two clutch gears on the steering, because the weight of the truck causes a single one to slip, I also used knob wheels where ever possible. I also had to install stiff springs on the rear suspension, because when the truck accelerated the suspension would squat down causing the truck to accelerate more slowly and to support the weight of the trailer.
I knew I should have put an explanation on that picture. its the push bar that steers the rear axle. the the its based the chereau trailer steering design. the axle that gear is on is also the kingpin, which locks into place in the center of the fifth wheel. as the trailer pivots around the fifth wheel that the push bar remains stationary while the rear axle moves with the trailer, thus steering the axle.