I specifically chose not to use pneumatics, to make the model totally free with no hoses connecting the model to the remote (as with my previous Backhoe Loader). Since the power functions-system only has 8 channels, I had to include a remote-controlled gearbox that swithes functions of 2 motors to achieve 9 funtions (5 + 2x2). Besides the motorized functions, it has a pendular front-axle and PF-lights on front and back.
The Power-Puller wheels were the largest wheels I have (and exist as far as I know of), so they were te obvious choice for the rear wheels. These wheels are too wide, resulting in a model which is too wide and a central chassis of only 9 stude wide. There was very limited space inside the body to put in all the functions. The batterybox was placed under the hood, and as much motors were places outside the chassis as much as possible. 2 motors are inside the backhoe and 2 other motors were placed at the sides. The model turned out quite heavy, too heavy for the wheels, but driving still worked.
The gearbox switches functions of 2 motors. The red lever on the remote switches between operation of the front loader and the backhoe. This way, operating the model is quite intuitive. I used Jason Railton thumbstick to operate the backhoe & the loader. It was combined with the steering wheel I designed for my small racecars.
Moving up and down the backhoe turnded out quite slow. I had to use an M-motor inside the chassis, there was no place for an XL-motor anymore. The driveshaft goes through the gearbox and through the turntable. The weight of the backhoe caused quite some friction, so some gear reduction was neccesary to prevent overloading the M-motor.
This is fantastic. I would really love to build this, but am just starting to get back into Technics after 15 years.
I'm already planning on using your mods for the 8043 excavator set.
Would you be willing to turn this into a set of instructions with bricklist / set numbers? I'd be willing to purchase the instructions.