A old MOC from early 2009 (now dismantled). That's some time before Lego offered their own hook loader model. I like to think mine was something of an inspiration for them, after I uploaded it onto their site gallery.
About this creation
The motion of the container is PF driven but close to authentic in terms of motion. the arms pull the container up and then it translates nearer the cab a little.
Look is ok. Standard Lego Technic style. My emphasis was on the functionality.
Now a close up of two features:
Four wheel steering at the front, achieved using different sized gears to drive the racks.
Then here's the hook loader mechanism that took me some time to sort out.
Linear actuators are driven by the PF motor. They pull the hook arm round and the container onto the back of the lorry. At the end it comes down onto the yellow cog that is also driven by the PF motor. You'll see a chunky rack formed in the bottom of the hook arm. When this engages with the yellow cog, it starts to translate the container further forward. As it does so it also flicks the red switch just visible in the picture, which disengages the linear actuators via a clutch. Works the same way when the container is unloaded.
The container is heavy and I only had a small motor at the time so I had to gear down a lot to get the power which means the motion is slow. This caused a little issue at the end of the linear actuator travel where the rack engages with the cog. Here a faster motion is needed to switch the linear actuators off quickly. It was a balancing act to get it right. If I did it again I'd use an XL motor and perhaps play with the links to try and fine tune the motion.
You'll note also that the motor is mounted on the side which leads to an odd power transmission. This was necessary because I didn't have a PF extension cable at the time and so had to mount the motor near the battery!
All in all, when I made it, I took it as my first real Technic success of latter years.