The motor grader. For me the quintessential Lego Technic challenge.
About this creation
(Built late 2010. Still in one piece.)
Focus here was to create a motor grader with a function that was as authentic as possible.
So I've used three linear actuators in sync. Two main ones to drive the blade up and down, and a cross actuator to maintain the stability of the resulting parallelogram. This cross actuator is synchronised to the left main actuator to ensure the blade remains level when it moves up and down. See below for a detail of the mechanism.
All functions apart from the pneumatic are controlled from the back of the vehicle. HOG steering is from the top of the cab. The black gear wheel behind the cab turns the blade. Both these functions travel down the length of the long thin body over the blade.
The two red levers switch the actuators on and off via clutches. They are driven by PF.
Pneumatic functions are two fold: Lowering and raising the front ripper, and shifting the blade left and right, an authentic function which helps ensure the blade stays roughly central despite turning from one side to the other. Pneumatic functions work well here where precision isn't essential.
I was happy with the amount of functionality and it's authenticity, but perhaps this ended up driving the whole model so much that the look is a little out of proportion. The whole scale is driven by the central blade mechanism which means the wheels now look a little small. Unfortunately I don't have enough of the bigger wheels!
The vehicle is also quite big which makes it a little floppy and puts too much weight on the front of the two aft wheel axles. So much so that I've made a little stand to ensure the axles don't bend out of shape when it's stood on the top of my book case.
The other problem with the MOC is that the linear actuators require a very long gear chain which means I had to power down to enable my available small motor to drive it all. So it's quite slow. The actuator mechanism is a bit floppy as well. Take a look below and you'll see that the actuators hang some way in front of the cross beam.
But hey, it does all work!
So here's the main blade mechanism.
Red gears show the right actuator synchronised with the cross actuator.
And here the left actuator operates by itself.
So both together lower the blade in a level fashion, and then one or the other adjust to the required angle.
In the end I was pleased with the extent of functionality, though I think I may attempt a smaller, simpler Motor Grader MOC with a little compromise on functionality in the future.
Quoting Jacob Fritz
Wow!This is pretty slick. How long did I it take yo to make this?
Thanks! It was 2 or 3 months. A week or so of research to find out how the real mechanisms operate and then some weeks trying out different approaches to mounting the actuators and getting the power to work. The rest was relatively quick.