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Already two years ago, I got inspired at defeating steep hills with the LiteJeep. That could already beat 50 degrees, but because of its high riding height (good for offroading) and relatively heavy PF L motors, I reckoned there would be more irons to put into the hill-climbing fire. Very important things for hillclimbing are sufficient grip, huge power and a low weight. Weight ultimately gives more grip, but it also causes the vehicle to flip earlier when it is located above the center of gravity. With these factors into the equation, I decided to create a vehicle with loads of grip, so with 4 rubber tracks, and with articulated steering to make a sturdy connection between right and left possible, which is essential for climbing: when any vehicle is climbing, the suspension does unexpected things, so a stiff frame and suspension setup are required. Lightweight design requires a low complexity too, so that is why articulated steering is chosen. Having a front and rear part to let the vehicle adjust its shape to the terrain is an option I used several times in my rubber-tracked vehicles. This is the first vehicle in which I used the maximum footprint instead of the triangular form, again for maximum grip. Please note that, when you choose for the sturdyness and simplicity of articulated steering ánd want to let it adjust to the terrain, the middle joint becomes very complex as it contains joints in two axes! There is always a place where pain comes back. The Law of Conservation of Pain holds here.. In this case, all the trouble was in the difficult joint, which took about 5 hours alone. Then for the power: initially an XL motor was used in the front, but having a driveshaft through the already complex dual joint proved to be impossible. And then the idea came. Why not generate the power at the place where it is needed? Why not, if there are two separate parts, have some powerplant in both front and rear? But then there was a problem: I have a very large project in which all my three L motors are used. This pushed me in the direction of using M-motors, which proved out to be a very good forced choice. Combined with the lightness of the overall model, they proved to have ample torque left with a 3:1 gear ratio, having enough torque to keep the four tracks spinning all time when grip was lost. This is amazing, and you can see why Lego has put two M motors in their latest Tracked Racer. But the limits of that thing are way lower than the Quattrack's limit. Using two PF medium motors for drive and one for steering, this one of my very few (and maybe the last) Lego Technic MOC with only 2006 components. The Sbrick will throw all range headaches away and have much less delay than the stone-age PF IR remote it is replacing. Why did I use such standard power functions components? The new PF servo is slow and quirky, a medium motor allows for much more smoothness in steering. Moreover, if you are driving at steep slopes like this, it asks all your concentration to keep it on the move. If you cannot feel where the remote control knobs are (The intrinsic problem of the Sbrick) the vehicle will fall of before you've compensated. So the old system proved to be the best system in this situation. The articulated joint actually contains 3 joints, to have a suspension force on it in both directions: up and down. That is why there are rubber bands and one shock absorber. By the way, also the steering joint is included. Now, because the front and rear part of the Quattrack are relatively conventional (no steering nor differentials), all the pain of good and accurate steering is shifted to the design of this central joint. I dare to state that the success of this vehicle relies for a big part on this 2D joint. In the video, the operation is explained. On this photo, it looks as if the ground clearance is half a stud. This is not the case; in fact, it is over 1 stud. The underside is very smooth, which helps the low superstructure to glide over obstacles. Because of the weight saving, I designed it to have very clean looks. Styling means more weight. However, I managed to squeeze in some little details like fake cabin flashing lights, front lights, rear lights, cabin seats and a steering wheel. The reason why I did this, is that I wanted it to be a possible real-life vehicle as well, not just a scientific experiment. Adding weight is bad for climbing ability, so I tested the Quattrack also with the cabin removed and say what !!? The climbing angle was the same. This front look shows all that. The Quattrack contains everything, but nothing more. You do not need a zillion pieces of Lego to break records. Only 556 grams of it is sufficient in some cases. The video is the proof of all my theories... [media] I have not put all text and photo's on Eurobricks. More is to be found on Brickshelf and MocPages. If you like my video's, you might want to take a look on my YouTube channel.