So, I decided to build a Pack-Bot, inspired by projects such as LNE and N-XTreme ATV. (It's the one on the right) The idea was that I could use power functions to operate the treads, and have a NXT minibot that came off the front (inspired by this project). I decided not to attempt this complex undertaking, and I built a simple pack-bot instead. I'm glad I did. The gear ratio allowed for good torque and adequate speed, while the front flippers allowed the machine to be lifted over even the largest obstacles. One of the only problem I ran into was that it could not turn itself back over when flipped onto its back - the front plate rubbed against the ground, and the flippers lacked the torque to "force" the robot back over. To fix this, I added a single beam projecting upwards directly behind the flipper motor. This allowed the packbot to like differently on its back, which reduced the load on the flippers. The other problem is that the treads also slip on their sprokets when the robot is run very hard. This might just be a result of the LEGO elements, but moving the flippers out one stud and adding a beam to the outside of the central tracks might help.
The thing on left is an exploration of the TECHNIC Unimog parts and pendulum suspension using a turntable. It is a four wheel drive truck with front wheel wheel steering and rear pendulum suspension. It is powered off two NXT motors, which power a 3-differential system that powers all four wheels. This system was inspired by victor28859's projects. All in all, I am very happy with the Unimog parts. The 3-stud differentials and universal joints make it easier to make narrower models. Also, no extra spacing is needed to comply with the TECHNIC system, which is based off of odd numbers. The portal axles are very rigid and accept different gears. The rectangular blocks allow for no slippage between the 3-stud differentials and the double bevel gears. Anyway, this model was reasonably difficult to complete, as I repeatedly dissembled the body structure, continually seeing ways to make it stronger or more compact. The only gear slippage I encountered in the drive train was between the 16-tooth gear and the 16-tooth differential gear. I fixed this problem by switching the gear ratios in the portal axles to 3:1, which reduces strain on the drive train under the same load.
Now to see which one is better!
