Range Rover III
Simple 4×4 off-roader built to test a new transmission design. Features two a 3-speed remotely controlled transmission that can be shifted while driving and lights.
Datasheet:
Completion date: 26/04/2020
Power: electric (Power Functions)
Remote control: SBrick
Dimensions: length 51 studs / width 24 studs / height 22 studs
Weight: 1.597 kg
Suspension: pendular axles
Propulsion: 2 x PF L motor via a 3-speed gearbox with ratios from 21:1 to 8.4:1
Motors: 2 x PFL motor, 1 x PF M motor, 1 x PF Servo motor
Some time ago I’ve repurposed one of my transmission designs to work with the selector pieces from the LEGO 42083 Bugatti Chiron set. It made the transmission smaller and simpler, but there was still the question of shifting it remotely. As an experiment, I’ve tried using a PF Servo to shift the transmission, which meant abandoning one of the available speeds (something that may not be needed with Control+ motors if you make them rotate 90 degrees). This entire model was built as a test bed for the efficiency of such a transmission design.
The transmission has taken most of the available room in the chassis, hence the limited functionality of the model. To make room for the transmission, I’ve actually placed the propulsion system – two PF L motors – under the hood, which also helped with moving the weight forward. A single PF M motor controlled steering, while a PF Servo motor shifted the transmission. The suspension was built around two simple pendular axles, with 2 shock absorbers stabilizing each of them and with an empty differential transferring the steering over driveshaft to the front axle. I’ve decided not to add any form of winch because of how many elements were packed in the model’s front end already. The wheels were equipped with RC4WD Rock Crusher M/T 1.2″ tires which offer superior traction to LEGO tires.
The body was a simple thin shell built with SNOT technique to make the sides curved and it had no opening parts whatsoever for two reasons. First, it would have compromised the integrity of the body, as the Range Rover’s doors traverse the entire height of the body, and second, the rear doors go far above the rear wheel arch, and I wanted to keep the wheel arch nicely rounded using a single-piece brick with arch. This didn’t allow to split the wheel arch into two sections, one opening and one fixed. The front wheel arches were built in the same way and they were colliding with the front wheels when turning, which is a common problem with portal axles. I’ve chosen a clean look with a minimum amount of accessories, a simple roof rack, and a spare wheel tucked away behind the rear axle.
I really didn’t like the way the finished model looked – it appeared crude and not like the real thing. The real Range Rover III has simple, boxy shapes, but there are subtle curves involved too, and apparently when these curves are ignored (partially because of small scale and partially because of the front suspension’s frame sitting directly behind the front grille with no room to spare), the authenticity of the model suffers. As for the performance, the transmission worked flawlessly and proved reliable and easy to use. No matter what was happening with the model, I was always able to easily select the speed I wanted, whether the model was driving or not, whether on an obstacle or on a flat ground. The transmission didn’t seem to have any problems when stressed, although once or twice the selectors weren’t rotated precisely. Which was easily fixed by simply re-selecting the desired speed.
All in all, the Range Rover was a success as a transmission design test, but failure as a model. It looked ugly, it lacked authenticity, and its performance suffered because of the steering limited by the wheel arches, low ground clearance, large rear overhang and open differentials, which were a serious problem on sand. Then again, I suppose many of these problems were inherent in the real Range Rover III’s design.
