Technical LEGO: Motorized 1:8 Lamborghini

This 1:8 LEGO Lamborghini (set 42115) was motorized as it was built. This meant giving up the passenger seat and the V12 engine and its cool decorations, but small price to pay for an RC Lambo! At 3.0 kg, the final result is reasonably fast and agile for a LEGO RC car. But like most LEGO RC vehicles, it's quite slow by hobby shop RC car standards.
Added motor and RC components:
1. Drive motors: Twin LEGO L motors in the engine compartment
2. Steering motor: LEGO servo (stepper motor) in the front compartment
3. RC receiver: SBrick Bluetooth receiver (www.sbrick.com) in the passenger compartment
4. Battery: 7.2V LEGO rechargeable LiPo in the passenger compartment
5. Control interface: Custom single joystick running on an old Android phone within the SBrick app.
After reviewing several different motorization solutions on CZcams, I decided to base my own on • [RC Tutorial] LEGO Lam... on the BrickYourDream (BYD) channel. After building the BYD drive and steering motor modules from the video, I switched to the official instructions. At the appropriate steps, I then adapted the modules to the build. Took a lot of page-turning to determine exactly which steps, but I eventually figured it out.
Except for color choices, the steering servo installation deviated little from the BYD video. But the drive motor installation took a good bit of fiddling for 2 reasons: (1) Didn't have the large Technic frame BYD used to mount the twin L motors, and (2) the gears connecting the drive motors to the drive train initially skipped under any load.
To make matters worse, I put the front differential in backwards. This made the front and rear wheels turn in opposite directions in every gear.
Solutions:
1. Redesigned all the BYD drive motor mounts.
2. Recruited unused chassis pin holes behind the seats to keep the skipping gears from separating under load.
3. Disconnected the front wheels from the front differential by removing their axles.
The last step effectively converted the model from AWD to RWD. It also turned the forward center console shifter position into another neutral, so the car could only be driven remotely with this shifter in reverse (all the way back).
Bummer, right? No! All that turned out be good for performance. The 8 forward speeds and AWD functionality add =tons= of friction and backlash to the drive train. But connecting the drive motors to the rear wheels through the much shorter and simpler reverse gear train eliminated most of those losses. And the single reverse ratio turned out to a very good match to the twin L drive motors.
The official instructions are generally easy to follow with only a handful of omitted steps. However, I have 2 big gripes about the instructions, and the supplemental online materials are no help:
1. Nowhere is there an explanation of exactly what the 3-position center console shifter does. (It selects between the 8 forward speeds, neutral, and reverse gear.)
2. Nor are there any clues to help you tell which of the 8 forward gears you're in.
Overall, quite happy with both the performance and the looks now that all issues are resolved.
Music: From Beethoven's 5th Symphony, artists unknown.

[@justingidman1684]

≋p≋r≋o≋m≋o≋s≋m 🙂

[@JeremyMcCrearyTechnicalLEGO]

Sorry, don't know what that means, but it looks cool!