[MOC] Red Beryl T (Trophy Truck) (INSTRUCTIONS AVAILABLE)

JLiu15 · August 13, 2023

A motorized trophy truck model controlled by BuWizz. It is propelled by two RC buggy motors. Features drive, steering, full suspension, and working headlights.

Functions/features:

Drive
Steering
Full suspension
Working headlights

Instructions available on Rebrickable: https://rebrickable.com/mocs/MOC-156104/JLiu15/red-beryl-t/#details

This is a MOC with an interesting backstory. I first decided to do my third MOC in the Red Beryl series (after my Red Beryl GT in 2018 and AWD supercar Red Beryl X in 2019) in late 2020 shortly after my first MOC featuring BuWizz and RC buggy motors - my Azure Racer XL. Unlike the finished model, my first attempt used CLAAS Xerion tires and had the RC buggy motors in the chassis instead of having the wheels directly attached to them. I don't recall exactly, but I even included a two-speed gearbox in the model thanks to the inclusion of a drivetrain and differential from the motors. The model turned out much larger than anticipated, meaning the bodywork would have to be very large as well. Given the model was already performing below my expectations, I decided to abandon the project...until two years later.

I knew a good first step would be to use smaller wheels, and the spiky treaded tires from the 42124 and 42126 sets seemed to be a perfect fit for a trophy truck. The rear suspension is similar to that of my Azure Racer XL (it even retains the same basic geometry), although it is a solid axle this time instead of the left and right wheels being independently suspended. However, the suspended section is longer on this model, providing a softer suspension with more travel. I guess the shock absorber setup here is not the most realistic for a trophy truck (as most trophy trucks I've seen have their rear shocks more or less vertical), but the suspension setup nevertheless performed well. The front suspension is a typical double wishbone setup with the entire front axle tilted 10.8° for positive caster. Because the front and rear shock absorbers sit approximately half-compressed while the model is on the ground, it did impact the front ground clearance a little, although it was not really an issue when I tested it. The BuWizz unit is located directly in front of the rear axle and is placed low in the chassis to lower the center of gravity. The two RC buggy motors are each connected to its own BuWizz port (as recommended by BuWizz), with another port used for the PF Servo motor for steering. Because there is one port left on the BuWizz unit, I added two pairs of PF LEDs to the headlights. Thanks to the BuWizz speed settings they can shine brighter than when powered by a PF power source, although in my video I did not film it with the lights on as I did not want the BuWizz to cut power from the drive motors.

Designing the bodywork was surprisingly challenging. I wanted to stick to pieces I already have as much as possible. The choice of wheel arches/fenders was easy - I used the black arches from the 42126 set paired with fenders from the 42125 set, adding some much-needed curvature to the model. The hood was also straightforward, as it is comprised entirely of 3x13 curved panels. Because the front axle sits at an angle for positive caster, I attached a front bar to it that allowed for an angle normally not achievable with angled connectors. I tried to avoid blue pins as much as possible, using red or gray pins in place of them. The doors were more challenging and it took me a few tries to get the desired result. I wanted to ensure the doors stand out from the rest of the model, but too much curvature looked weird. I went with a design where they slightly recess into the model. The section between the doors and rear fenders was perhaps the most difficult, as it needed to provide a transition from the relatively flat doors to the curved rear fenders. I went with all curved panels and liftarms for this area. I did have to order some new red pieces for the bodywork, namely the curved 1x2 and 3x2 panels at the top edge of the doors and the red 2x3 and 2x5 liftarms in the section between the doors and rear fenders, but the bodywork still mainly consisted of red pieces I already had. System pieces (tiles and curved slopes) are used to fill in the gaps in these areas. The roof was a simple build, although securing it was a bit challenging as it had a tendency to tilt forward. I had to experiment with the A-pillars a little bit but settled on a setup with 7L flex axles. The rear of the model is left rather unfinished to reduce weight, although that is pretty typical of real-life trophy trucks, and the single spare wheel in the back provides just enough weight for the front and rear axles to sit at similar heights when the model is on the ground.

The model performed pretty well, and the two RC buggy motors gave it plenty of power. I had wanted to drive a fast off-road MOC at a skate park for years now, and this is my first MOC that I filmed at a skate park. It was fun seeing the model drive up and down the slopes, although it still lacked torque to completely drive over the smaller slopes. I had to be careful with letting the drive motors run at full power as in the Fast and Ludicrous speed settings (or even Normal sometimes) the BuWizz would cut power to the motors when overloaded. Accelerating from a stop on Ludicrous mode was pretty much off the table, although I was able to switch into Fast mode after accelerating on the Normal setting. Two RC buggy motors with their inner outputs geared 3:1 was good for fast driving and small obstacles, although more torque and traction are needed to overcome larger slopes/obstacles.

Overall, I'm quite impressed with how this model turned out. Despite having more than twice as many pieces as my Azure Racer XL model, the performance did not suffer much and I had a lot of fun driving it around at the skate park. The suspension is also satisfying to watch, as the model can "float" over obstacles with both the front and rear shock absorbers approximately half-compressed when the model is on the ground. Compared to my first attempt at the model two years ago, it shows that the ideal approach to such fast RC buggy motor-powered models is not to build big, but just big enough to achieve optimal performance.

Video: