[MOC] Rock Crawler Jesse Haines Moon Buggy with RC Electronics

gyenesvi · 2025-11-22T12:45:33Z

Hi Everyone!

This model is long overdue, it's been sitting on the self for a while, and I'm happy that I can finally present it to you! I've always liked proper rock crawler buggies for their extreme capabilities (both in real life and RC models), so I wanted to build one for a while. I believe some of the best ones are made by Jesse Haines, they are race proven, they look cool, so I decided to attempt to build one of those, with as good performance as possible, and this is the result. Let the video speak for itself!

Features

Highly articulated 4-link live axles with fake portals
RC electronics: Injora MB100 ESC, LiPo battery, RC transmitter/receiver
Two buggy motors inside PF L motor housing for drive
GeekServos for steering on both axles
Low center of gravity, good weight distribution

Design process and details

For a real version to model, I quickly settled on the one raced by Jesse Haines for a while, and more recently by Dave Wong (although I just saw a few weeks ago on FB that the buggy is on sale now). Here's a good picture of it, and here is a very good video overview of it by Dave himself.

The main challenges of building it were the following:

what electronics to use for proper precise control,
how to build a the massive 4-link suspension and portal axles
how to build a (small) light tubular looking body in a stable way

Axles and suspension

As usual, I started thinking from the axles, as those are the most critical part. Lego currently does not have good solution for portals (the existing ones have awful steering properties and also leave little room in the middle of the axle for mounting links and shock absorbers, so that was a definite no-go), but luckily @Attika's axle design comes to the rescue (mounting planetary hubs with slanted lower A-arms and driveshaft), as they raise the axle by one stud, contain a down-gearing by the portal hub, hence I call them fake portals.

Furthermore, I have previously used these axles in my Toyota Hilux Truggy with GeekServos mounted to the axles, and those seemed like the perfect option here (the real buggy's axles also have servos mounted directly on them): they provide a strong and precise solution, while still leaving some room for mounting the links. So I settled for RC electronics, along with the custom PF L motors that I have borrowed. However, the Toyota's axles used 9L links and 9L shock absorbers, and I knew those won't cut it here, simply they would not be long enough.

As for lego springs, their travel is quite limited for such large articulation, especially as it needs to be fixed far out on the axle, but I also faced another puzzle of the real buggies. At first I did not understand how is it possible that they sit very low, yet they can articulate sooo much. I realized, that those shocks are air filled (and adjustable) and what's probably happening is that they are very soft, so that they sit in almost completely, and the wheels mainly articulate downwards from the base position (instead of up, as usual). I thought this is kind of fortunate because it could be nicely modeled using long pneumatic cylinders, which have a lot of travel. My first attempt was to fill them with a bit of air, adding complete tubing with switches and a small pump to the model. However, the system was a bit complicated, always leaking some air and never really leveling up properly on all 4 wheels. So I decided to try and just get rid of the tubing and the air, and let the model sit completely on the cylinders and only articulate outwards, the cylinders only acting as dampers for the movement. And this worked surprisingly well, simplified the build substantially, so I kept it!

For the links, the only option was to build them from parts, but then, triangulation becomes more difficult due to needing to add degrees of freedom to their movement, which makes things clunky and collide with other parts. I experimented a bit with aggressive outward looking lower links, but it just did not fit nicely, so I just decided to keep the lower ones almost parallel (the mounting of the ball socket providing minimal outward direction), simplifying the mounting at the chassis end, and only triangulate the upper ones aggressively.

Drivetrain

In the real model, the motor is placed on the back, all the front is kept for legroom and visibility. The transmission is routed on the right, while the seat is on the left. So I aimed to keep this layout, I wanted to keep the space for the seat. The two L motors (with the buggy motors swapped into them, same I used for the Hilux) went to the rear, while the front was a good place for the battery to balance out the weight. The only slight difficulty was the routing of the driveshaft with the right gear ratio, in a way that it leaves room for the seat low enough. In the end, this is what worked:

The differential is locked in the form of a 12:20 gear ratio, leading to the planetary hubs. This way the final speed/torque ratio is very good because the model is very light compared to the Toyota. Furthermore, it's center of weight is very low, hence it is very stable.

Here is the core of the complete chassis:

Bodywork and interior

As for the rest of the chassis and bodywork, this time I kept it simple and stable, didn't aim for complexly angled tubular structures, just decided to use beams and the paneling itself as the main structural elements, and throw a few angled parts (like those F1 suspension arms) mainly for enhancing the looks. The seat itself is a detailed one (borrowed from my previous rock bouncer), and there's minimal cockpit design with steering wheel and gear stick, but the other half of the cockpit is occupied by the transmitter and wiring, while the ESC is on top of the drive motors for easy access to turn it on. Actually, the usable space is quite small compared to the overall size, because, well, it's all about the huge wheels.