[MOC] JCB Fastrac Two (INSTRUCTIONS AVAILABLE)

JLiu15 · July 26, 2022

Model of a modified JCB Fastrac. Features drive, steering with working steering wheel, 6-cylinder engine, opening hood, and custom stickers.

Functions/features:

Drive
Steering
Working steering wheel
6-cylinder engine
Opening hood

Instructions available on Rebrickable: https://rebrickable.com/mocs/MOC-118212/JLiu15/jcb-fastrac-two/#details

After publishing instructions for two of my MOCs, I realized that both of them would cost a lot to build if you didn't have all the pieces. My Azure Racer XL, while simple with just over 600 pieces, had the expensive and hard-to-find RC motors. My large New Flyer XD60 Articulated Bus model mostly used currently available pieces, but 5000 pieces is still a lot. Furthermore, both models used third-party electronics: the Azure Racer XL used BuWizz and the articulated bus used SBrick. Because of this, I wanted to build a medium-sized MOC that is not only functional, but can be built without potentially spending a ton of money on LEGO pieces. I thought of making a model of the JCB Fastrac tractor, but then I found something that looked even cooler: the JCB Fastrac Two. I originally started designing the model in Stud.io back in February, but got bored of it after a few days. I did not make any updates to the model until May, which was when I got into designing the bodywork. I finished the digital model in early June, and built the physical model over the past few weeks. Thanks to already having worked on the instructions along the way, I was able to simply follow the instructions I made while building the physical model, allowing me to finish this model much faster than some of my other ones.

Some information on the JCB Fastrac Two: it is a modified JCB Fastrac tractor that is built purely for speed. It is the world's fastest tractor, and more information on the original JCB Fastrac Two can be found in this video. While the real-life JCB Fastrac Two is the world's fastest tractor, my model was not intended to break any LEGO speed records. I decided to use the Control+ system for this model, as the system is widely available and I can keep the model 100% LEGO. The model is powered by two Control+ L motors sitting above the rear axle. The chassis essentially consists of two halves with the hub in between, with the whole structure reinforced with longitudinal beams. The placement of the hub allows for easy battery access, and the hub is turned on via a hidden switch by the driver's seat. Steering is controlled by a Control+ Large Angular Motor (the one from the 42114 set). I preferred it over using a L motor as it has more torque, and it just feels more suited for steering operations to me. The rack and pinion setup is placed sideways, with transverse reinforcement for the rack. My initial setup was prone to skipping at either end of rack's range of movement, but moving the transverse support closer helped eliminate this skipping. Additional gearing from the steering mechanism connects it to a working steering wheel in the cabin, and the drive motors are connected to a 6-cylinder fake engine in the front.

My plan was for this MOC to be a primarily Technic build, with System pieces used where needed. However, the model still saw a fair amount of System detailing, and it has nearly 90 half pins (not including the new friction ones), which goes to show the amount of System pieces that went in to add additional detailing. The cabin area of the bodywork was largely straightforward, with most pieces connected at right angles with an occasional slanted or curved section. Modeling the hood and fenders were more challenging, as these parts have much more of a curvature. While I'm not totally satisfied with how some of these parts turned out, I was able to model the design digitally before physically building it thanks to Stud.io which eliminated the need for trial and error. After finishing the build, I designed custom stickers for the model which were printed on opaque sticker paper at Staples. The paper is very good quality (beats the label paper I started out making stickers with), and is easy to apply to LEGO pieces.

As for the performance and functionality, the model is decently fast for a Control+ model. It isn't crazy fast (e.g. RC motor/BuWizz speeds), but is fast enough while not straining the drive motors. And while there are only two independent controls (drive and steering), I feel that the fake engine and working steering wheel really gave the model something extra. Mini piston engines (the ones made with half bushes) are always satisfying to watch, and the rattling noise when running is pretty nice too. I feel that there could've been a better way to open the hood that did not require a prop (e.g. a locking linkage), but there wasn't as much space to install a linkage mechanism especially with the fake engine occupying the space right under the hood.

Overall, I'm pretty satisfied with this project. Although I quickly got bored of this project after starting the design in February, my interest quickly rebounded after I got back to working on the instructions in May. Some parts could've been better, such as the hood and fenders, and I feel that the model could've gone a little faster. Still, the model isn't exactly light, and achieving a higher speed probably would mean compromising on some parts of the build.

Video: