Jan 02

ThunderSmart IV – EV3 Rally Car

Hello! Two years ago today, I shared with you the ThunderSmart III, a fast, fun to drive RC car made with NXT. Two years later, I am today excited to share with you the ThunderSmart IV, a lighter, faster, more efficient and cooler EV3-based evolution of the ThunderSmart line. Read  to check out this awesome new ride!





This ThunderSmart focused on two main aspects, one of which was looking cool! The ThunderSmart IV achieves this first by adding the standard TS ornaments: the ThunderCharger (pic 1) on the hood, a lightning rod on the roof, red power cables and the shoulder blade (pic 2); and a front bumper borrowed from the TS III. However, the TS IV goes one step further, with a cool, muscular-looking hood and a spoiler made from the blade pieces from the EV3 set. Finally, the right balance of black, white and an accent of red make the TS IV stand out against its predecessors.




The TS IV uses steering architecture borrowed from the TS III (because if it ain’t broke, don’t fix it). However, it ditches the last car’s cool longitudinal rack steering system for a more traditional rack-and-pinion system. This is because a traditional rack system is more practical on a front-output motor like an EV3 Medium motor. In addition, this setup is less susceptible to bump-steer than the last car’s, and offers a much wider steer range, which allowed me to fine-tune the steering to my liking. The new steering system gives the TS IV superior handling and improves the fun-to-drive factor that the last car brought.




This is where the new car really separates itself from the old one. The motif here was if it doesn’t make it faster, don’t add it. The TS IV uses an all-wheel drive system, like the TS II and TS III, but this time, it is driven by two PF XL motors (pic 1). These motors spin faster and have less internal friction compared to the NXT motors. This is what gives the TS IV a huge speed advantage over the previous models (higher RPM + less moving parts + less friction = more fast!) The two XL motors route their power to the center shaft on a 3:1 ratio. This center driveshaft then spins the front and rear differentials (90 degree) on each of the axles. The AWD system provides good traction and off-the-line speed. To make the XL motors work with EV3, a Mindsensors GlideWheel-M is attached to the front of each motor (pic 2); they are motor controllers that allow you to use PF with EV3.




Though the styling and steering may suggest a lot of similarity between the TS III and TS IV, the drivetrain and especially chassis are almost completely different. The new chassis comes as a result of using the PF XL motors, and it is overbuilt and rugged; perfect for the rally stage!




There really isn’t too much exciting going on here. The TS IV’s focus on going faster eliminated a lot of frivolous add-ons, so there are unfortunately no alternative drive modes (but on the bright side, as you’ll read in the next section, it does accomplish its speed goal!). The program is a simple RC with return-to-center steering, using the EV3 IR sensor. It uses the Mindsensors GlideWheel-M blocks in place of regular motor blocks. However, I did spend a lot of time fine-tuning the tightness of the steering, something that you’ll see really paid off! Pictured is the full program.







Evolution of the ThunderSmartIMG_1153

So how fast is the ThunderSmart IV? In a word… very! I was personally surprised at how well it did. Around my 74 foot racetrack, it posted a time of 19.97 seconds, besting the TS III’s time of 25.07 sec by 5.1 seconds! It also becomes my second MOC to break the 20-second mark; Terminal Velocity posted a time of 17.02 seconds. The fact that the TS IV was closer in speed to Terminal Velocity than the TS III was really surprising. In addition, it is super controllable and consistent; all of the times were close to each other and could be easily repeated, something that can’t be said of Terminal Velocity, which is very difficult to drive. The TS IV has it all; speed, style, control and is fun to drive. Really not bad at all, considering I didn’t think I could have beaten the TS III when I started. I have included an image of all the ThunderSmarts side-by-side. I Thank you for reading I hope you enjoyed it, and I will see you next time!