RC CAR | BMW E91 | SCALE 1:7

This is my biggest project so far – a 1:7 scale RC BMW E91.

I really like RC cars, both commercial and DIY ones. But many of them use a lot of bought parts, and that leaves less room for your own creativity. Maybe it's just my opinion. So I decided to build an RC car that is mostly 3D printed and uses very cheap parts. The finished car is 645 mm long.

Even though I used low-cost components, I still wanted the car to perform well. I think I managed to do that, and now I’d like to share it with you.

Let’s get straight to the point:

You’ll find all the instructions, videos, and files in the attachments or linked online. If I forgot something, just let me know and I’ll try to add it as soon as I can.

You’ll need the following to build the car:

• 160x M2.5 8mm Screw

• 120x M2.5 12mm Screw

• 30x M1.6 5mm Screw

• 25x M3 x 20mm Screw

• 4x M4 x 20mm Screw

• 50x Nut M2.5

• 20x Nut M3

• 4x Nylon Lock Nut M4

• 4x Washer M4

• 5x Compression Spring, length: 25mm, wire dia: 1mm, outer dia: 12mm

• 2x Compression Spring, length: 25mm, wire dia: 0.7mm, outer dia: 12mm

• 3x 18650 Li-ion Battery

• 12x 10x15x4 Bearing

• 4x 17x26x5 Bearing

• 1x BLDC 3530 1400KV

• 1x Bidirectional ESC 50A

• 1x 3S 1A Li-Ion Battery Charger

• 1x 3S Balancer (do not use protection part of this module, wire power cables directly from battery pads OR use different balancer)

• 1x 20Kg 180º Servo

• 4x Connector XT60 (2x male, 2x female)

• 50x Stainless Steel Ball, dia: 5mm

• 1x Arduino Nano

• 1x NRF24L01 module

• 1x 220uF 10V Capacitor

• 1x 1000uF 16V Capacitor

• 1x Prototype Board

• 1x Pin Header 2.54mm

A bit about how it was made:

Before I started this project, I had the idea to make my own RC car using my 3D printer. I own a real BMW E91, so the model was an easy choice.

I also wanted the car to be as cheap as possible. I know DIY projects can sometimes get more expensive, but for me, the process is the fun part. I also enjoy working with electronics, so I made some of the electronics myself instead of buying everything. I used a lot of cheap modules, mostly to save money.

You can find some of my other electronics projects on my profile – like rc transmitters and battery holders. They can also be used in this build.

One of the biggest savings was making my own tires. I used black silicone that you can buy in a regular hardware store. Store-bought tires didn’t match the look of my specific model and were also quite expensive. I made one tire for less than 2€, and the grip is surprisingly good. The process is a bit tricky, but it works great. If you don’t want to do it this way, you can also 3D print the tire from TPU and press it onto the rim.

Another way I saved money was by using only springs instead of full shock absorbers. I know dampers are useful, but in my case, the springs worked fine. It’s just my opinion, but it helped keep the cost low.

The car has both front and rear wheel drive. I didn’t use a differential because I wanted the car to drift better. For me, it drives more nicely with all wheels connected directly, but if you prefer, you can easily disconnect the front-wheel drive.

The whole car (shell) was printed in a single color. I don’t have a multi-material printer (AMS), and I didn’t want to spend extra time splitting the model for color printing. So, I added some color details by hand using a tire marker. A regular marker doesn’t work well, because the material absorbs the ink and it smudges. Some people will like the painted look, some won’t – and that’s totally fine. You don’t have to paint it like I did. One of my friends even said it looks like I let my kid do the paint job 😄 Fair enough – I get it.

The entire model is printed from PLA. I didn’t use any special materials. Some parts are reinforced either by adding walls or increasing infill.

I also adjusted the models so that most parts include built-in supports where needed – this should save you time. The only exception is the front bumper, which has no built-in supports. I used automatic tree supports for that part.

And yes – because it’s a BMW, repairs are not easy (just joking 😄). There are many ways I could have made the design simpler. I still have new ideas for improvements. But compared to my first version, this one is much better. It held up well even in tough driving. I even crashed into my real car at the start of the video (you’ll see it), and filmed the rest after that crash. The RC car survived! I was surprised too 😄

This project took a lot of time, and I spent many days and nights working on it.

I really hope you like it. Big thanks to my amazing and patient wife for all the support. And of course – I’d love to hear your feedback. Any ideas or criticism are welcome. That helps me learn and get better.

Enjoy the build – and enjoy a real DIY project! 😄

Updated with improved drive shaft

The old shaft kept breaking and its assembly was quite complicated. That’s why I designed a new drive shaft – it’s much stronger, doesn’t break, and the assembly is far, far simpler. I printed it directly in PETG, and it works great. The updated files are now available for download.