BeeRotor u130 UltraWhoop Micro Racer
BeeRotor u130 UltraWhoop Micro Racer

In this article, I walk through the iterative design process of building my ultimate micro racer. I took a BeeRotor u130 and custom printed some parts (links below) to turn this into a bigger, faster TinyWhoop that I'm calling the UltraWhoop. Here is is next to it's smaller counterpart, the eWhoop.

I went through many iterations of this project, first building it with the u130 part kits, then with the ducts and a OMNIBUSF4. I tried a Spektrum satellite receiver, then the FrSky X4R SBUS. Normally my blog posts are much more focused, but I'm leaving this one as is, since I hope it will help show some of the iterative design process.

This guide will focus mostly on the customization of the u130, using custom 3d-printed parts. I'll share my general u130 build tips and tricks in this guide as well, but if you're looking for detailed build guides checkout the BeeRotor 160 and BeeRotor u210 build guides.

However, after trying so many iterations of the different 3d printed parts, I ended up removing the 3d printed ducts as they were heavy and did not add that much protection to the props or extra lift. Maybe I'll design some new ones at some point, but here's the configuration I'm currently using:

It looks pretty awesome flying around.


Let me start by saying that the BeeRotor series is awesome. No matter which size you choose, the uncompromising quality and thoughtfulness put into each of these products makes them all a must-have.

The latest kits, including the BR u130, are no exception. The details are what matter and the u210 thinks everything thing out. From the carbon fiber frame's high quality and solid layout to the PDB's inclusion of female headers, so you have the option of removing your BRF3 later, without un-soldering. The VTX comes with a SMA cable, instead of a directly connected SMA plug, so the VTX fits seamlessly into the frame, plus it includes a circular polarized antenna.

My only suggestion is to grab some regular and reverse thread locknuts to use instead of the prop spinners included with the motors.


On the first version of this build, I used the parts in the BR130 kit.

In the next version of the build, I switched out the flight controller from a BeeRotorF3 to an OmnibusF4.

I also switched the TS5840 VTX and added an LED Strip for the little holder I built.

Everything you need except the transmitter and receiver, battery and charger is included in the kit! You'll also want some good goggles if you're just getting started.

This basic setup is great for a beginner:

FlySky FS-i6 with iA6B Receiver, $53
Eachine VR D2 Video Goggles, $89
3s 11.1V 1800mAh 45C LiPo Battery with an XT-60 Plug, $15
Eachine WT50 6A 50W AC/DC Balance Charger Discharger For LiPo/NiCd/PB Battery, $34

I picked this setup because these are the most feature-rich and cost effective components you can use to get into FPV flying! The FS-i6 radio with iA6B receiver is the best value radio that supports PPM. The Eachine VR D2 are a great value at $99. The 1800mah battery will work well in any 150-350mm size quadcopter and the 45c rating means it can deliver 81 Amps, which should be more than enough for your mini-quadcopter. Finally, the Eachine WT50 charger includes a built in AC-DC converter, so you won't need an external power supply, like you would with most chargers.

Total Cost: ~$180

If you already have the items above, get just the drone kit. It has everything you need including video transmitter and camera.

Modeling the ducts

Ok, onto the fun part. Here is how I designed and built the ducts.

Take high res photos, directly from above, evenly lit.

Turn up brightness and contrast to max in photoshop.

Cut out the main piece using the magic want tool with tolerance set to 50, but change this to what works for you.

Apply a layer style to make the whole thing one color. Save this and open in Illustrator.

In Illustrator, open the Image Trace window and choose paths: low, corners: low, noise: high. Rasterize the image with Object, Rasterize (screen resolution of 72dpi) then hit Trace in the Image Trace window and Expand in the top bar.

You should have a nicely traced image, so export it to an AutoCad (dwg) format file and import it into SketchUp.

You'll want to do the same thing with some photos of a prop, to get a good duct size:

From here, you'll want to do the normal Sketchup things, like trace out the image and extrude out the parts you want to create. The 3D modeling is another topic in itself, but if you're new and looking to learn a software package, know that this was my first and only part I've done using SketchUP. I've since switched to Fusion360, so perhaps I'll do a guide on this in the future.

I only modeled 1 side, then I mirrored that side and printed it again.

You can get all the parts for the build over at Thingiverse.

This video is from before I got a sheet of glass and PEI Sheet. Back then, I would dissolve old ABS prints into acetone and paint this mixture on the 3D printer. With the PEI sheet, this is no longer necessary (and so much easier).

For more details on how to get started 3D printing, checkout the build guide for my first 3D printer.

This was the first real part I made on my 3d printer and it took me so, so many tries to get these right. From warping to poor bed adhesion to uneven cooling, I think I went through at least 10 attempts before I got one right.

Once I did get it printed, I test fit everything to make sure it fit ok:

V1 Assembly

I had to ream out the holes in the PCB a little bit, so the standoffs fit though.

Here is the VTX, we'll prep it in a second.

Solder the necessary wires onto the PCB.

Then solder the included cap onto the capacitor.

You'll notice I'm wiring the camera cable right to the VTX, skipping the PCB, this is so I can better position the VTX on the tiny frame.

Solder on the power leads and the FC can be mounted.

Now test fit the electronics with a duct installed.

The V1 desing was OK, except, as you've probably noticed, the USB port will no longer be accessible once the other duct is installed. This is a major downside if you like to have the latest and greatest firmware all the time. No big deal if you want to flash once and forget.

I tried a Spektrum satellite receiver at first, but it kept dropping out, so I switched this to an FrSky X4R SBUS RX later.

Soldered on the ESCs.

Don't forget to put heat shrink on them before soldering on the motor wires.

Test fit the ducts.

The ducts barely fit. Also, you wont be able to access the USB port if you use these ducts, so it would probably be good to use a bluetooth module for configuring the quadcopter.

V2 Assembly

In version 2, I used an OmnibusF4 and a prototype Typhoon ESC.

First attach the flight controller and ESC using some nylon standoffs.

I designed a custom VTX and LED Strip holder that fits a TS5840 and the BR130 frame. I measured both the VTX and the LED strip, then built the model in Fusion360.

Attach the camera, video transmitter and receiver, then test it all on the bench

Here are how the motor wires connect.

Then insert the motors into the ducts and solder the motor wires to the ESCs.

Here's how it looks all wired up.

Here's how it looks with all the components inside.

Finally, install the landing gear.

Future improvements

While I'm happy with this as my first attempt at a custom, 3d printed quadcopter. There is room for improvement, mostly around the ducting.

The ducts should be more modular, so they're easier to replace if broken. They should be more durable, so they have to be replaced less and they should improve the motor efficiency.

The next step is to re-design the ducts to meet the specs in this article, which describes the optimal duct design from Jason L. Pereira's research paper on the subject.

Checkout my other guides at
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