Back in December, we put together an overview of ready-to-fly quad-rotors. I intended to follow that article with a similar piece that focused on racing quads. It quickly became apparent, however, that racing quads are a very different kind of beast and would require an altered form of presentation. What I provide here is a beginner's buyers guide for aspiring quad racers. I’ll cover the components that you’ll need, some of the different equipment options, and a few recommended retailers for you to get started.
Before We Get Start
It should be noted that racing quads are not for beginners. They are small, fast, and maneuverable. Those traits are what make racing quads fun, but they also exaggerate the difficult aspects of learning to fly multi-rotors. I’d be remiss if I didn’t point out that racing quads are rather expensive as well. You can easily spend $1000 for all of the equipment that you’ll need to get started.
I’ve preached my suggested route for beginners several times, so I won’t repeat it here. I’m just starting to explore racing quads myself, so I’m hardly qualified to make any skill-level recommendations. However, I can say that I would personally feel uneasy about trying racing quads if I didn’t already have significant experience flying slower quads outdoors (without GPS aids) and with First Person View (FPV) gear.
Most modern racing quads are in the 250mm class, although it isn’t uncommon to find models ranging from 230-270mm. This measurement denotes the distance between the propeller shaft of a front rotor and the propeller shaft of the rear motor on the opposite side. At less than 10”, a 250mm racing quad is rather small compared to a DJI Phantom 2 or Blade 350 QX. In fact, they are only slightly larger than many of the beginner-oriented mini-quads. The difference is that racing quads pack a lot more relative power into a very small footprint.
In general, racing quads are offered as kits that must be assembled. Some vendors offer only specific components such as frames or motors. Other shops provide everything you’ll need in one box. In a few instances you will find stores that offer pre-built and flight tested racing quads. Keep in mind that quad racing is a contact sport, so crashes and repairs are inevitable. This spawns two schools of thought regarding pre-built racers. On one hand, the education and familiarity provided by building your quad will be useful assets when the time comes to fix it. On the other hand, going pre-built removes the variables posed by rookie set-up blunders. Choose your poison.
Before shopping for a racing quad, I suggest that you seek out other quad flyers in your area. See what equipment they are using and what works for them. Having access to someone with first-hand experience is one of the best ways to sort through the overwhelming array of options. Locals can also help you clear any hurdles you may experience during the build and set up of your racer.
Anatomy of a Racing Quad
When shopping for a racing quad, you will need a number of different components. It is helpful when you can buy everything from one vendor to help ensure that the parts you get are compatible. You may be able to save a few bucks by shopping around for each item. Just don’t forget to consider the additional hassle and shipping costs of sniper-style shopping.
The following list describes the basic components that you will need to set up a racing quad:
- Electronic Speed Controls
- Flight Controller
- Radio System
- Video Transmitter
- Power distribution board (PDB)
- Low-Voltage Alarm
Most racing quad frames are comprised of G10 (fiberglass sheet) or carbon fiber parts. They are generally arranged in two levels and fastened together using screws and spacers. You will see that some frames do not articulate, while others feature folding arms that make them easier to transport. G10 frames are typically much less expensive than carbon fiber, but they are also heavier and less rigid. Carbon fiber is very strong (and looks awesome too). Keep in mind that carbon fiber is electrically conductive, so it requires a bit more care to keep power sources isolated.
The choice between G10 or carbon fiber is a purely personal one. You may even want to consider a frame made of nylon or wood. There are no wrong answers. It’s all about balancing your budget with your wants.
Racing quads use small brushless motors. There is actually surprisingly little variation here. 2204-sized motors are very popular, although 1806 and 2206-sized motors can also be used. The first two digits denote the diameter of the motor’s stator (in millimeters) and the last two digits denote the length of the stator. You also should pay attention to the “kV” value of the motor. This indicates the RPMs that the motor will turn with 1 volt applied (and no load on the motor). Don’t assume that a higher kV motor is necessarily better or faster. The kV is inversely proportional to the motor’s torque (more RPMs = less torque), so a balance must be struck. When in doubt, choose a 2204 sized motor with 2000 or 2300 kV. Obviously, you will need four of the same motors for your racing quad.
There is a very important connection between the motor’s kV, the voltage of the flight battery, and the size of the propeller. Choosing a propeller that is too large will cause the system to pull excessive current and possibly destroy something. An undersized prop will not realize the power potential of the motor. Many vendors will list the suggested propellers for a given motor with various input voltages. Follow those suggestions to start with while realizing that you can fine tune your prop selection down the road. You will need two clockwise-rotation props and two counter-clockwise props to fly…and plenty of spares!
Electronic Speed Controls
Each motor requires a dedicated ESC, which is essentially a throttle that manages the speed of the motors. You must ensure that the ESCs you choose are rated to handle the voltage of the battery you will use as well as the expected amperage that the motor will pull. 12-amp ESCs are commonly seen in racing quads, running firmware like SimonK.
The Flight Controller (FC) is the brains of your quad. It is linked between the receiver and ESCs. The FC takes your control inputs (or lack thereof) as well as data from its onboard sensors and translates it all into commands for each of the ESCs. This is what keeps your quad in a stable hover or sends it zooming over the landscape. Unlike FCs used on larger sport and photography multi-rotors, the FCs used on racing quads do not typically have GPS features. Popular FC models for racers include cryptic names such as NAZE32, CC3D, and MultiWii. Pay attention when shopping for a FC, as some require you to solder connecting pins to the FC board.
Radio Transmitter (TX)
The radio systems used to control quad racers are no different than those used for RC airplanes and helicopters. Resist the urge to go cheap here. You only need a 4-channel system to fly a quad, but you will often find much more adjustability and useful features on radios with 6 or more channels. Note that some radios systems are sold as the transmitter alone. Be sure to also get a compatible receiver (RX).
My suggestion is to get a 6-channel computer radio from one of the major brands (FrSKY, Futaba, JR, Spektrum, Hitec, Airtronics). All of these brands have been around for a while and have good reputations. Just don’t be surprised if you hear one flyer praise a particular brand while another flyer curses it. RC flyers tend to develop deep-rooted brand loyalty when it comes to radio equipment, so opinions can be strong.
Racing quads use 3-cell or 4-cell LiPo batteries typically sized around 1300-1800mAh. The 4-cell route will provide more power and likely more speed. Keep in mind that the battery is just one part of the power system. If you decide to use 4-cells, you must also choose motors, ESCs, and props that are capable of handling the additional voltage and power. Personally, I’m starting out with a 3S system to build my racing skills. I may transition to 4S down the road.
One appeal of quad racing is the FPV perspective it provides. To make this happen, you will need a Video Transmitter (VTX). Odds are, you will also need a FCC amateur radio license (aka ham license) to legally operate the transmitter (although a license-free unit may work for you).
There are many variables that determine what frequency band and output power you should choose for your VTX. For that reason, I’ll refrain from making any broad-brush recommendations. This is another case where the advice of locals can be extremely helpful. As you go through the process of getting your ham license, you will learn much of what you need to know to make an educated buying decision for your situation. Other local “hams” can also be a valuable resource.
Let’s not forget that you will also need a way to receive your VTX signals. Video goggles with an integrated receiver (matched to your chosen VTX) are the most popular option for quad racers, such as ones made by FatShark or SkyZone.
Most quad racers use small security cameras for their FPV system. These small, lightweight cameras adjust quickly to changing light conditions. This keeps you from being blinded as your quad flies through transitions of sunlight and shadow. There are many viable cameras to choose from. The PZ0420 model with a 2.8 lens and IR filter is a popular choice.
If you also want to record your flight, you will need an action camera onboard your ship. Unsurprisingly, GoPro Hero cameras are often used. The Mobius camera is a common alternative that will save a little weight and cost.
Power Distribution Board
The single battery discussed above powers every component on the racer (except for the optional recording camera). The power distribution board provides a sanitary means to link all of the powered components to a single node. In many cases, the PDB also provides a 5 volt tap for your FPV camera or other low-voltage equipment. Some frames require a proprietary PDB and others have the PDB integrated into them.
You will want to know when your battery begins to get low, so that you can bring your quad back for a controlled landing at your feet. There are a few different ways to approach this. Some radio systems have built-in voltage monitors that will sound an alarm on the transmitter when your flight battery reaches a set voltage. There are also on-screen display (OSD) devices that can integrate selected data, including real-time battery voltage, into your VTX downlink. The data is overlaid on the camera image when you look into your goggles. The simplest method involves a small device that plugs into the battery and emits a loud, shrill alarm when the battery gets low.
Who Gets Your Money
As popular as racing quads have become, they are still niche items that aren’t carried by any of the big hobby distributors. Consequently, you’re not likely to find much that you will need at your local hobby shop. Once you move your search online, the selection suddenly becomes overwhelming. There is a wide array of web-based vendors selling racing quad parts and full set-ups.
The main driver for domestic buying is one of logistics. Buying close reduces the shipping transit times.
The best way to cut down the selection pool is to buy domestically. From what I have seen, most of the stuff that you can buy direct from China is also available from US vendors for similar prices. I assume the same is true in Canada, Europe, and Australia as well. The situation may be different in your specific corner of the globe.
Although there are many reasons for keeping your money in-country, the main driver for domestic buying is one of logistics. Buying close reduces the shipping transit times. More importantly, if a package arrives with missing or inoperative parts, your odds and timeframe for a resolution are much better. It is also worth noting that there is a cottage industry of US-based companies that offer custom racing quad frames and other equipment. They should not be overlooked.
Even after filtering for only US-based vendors, the list of shopping options is large. I can personally vouch for a handful of vendors that I have used with good success. These include GetFPV, Ready Made RC, Atlanta Hobby, Buddy RC, Tower Hobbies, and DIY Quad Copters.
Up Next: Building!
I have gathered all of the parts I need to build a racing quad. I will soon be posting a series of guides that will cover my build from unboxing to the first flights. Check back and follow along as I share my experience entering the world of racing quads. The components that I’m using and their origins are listed below:
- Frame: Red Rotor RC Strider (PDB and Low-Voltage alarm are integrated into the frame)
- Motors: SunnySky 2204 2300kV motors
- ESCs: Velotech Magic 12-amp
- FC: CC3D
- Radio: Futaba 7C with R617FS receiver
- Battery: Electrifly 3-cell 1300 mAh lipo
- VTX: 5.8GHz 600mW Tx with SkyZone goggles
- FPV Camera: PZ0420M, 2.8mm Lens, IR blocked
- Record Camera: Mobius Wide Angle
My thanks to custom quad builder Benjamin Breth for providing technical advice and photos for this article. If you are considering the pre-built route for your racing quad, you can contact Benjamin at firstname.lastname@example.org.
Terry spent 15 years as an engineer at the Johnson Space Center. He is now a freelance writer living in Lubbock, Texas. Follow Terry on Twitter: @weirdflight