This is the category where we can choose from the widest selection of frames. Typically, a racing frame is 250 sized, that means 250mm M2M, that means motor to motor distance, diagonal. This size is large enough to place all the necessary electronic into, but small enough to perform easy acrobatic figures, and fit into very small holes, that can be essential when racing.
For racing, we nearly explicitly use quadcopters, however, using tricopters or hexacopters is possible as well. Races are mainly done in FPV mode.
However, the racing community frames are changing a bit recently, by moving to smaller frames, sized of 220, 200, 180, 170 M2M. The reason for that is mostly the smile factor when someone sees these little beasts passing by with very high speeds (100+ km/h).
- weight (as low as possible)
- durability (as crashproof as possible)
- material (many use CF but personally I do not recommend it, see later)
- maximum prop size that can be used
- battery mounting (upper deck, bottom, inside the frame)
- spare parts (replace parts after crash)
- look (yes, for many it is more important that the other attributes)
- video gear
Of course, as we speak of racing frames, there are some factors very important, let’s check these:
The lower the weight, the more flight time is possible, and flight times are much lower with race quads than with any other type (e.g. AP). This is because we want to achieve high speeds that needs more power, lowering the time being airborne. In some rare case the higher weight may be beneficial, specially when going for very high speeds (will talk about later). Generally, keep the weight of the frame as low as possible.
Everyone who does racing will crash his frame for sure. The question is not if ever, but only when. Having the frame as crashproof as possible is essential. The goal can be achieved either by using thick material (weight goes up) or kinda material that is very durable. In the first case, we have to create own own custom frame, as there no frames at the market recently that can comply to that. Personally I prefer creating DIY frames, when the arms are more thick, thus, unbreakable and the whole frame is fixed on many places to get it massive and crashproof. In the second case, the average user can buy a stock frame that is made of carbon fiber material, that is durable enough to stand most of the abusement. However, sooner or later any of these frames will break because the carbon fiber material manufactured in China is not of an industry standard, but much weaker.
Even note that CF will shield RF signals and while most of the racing quad videos are on 5.8GHz that may cause big problems at moderate distances.
* maximum propeller size
When getting the frame, it is important to check what is the maximum propeller size that can be used on it. Sooner or later everyone wants to get more speed, more power and sometimes time this can be achieved only by raising the propeller size.
When we speak about the drive, we mean ‘motor+esc+propeller+battery’ combo.
All these components work together and by changing any of these may affect the behaviour, speed, power, flight time and so on. Beside of maximum prop size used, it is also very important to plan what kind of battery we shall use. Always think of the future a bit. Many start with 3 cell batteries but decide to turn to 4 cell later on, of course, on the same frame. However, that decision usually means changing the motors, escs, props as well. Suddenly they realize that after changing the motors and escs, the battery would not fit into the place the 3 cell was used previously, because the 4 cell battery means plus 1 cell, and that means battery of bigger size, assuming the same capacity. In that case they need to choose a lower capacity battery or find another plce on the frame to position it.
Generally, when buying a frame (especially an expensive one), always think ahead.
The importance of the look of the frame is many times higher that the other main factors. When speaking about a racing quad, never prefer the look to the other main factors that can affect the performance. There are some fancy quads out there that look aggressive and cool but their aerodynamic parameters are much worse than of some basic constructions. Many use LEDs on their copters to have it look cool but forget about the LED current consumption, LED drivers electromagnetic noise and so.
It always to keep the quad as simple as possible, while getting the maximum performance from it.
* video gear
When choosing a racing frame, be aware of the fact what kind of video gear will be used. A higher frequency vTX is usually smaller thana lower frequency one, not speaking about the antenna sizes! An 5.8G gear will be small, as well as the antennas. In case of a crash no component should be destroyed. An 1.3G gear will be larger, and the CP antennas are huge comparing to the 5.8G antennas. In case of a crash the 1.3G antenna can easily be broken, not speaking about the fact that the height of the quadcopter will significantly raise, excluding the bird from places (holes) where the quad with 5.8G video can easily fit. The 1.3G gear is usually paired with 2.4G RC link and that means that at least one more component (lowpass filter) is needed, and there has to be enough place for it on the quad.
Regarding the camera, most of the todays frames support mounting the fpv camera in between the two main deck plates, but not all cameras will fit in there, depending on whether they are cased or not and depending on their size as well. prior to buying the frame, check what camera you plan to use and whether it will fit into the frame.
* battery mounting
The vast majority of quads hold the battery even on the top or inside, between the two deck plates. This is because of the CG to keep in place. When buying a frame, consider the fact that in case the battery is inside and there is a crash, many other components can simply get smashed just by the weight of the battery. On the other side, the battery is better protected. In case the battery is on the top, no bad things can happen, except when the bird is landing on top and the battery gets destroyed by piercing or hitting something. Again, think ahead and consider the measures in case when changing for another battery, so it can fit.