How to choose drone frame for racing or freestyle?

Whether it’s made of Carbon, Wood, Metal, Plastic or Fiberglass the frame is the thing that holds your Drone together. Without it, you simply would not be able to take to the sky. Unfortunately, it is not as simple as one perfect frame to rule them all. There is a lot of considerations you need to make based around what you want your Drone to do.

This guide will take you through all the things you need to know when you are picking the right frame for you. We will be focusing the most on quadcopter frames.

What is a Drone Frame?

The frame of your Drone is probably the first thing you need to decide when you want to set about building; the size, materials, thickness, space, style and even the geometry will play a critical part in your build, whether it is a Super Lite highspeed racer or a Battle-hardened Bando Slayer.

drone- frame-carbon-fiber

Your Frame (like a car chassis) is there for 2 reasons:

  • Protect the components inside
  • Hold everything together

However, in some racing frames, protecting the components comes secondary to ultimate performance. Aerodynamics do play some part in the design, the focus is on reducing drag and limiting the effect the arms have on the thrust from the prop.

The aerodynamics do not provide any lift or control surfaces like you would see in a conventional aircraft. Put quite simply a Drone will fall out of the sky without its motors.

My preference is for a strong freestyle focused frame which can be crashed with limited chance of a total write off. This means my quads are heavy compared to most race frames, but I don’t need that all out speed. I have a few racing frames, but my favourites are my 5 inch freestyle frames.

The main thing I look for in a frame are:

  • Strength - This is important simply because you’re going crash.If you’re a beginner, you will crash a lot. A strong frame will keep on going and will protect all the electronics you build into it.
  • Space - I am always impressed with people who make super neat tiny builds.However, I like the room to be able to install parts and to take the drone apart to work on it when needed. Therefore, having a little bit of extra room makes all that easier. Especially if it’s your first time building.
  • HD Camera mount - This is not critical for everybody, but for me I like to film my flights. I love the footage I can get.

TOP PICKS

Name

Size

Prop

Motor

Weight

Rate

220mm

5"

22xx >

140g

220mm

5"

22xx >

123g

225mm

5"

22xx >

122g

220mm

5"

22xx >

145g

225mm

5"

22xx >

120g

Materials

Most Frames you will find on the market are made of carbon fibre because it is light weight, strong and rigid. The disadvantage is that it is not that cheap, it’s hard to work on and it conducts electricity so you need to insulate the wires (I think every pilot has a story of when something broke because a live wire touched their frame).

Also, carbon fibre is great at blocking radio frequencies, so you need to place your antennas carefully.

There are other frames that are made from plastic (Ragee). These are made of a plastic (HDPE) that is made to take significant impacts without breaking. The disadvantage with these is the weight and working area.

To get the same strength you need more material and to make the frame work you need to find parts that will fit in the predefined spaces.

Ragge-drone-frame

You also need to consider what the hardware (stand offs, bolts and screws) are made out of. Steel and titanium are often used for screws and bolts. Steel is softer and cheaper, whilst titanium is hard and more expensive, but can cause issues when mixed with other metals (galvanic corrosion).

Some frames have aluminium or titanium parts to them. This offers a great deal of strength, but normally it comes at the cost,with a higher price point and weight.

Construction

Frames have 3 main parts; a top plate, a bottom plate and Arms.
The top plate is normally thinner and often has holes for cable tie and battery straps. Also, people attach gopro mounts either by top plate screws or velcro straps.

The bottom plate is normally the thickest part of the frame. It is designed to soak up crash impact. It also has the holes to fit the stand off for all your electronics. This is in either a 20x20mm lay or 30x30 layout (most 5 inch frames are 30x30mm).

The arms may or may not be part of the bottom plate. They hold the motors and sometimes the ESC’s. They are either part of the frame or removable.

Drone Frame SizeS

Frames are normally measured by the diagonal distance between motors. This dictates the size of props you can run on any specific quad. Oddly we measure the frame in millimetres and the props in inches. However, it is common to refer to quads by their prop size. E.g. 5 inch or 6 inch.

While the frame shape can affect the size of props, mainly you can work to the following as a rule:

Frame Size

Prop Size

Use

Example

280mm+

7 inch

Long Range

Mode 2 Shredder 7"

250mm

6 Inch

Long Range / Freestyle / Racing

Halo Archon

210mm

5 inch

Freestyle / Racing

Impulse RC Reverb

180mm

4 inch

Freestyle / Racing

Armattan Gecko

150mm

3 inch

Freestyle / Racing

SlightClub Phuket 3"

112mm

2 inch

Freestyle / Racing

Emax Baby Hawk R

100mm-

Whoops*

Indoor / Limited outdoor

Tiny Whoop

* Under 100mm are not strictly Whoops ( Tiny Whoop type Quads), but they are by far most common.

By far the most common frame is around 210mm, which most people would refer to as a 5 inch frame. This is used in both freestyle and race as it often the best compromise between power, weight and responsiveness.

This is because the 210mm frame (5 inch) allows you to run 5 inch props, which give great power and efficacy. The weight of the frame is slightly lower and the centre of the props being closer to the middle.

This has a positive effect on the moment of inertia in that you have a greater amount of force being applied closer to the centre of mass of the quad.

The freestyle scene is pretty much dominated by this type of frame with a few outliers who use 6 inch frames.

example of 200+mm frame kit build

As you increase the size of the frame wind resistance does play a factor too.150mm (3 inch)frames are massively fast,but they get blown around and usually have short flight times because they need to carry smaller battery to compensate for the lack of thrust.

You would think this would make the 4 inch quad popular, but this is not the case. The speed is not a match as the 3 inch and the control is not that of the 5 inch. So you don’t tend to find many people who fly 4 inch quads.

When you step up to the 6 and 7 inch frames you find air resistance more of a factor. However, you have bigger props pushing you forwards, so power is readily available. Given you’re likely to be looking at long range flights you also have different goals.

You are looking for efficiency rather than all out power, so you are more than likely going to run lower pitched props with a more efficient shape. In addition to this you are probably carrying a larger battery and slightly more electronics (GPS etc).

As a rule of thumb you can use mostly the same electronics hardware between 7 inch and 4 inch frames. They mostly will take the same flight controllers etc (always check first) on a 30x30 mounting pattern, However, some do other both 30x30 and 20x20. 7, 6 , and 5 inch frames mostly all have the same motor mounts nowadays (16x16).

One word of warning, while a 210mm frame can take a 5 inch prop the clearance between the frame and the props on the both motors can be tiny (1 – 2 mm in some cases). Always check these clearances before you fire up.

Frame Shape / Arm Layout

The shape of the frame is dictated by the layout of its arms. We'll focus on the mainstream 4 arm setups. There are other options including more or even less arms as well as other layouts of 4 arms like V-tails or + frames. However, I am not going to discuss them here as they are much less common and mainly flown by specialists.

quadcopter-frame-shapes

The main layout used today are:

H: This is where the frame looks like an H on its side. The Arms stick out directly from the body. This normally leads to a longer body section to avoid the blades touching. While you may find some of these frames around, they are much less common due to the fact they are quite bulky and the motor position is less optional for good moment of inertia (due to the long arms).

True X: As the name suggests, this is where the frame is shaped exactly like an X. The Distance between all the motors is equal. This provides the most balanced performance as each motor operates equally. The angle of the arms means that the body can be smaller as it does not need the length to separate the arms.

Hybrid X: The title does not really describe it too well. This is frame type takes the best of the H and X frames and joins them together. You get a longer body which is good for space and you get the more optimal arm placement of the X frame. This setup is what you see in something like the highly regarded Impulse RC Alien.

Stretched X: The main objective of a stretched X is to move the front and rear propellers away from each other. Imagine either an X that has been squeezed from the sides or an X with a bit added to the middle. This frame shape is designed to reduce the effect the front and rear props have on each other. The aim is to improve the highspeed handling. However, due to the unequal distribution of force over the centre of mass, there is often a need to tune these frames more to get them to fly as desired.

Square: This is frame type is pretty much an enclosed X Frame. In effect you are joining the arms together with material between each motor. Like drawing a square around anX. There are a few frames that do this but the most obvious is the TBS Oblivion. The advantage of this type of frame is strength. This comes at the cost of increased weight as well as an increased surface area which is lightly to increase drag.

Unibody Design

What is a Unibody? It’s a frame that has all the arms as part of the bottom (or in some cases top) plate. The other option is separate arms. This can either be totally individual arm or pairs (e.g. Both front arms as one piece).

unibody-drone-plate

Why does this matter?

The Unibody design is normally considered to be stiffer and stronger due to there being less joints and thus less week points (or so the theory goes). However, if you break an arm then you have to replace the whole plate, which is not always that cheap.

In comparison, with separate arms you can simply replace the arm if you break one. This is very common in racing frame where they run light weight arms to decrease mass and are happy to just replace the arm if its get broken. There are some designs which pretty much overcome the issues of having more joints by having clever mountings and screws.

This is one of the areas that personal preference is the main factor.

Carbon Fibre Thickness

There are many factors to the strength of carbon. Quality, lay up, flexibility and thickness. It’s is not totally true that thicker carbon is always stronger. But it is fair to say that you want the thickest carbon on your frame to be where your frame is most at risk. However, the thicker the carbon the, heavier the frame.

So, where do you want thick carbon? Well the Bottom plate is always important, it normally takes the brunt of the impacts and also holds everything together. If you have separate arms you normally have 2 choices;light arms you are willing to replace when you crash, or heavy arms that will take a beating.

As a rule of Thumb 4mm Carbon will give you good rigidity and strength on your main components.You want this for your Bottom plate and Arms (3mm if you want to save some weight). For your top plate 3mm or 2mm is fine as these are easier to replace.

Filing Carbon Fibre Edges

Do you need to file down the edge of your Carbon?

Possibly, some frames come with chamfered edges which mean the hard work is done for you. Other more premium frames have very well-cut carbon where is it not really needed. Cheap frames quite often need some finishing off as they have very sharp unfinished edges.

Why do I need to do it?

Carbon fibre, like metal, when cut normally leaves shape edges. This can cut your hands when handling the craft, but also more importantly it can cut your wires if they are rubbing against a sharp edge over time.

Warning! If you do file the edges of your frame, do so outside or in a well-ventilated area and with a mask. Carbon when it gets into your lungs is bad for you. Your body cannot do anything with it, so you are stuck with it forever.
Tip: If I ever file carbon, I do so under running water so that it’s washed away.

Racing vs Freestyle

There are people that race freestyle frames and freestylers that use race style frames. There is not hard and fast rule. That being said, freestyle frames are normally stronger and have more space for gopro mounts, whereas racing frames are lighter.

fpv-racing-drone-freestyle

For me, I use both. Infact, having a dedicated race frame allows me to focus the setup on speed and responses. Whereas my freestyle setups are aimed at flow and Punch.

If you are starting out, I would recommend a freestyle frame as they are easy to work on and tend to take more punishment (because you’re going to crash, it’s inevitable).

Battery Location

Battery placement is a very much a preference. The weight of the drone battery is quite a large proportion of the craft, so where you place it very much effects the handling. The ultimate aim is to get it as close to the centre of gravity as possible. Ultimately you can put it in 2 places; on top or underneath.

top-mount-quad-frame-battery

Most free style frames have top mount batteries with the battery inline with the frame. This protects the battery in most crashes. However, it is not optimal for performance due to the weight being balanced above the centre mass of the craft

Bottom-mount-quad-frame-battery

Racing frames mostly opt for bottom mounted batteries. This means they are slung under the frame, so the weight is hung under the frame which is good for cornering as it has a positive effect on the handling as you are not having to balance the weight so much. However, the battery is more a risk in crash landings.

There is also the concept of a mid-mounted battery which is where your battery is sideways to the top of your frame. This spreads the weight in a more even way over the centre of the frame, however you need a very specific frame setup to avoid the battery getting caught up in the propellers.

Other Considerations

FPV Camera tilt angle, protection and size

quadcopter-frame-camera

Your FPV Camera is what you use to see, so you need to makesure it is well placed. You need to be in a location where you can get a good clean line of sight. It is common to have some props in view especially on stretched x frames, but you don’t want to have it blocking most of your view.

You need to be able to have a range of angles. The Camera angle is such an important part of your xxx. If you get it wrong you will make your life really difficult. If it’s too low, you will end up looking at the ground more often than where you are going. If it’s too high you will end up going to fast everywhere. If you are starting out 25 degree to 30 degree is a pretty good place to start. Some pilots use 60 degree tilts, but I would strongly advise not to start there if you are a beginner.

Camera protection is a preference. Some pilots will hang their camera out the front with no protection to give them best view and extreme angles. This puts them at a much great chance of being damaged or destroyed in a crash.

Others like to keep their camera slightly more protected inside the frame. This often limits the angles, but means you don’t spend your time constantly replacing cameras when you crash into something.

Finally, you must consider size. Make sure your frame can fit the camera. There are 3 main sizes of camera:

  • Standard: 28mm wide, often referred to as Hs1177 size cameras
  • Mini: 21.8 mm wide, but often come with brackets to fit standard mounts.
  • Micro: 19mm wide, Some come with upsizing mounts but most don’t

HD Camera Option

Most freestyle frames either have a built in Gopro (or other HD camera) mount, for recording high resolution footage or a space of a 3D printed mount. There are mounts for racing frames, but they not always the primary consideration.

I use 3D printed mounts as I want my gopro as well attached as possible to the frame. I don’t want to lose A: the Camera and B: the footage.
- Protection for the motors

carbon-fiber-drone-frame-protection

Damaging motors is a real pain. Usually, any damage means the end of your flying day, so protecting the motors is very useful. When you look at the ends of most frame arms you will see the end extend past the bottom of the motor. This is to protect the motors so the frame takes the hit first. In some cases, people use 3D printed bumpers, to help, however this add weight.

Spare parts

Having easy access to spare parts is useful to keep yourself in the air. If you have separate arms having at least one spare can make your day of flying might not be over after a heavy crash. Having a frame that is hard to get spare parts for can keep you grounded for a long time.

If you have a Unibody design you may not want to have the expense of the having a spare bottom plate, so you may just have to accept the downtime.

Stand off etc are fairly easy to come by if they are broken. In fact, in a lot of cases there are spares in the pack.

Warranty

For me this is one of my main considerations. There are some suppliers in the market who offer either a limited or unlimited warranty on their frames. Now there are rules to what qualifies (you need to see the suppliers websites for this information), but if you crash and break say a bottom plate or an arm, you can claim this under warranty and get a replacement free of charge (there maybe a shipping cost).

This really reduces the risk for me as I know that I am an email away form replacement part being sent to me for free (which on Unibody is fantastic). I have used this on more than one occasion and it has saved me money in the long run.

In my opinion Armattan offer one of the best Warranties on the Market. As long as you stick within their rules, they will always keep you in the air, and they have done for me for the past 2 years.

Top tip: If you have a Warranty and you have separate arms, having a spare arm mean when you break it you don’t have to wait for the replacement to come, you simply replace you spare with a new one.

Contributor: Paul Rose

DN

Drone Nodes is online communication platform that brings together experts&enthusiasts in drone research, start-ups, education and business across the globe.
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