fingers_in_ears

Droning on and on and on…

Preamble

Continuing with my new found love of the unholy trinity of RC, robotics and motors, it was but a simple step to think about turning my hand to drones. Furthermore, it is a logical extension of the thought train, as described in I, robot, which has meandered via 4WD tanks and octopodbots, which concentrate mostly on DC motors, servos and stepper motors for locomotion, to arrive at drones and whatever joys that their means of movement will bring.

In addition, would there be differences, or further challenges, between their communication and control? This will obviously depend on the technique employed, be it BLE, 2.4GHz433MHz, XBox, PS2/PS3, USB, XBee, APC220, ESP8266 or what have you… Now some of those methods may seen rather tethered for a flying drone, as in the case of USB, or short ranged, for example the various console controllers, which is limited to around 10m (30′), and so may they be. However, all options should be weighed up.

See also the blog on Octocopters.

For a look at Reptile 500 chassis based quadcopters, see the blog Reptile 500 Drone kits. Other kits are also looked at in Drone kits. See also Getting started with Drones.

Some initial guidance

There is a simple beginner’s guide, Build Your Own Multicopter | Copter. Plus DJI Quadcopter – RC Tutor. Also, MyFirstDrone.com has a lot of great guides, including Want To Buy a Drone? – 5 Things You Should Know Before You Buy.

Building Your First Drone

This is an excellent step by step guide, with videos, again from MyFirstDrone.com:

  1. Building the frame – Part 1
  2. Mounting the motors and speed controllers – Part 2
  3. Mounting the electronics – Part 3
  4. Flight controller setup – Part 4
  5. Prop balancing and mounting – Part 5
  6. Soldering – Part 6

Here is the list of parts required.

Finding one’s way

Familiarising oneself with the kit required seems to be best gleaned from eBay, by repetitively looking at item descriptions and seeing what kit is most commonly employed. One superlative example of this, to the untrained eye of a noobie, is the S500 Professional Large FPV Drone Quadcopter & Monitor Ready To Fly GoPro Gimbal, for £375 + £20 (p+p) – the designer has obviously thought about the design a lot and gone for the best components for its construction.

S500 Professional Large FPV Drone Quadcopter & Monitor Ready To Fly GoPro Gimbal
S500 Professional Large FPV Drone Quadcopter & Monitor Ready To Fly GoPro Gimbal

Here are the other pieces of kit that come with it, remote controller with a display for the streamed feed from the camera.

S500 Professional Large FPV Drone Quadcopter & Monitor Ready To Fly GoPro Gimbal 2
S500 Professional Large FPV Drone Quadcopter & Monitor Ready To Fly GoPro Gimbal 2

Here is the lengthly description, from which we can get an idea of which kit is good kit. Basically, this provides us with a shopping list.

Hello and welcome to my auction for this Custom Built ready to fly FPV Quadcopter Drone, with stabilized camera mount.

I built this a few months back with the intention of keeping it myself, I have built quite a few of these now and this was my last, however I’m going on holiday soon and I’m a little short of cash, this has definitely been a labour of love, I have put a lot of hours into building and tweaking it, I am an electronic engineer by trade, I have to work with extremely high tolerance equipment & components on a daily basis, attention to detail is not only essential but highly in my nature so you can be sure that this drone has been very well built.

Despite its size and power it is a fairly fast drone, with 10×5 size propellers it is capable of flying at an absolute maximum of around 40mph (without propeller guards) which is fast for a large quadcopter, however I would recommend using 10×4.5 or 11×4.5 propellers for the most stable flight, and of course the speed will increase further with a lighter battery, the dimensions are as follows, Diagonal width: 50cm,  Width & Height without propellers 40cm, Width with propellers at 90degree angles 55cm, and height with landing gear: 34cm.

This is based around an S500 fibreglass reinforced plastic FRAME with carbon fibre stiffening rods which not only makes it very strong and durable but also very stable due to the leaning arms, replacing parts can be done easily & cheaply as there are many parts available on eBay, it features wide landing legs & rails for attaching things like electronically stabilized go Pro camera gimbals such as the one included or extra battery mounts, the balls on the legs are also easily removable they are just pushed on for training uses.

The MOTORS are made by a company called Sunnysky (V2216 900KV) which are possible the most popular amongst the DIY drone community for their performance and reliability I have bought many of their motors in the past which have always performed very well and none have let me down, they have the best power to weight ratio of this class of motor, these handle 10×4.5 propellers with ease giving fast & responsive movement however it could work well with up to 10×5 or even 11×4.5 propellers for maximum lift / speed, the spindles are 5mm so are pretty much compatible with any propeller available.

The ESCs are 30a SimonK based speed controllers which use a custom software especially designed & tweaked for drones they are pretty much the go to ESCs for performance they are all completely modular so can be easily changed if you ever need to, they will also happily run a larger size motor should you want to carry anything seriously heavy (other than its huge battery, stabilized gopro mount and camera)

The FLIGHT CONTROLLER is a genuine Crius MultiWii AIO Pro loaded with the laest version of MultiWii (2.4 although it says 2.3 to keep it compatible with older software) this was chosen because it is without a doubt the best modular & configurable controller on the market, it has more inputs & outputs than you could ever need, it’s extremely powerful and flexible too because it can be completely tweaked and reprogrammed with just a micro USB cable & free Arduino software, it supports pretty much every type of sensor & communication device such as USB, Bluetooth, UART, i2c, long range telemetry, GPS, Sonar and so on… the board itself has 10 degrees of freedom (DOF) which means it has sensors built in to measure pitch, roll, yaw as well as forwards/backwards, left/right & up down acceleration and height in the air, there is also a 3 axis magnometer which measures pitch, roll, yaw from a fixed magnetic point  this is often misleadingly called 10 axis, you may see 6 axis on a lot of other cheaper drones but this is the best you can get.

The BATTERY fitted is a Turnigy 5000mah 4s 20c – 30c Hard Case LiPo which offers around 20 minutes of general flight, obviously less if you are pushing it, the hard case also ensures that the lipo cells are kept protected in the event of a crash as they can be easily damaged, this does add a bit of extra weight to the battery but the drone can easily handle it, of course larger or smaller batteries can be fitted if required.

The VIDEO GEAR consists of a 2 axis automatically stabilised GoPro camera mount (but no GoPro) this means that however the drone tilts in the air, the camera will always stay level this helps to give fantastic smooth video footage, it also has the added advantage of being able to tilt the camera whilst the drone is in the air to look further up or down, by simply changing the video cable the video output from the gopro can be fed into the video transmitter and back to the controller in your hands, I have included the cable to do this however it may be harder to fly the drone if just using fpv as the video feed will remain stable as the drone tilts in the air, I would also just like to mention here that I had the remove the front sony camera temporarily to get the gimbal to fit on but I didn’t try very hard so it may be possible to get both fitted on together, some longer camera rails would definitely do the trick or maybe even just some reorganisation.

The TRANSMITTER is a FlySky FS-TH9x which is often said is a fantastic controller let down by the software its shipped with, for this reason I have flashed it with a custom er9x which instantly upgrades it to compete with other transmitters worth in the hundred pound range, it just works flawlessly and you have a whole 8 channels to play with, you only need 4 for full flight so the rest can be very useful for changing the drone modes and moving the stabilised gopro mount remotely, the transmitter is also module based so upgrading it is as simply as unclipping the old one and slotting in a new one should you need to although the manufacturer stated range is 1km so you would probably need a good reason to do so, this of course may be less this will probably be in lab conditions.

The FPV gear consists of a Sony cctv style 12v 700tvl board camera with a wide angle lens allowing you to see more when you’re in the air, the video transmitter is a Boscam 5.8Ghz 200mw transmitter which although is not the highest specification video TX it is stated to have a range of up to 1km in open air, this of course could be changed as is with everything on the drone its very modular if you wish to use the drone with Fatshark goggles for example, there is a 7” LCD monitor attached to the transmitter with a built in receiver which will allow you to see what the drone sees whilst its in the air, this is completely independent from the transmitter, it just screws on so either can easily be changed should you wish, please note that that camera does have a tiny scratch on the lens but this cannot be seen on the video feed.

This quad is also fitted with a Ublox M6 GPS module which allows for features such as automatic return to home, flight path recording on maps & automated gps navigational flight however the software / firmware might need a little tweaking to get the automated flight working, I have not yet tested this but the gps is definitely set up for location tracking, so I can confirm that its working there may also be issues with compatibility of certain apps & software as its all 3rd party, my point being the features are there they may just not work with every application.

TELEMETRY I have fitted this drone with a HM-10 BLUETOOTH BLE 4.0 module which allows the drone to be wirelessly connected to your iPhone / iPad or macBook (iPhone 4s onwards or iPad 3 onwards) this may also be supported by android, I have managed to get it to work on my cheap Chinese android 4.4.4 tablet with the free ez-GUI app but Bluetooth LE support has only just been added so its in beta form, if you only plan to use it with android devices please let me know and I can change it for one that is supported by android and windows fully but will not work with ios devices.

some laptops also support Bluetooth 4.0 ble but please check first, you may need a usb 4.0 adapter to make it work with a windows laptop, however I have had it working flawlessly with my iPhone 4s, just download a free app called “MultiWii GUI” this Bluetooth module will allow you to monitor stats from the drone as well as gps position, and to tweak all of its flight & sensor parameters, it also allows you to set a gps flight path for autonomous flight but again I have not tested this fully.

I will also throw in a few spare parts and a couple few sets of propellers as well as a spare set of landing skids (in black) please note that the blue ones have small cracks as they were from another drone but still work fine, especially for learning to fly, a lipo alarm and any other bits I have lying around, and of course a charger to give you plenty of juice.

I would recommend these propellers:  http://www.ebay.co.uk/itm/APC-Style-Carbon-Nylon-Propellers-9-x-4-5-10-x-4-5-cw-ccw-quadcopter-props-/321429647065?pt=LH_DefaultDomain_3&var=&hash=item4ad6b32ed9

PLEASE NOTE: this is not a toy, it is a very high specification precision tool for videography / exploration or just fun, it is not as easy to fly as the toy quadcopters because it has a lot more power / features, it will not stand up to heavy crashes and should not be flown by anyone who does not have any experience as it can be very dangerous, on this basis I cannot accept any returns due to the nature of this hobby, it is likely that you will crash this drone at least once eventually if you are not an experienced pilot, having said that this is a fairly stable quadcopter so with persistence, patience & care it can be learnt to fly by most people, DIY drones require the pilot to actually know what he or she is doing, with some slight parameter tweaking it is possible to get it to hover still in the air without touching the controller but it may take some patience, practice and drone knowledge to get it flying exactly how you want it, I was able to record very stable footage with a little practice.

A simpler, less specialist option is the GPS Drone HMF600 Carbon Fiber Foldable Quadcopter APM with ESC TX&RX F11101-F, still not cheap at £391.77

GPS Drone HMF600 Carbon Fiber Foldable Quadcopter APM with ESC TX RX F11101 F
GPS Drone HMF600 Carbon Fiber Foldable Quadcopter APM with ESC TX RX F11101 F
HMF600 RC Drone Quadcopter frame Specifications:
Features:
This is a new folding copter quadcopter designed for professional FPV system.
16mm thickness tube.
Carbon fiber material.
All the arm tube with standard hole, and easy to assemble.
Folded Size: Length 355mm,Width 205mm
Recommend configuration (not included):
Flight controller: Compatible with most flight controller board (DJI MWC, WKM, FC1212-S, FY20A/30A, MK 2.0, GAUI INS).
Motor: 2212/2216/2814/4822 * 4
ESC: 20-30A
Propeller: HJ1238 Propeller and canopy
APM 2.8 Multicopter Flight Controller 2.5 :
Features:
– Arduino Compatible!
– Can be ordered with top entry pins for attaching connectors vertically, or as side entry pins to slide your connectors in to either end horizontally
– Includes 3-axis gyro, accelerometer and magnetometer, along with a high-performance barometer
– Onboard 4 MegaByte Dataflash chip for automatic datalogging
– Optional off-board GPS, uBlox LEA-6H module with Compass.
– One of the first open source autopilot systems to use Invensense’s 6 DoF Accelerometer/Gyro MPU-6000.
– Barometric pressure sensor upgraded to MS5611-01BA03, from Measurement Specialties.
– Atmel’s ATMEGA2560 and ATMEGA32U-2 chips for processing and usb functions respectively.1. data transmission port
2. analog sensor port
3. autostability gimbal output
4. ATMEGA2560 SPI online programming port (be useful for optical flow sensor)
5. USB port
6. remote control input
7. function selection jumper
8. GPS port
9. 12C external compass port
10. ATMEGA32U2 SPI online programming port
11. multifunction configurable MUX port (OSD is the defaulted output)
12. current voltage port
13. ESC power supply selection jumper
14. ESC output port

RadioLink AT10 2.4GHz 10CH Remote Control System :

Features:
Multiple function remote control system,including helicopter,airplane and slider three type flying machine and five models,cover almost every popular model,you can fly any model by this radio.
3.5 inch colorful screen 320×480 resolution,clear display menu and graphs.
Great control distance: 1.1km on the ground,2km in the sky.
Expansion feedback module,users can get plane details in real time.
Make very setting clear and exactly output result.
Fast response time only 3ms to the operation,faster then the other transmitter 20ms,even ten channels also let you feel it.
High channel resolution reaches 4096,0.25us per resolution let all the servos keep tranquil.
Strong anti-jumping,DSSS(Direct sequence spread spectrum) technology.
Unbelievable price, high quality as supper bland, and more exactly, faster response, higher resolution,one and the only one anti-jumping DSSS technology.really worthy to have it.
Technical Parameter:
1. Dimension:18×9.5×22cm;
2. Weight:0.95kg;
3. Frequency:2.4GHz ISM band(2400MHz~2485MHz);
4. Modulation mode:QSPK;
5. Channel bandwidth:5.0MHz;
6. Spread spectrum:DSSS;
7. Adjacent channel rejection:>38dBM;
8. Transmitter power: <100mW(PCB testing),
<20dBm(3 meter air testing);
9. Operating Voltage:8.6~15V;
10. Operating Current:<95mA;
11. Control distance:800 meters ground;
12. Channel:10 Channel,8~10 channel are customizable;
13. Compatible model: Include all 120 degree and 90 degree swashplate helicopter,all fix wing and glider,five flying model;
14. Simulator model:under the simulator model the transmitter action turn off,change to power saving model;
15. Screen:16 colorful screen,size 78×52mm,320*480 pixel.

Pictures in details:

IMG_1148

Tricopter

There is the tricopter: HMF Y600 Tricopter 3 Axis Copter Hexacopter APM GPS Drone with Gimbal F10811-D, for £398

Tricopter
Tricopter

It contains

Package listing:

1* HMF Y600 Tricopter 3 Axis Copter Frame Kit

3*750KV Brushless Disk Motor

3*HOBBYWING Platinum-30A-Pro 2-6S 30A Speed Controller ESC

2*Three-hole High Quality Carbon Fiber 15×5.5 Propeller set

1*APM 2.8 Multicopter Flight Controller 2.5

1*6M GPS with Compass L5883 25cm Cable

1* 10cm Servo Extension Lead Wire Cable

1*GPS Folding Antenna Mount Holder

1*8S-5A U-BEC

1*RadioLink AT10 2.4GHz 10CH Remote Control System TX&RX

1*RC B3 Pro Compact Balance Charger

1*11.1V 3300Mah 25C lithium battery

1* Aluminum 2-axis Gimbal Camera Mount PTZ

1*tool set

Hexacopter

Six blades? No problem with the S550 Hexacopter , DJI Naza lite with GPS , Turnigy 9X transmitter, for £20 with four days to go. Another kit, with equally impressive specs:

  • Included in this auction:
  • S550 Hexacopter PRO frame with carbon fiber landing gear
  • Turnigy 9x transmitter and v2 receiver
  • 2500mah Lipo battery for transmitter
  • DJI NAZA LITE with GPS (2015 version). Folding GPS mount
  • 6 x 20amp Afro esc with simonk firmware
  • 6 x AGM 2213 935KV motors  ( 3x CW and 3xCCW)
  • 10×45 propellers ( 6x CCW and 6x CW ) so 3 pairs are spare
  • Genuine XT60 power plug

Getting the hang of it

So, the S500 is the quadcopter, and the S550/F650 is the hexacopter chassis. There is a F450 quadcopter. FY680 is a folding hexapod, Tarot FY680 Full Folding Hexacopter 680mm FPV Frame TL68B02 carbon fiber boad, for £60.

Ingredients

So, the kit required, for a quadcopter, is as follows:

  • FRAME S500 fibreglass reinforced plastic  with carbon fibre stiffening rods
  • MOTORS – Sunnysky (V2216 900KV) – Choose from 2212/2216/2814/4822
  • ESCs are 30A SimonK based speed controllers which use a custom software especially designed & tweaked for drones
  • FLIGHT CONTROLLER is a genuine Crius MultiWii AIO Pro loaded with the latest version of MultiWii (2.4) (compatible with DJI MWC, WKM, FC1212-S, FY20A/30A, MK 2.0, GAUI INS). Or, APM 2.8 Multicopter Flight Controller 2.5
  • BATTERY fitted is a Turnigy 5000mah 4s 20c – 30c Hard Case LiPo
  • VIDEO GEAR consists of a 2 axis automatically stabilised GoPro camera mount
  • TRANSMITTER is a FlySky FS-TH9x
  • FPV gear consists of a Sony cctv style 12v 700tvl board camera with a wide angle lens
  • VIDEO TRANSMITTER is a Boscam 5.8Ghz 200mw transmitter
  • GPS Ublox M6 module
  • TELEMETRY HM-10 BLUETOOTH BLE 4.0 module
  • PROPELLER HJ1238 Propeller and canopy (10×4.5/10×5/11×4.5)

The cost of such an endeavour, in the parts alone, would be:

GRAND TOTAL = £359

The chap who built the above drone, nulumen, has built another, racing drone: Custom Pro FPV Racing Drone QAV250 80mph plus Goggles Silverblade 4s emax MT2206

Racing Drone
Racing Drone

This is based around a SilverBlade 250mm Carbon fibre fibreglass composite reinforced FRAME with carbon fibre and fibreglass sheets sandwiched together which not only makes it very strong and durable but also very light, replacing parts can be done easily & cheaply as there are many parts available on eBay from UK sellers I will of course be including a few spare parts, the frame has very little wind resistance which is in part thanks to its small size but also its thin sheet design this all together makes it extremely fast and agile when in the air.

The MOTORS are made by a company called Emax (MT2206 1900KV) which are possibly one of the most popular amongst the DIY drone community for their performance resilience and reliability I have bought many of their motors in the past which have always performed very well and none have let me down, they have the best power to weight ratio of this class of motor, and I have opted for the more powerful 2206 version because they can provide a much bigger boost of power to the propellers which translates to not only the capability to run bigger propellers for more speed but also the ability to make lightning fast movements when needed.

The ESCs are 15a (20a boost) SimonK based speed controllers which use a custom software especially designed & tweaked for drones they are pretty much the go to ESCs for performance they are all completely modular so can be easily changed if you ever need to, they will also happily run a larger size motor should you ever want.

The FLIGHT CONTROLLER is a genuine Crius MultiWii SE v2.5 loaded with the least version of MultiWii (2.4 although it says 2.3 to keep it compatible with older software) this was chosen because it is without a doubt the best modular & configurable controller on the market, it has more inputs & outputs than you could ever need, it’s extremely powerful and flexible too because it can be completely tweaked and reprogrammed with just a micro USB cable & free Arduino software, it supports pretty much every type of sensor & communication device such as USB, Bluetooth, UART, i2c, long range telemetry, GPS, Sonar and so on… the board itself has 10 degrees of freedom (DOF) which means it has sensors built in to measure pitch, roll, yaw as well as forwards/backwards, left/right & up down acceleration and height in the air, there is also a 3 axis magnometer which measures pitch, roll, yaw from a fixed magnetic point  this is often misleadingly called 10 axis, you may see 6 axis on a lot of other cheaper drones but this is the best you can get, which may all sound like waffle but it most importantly means that the drone can work in acro or self-level mode, the latter is much easier to get to grips with if new to flying drones, most do not have this.

The BATTERY fitted is a Turnigy or Zippy 2100mah 4s 20c – 30c LiPo (whichever works better at time of posting) which offers around 15 minutes of general flight, obviously less if you are pushing it, of course larger or smaller batteries can be fitted if required for longer flight times or faster speeds.

The TRANSMITTER is a FlySky FS-T6 which is a fully programmable digital 2.4ghz 6 channel controller the manufacturer says that its good for ranges up to 1km but this is probably under lab conditions so should probably be taken with a pinch of salt, that said I have never had any signal drop outs, pretty much any parameter can be tweaked to get it working exactly how you want to.

The FPV gear consists of a Sony EFFIO cctv style 12v 700tvl board camera with a wide angle lens (NOTE there are some light scratches on the lens but these cannot be seen on the video feed) allowing you to see more when you’re in the air, the video transmitter is a Boscam 5.8Ghz 8 channel 200mw transmitter which although is not the highest specification video TX it is stated to have a range of up to 1km in open air, this of course could be changed as is with everything on the drone its very modular if you wish to use the drone with Fatshark goggles for example, and of course at the receiver end I am including a set of quantum diy fpv goggles these are not the best quality goggles but they are a great place to start, they are effectively the same resolution as the fatshark teleporter goggles, just on a much cheaper scale, I have only half built these because they work best when shaped to an individual’s face shape, I have seen that some people attach these to a hat but I will be including just straps to attach it to your head it will only take a few small adjustments to finish these off, I have done the hard bit, including modifying the small screen with a matching receiver, of course if you want to use this with fatshark goggles as I did this can be done, the transmitter is not compatible with the standard receiver in the fatshark goggles, I built my own receiver module for my fatshark dominators (enquire if you are interested as its not included) but of course the video transmitter can be changes for one which will support the fatsharks natively.

The quad is not currently fitted with one but it is set up ready to attach a gps receiver so that you can use features such as auto return to home and autonomous flight this can all be done for around £20

TELEMETRY I have fitted this drone with a HM-10 BLUETOOTH BLE 4.0 module which allows the drone to be wirelessly connected to your iPhone / iPad or macBook (iPhone 4s onwards or iPad 3 onwards) this may also be supported by android, I have managed to get it to work on my cheap Chinese android 4.4.4 tablet with the free ez-GUI app but Bluetooth LE support has only just been added so its in beta form, if you only plan to use it with android devices please let me know and I can change it for one that is supported by android and windows fully but will not work with ios devices.

some laptops also support Bluetooth 4.0 ble but please check first, you may need a usb 4.0 adapter to make it work with a windows laptop, however I have had it working flawlessly with my iPhone 4s, just download a free app called “MultiWii GUI” this Bluetooth module will allow you to monitor stats from the drone as well as gps position, and to tweak all of its flight & sensor parameters, it also allows you to set a gps flight path for autonomous flight but again I have not tested this fully.

I will also throw in a few spare frame parts and a few sets of propellers as well as a spare ESC just in case you crash.

I would recommend these propellers don’t bother with any others, these are the best:

http://www.ebay.co.uk/itm/221487867921?_trksid=p2055119.m1438.l2649&var=520347663470&ssPageName=STRK%3AMEBIDX%3AIT

http://www.ebay.co.uk/itm/HQ-Prop-4-5-6-x-3-x-4-x-4-5-Carbon-reinforced-Quadcopter-propellers-props-/321407056976?var=&hash=item4ad55a7c50

For maximum performance this drone will happily run 6×4.5 size propellers all day long but of course I would recommend that you try different sizes to see what works for you, smaller pitch propellers will give smoother less aggressive flight which may be useful for learning to fly, I will throw in 3 sets (I think) of 5×4 propellers a set of 6×4.5 2 blade and a set of 6×4.5 3 blade

See also the blog on Octocopters.

After watching MythBusters, where they source some plans from the web for a  personal “jetpack”, with is actually a birotor backpack, they noted that cowlings increase both thrust below, and suction above, the rotor. A quick google led me to a thread which had been inspired by the self same MyhBusters episode. From Do cowlings around props increase thrust?

The primary efficiency-related purpose of a duct/shroud/ring around a propeller is to fix a problem created by abnormally high disk loading (trying to get too much thrust out of a prop that is too small).

All wings, whether fixed or rotary, generate thrust by accelerating air.  A natural by-product of this is the creation of a low pressure zone above the wing and a high pressure zone below.  The pressurized air seeks a way to return to equilibrium, and fortunately, most of it goes in the desired thrust vector direction.  However, the air near the tip of the wing finds a path of least resistance by merely wrapping around the tip toward the low-pressure zone, creating a vortex field or “tornado” like effect.  These wingtip vortexes can often contain (waste) a lot of energy, and the higher the upper and lower pressure differences, the worse they get.

You’ve probably seen the little fins sticking up on the wing tips of some larger aircraft – these are there to mitigate this undesirable vortex phenomenon and help the efficiency of the wing.  On a rotary wing (propeller), you really have only two options – you can make the blade longer, thereby accelerating more air and producing the same thrust (F=MA) with less pressure differential, or place a solid, fixed barrier near the blade tip in the form of a ring/tube/cowl/duct.  Naturally, the dimensions and contours of the barrier are as much a subject of engineering analysis as the design of the blade itself.

It is interesting to note that quite a number of aeronautical techies get wrapped up in the whole duct-design-thing and start evangelizing their use as if they were a panacea of efficiency.  In every case, their data compare an already overloaded propeller with the same prop using the magical shroud.  Viola!  They see tremendous results in fixing a mistake they should not have made in the first place.  Having been thoroughly researched by literally hundreds of scientists since the 1930’s, the properties of ducted propellers are well understood.  Assuredly, if there were such great advantages in using them, we’d almost never see a “naked” prop on any scale of aircraft.

However, there are indeed proper applications for a shroud, the most notable being one of dimensional constraint.  If for some reason you must generate lots of thrust from a short prop, such as with an autogyro (gyroplane) where you obviously don’t want the prop to collide with the main rotor, then having a duct is a good idea.  The Carter Copter and the high-speed-record-setting Sikorsky helicopter both come to mind as appropriate applications of duct technology.  If you need a compact form factor for some reason, a duct might be the answer.  If you want to reduce the prop strike dangers, it’s hard to ignore the potential safety benefits of some sort of barrier, efficiency considerations aside (the shrouded tail rotors on some helicopters comes to mind – they are a significant ground ops hazard).

On a small-scale quad, there is no point in applying a duct for efficiency – there are too many other areas of design attention which would yield greater results.  The collision ring bumper is a good idea, especially if you plan on flying around people or pets.  But don’t expect any great efficiency gains.

 

 

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