Advanced QuadCopter Design
- Please Note! this wiki section is for those interested in constructing and possibly even designing their own Quadcopter.
- For information on understanding how a multicopter works please go Here
- For information on how to build your own simple Quadcopter using kits or frames go Here
- For information on building or setting up a copter for first Person View (FPV) go Here
Motors, propellers and ESCs
For multicopters, motors, propellers and ESCs (speed controllers) are critical and have been failure prone in the past.
This ECalc based Xcopter: motor - propeller - battery - ESC calculator will help you pick the best parts for your copter.
- Quadcopter design is featured here as they are the most wide spread and the most versatile.
- But this information also applies to Hexacopter and Octocopter designs, either conventional or the coaxial Y and X types.
- The brushless out-runner motors have to support the full weight of the copter continuously while turning at high speed.
- Hobby grade motors have often used inadequate Conrad type unsealed bearings which are good axially but not in thrust.
- And the motors are usually open frame to permit the greatest cooling but providing little or no protection
- This has meant an unnecessarily high failure rate and very poor survival in wet or dusty conditions.
- The cheapest possible Chinese motor is never a good choice for something that literally hangs in the air by it’s motor.
- The best motors have 2 or better 3 easily replaceable ABEC-7 bearings, RCTiger-Motor Pro series and KDE for instance.
- Top motors are well ventilated, made with high temperature components and coated and sealed for environmental protection.
- The best motors like TMotor and KDE have performance comparison charts, these should be reviewed when designing a copter
- You are best off selecting motor - prop - battery cell combinations that will provide 10% or higher G/W efficiency at 50% throttle.
- You should target you copter design weight so that it hovers at approximately 50% throttle for optimum efficiency and flight time.
- Top motors can cost considerably more, but reliability, performance and efficiency will be better and worth it in the long run.
- Low KV motors running on lower voltage (fewer cells) with large propellers are more efficient and provide longer flight times.
- Selecting the best motor, propeller, battery set will enable you to build a copter with 20+ minute flight times including a camera.
- You can get 20+ minutes from 330 copters with 8 inch props to 700 copters with 18 inch props depending on payload weight.
- It is very hard to get much more than 30 minutes of usable flight time from any useful multicopter regardless of size.
- For hobby grade components, 15 to 20 minute maximum flight times are a more realistic goal.
- ESCs are also very important.
- High quality ESCs are more reliable than cheap ones.
- And ESCs need to be properly sized to ensure they can provide the maximum current that is necessary.
- Generally use the right size not over sized because they are more efficient if operated in the appropriate range (and lighter).
- Sufficient cooling is also very important especially for Heavy Lift copters, and the ESCs may need to be placed in the air stream.
- For small to medium QuadCopters there are four in one ESCs in the 20 - 30 Amp size range with several advantages.
- They eliminate the need for a power distribution plate or block and all the attendant wiring.
- The considerable reduction in DC wiring results in less magnetometer (compass) interfering DC EMF radiation.
- They can often be conveniently installed tidily in the center of the copter frame.
- The 20 and 25 amp ones work with 3 or 4 cell LiPo batteries and the 30 amp one works with 3 to 6 cell batteries.
- They have a built in aluminum heat sink plate on one side (which you can augment with a finned heat sink if necessary).
- You can use a thin layer of Fujik silicone thermal glue to attach a finned heat sink if one is needed.
- They generally have higher reliability than individual ESCs and are reasonably priced.
- Larger diameter slower turning propellers are normally a lot more efficient than smaller, faster ones.
- But there are limits and drawbacks:
- Trying to turn too large a prop for a given motor can cause it to overheat so motors usually have a maximum prop size.
- Also, really large, slow props can reduce the responsiveness of the multicopter and even cause it to oscillate in the air or vibrate.
- Unless taken to extremes these difficulties are not usually significant and can be compensated for by various means.
- And you can always drop the diameter an inch if the handling characteristics or motor stress are not what you want.
- There are also different designs of propellers and for larger ones turning at slower speeds design is especially critical.
- Carbon fiber designs with cupped blades that are wider at the hub and narrower at the tip are best for 14 inch and larger.
- Propellers 14 inch and under can be of more conventional design with a wider than normal blade and of plastic or CF.
- Often motors are charted with specific propellers and these are certainly the best starting point for optimum performance.
- TMotor is considered a premium prop, but good results have been obtained with RC-Timer and Tarot in the large tapered props.
- APC, DJI, GemFan, RC Drones and Graupner all produce good props in the 14 inch and under category.
Professional Grade Power System for large Quadcopters (28 inch Propellers)
- The Tigermotor U8 Pro Series motor is currently top of the line for a commercially available (large) copter motor.
- It features Environmentally protected, closed construction and easily replaceable bearings.
- They have very high quality two piece 27, 28 and 29 inch carbon fiber propellers for them as well.
- And a top quality 70 AMP ESC (speed controller) to go with it.
- U8 Pro T-Motor $300.00, 28 inch carbon fiber Props $370.00 a pair, 70 Amp Pro ESC $110.00 @ four each = $2380.00.
- These are used in the large Steadidrone Quadcopter shown above, clearly a top quality professional and expensive product.
- This is a very heavy lift and long endurance copter and is completely excessive and hazardous for most uses and needs.
- This combination will work well for a Quadcopter with a total weight of up to 24 pounds and can achieve 30 to 40 minute flight times.
- This is a copter designed for very serious uses that demand it’s heavy lift and long endurance capabilities and is not for amateurs.
- Disaster relief, search and rescue, fire spotting, surveillance, ecological and geographical survey and mapping are appropriate uses.
Professional Grade Power System for Medium Quadcopters (16 inch Propellers)
And a top quality 70 AMP ESC (speed controller) to go with it.
- Clearly, applying similar quality to a more reasonably sized (and cost) copter is normally going to be a lot more practical.
- A 380KV T-Motor 4008 is $85.00, 16x5 CF Prop $90.00 a pair and 30 Amp Pro ESC $50.00 @ four each = $720.00.
- This setup will work well for a copter up to 10 pounds or so and provide exceptional durability, efficiency and endurance.
- This is a very practical setup for a professional Quadcopter for photo or video use with full sized cameras and a brushless gimbal.
- You can choose 4S 14.8 volt, 5S 18.8 volt or 6S 22.2 volt batteries and 14 to 17 inch props according to your total weight.
- With a proper setup you could reasonably expect to achieve practical 30 minute plus flight times with full camera equipment.
- This is a very superior ($120.00) KDE 4014XF-380KV Motor with 3 large replaceable ABEC bearings rated at 200 hours.
- This motor is capable of using 13" to 18" propellers and operating efficiently with a wide range of batteries from 3 cell to 6 cell.
- This KDE Motor has a phenomenal range of operation and can be used on a 7 pound to a 20 pound Quadcopter.
- Every component and manufacturing technique was clearly optimized to produce the best possible motor without compromise.
- This motor has a finned heat-sink case and a self ventilated design with high temperature encapsulated components.
- In fact it is designed to run, if necessary, continuously at temperatures that would instantly destroy most other motors.
- It is reasonable to expect that various configurations could provide well over an hour of useful operating time with cameras.
- It is feasible to produce a QuadCopter that will approach the performance of the $15,000.00 Steadidrone at a fraction of the cost.
- A similar practical lifting capability and nearly 40 minute useful flight times should be achievable even with 18 inch Propellers.
- And given the extreme over design and ruggedness of the motors, similar reliability and longevity could also be expected.
- This is the motor I will be using in my next Quadcopter and I will allow for up to 18 inch propellers.
- KDE has recently announced additional motors in a variety of sizes and these are the top choice wherever possible.
A Hyper Efficient Medium Smaller Professional Grade Motor For Long Endurance
- The $70.00 T-Motor MN3508 380KV Navigator series motor is ideal for long flight time applications.
- This is the only motor in this size that can get G/W efficiencies over 17 at 50 percent throttle.
- If you want to build a 4-8 pound copter for maximum endurance this is the motor to use with a 4 cell LiPo.
- Because of it’s extremely high efficiency in it’s hover range it is also a candidate for high efficiency lithium batteries.
- Panasonic or LG’s high power Lithium batteries have about twice the energy density of the LiPos we normally use.
- But maximum discharge is only 2C so low current draw is required, the high efficiency of these motors can provide that.
- Carbon fiber 14 inch to 16 inch propellers will be required.
Professional Grade Power System for Small Quadcopters (10 inch to 14 inch Propellers)
- The largest market segment is for Quadcopters in frame sizes that use 10 to 14 inch propellers and weigh 3 to 7 pounds.
- The 650 KV T-Motor MT3506 at $65.00 is a high quality small, powerful pancake that can turn 10 to 14 inch props.
- With a 3 cell LiPo battery and T-Motor 14 inch prop at $73.00 a pair it can lift up to 7 pounds and achieve very good endurance.
- Add 4 T-Motor 18 Amp ESCs at $27.00 @ four each = $514.00 for top quality motors, props and ESCs.
- This small pancake motor can achieve good efficiency with 3S 11.1 volt or 4S 14.8 volt LiPo batteries and an appropriate sized prop.
- The frame should be sized to accept up to 14 inch propellers and various battery configurations.
- It should be configurable to achieve 20+ minute flight times with a GoPro size camera and brushless gimbal plus FPV or telemetry.
- This would still be a very capable and rugged Quadcopter capable of professional results and reliability.
- The above Motor - Propeller - ESC setups are all as close to professional quality as we can currently make them.
Consumer Grade Power System for Medium Quadcopters (14 inch to 16 inch Propellers)
- And they both work well with RCTimer 15x5.5 inch (4 for $28.00) or 16x5.5 inch (4 for $35.00) CF propellers.
- The Sunnysky Combo will cost about $260.00 and work very efficiently for copters up to about ten pounds.
- The RCTimer Combo will cost about $150.00 and will provide extended flight time for copters up to about 6 pounds.
- These motors will both actually support up to 17 inch propellers and work with 3 to 6 cell LiPo batteries.
- You could still design a copter that would get 30 minute flight times while carrying a GoPro and gimbal if desired.
- The frame for either of these motors should be designed to support at least 16 inch prop diameter and 17 inch would be better.
- These will not last as long nor be as reliable as the previous T-Motor configurations but will still deliver lots of solid use.
Consumer Grade Power System for Small Quadcopters (8 to 12 inch Propellers)
- Here is a durable and low cost alternative for powering smaller hobby or even semi-pro sub 5 pound Quadcopters.
- The DJI 2212 Motors provided with their low cost ARF Flamewheel Quadcopters are unusually durable and cost $24.00 each.
- And DJI specially hubbed 10 inch plastic props at $8.00 a pair are well balanced, efficient and rugged.
- And this easy to use $40.00 four in one ESC eliminates a power distribution board, reduces EMF and provides good reliability.
- For $150.00 you can actually get quite a useful and durable power system for a smaller sub five pound quadcopter.
- The $40.00 SunnySky X4108S pancake motor is also capable of being used on Quadcopters lifting up to 10 pounds.
- It is well regarded, efficient and durable and is suitable for use with 14 or 15 inch propellers and 4 cell to 6 cell LiPo batteries.
- Clearly these are not the only alternatives.
- If you want to use your copter for constant, professional use you will want something like the first 3 configurations.
- For occasional, hobby or non-critical use for flying, FPV and / or personal video or photography the others should be OK.
- The KDE and Pro T-Motor’s bearings last longer and are more weather proof and reliable than less expensive alternatives.
- And the more expensive Carbon Fiber props are more efficient, better balanced and more durable than cheaper alternatives.
- But properly installed on an appropriate copter the less expensive alternatives listed can provide many reliable hours of flying.
- I have favored slow speed pancake motors because efficiency and flight time benefit from the larger propellers they can use.
- The above illustrates just some of the possibilities in identifying an appropriate power system for your project.
The QuadCopter Frame
There are many types of frames and it is most important to put together a frame that is appropriate for your use.
- Multicopter frames are available as bare frame kits, Almost Ready To Fly or Ready To Fly copters.
- Most professional grade Multicopters are made from fiberglass and carbon fiber cut tubing and plate.
- Carbon fiber is very strong, but is also brittle and can shatter on impact, it is also hard to machine and to glue to.
- Fiberglass weighs a bit more for equivalent strength but is more shatter resistant and easier to machine and glue to.
- Fiberglass or carbon fiber tube and sheet construction are very suitable to use for making your own copters.
- Many consumer grade Multicopters are made with injection molded plastic parts and aluminum tubing.
- Some injection molded parts can be very durable (Iris’s Zytel frame arms for instance), but others are not and break easily.
- Square aluminum tubing frame arms are common, but they tend to bend or break with annoying frequency in normal mishaps.
- Except in specialized welded H or box frames aluminum tubing frame arms are sub optimal and will not be covered here.
- Some of the newer, smaller, commercially made Quadcopters have monolithic injection molded plastic shells.
- On smaller copters shells can be quite durable but they would be too fragile on larger ones even if mold costs were justified.
- A few Quadcopters have monolithic shells made from vacuum formed laminated Kydex or other plastic sheet
- Vacuum formed shells of laminated Kydex have proven very durable on small copters and are very good for waterproof uses.
- At least one vacuum formed copter has been made with blade guards, the Safe Flight 4410 (unfortunately out of business).
- Hand laid fiberglass or carbon fiber is also popular on high end quadcopters.
- There are some very attractive, hard to get and not inexpensive hand laid fiberglass and carbon fiber shells made by DeX.
- There are also a variety of fiberglass shells for civilian, commercial and military use including an amphibious one.
- Fiberglass shells tend to be expensive and may get damaged in use and can be difficult to repair.
- Each type of construction has advantages and disadvantages, it is important to figure out what meets your needs.
- Prop to prop and prop to frame clearance limit the max diameter of your propeller blades.
- Allowing for various prop diameters will let you tune the copter for its current weight, batteries and function..
- Allow an additional half inch of clearance from prop tip to tip or to center frame to avoid asymmetrical prop wash vibration.
- A major design criteria is to size the frame appropriately for the largest propellers you might ever want to use.
- Generally bigger propeller diameter equals better efficiency and an X frame layout normally permits the largest possible props.
- The motor speed and power and frame strength have to be matched to the propeller diameter and to total lifting capacity.
- Pancake Low KV, Low RPM motors can turn bigger propellers efficiently.
- It is possible to overlap prop tips if you have one above the other, but it does affect efficiency and induces asymmetric vibration.
- Big slow props can have adverse vibration, instability, gust compensation and response rate issues also so that is a downside.
- The additional motors of Hex and Octocopters can permit single motor out recovery and provide smooth flight for video.
- They need to use smaller propellers because of motor to motor clearance which is less efficient resulting in shorter flight times.
- There is also additional cost and weight of the frames and extra motors and propellers.
- And, the overall increase in complexity also reduces reliability.
- High quality extended service larger pancake motors and props are just starting to become available.
- We are likely to see a shift to large Quadcopters from Hexacopters and Octocopters even for professional and commercial uses.
X Frame or Dead Cat
Conventional Small X Frame Quadcopter
Typical Dead Cat or H Frame Quadcopter
X Frame versus H or Dead Cat: Advantages and Disadvantages
The Original X frame and more recent H or Dead Cat frames each have good and bad points.
- The original X frame design is a good all around choice.
- It is a symmetrical design, motor propeller units are spaced the same distance from each other and from the center of the copter.
- The weight (or mass) is also concentrated in the center of the copter.
- This symmetry means all motor propeller units can be treated as equals and control forces distributed equally.
- For photo, video or FPV use, the camera(s) must be placed under the copter in order to have visual clearance of the popellers.
- This lowers the center of mass increasing forces required for pitching and rolling the copter reducing performance somewhat.
- It also requires an extended landing gear (which must also not visually interfere with the camera) to clear the camera / gimbal.
- With a camera the X frame also presents a taller profile which is affected more by wind and gusts.
- The H or Dead Cat frame is specifically designed for photo / video applications and permits a front mounted camera.
- H design implies a central frame member interconnecting front and back members that mount the prop/motor units on each end.
- Originally H might have had a single central tube and could be subject to twist, but for our examples we assume a rigid frame.
- Dead Cat is named for a German enthusiast who turned his stuffed pet cat into a quadcopter.
- Dead Cat infers that clearance between front and back props will be larger than side to side clearance.
- Since the camera is in line with the frame, it presents a minimal side profile and is less affected by wind and gusts.
- On an H or Dead Cat a short landing gear is normally used and mechanical complexity and weight is somewhat reduced.
- The mass is still centered and is narrow side to side but long front to back with the battery counter balancing the forward camera.
- This long, thin mass means that more force is required for pitch control than for roll control.
- Prop/motor units are close together on the sides but wider apart in the front and back to clear the frame and the cameras view.
- This also means more force is necessary to change pitch than is required for roll.
- The combination of these two effects definitely requires that pitch be given more "authority" than roll.
- On an APM or Pixhawk, this means that the "Rate" Pitch PID P value needs to be higher than the "Rate" Roll PID P value.
- Normally APM parameters assume Rate for Pitch and Roll are the same, so they need to be unlocked and set separately.
- For a small to medium quadcopter with a small camera and brushless gimbal an H or Dead Cat is a more efficient design.
- An H or Dead Cat also generally has higher performance than an equivalent X frame with an under mounted camera.
- For larger cameras, and just due to wide spread availability, the conventional X frame is also a perfectly good option.
- Both frame designs provide an adequate camera platform, but where feasible, the H or Dead Cat can be superior.
The Carbon Fiber or Fiberglass Tube and Plate Frame
The carbon fiber or fiberglass tube and plate frame is popular because it is strong and light and easily manufactured.
- The Tarot 650 is a typical layout medium sized carbon fiber Quadcopter frame that can work with up to 17 inch propellers.
- It features folding arms and landing gear.
- It’s ability to support pancake motors and 17 inch props means it can provide long flight times.
- Some people have said the quality of construction is not as good as it could be but for $125.00 it is an amazing bargain.
- Fabrication requirements and techniques for fiberglass and carbon fiber tube and plate copters.
- On the copters shown above the method of attachment is by clamping carbon fiber tube frame arms with aluminum brackets.
- This is because of the difficulties in attaching carbon fiber parts as well as the stress that can result from drilling the tubing.
- Fiberglass is not quite as strong or light as carbon fiber but it is more flexible and easier to join and machine.
- If what you need is available in a commercial frame kit you are normally better off buying it as you will spend more making your own.
- It will also take a lot of time and effort to design the copter, to obtain the components and to, cut, drill, machine and fabricate them.
- There is also a strong possibility that design and fabrication mistakes and misperceptions will require that some things get redone.
- If you have sufficient reason to make your own frame, tube and plate construction is often most practical for home production.
- It is reasonable to mix materials, commonly carbon fiber frame tubes and fiberglass central and motor mounting plates.
- Carbon fiber and fiberglass tubing and plate can be cut with a hacksaw or power jig or band saw (with metal or fiberglass blades).
- It can also be drilled and milled with HSS or TC coated drills and mills, but all tooling wears out very quickly cutting these materials.
- Carbon fiber in particular is tricky to cut, drill and machine, it can tear, shatter or de-laminate if not done smoothly and slowly.
- A drill press is mandatory for carbon fiber, you cant center punch a pilot drill hole, so it needs to be held precisely in place.
- Avoid milling of carbon fiber if at all possible, it is very difficult to accomplish satisfactory results.
- You will see carbon fiber plates that have milled slots on consumer copters but these have generally been cut with a water jet.
- With carbon fiber you will generally get better results drilling precision placed holes rather than attempting to mill slots in it.
- You can carefully and slowly cut a carbon fiber plates exterior edges with a power saw and smooth them with a Dremel tool.
- If you must put in slots consider drilling a hole at each end and using a small circular saw on a Dremel or flex shaft to connect them.
- It will be necessary to provide appropriate brackets to clamp the motor mounts and central hub to the frame arm tubes.
- Tubing needs to be clamped but must not be crushed, silicone or rubber gasket can provide protection and vibration isolation.
- Hardware should be aluminum or stainless steel machine screws and you can use Nylok nuts or Blue Loctite on regular nuts.
- Plate separation and mounting can be provided with Nylon or aluminum standoffs.
- (Note: It would be nice if somebody made an X internal slip-glue fit ferrule for the center of the frame tubes but they don’t - yet!)
- There are a wide variety of Carbon fiber and epoxy fiberglass components to choose from.
- Carbon fiber products are available from RockWest Composites and Carbon Fiber Tube Shop and Dragon Plate
- A really good article on cutting and gluing carbon fiber products from Carbon Fiber Tube Shop
- Fiberglass and Carbon Fiber products are available from: CST Sales and ACP Sales
- A datasheet for 3M 2216 Epoxy Glue and a source for it Amazon I use this myself and it is great!
- A datasheet for Loctite 9430 Glue and a source for Loctite 9340 Amazon
Using manufactured Plastic and Fiberglass Components in Your Own Frames.
- Although often not reasonable to make yourself some parts can be used effectively in your own designs.
- There are retrofit kits like the Team Blacksheep FPV subframe for a DJI Flamewheel quadcopter that reuse it’s plastic frame arms.
- And there are many cases where components from various frames can be used to good effect in our own designs.
- It is necessary to research your individual design to assure that the component pieces are actually available from the distributors.
- Research can provide an excellent source of very desireable components:
- Like $14.00 CNC milled ultra tough fiberglass frame arms used in Hoverthings Quadcopters: (Their FPV Pro is a great frame).
- DJI injection molded frame arms from their Flamewheel copters are used in the TBS Discovery FPV frame.
- And although this injection molded 3DR Iris arm isn’t cheap at $27.00 it is made of ultra strong and resilient Zytel.
Homemade waterproof frame using a hinged electrical box
An excellent, very clean, rugged and waterproof design using carbon fiber arms and plastic electrical and plumbing parts.
- Here is a link to Alec Short’s construction article in Makezine
- I like the use of the central 4 way hub for stabilizing the tubes and the slip fit adjustable tension Ts for motor mounts are also great.
- The mounting of an APM or Pixhawk would really require the separate GPS / Magnetometer module in order to work correctly.
- There are a wide variety of latch type weatherproof electrical boxes which could be used for this.
- The main requirement is to get CF tube with an outer diameter appropriate to the plumbing / electrical fittings you want to use.
- I’ll definitely be visiting the electrical and plumbing section the next time I’m in Home Depot.
Vacuum Formed Frames and Components.
- Although this is specialized and requires a vacuum forming press it may be justified for some applications.
- A vacuum molding press can be made relatively inexpensively that can make whole small shell type frames or for components.
- Copters made this way can be made weather tight and even water proof and they can be incredibly tough.
- Kydex is a laminated plastic sheet that produces a quite strong monocoque shell when molded properly.
- The no longer in production Safe Flight Copters SFC4410-1 has a vacuum formed propeller protected H Quad Frame.
- And the inexpensive ($120.00) and extra tough, water proof Aquacopter frame (A really excellent tough frame).
- A fully functional vacuum forming system can actually be constructed with a shop vacuum and an electric grill.
- Vacuum forming can also be used to make central shells for copters with tube, plastic or fiber glass frame arms.
- This may be over specialized for most uses, but if you want to make tough, light central frame shells or covers.
- Or, if you want to build multiple small to medium Quadcopters that are tough and waterproof this could be just the ticket.
- (Or you could just buy an Aquacopter frame!!!)
Specific Building Examples and Techinques
- Some design considerations for a medium large, high efficiency, heavy lift Quadcopter build.
- A simple, rugged and very versatile X Quadcopter with a frame sized large enough to accept 18 inch propellers might include:
- High quality 20mm carbon fiber tube frame arms with SteadiDrone motor mounts and frame tube clamps from EBay or China.
- Cut and drilled carbon fiber or fiberglass top and bottom central frame plates mounted to the tube clamps and standoffs.
- A custom or commercial off the shelf landing gear system.
- A Pro configuration might include top rated $120.00 KDE 4014XF-380KF motors and a 30 amp 3 - 6 cell four in one ESC.
- The motors and ESC would cost about $540.00 and you would get a copter tuneable to lift up to 20+ pounds in total weight.
- It is reasonable to get this configuration to achieve usable 60 minute flight times even with photo or video equipment aboard.
- A more conservative hobby configuration might include $40.00 SunnySky X4108S 380KV motors and a 25 amp four in one ESC.
- The motors and ESC would cost about $200.00 and you would get a copter tuneable to lift up to 10+ pounds in total weight.
- Even with this setup you could achieve usable flight times in excess of 30 minutes with small to medium consumer size cameras.
- Some additional features that need to be considered are:
- A third frame plate under the two frame tube sandwiching plates can accommodate the batteries, ESCs and Receiver.
- A vacuum formed, fabricated or adapted top and bottom shell can weatherproof the copter and increase its survivability.
- This frame is less than 27 inches from corner to corner, but props can be removed for transport or folding arms could be used.
- This frame will be very light and strong and it will allow lots of latitude in how it is set up and it will be easy to upgrade.
- It’s ability to accept larger props even with an inexpensive power system will provide much better than average flight times.
- The copters capabilities will be according to the power system selected, the battery combination used and the total weight.
- You can include a camera gimbal under the center plate, make sure the landing gear does not interfere with the cameras view.
- The landing gear should minimize interference with prop wash and provide strong, resilient and stable support.
- If you really are determined to build your own frame, this (or a smaller lighter version of it) is a good place to start.
- The above design is a capable pro-grade Quadcopter with an exceptionally wide performance and endurance envelope.
A Small Quadcopter Optimised to Use High Efficiency Lithium Batteries
- Modern ultra efficient Lithium batteries can have nearly twice the energy per unit weight of the LiPo batteries we normally use.
- 3300 mah 3.7volt Panasonic NCR18650B batteries weigh 47 grams versus a normal LiPo equivalent of about 100 grams per cell.
- Their disadvantage is that their maximum discharge rate is only 2C so 6.6 Amps.
- They will also last for many times the number of charge discharge cycles of our normal LiPos.
- Used properly a copter using these batteries can get nearly twice the flight time of one with the same weight of LiPo batteries.
- The most important factor in designing a copter to use these batteries is to keep the weight low enough that their is sufficient current.
- This quadcopter design uses T-Motor MT2206 1200 KV 30 gram motors and 10 inch props with a light carbon fiber frame.
- It includes a 2S 2P 6600mah lithium battery, flight controller, receiver and even an FPV camera and transmitter.
- It weighs about a pound and since the battery is 2 parallel it can provide 13.2 amps of current (max current is less than 10 amps.)
- Xcalc computations show that a hover time of 60 minutes might be possible with a realistic fly around time of over 40 minutes.
This is an easy to build practical and rugged design with exceptional capabilities and double the normal flight time.
A small practical Dead Cat H Frame for FPV and GoPro with Brushless Gimbal
- This is a frame designed to be as small and light as possible for carrying a GoPro with a Brushless Gimbal and FPV.
- The Dead Cat design has proven to be very efficient and does not require a downward protruding camera gimbal.
- Depending on the battery this copter can weigh less than 2 pounds with cameras and a brushless gimbal.
- You gain considerable agility and safety using as small a copter as possible.
- This frame also presents minimal side profile so is less affected by winds and gusts.
- In the future, harsher regulations for heavier UAVs will probably force migration to small optimal multicopters like this one.
Ecalc calculations show realistic times for expected hover, but mix times for normal flight would be much longer.
ECalc calulates mix as 50% hover to 50% max throttle use and with this efficient copter you would never get close to that.
Normal flight times could be expected to be over 15 minutes with the setup shown.
Links To Specific MultiCopter Builds
- And some links to some of Forrests extremely ambitious copter building techniques and concepts.
A Commercial MultiCopter Exhibiting Advanced Design Concepts
The Aeryon SkyRanger is an innovative and professional quality QuadCopter design for high end UAV applications.
This copter has a lot of things right and is really a study in good design and quality construction.
- The rotating ball full enclosure camera Gimbal provides good weather protection and improved performance.
- The motors are on the bottom under the arms.
- More aerodynamically efficient with no prop wash interference and very little intake interference.
- Noticeably increased flight times, greater lift capability and quieter as well.
- High torque, low KV pancake style motors and slow turning, large diameter, high efficiency props.
- This is much more efficient than faster motors with smaller diameter conventional design props.
- This also increases flight times and load capacity and reduces the sound footprint.
- Tapered carbon fiber frame arms are more aerodynamically efficient and are light and very strong.
- The fully enclosed weather tight framework with snap latch type access makes maintaining the copter easy.
- A simple spring loaded landing gear provides for uneven landing sites and minimal interference with the prop wash.
This QuadCopter incorporates several excellent design concepts and shows what can be done without budget constraints.
The Skyranger has features we can use in our own designs but it is important to understand all designs are compromises.
The 3DRobotics Iris is one of the best designed QuadCopters that you can actually get and it is a real bargain.
Conclusion and Additional Design Considerations
- I have not covered either 3D printing or CNC machining.
- These are both perfectly valid techniques for either whole frames or for parts or accessories.
- But most people do not have the equipment or capability which is why they are not covered here.
- Clearly if you have either of these capabilities they can greatly enhance your copter projects.
- I have also not covered in depth hand laid fiberglass or carbon fiber or vacuum bagging.
- You can make Dynamite frames or shells this way but it requires serious individual skill and capability (especially carbon fiber).
- I have also not gone into detail about the engineering criteria for multicopters:
- A. I don’t know.
- B. From what I’ve seen very few people do.
- C. One who does is Paul Pounds PHD and here is his Paper on the subject: Quadrotors
- If you stick to a simple design and try to keep frame arm to a simple single small tube under the prop wash it will work fine.
- Round tubing has about half the flat plate area (prop wash interference) as the same sized square tubing.
- You can improve efficiency by putting the motor prop under the frame arm but then there are frame design and clearance issues.
- Try to keep the weight centralized as much as possible and keep the flight controller near the horizontal center if possible.
- So that the copter tends to roll and pitch as though pivoting around the center of mass and around the flight controller.
- But it is not as critical as some people have made it out to be because the stabilizing throttles will automatically compensate.
- You can do a lot with a rudimentary understanding of the forces involved, if you need more it is a career, not a hobby.