GT-AE Indoor Flight Laboratory

Building multi-rotor UAVs

Recommended parts suppliers

There are many great places to acquire off-the-shelf components for building UAVs, but these are Lee's recommended ones. Please feel free to contact me with other options not covered here and I'll ad to the list for future users.

Retailers for all components

Online

For purchasing pretty much all components needed to build UAVs, the following are great online retailers:

The following options are ones I recommend on the huge caveat that you proceed with caution as quality, assured supply, and consistency cannot be guaranteed. Alas, they do occasionally throw up some great options if you're willing to spend the time/money risking it:

Local

There are also brick-and-mortar options in the Atlanta area that have a good stock of components that you can go to in-person without waiting for shipping:

Propulsion System Combos (Motor+ESC+Propeller)

For high-quality, reliable, and super-efficient propulsion systems I highly recommend using propulsion system combos from either T-Motor or KDE Direct. These two manufacturers are of particularly high standard and produce a wide range of sizes. KDE Direct should be the go-to choice for projects requiring 100% USA manufacturers since T-Motor are Chinese.

The primary reason for recommending these two manufacturers is that they publish *actual* data for their recommended combinations, taking much of the guesswork out of sizing an aircraft. To find recommended combos, go to the product page for one of the motors and click on Specifications (T-Motor) or Performance Data/Compatible Configurations (KDE Direct). Furthermore, T-Motor offers some "Combo Packs" and KDE Direct has a "Build Your System" tool.

Individual motors, ESCs, and propellers, from T-Motor and KDE Direct are also a good way to go, in case you wanted to mix and match with other options.

Motors

For high-end options, pick T-Motor or KDE Direct. For less expensive options check what's in stock at any of the online or local retailers listed above, being sure to check for good reviews.

ESCs

There are a couple of particularly high-end options for ESCs: Castle Creations, and Advanced Power Drives. Both of these manufacturers offer highly-engineered ESCs that also include telemetry (RPM, voltage, current, temperature, and more) for you to interface with flight control, ground test rigs, or just for logging. For other high-end options, pick T-Motor or KDE Direct. For less expensive options check what's in stock at any of the online or local retailers listed above, being sure to check for good reviews.

Propellers

For high-end options, pick T-Motor or KDE Direct. For less expensive options check what's in stock at any of the online or local retailers listed above, being sure to check for good reviews.

In my view the gold standard of affordable propellers (as opposed to the high-end props of T-Motor/KDE Direct which are awesome but expensive) is APC Propellers. Not only do APC stock a huge range of inexpensive props that are customized for different applications (gasser, multi-rotor, etc.), but they publish data on the performance of all their props in their Performance Data section in the form of .dat files. These .dat files, believed to be analytically determined as opposed to directly measured, give you thrust and torque/power data as function of both rotor RPM and advance ratio (forward speed for fixed wing flight). This enables you to size props for multi-rotor drones particularly easily.

Batteries

There are two candidate battery chemistries for use in VTOL flight: lithium-polymer (Li-po) and lithium-ion (Li-on). Both are feasible, however Li-po batteries are typically selected based on them being readily available off-the-shelf for UAV usage. Li-on packs should be considered, however, since they offer a considerable amount to the more advanced user. The four main discussion points for deciding between the two are as follows:

  • Energy density (mass per unit of stored energy): Li-on has up to around 20% higher energy density than Li-po, which directly relates to flight time i.e. 20% longer flight for no weight increase.

  • Power density (mass per unit of discharged energy): Li-po has significantly higher power density, meaning it can tolerate higher rates of discharge than a Li-on of equivalent mass. This difference is significant enough that many VTOL aircraft cannot even get off the ground using Li-on. However, Li-ions are seeing increasing use in super-lightweight applications such as this one, and this one.

  • Off-the-shelf availability: Since Li-on cells are prolifically used, they are widely available in standard cell shapes such as 18650 (18mm diameter, 65mm tall) and 21700 (21mm diameter, 70mm tall), however they are not commonly found as packs of cells ready for use in UAVs. Conversely, Li-po battery packs are widely found ready to be used in UAVs but are rarely found as single cells.

  • Ability to optimize integration through shape and size: Following on from the previous note, the ability to source single Li-on cells in many different sizes gives us the opportunity to architect battery packs in shape and capacity with significant fidelity compared to Li-po. However, in order to do this it is necessary to spend a non-trivial amount of NRE (non-recurring engineering) time designing the packs and setting up the ability to configure them electrically. Furthermore, it is necessary to purchase a spot welder. All of this is feasible, but not for the scope of this project given Li-Pos are readily available off-the-shelf.

Lithium Polymer

Arguably the best Li-po supplier is GensAce/Tattu, with batteries ranging from the smallest you can buy up to the biggest. In fact, they are the only supplier of high-capacity, high-voltage, "smart" batteries, without needing to gang smaller cells. For example, this 12S 22000mAh 25C battery that has CAN bus and onboard memory for storing performance data.

You can also find Li-pos at any of the online or local retailers listed above, but be sure to check for good reviews.

Lithium Ion

Flight-ready Li-on pack are not currently sold, to my knowledge. Instead, you will need to find individual cell suppliers. My favorite is IMR Batteries. Since battery technology is constantly evolving, you should always check the stocked cells for those with the best performance at the time of buying. It's typically a good trick to sort all cells by price and start at the most expensive, checking the rated capacity and discharge rating for all cells. Reputable manufacturers such as Samsung and Sony should be prioritized since, despite being more expensive, they typically publish accurate specs. You will also need to decide which cell geometry to buy, with 18650 and 21700 being the most popular currently. If I were building a Li-ion pack today (6/29/21) I would almost certainly use this Sony VTC6A cell with a whopping 40A discharge rating and a 4100mAh capacity.

If you decide to also integrate a battery management system (BMS) to provide health monitoring, balance charging, current limiting, etc. (highly recommended), there are two recommendations worth considering: this one and this one. I haven't personally used these, but I trust the recommendation.

For a good high level guide on how to build Li-on packs, see this YouTube video.

Airframes (out-sourced)

TBD in detail but check out the online and local retailers listed above. Tarot in particular makes some good frames.

If you wish to have custom carbon fiber frames made, Plastic Spider has provided multiple projects in GT-AE with great quality parts in quick turnarounds. You will just need to produce DXF files of your design and send to them for quote.

Flight Control

TBD in detail but I thoroughly recommend Pixhawk Cube-based systems. Check out IR Lock (Georgia supplier) and Spektreworks.

Wiring and connectors

TBD in detail but for wiring you should always use highly flexible silicon cable of sufficient thickness (low AWG number) to carry the current of your application without introducing too much resistance into the circuit. Amazon stocks good quality wire selection kits of various diameters, such as this one, but you should try and order good quality wire from your motor/ESC supplier.

You will likely need various connectors over time, such as XT60, XT90, EC5, AC150, Deans, generic bullets, Anderson PowerPole, since different motor/ESC/battery suppliers use so many different types. In all cases you should always strive to buy genuine connectors (not cheap copies) from the motor/ESC/battery supplier or the original manufacturer although I have bought lots of good quality connectors from the above online and local retailers.

Miscellaneous materials, hardware, and fasteners

TBD in detail but you will need at some points to buy miscellaneous materials, hardware, and fasteners. Good local resources for this are Home Depot, Lowes, McMaster-Carr (online order but local pickup within an hour is possible), and Metro Bolt & Supply Co. This is in addition to the above-mentioned online and local retailers.

Building airframes in-house

TBD in detail but it is also very much possible to make airframes in-house. Depending on the scale of your build you will use some combination of the following parts/techniques:

  • Tubes (carbon fiber or aluminum)

    • Cut to length using a miter saw with appropriate blade or on the Do-All in the GT-AE machine shop (or mill if you need particularly well-machined ends)

    • Circular or square/rectangular profiles can be used

  • Plate (carbon fiber, aluminum, polycarbonate, acrylic, garolite, plywood)

    • Hand-cut if it's simple geometry - just print your design 1:1 on paper and glue it to your plate then cut with whatever tool makes sense (bandsaw, drill press, hole saw, Dremel, etc.).

    • Laser cut in the GT-AE Yang Aero MakerSpace if it's a laser-able material (acrylic, plywood, some other plastics)

    • Waterjet cut in the GT-AE Machine Shop

    • Outsource to Plastic Spider

  • 3D-printed brackets, arm clamps, etc.

  • Aluminum tube clamps

    • Servo City has a large range of tube clamps, including side-tapped clamping mounts which can be used to connect round tubes to flat plate and thus make significantly large airframes really easily

Some good resources for purchasing raw materials to perform in-house builds, in addition to the risky online retailers listed above, are:

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