Summary: FPV racing multirotors with side force generators (SFGs), will drift less during turns, making them potentially faster on race tracks (watch the video comparison here). But the SFGs need the be carefully placed and dimensioned, so that aerodynamic centre and centre of mass are at the same position. Otherwise it will not work.
Recently, I was thinking about how to improve the handling of racing copters. I noticed since quite a long time, that different copters behave quite differently in fast turns: Some drift quite a lot (especially when they carry a larger battery or an action cam), others drift less. I was always preferring copters that drift as little as possible. That is also why I am trying to reduce the weight of my copters as much as feasible.
The amount of drift depends on the weight of the copter and the lift and drag of the fuselage for sideways air streams (side-slip). The larger the lift and drag, the more side force the fuselage produces at a given…
About a month ago, I was presenting an idea to make drones faster on race tracks: The so called ‘side force generators’ (SFGs) enable racing drones to drift less during turns, making them potentially faster. The placement of the ‘wings’ is very critical and mentioned in more detail in my earlier post on SFGs. Some people tested the SFGs and confirmed the enhanced flight characteristics. Other people didn’t try and didn’t believe that SFGs could help. I must agree that the concept of the SFGs is not so easy to understand. That is why I will explain it in more detail here.
Let’s start with something that everyone knows (figure 1). When you are going through a fast turn with your car, then your car needs to provide two forces to stay on the track (grey line): The ‘thrust’ (green) of your car needs to equal its aerodynamic and friction drag (yellow). When the car turns, then there needs to be a constant force towards the centre of the turn, called ‘centripetal force’ (red). This force is …
Ever wondered what propeller or what motor performs best for your needs? Here is a simple way to determine the performance of different propellers (or motors) directly in flight, using your multirotor, the blackbox and some math. In the past, a lot of static thrust tests have been done to determine the current, thrust and efficiency of multirotor propulsion systems. However, they don't tell you anything about the propeller or motor performance in fast forward flight. Aerodynamics in forward flight and with a non-uniform inflow of the air are very different from static measurements.
My questions were: What propeller has the better acceleration?(acceleration performance of propellers is theoretically closely linked to the 'grip' during turns. Because turning is also just an acceleration, see this post)What propeller will reach the higher top speed? And which one decelerates better when throttle is cut?
My idea was to mount one kind of propellers on the left side…
Letting the cat out of the bag
The TBS GEMiNi is a small hexrotor that is meant for fpv racing. The frame is based on my Shrediquette GEMiNi that I developed in spring 2013. Team Blacksheep (Trappy, Riscyd and Perna) contacted me a while ago, and we started to modify the design in order to improve it further and to make it more user and crash friendly. After some information had already leaked before the offical release (may it be on purpose or not... ;-D), the new TBS GEMiNi has now been officially announced on fpvlab.com. This means that you can very soon buy the GEMiNi multicopter!
Features of the TBS GEMiNiForward-tilting motors for efficient, high speed flightBuilt-in FPV camera (TBS ChipChip V2)Optional HD camera (Mobius Action Cam)CORE OSD/power supply with integrated current sensorReady for long range FPVCustom 4A ESCs with SimonK firmwareCustom T-motors4" propellersMotor distance: ca. 215 mm = 8.5" Taulabs Quanton-based flight controlCrash-friendly, yet integrated…
The last nights were a bit shorter for me, since the PCBs I ordered at bilex-lp.com arrived. They look really good and seem to be of high quality (I ordered a different "solder resist" colour, well, I like bright colors, but anyway... ).
So I had the opportunity to do my very first SMD solderings. This really seems to be comfortable... I will completely switch to SMD I think.
The I²C to PWM converters work! Here are the features: Weight under 1 g Works with (most likely many) standard ESCs (currently tested: HK SS 18-20A, ...) I²C address selectable via solder jumpers (4 standard mikrokopter addresses dec 82, 84, 86, 88)Refresh rate selectable via solder jumpers (417 Hz, 292 Hz, 155 Hz, 49 Hz)Pulse width (I²C 0-255): 990µS - 2010µS Pulse width at startup (3 s): 920µS Motor off when no I²C connection longer than 256msMotor off when microcontroller crashes (veeeery unlikely)Powered by the BEC of the ESC, or by an external 5V source (prepared as well)Very easy to connect: plug th…