The Happymodel Crux3 is an ultralight 3 inch micro quadcopter capable of running 2s and 1s batteries. It ships with multiple on board and external receiver options including FRSKY, DSM and now TBS crossfire as well.
Happymodel have been quiet recently with their own brand so it is good to see them with a release again in a evolution of the ultralight micro class. This started with the Sailfly-x and Larva-x which were both in the 2.5 inch / 65mm class. The Crux3 steps up to a full 3 inch blade and uses all of their past learnings on making things lightweight in what I feel is more of a finished package.
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First look: FC/ESC/VTX
At the heart of this lightweight quad is the CrazybeeX AIO board which houses an incredible amount of gear: F4 flight controller, 5a 1-2s BLHeli_S ESC, 25-200mW VTX and in some versions and SPI receiver (although I've chosen a model with an external receiver here). This is an evolution from the excellent board used on the mobula 6 but adds 2s capability and increased VTX power, both a welcome bonus. The nature of this board means that all you need to do is plug in a camera, motors and battery and you are away - no messing around with small wires for 5v, ground, UARTs etc. It also makes manufacture and assembly much easier for the manufacturer BUT if something fails you are up for a whole new board
First look: Frame
There is quite literally not much to the Crux3 frame. It is ultra-minimalist and will surely be relying on the low weight of the craft to avoid damage in a crash. Be wary if you fly over hard object or a frequent crasher. If you do wish to swap for another frame this would not be difficult given this components are very simple
First look: Motors
Happymodel have opted for the EX1202.5 motor here which is no doubt inspired by KababFPV's 1s babytooth 3 inch ultralight quad however the choice of 6400kV suggests this has been designed for 2s rather than 1s. Motors are mostly typical of happymodel but good to see improvement over time - standard 4 screw mounting and I can see they have now gone with curved magnets and a tighter magnet-stator gap which should make for better power. Shaft size is 1.5mm which is typical for the category (although KababFPV has gone with 2.0mm for his micro motors)
First look: Camera
I'm impressed by the specs of this little camera - the Caddx Ant camera used here is a screw mounted 14mm wide unit that weighs just 2g. More impressive is that fact that it has 1200TVL and is fully controllable via the included remote for fine tuning. I'm looking forward to seeing how it stacks up in use. Nice to see that the canopy has four mounting points which should solve the Jello issues from the Mobula 7 and it's canopy with only 3 mounting points.
Assembly overall is super simple since components just plug in to the AIO board - it must make assembly a dream for Happymodel. Since I opted for an external receiver this had to be wired in but there is a perfect spot that is easily accessible through a large hole in the frame - plenty of room for the larger of micro receivers, namely Crossfire Nano and FRSKY XM+. A slim, foam battery pad goes over this to lock it all in place. So pleased they chose to go with a rubber band battery hold rather than a more bespoke and limited 3d print. It just makes so much more sense on a quad this size - cheaper, lighter, more durable and way more versatile to run any battery size.
Typically with a new bind and fly quad I look at the betaflight settings out of the factory and if there are no significant changes I'll update the firmware and use my own setting. The Happymodel Crux3 has really surprised me though - it has the very latest firmware (4.2.x at ime of writing) AND more importantly it has been tuned - RPM filters, dynamic filters, PIDs, rates, VTX tables. All the things that usually take time and experience to set up. The factory diff is below and the screen grabs explain the differences to default settings.
The Caddx ant lite actually produces a pretty good picture albeit a bit oversharpened as is typical with Caddx. With that said colours were crisp and it certainly looked good in the goggles (and obviously better than DVR below). These setting can be fine tuned via the (included) remote if required.
I ran the on-board VTX at 200mW - it's maximum power which is pretty impressive given given it is on the same board and ESC. My gut feel is that power is probably closer to 100mW but I believe that is plenty if you are using the right antennas. Most importantly I was looking for signs of electrical noise and I'm pleased to say there was very little - much less than I was expecting. If you want, I suspect adding a capacitor to the power supply lead would make this very clean (and help with voltage spikes too). Check out the DVR below to judge for yourself
Flight performance - Control
If you have had a chance to look at the DVR above, I can hand on heart say this is the very first light I took, right down to it being my worst 2s battery (more on the battery in a moment). My flight was not especially risky but it is in a tight area and I didn't crash once. This is not a testament to my flying ability but a nod to the excellent tune from the factory and well balanced components that Happymodel have chosen. It is very predictable to fly with a high level of control which makes it enjoyable
Flight performance - Power
This is a VERY lightweight 2s quad, around 70g with a 2s 450mah battery. I think for this weight they have their motor choice spot on - the EX1202.5 motors are as small as they could have chosen without sacrificing the ability to manage these lightweight 3 inch Gemfan 3018-2 props. I believe 6400kV is exactly the right kV option for 2s based on my experience with 5000kV on my TP3 build being a little slow on 2s and too much for 3s (see the review here). So it's a fairly quick little quad but not as fast as a heavier, higher powered micro that runs a higher cell count. If I were to put a number on it I'd say the same as a TP3 build on 2s or about 80% of the speed of a TP3 on 3s. This board is obviously limited to 2s max but it isn't really about top speed, it's about control and efficiency - read on...
Flight performance - Efficiency
Quite simply, this is the most efficient quad I have ever flow in any size. The easiest way to prove this is by taking your worst, oldest battery and checking the sag and flight time and this is exactly what you are seeing in the DVR above. The battery used was a 2s 450mah 30c battery that came with the original Fullspeed Leader 120 that I reviewed here over 3 years ago. This battery was rubbish way back then too! Even on this embarassment of a battery I got over 6 minutes of flight with the battery recovering to 3.77v per cell afterwards. On a more modern GNB 2s 450mah battery I got 7 minutes of flight which is just crazy. All I can say is, make sure your goggle and transmitter batteries are well charged!
As seen in the product shots this comes with a very basic insta360go mount but the mount itself is pretty useless and obviously a bit of an afterthought. Specifically it looks to mount with a weak looking twist-keyway that is sure to help lose your expensive HD cam when you crash. Furthermore the loose mounting will certainly give you a severe case of jello. I'm not saying this quad is incapable or unsuitable for using and insta360go but I'd definitely mount it differently. A quick look on thingiverse suggests that there are lots of options that can be 3d printed that look more suitable including the one below
3 1/2 years in to flying quads I don't crash much these days and if I do it is usually over grass so I'm probably not the best judge of durability. Using 4 m2 screws to hold the motors on is a massive improvement over the 3 x M1.4 screws used in the Larva-x which was well overdue (see why in my larva-x review). The canopy is also tough the overall low weight of the quad means it should hold up to mast accidents. I think the component to keep an eye on though is the frame. Even though it relatively thick at 2.5mm, there is simply not much to it especially through the centre section. This may well be the primary dowside in the extreme weight savings but I will reserve judgement unless I damage it myself.
Two things really stuck out for me, the ease of flying right out of the box as result of clever hardware choice and a very good tune and the efficiency. On the efficiency in particular I have never seen anything like it - over 6 minutes on an old 2s 450mah battery. Sure you could fly harder than I did above but this puts it well ahead of anything I've ever reviewed especially with the not unsubstantial power this has.
As a result of the main AIO board that has ESC, flight control, VTX and SPI receiver this truly is a simple, no fuss quad. FPV performance is pretty good and overall this comes across as an excellent little package that should please everyone from the beginner-intermediate range right up to an experienced pilot. Based on my experience with it so far I'm very pleased to recommend it as an excellent quadcopter in performance and value.
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