With the (hopefully) incoming new rules on RPAS classification, I was looking for a sub-2KG frame that could be used for aerial filming. The HobbyKing Q450 Quadcopter seemed to be the ideal solution…
There’s no denying it, the HobbyKing Q450 Quadcopter is a direct clone of the DJI F450 “Flamewheel”. The only noticeable difference I can see is that whilst the DJI frame will set you back around $62, the HobbyKing clone comes in at a budget friendly $10. I’m sure someone out there can tell me the difference but at the moment I’m having a hard time working out how DJI (or rather its distributors) can justify charging the extra $50.
Anyway, here at Red20RC we are always looking for the best value route to a successful outcome so a Q450 frame along with some NTM2826 1100KV motors and Multistar ESCs were soon on their way. I already had an HKPilot APM 2.5.2 sitting on the bench looking for a home so the scene was set.
Of course, this wasn’t going to be just a quadcopter for flying around the field. I wanted a stable filming platform. This was of course the driver for using the APM clone, the ability to altitude hold, loiter and return to launch a pre-requisite for steady filming. But what about mounting my trusty GoPro Hero 3 to get that perfect shot? Once again I had a look through the HobbyKing catalogue and read good things about the Tarot 2D gimbal for GoPro type cameras.
At this point I usually go into a detailed build log but this project has been going for a long time with many twists and turns. I’m only going to give you the highlights and maybe a nice gallery of pictures. Read on…
The first build of the HobbyKing Q450 Quadcopter progressed much as you would expect for a frame of this type. Everything screws together nicely although some preparation work was required soldering the power leads and ESCs to the excellent power distribution board that makes up the lower plate. Everything fits together nicely with the motors bolting directly to the arms.
The flight controller needed some isolation from the main frame so I used an old plate from the SK450, mounted on some cut-down foam earplugs – sounds wierd but it works well.
It was whilst trying to mount the gimbal however that I hit my first snag…
HobbyKing sells a great range of affordable “crab” landing gear that are just perfect for lifting your frame up out of the dirt so you can hang a gimbal. They even have rails set at the standard 60mm for clipping on a whole host of different gimbals. Unfortunately I soon discovered that the rail mount arms on the Tarot 2D are set at 50mm so were utterly useless on this frame. In the end I had to bodge a direct mounting to the bottom plate. Not ideal but it worked.
With the APM up top and the gimbal down below the only space left I had for batteries was between the plates, fortunately this space is quite large so anything up to a 5000mah 3 cell fit easily, although was difficult to secure without wedging it in with foam.
The first few flights were conducted out behind the house and demonstrated a couple of things:
- It flew
- It didn’t fly very nicely!
I had spent a lot of time tuning the APM using the real-time tuning methods described on DIY Drones. By allocating different parameters to the channel 6 knob on the Taranis I was able to tune out the wobbles by holding the frame in my hand and adjusting the settings with the motors running. The result was a nicely locked in frame but it still seemed hard to keep still. Switching to altitude and loiter modes highlighted the problem as the frame instantly tried to drop out of the sky – something wasn’t right with the APM!
I did a few tests and discovered upon running the “compassmot” test that there was a LOT of interference from the ESCs. The only solution was to get the APM higher up…
More problems 🙁
It was during this initial testing phase that I hit my next problem. After re-attatching the gimbal I went up for another test flight. All was going well until, with a judder, the gimbal simply stopped working. Tests later revealed that whilst the board would initialise fine the motors simply locked into place and wouldn’t stabilise a thing. I got grumpy as I needed a gimbal for this frame and quickly had a replacement on the way in the form of a much cheaper Quanum 2D gimbal.
At this point I need to give a nod of thanks to the HobbyKing returns service. A lot of people knock HK, especially for their customer service, but I have never had a problem and my Tarot gimbal was quickly returned and replaced without a fuss.
For the second build I stripped everything down once more and made some changes to the frame.
The APM got raised up another couple of centimeters on yet more earplugs. It was starting to look a bit silly but I had to get that compassmot result down.
I also changed the landing gear mount to try to make the new gimbal more accessible. I found another old plate and attached this to the bottom of the landing gear mounts. I also mounted rails to the underside of the frame so the landing gear could clip on rather than using hard mounts that were weakening and distorting the lower plate of the main frame. Rather than bolt the gimbal in place I chose instead to mount it using cable ties – this as we shall see later is a good idea!
With these changes the compassmot readings had now come down to just within acceptible limits so it was off to the field once more.
I had also now added a 250mw video transmitter so I could use my new Quanum FPV groundstation to see the view from the GoPro.
The frame now felt a lot better in the air. Altitude and loiter was considerably more locked in and I was finally able to test out the autonomous flight capabilities. There is some flight videos but to be honest they are REALLY boring so I haven’t done anything with them yet – maybe later.
The Quanum gimbal performed well although didn’t feel quite as solid as the Tarot. I liked the setup though and hooking up the pitch control was really easy.
The things I liked about this frame were the automated take-off and landing phases controlled through mission planner. To be honest, the computer was better at landing the thing than I was! The Quanum ground station is excellent and with the Immersion RC Uno reciever I had a nice clear image on the monitor throughout the flight.
I still wasn’t happy with this frame as a serious filming platform though. With the GoPro set to 1440/48 I was getting a lot of landing gear and frame arms in the shot. To top it all off it kept on yawing to one side, which wasn’t ideal for that steady shot.
Enter the HKPilot APM 2.7
HobbyKing came up with the solution in the form of the new HKPilot APM 2.7. Making it easy(ish) to connect an external compass I now had the means to get that problematic compassmot level right down. With one on the way I stripped the frame down again and got going on build three…
This third and final build was going to be the ultimate solution. With a brand new controller and a custom isolation mount the computer systems were finally coming together. The new Tarot gimbal had arrived and I even splashed out on some carbon props!
Things were looking good. Running the tests showed the effort was worthwhile – compassmot was down to an astonishing 2%. I moved the gimbal forward slightly and trimmed down the landing gear to clear the field of view.
Test flights showed that things were a lot more stable, although I still had some little niggles when flying it manually.
It was a windy day when I finally headed down to the field for some serious filming practice. The first flight went really well. I hopped up to a good altitude and switched to loiter mode. Control was positive and I found I could easily push the frame around the field whilst concentrating on positioning the gimbal through the monitor.
With the first battery spent, I plugged in another and went up again. This time it seemed to be having trouble holding position so with only about 30 meters of air beneath me I hit the RTL switch to get the frame down safely…
The post-mortem discovered that those carbon props are a problem if you don’t have motors with a T-mount system. I had been forced to use some spacers to fit them on the prop adapters and a couple of the prop nuts had come loose during that first flight – one with fatal consequences.
TOP TIP: Quads just don’t fare too well when you convert them to a tricopter in midair!
Fortunately the damage was minimal. I snapped an arm and the landing gear is toast but that is about it with the exception of a few props. Deciding to cable tie the gimbal in place was a genius solution as the impact simply snapped the ties rather than damaging the gimbal. The flight controller and everything else up top was completely untouched. I’m just lucky I was at 30 meters and not 130.
So that was the sad end to a long and frustrating project. The HobbyKing Q450 Quadcopter is a nice little frame with bags of potential. I got annoyed with how messy the build became and the problems with the undercarriage and gimbal mounting made for a solution that just wouldn’t be repeatable commercially (I had intended to offer this package through Remote Pilot).
The external compass is the way to go on this type of frame, espescially if stability and autonomous control are your end goal. The Quanum gimbal is excellent for the money but I’m not sure it quite measures up to the Tarot in terms of performance.
As a side note – the motors, ESCs, Taranis and APM with telemetry never missed a beat throughout.
It’s just a shame it ended the way it did.
I decided after the crash to put this one to bed. I’ve got another HK frame coming that I will play with as a straight X quad for filming but in the meantime I’m working on something even better as a long-term solution to my camera platform needs.