Simple Mobius FPV

...cheap and effective

For a while I've been considering getting an FPV system but, with the complexity, cost and choice of systems and components out there, I had deferred on the matter indefinitely.

A few things bothered me; firstly having to have two cameras because the supplied FPV cameras only supply video without storage capability. Secondly goggles; purported to be the best to provide an immersive experience but having low resolution and a limited field of view for the most-part, unless you're happy to spend the best part of $1,000 on HD goggles. And having to buy corrective lenses separately if you wear glasses.

Then I discovered that they'd released a Mobius Docking Station with a built-in transmitter. This takes care of getting the video stream from your mobius while still enabling you to record as you would usually. All that is required is a 2-4S power input on a JST plug, making it a simple plug-and-play application.

Next, reviewing FPV screens as a cost-effective alternative, I came across the RX-LCD5802, a  7 inch FPV Monitor with a 800x480 screen. What's nice is that is has integrated 5.8GHz 32CH diversity receiver and built-in battery. Furthermore, the screen image is clear and bright and it has OSD and an auto-search facility. Only, get this off eBay; the same thing just much cheaper!

The net result is remarkably simple and effective; connect the antenna to the dock, slide the mobius into the dock and connect a power via a JST lead. The mobius should power-on automatically and you'll now be transmitting video!

Then, screw the antennas onto the RX-LCD5802, hit the power button and within a second you'll be seeing crisp clear footage straight off your mobius.

It's as easy as that...

GeeBee R3 750mm TRILOGY. PART 2: The Build

...so how does this work?

The GeeBee is a nice-quality kit, with solid EPO fuselage making it a smarter-looking proposition than a Rarebear, for example. While having a simple screw-together construction, it does however its construction poses a few questions.

How does the battery setup work, and where's the best spot for the receiver?

The first question is a puzzler, for me anyway having only had planes with unfettered access to the battery. Obviously, unless you're happy remove the wing every time you fly it, you need the ESC lead to remain in the battery hatch so it's accessible through the small hatch opening.

This I found achievable by mounting the ESC against the side of the fuselage, preventing the lead from falling back into the fuselage. This setup seems quite reliable, although packing the battery in and then feeding in the lead and connectors is still squeezy and awkward.

Regarding the receiver, in this case a twin-antenna Orange R615x, I mounted it in the central fuselage cavity which corresponds to a cavity in the wing moulding above. And, connecting all the servos from the back and the ESC from the front gives a very neat installation.

Next challenge is the bracing wire; five pairs of different length wires needing to be clipped into tiny hooks. Fifteen tediously fiddly minutes later I was finished.

The last trick was spinner and propellor. The latter simply gets tightened with a nut, with the spinner base in behind it. Then the spinner is installed; it comes with double-sided tape but, really, that's never going to hold. So I superglued it in place, with cardboard slipped in behind the base to keep it spaced off the cowling.

With everything in place the little GeeBee was looking good...

Trainstar Battery ESC & Receiver Packaging

...there's lots of room

The Trainstar has a very roomy fuselage, so there's bags of room for your equipment. The battery is housed under the nose, held in place with velcro and a velcro strap. The supplied ESC also gets mounted to this tray, alongside the battery.

Under the wing is a huge cavity for locating your, um, receiver and satellite reciever, if you want. The picture is taken from the underside as I have the wings attached. 

As I said there's lots of space...

In the Air

...with a little help from providence

I arrived at the field this morning to find it absolutely still and calm, a perfect sunny morning. So I happily unloaded the Walrus and set about getting it ready. I plugged the battery in then switched on the radio. The receiver lights came on but there was a lot more beeping than usual, and then the ESC started playing tunes...this was definitely not right.

A quick glance at my transmitter solved the riddle - it had shifted in the car over the weekend and the throttle was on full, setting the ESC in programming mode. Hastily I flicked the throttle off and checked the controls. Everything was working, excellent. Holding the Walrus aloft for pre-flight throttle check. No response. I'd somehow reprogrammed the ESC to isolate the motor.

So, standing at the field with a plane on a perfect flying morning, unable to fly because I'd disabled the plane...

I set about trying to reprogram the ESC with little hope of success, considering there are about half a dozen options identified only by a sequence of tones. First attempt made no improvement. Deep breath, yell of frustration and then try again. 

Mentally picturing when I had changed the throttle earlier, I pushed the lever down and then powered the transmitter off and on.

Lifting the Walrus up I flicked the throttle and success! The propellor powered up, and we were back in business. Prayer of thanks and the glider was flying into the clean morning air...

I'm All Walrussed Out

..but still got the wing cam to go

Well, after a Herculean effort, the Walrus is assembled, packaged, tested and ready to go.

Apart from the usual head-scratching over servo orientation, the cockpit proved the biggest challenge of all. Despite the generous appearance of the fuselage, it doesn't really provide a good packaging. 

Yes it is wide; I eventually installed the battery and receiver in a tandem layout. However the the cockpit is only just long enough to fit the 1800mAh battery - it literally butts up against the motor at the front, which is not optimal for cooling, and narrowly misses tail servo arm travels at full stretch.

I also had to make up a battery tray to allow a space for everything and provide a secure mounting for the battery. After having installed the tray for the second time (I removed it to swap out ESC's during my no-power troubleshooting session), I discovered that there was insufficient space for the bundle of servo cables going to the receiver.

So I removed the battery tray again, and cut a large slot through which the cable loom could pass from underneath, now running alongside the ESC under the tray, with the battery velcro'd onto the tray and the Orange R620 receiver velcro'd to the side wall of the fuselage in the canopy area. The R100 satellite receiver I stuck to the rear bulkhead.


But that's not all, with all this kit crammed into the cockpit the canopy wouldn't fit. So, I had to do extensive modifications to the canopy, cutting out the lower section, as well as a small cutout to clear the satellite receiver at the back.

However everything is now installed and working, control surfaces trimmed, flap travel set etc etc. Just the wing cam that now needs a home - external mount or internal canopy installation - some deliberation still required. I reckon the Walrus cockpit layout would qualify for a packaging award...

Why's there No Power?

what's going on...?

I've encountered a mystifying problem when I connected the receiver on the Walrus to the control leads. The setup in this particular case was as easy as you get, with each lead having with a numeric tag and the receiver having corresponding labels.

To make life even easier, the ESC already has an XT60 plug to connect straight to the battery. The only change I needed to make was to put an extension lead onto the control lead from the ESC, as this was just way too short.

However, when I powered it up nothing happened. Usually one hears a momentary chatter of the servos powering up, but this time absolutely nothing. To cut a long and most frustrating episode short, after having swapped ESC's and receivers to no avail, I have transplanted my six-channel receiver from the Floater with success.

The Floater, by the way, is still resting in the study...

The Death of a Phoenix

This morning I totalled my glider. Very annoying.

In the wake of my transmitter issues I hadn't flown for the best part of a week. But, with having the DX6i figured and the windy weather abating, the planets seemed to have aligned in the favour of flying. Sort of. As before, a break from flying didn't make the heart grow fonder. Only a bit nervous and a little uncertain. Not exactly ultimate zen.

Nevertheless, with a cool still morning, conditions were excellent with the sun just rising and the flying field deserted as usual. I attached the wing camera onto the Phoenix, my plans for a sophisticated aero housing scuttled when I discovered people used velcro to attach the miniature device. So, after a quick control check, I lobbed the plane into the air.

Now, I have elaborated before about the importance of a properly trimmed craft. As I recall, on the morning I forgot to check the direction of control movement. Yes, we really have covered all bases here. Well, I thought everything was even and good to go, but for some reason the Phoenix was making big left-hand banks. I'm not sure about other people but I find this very alarming.

You have to hold right aileron and rudder over just to keep it fly straight. I find that alarming. My attempts to keep trim on the go being less than effective, I turned the Phoenix in for a landing. Then decided I could keep going. Then flew into a tree. Yes, the same tree. Thanks for asking.

In the air again the Phoenix was now at least flying fairly straight, although I got the feeling that it still wasn't quite happy. Nevertheless, with it going into a climb I gave it full power then rolled over for a gentle loop and turned back towards the field. Now this is actually the first time I've flown in the morning with the sun above the horizon. As it happened, the Phoenix swooping, turning dive out of the loop put it straight into the sun.

I tried to turn it more but I wasn't really sure what it was doing in the glare, but I did know it was coming down quick. A split-second later the Phoenix cartwheeled at speed into the duck-pond, shedding wings and canopy, leaving a trail of flotsam and a submerged receiver beeping a sad alarm...

Some Progress

...and sanity maintained

Unfortunately trying the radio the next day and the chatter was back again - unfortunately my quick fix had limited remedial abilities. It was too much of a risk as the random movement could put the Phoenix absolutely anywhere and I didn't feel like that sort of a risk!

After having scratched my head and swapped everything in sight I finally bit the bullet and decided I needed to get another transmitter. Not that I really wanted one, in fact I didn't want to have to get another, but as far as I could see there wasn't any other option. Everything pointed to the aileron gimble on my unit as the culprit.

Thinking back, the ailerons on the Phoenix had actually chattered from the very first time I powered it up. Of course I didn't know then that it was actually the radio and not my crappy assembly effort.

So, after doing a little research I bought a programmable Spektrum DX6i 6-channel unit, the same make as my DX5e so as to be compatible with the receivers I already have. Now what I have found very interesting is that the programming abilities address two of the main issues I've experienced.

Firstly, it has two modes, flying and landing, allowing you to customise settings (flaps, elevator) to suit each regime and switch between them. In my case I want to use it for powered flight (reflex the flaps and a maybe a touch of negative elevator) and for gliding with everything neutral.

Secondly it has programmable travel, exactly what I want to make the Phoenix flaps manageable instead the source of mirth they are at the moment.

Anyway I have bound the radio and, after wondering why I was getting weird mixing between elevator and ailerons, switched from helicopter to aircraft mode.

I still need to do the servo-reversing for rudder, program mode settings and flaps. So the manual is getting studied well and truly as i don't want to fail this exam...

Resurrecting the Phoenix

Time to take the Plunge

The Phoenix 2000 had been resting nose-down against the wall ever since completion of repairs following its disastrous last flight. Walking into the study its presence served as a poignant reminder of the damage I'd inflicted. However its sleek graceful shape also provided aspiration that I might eventually develop skill enough to do it justice in the air.



That evening, its long-held position against the study wall was replaced by the terminally battered form of the Floater Jet.

The Phoenix took up the station on the desk, ready for final flight preparations. Deep breath, very excited...Working again with the Phoenix the great layout of its fuselage compared to the Floater became immediately obvious.

The moulded fuselage, while not outwardly much wider than the Flyer has much more space due to its thin-walled nature. It also has a battery tray, meaning that the ESC and the battery can occupy the same zone. The tail servos are also well clear of the “busy” zone as the Phoenix has removable wings with these located directly under. Consequently there’s lots of room left to locate the receivers.

I attached the receiver itself to the sidewall with velcro and taped the antenna running forwards. It certainly looks very neat and is wonderfully accessible. The small satellite receiver I velcroed to the top of the fuselage just aft of the canopy, orientated across the plane.

This layout fulfils what I understand to be the requirements for robust signal reception - receivers not blocked, with motors and batteries being the main culprits. Secondly the two antennas (single receiver antenna and satellite in this case) are orientated at 90 degrees to inhabit different radio environments, or something along those lines.

So everything's fitted, and the Phoenix's ready to fly, once again...