When I recently got send the latest incarnation of the Axial Wraith to review, as well as adding a winch and the usual weight biasing of the front wheels I also intended to add FPV into the mix too. For those not familiar with the term, First Person View lets you drive the vehicle as though you were inside it, often putting the camera that facilitates this in the same position that a real driver would sit.
This wasn’t an ordinary kit either, in addition to the full tube-frame chassis design, manufactured with high strength composite materials that’s the trademark of the Wraith design, Axial have also added into the Spawn kit some pretty impressive components. For a start the kit comes as standard with Licenced ‘METHOD IFD’ beadlock wheels. These are black composite plastic 12 spoke and unlike many other beadlocks on the market are easy to assemble (using just six bolts) and they will work with most commercially available 2.2 tires. The standard 12mm hub design allows the wheels to be mount to any Wraith, AX10 Ridgecrest or SCX10 (not to mention ‘almost’ every other rig out there running 12mmm hex’s). The IFD aspect (or Interchangeable Face Design) makes it easy to change the look in the future as Axial plan to realise different outer ‘face’ options. They even come with adjustable breather holes built in (one to three holes are available as a fine tuning aid), so no more making holes in tyres or trying to drill wheels at weird angles once assembled!
My biggest bugbear with the RTR was the use of plastic lower links and shocks. The links tended to bend under load and cause instability in geometry, and while the plastic shocks are fine initially, they can start to leak and wear far faster in use than their alloy equivalents. Axial have more than countered my criticism by including with the kit a full lower alloy 4-Link suspension system, and performance, threaded-bodied, polished to perfection ICON Vehicle Dynamics shocks (and then clear coated to protect their finish too!) Not only do the licensed shocks look way cooler, they are made to far higher tolerances, so perform better too!
The 4-link system uses 7mm oversized diameter alloy tubes and has been optimized by the designers to reduce axle steer and to have the proper amount of anti-squat and roll characteristics in use. For a rig with two fully locked diffs the torque twist evident when you hit the throttle is minimal, and this system also aids against ‘suspension/axle wrap’ in high power brushless applications.
The most iconic part of the original Wraith (other than that cool cage!) was the AR60 axles. Compared to the AX10 axles we had all got used to on our crawlers and scalers the much wider offset pumpkin provided more ground clearance running 2.2 wheels and a much better driveshaft angle. The rear axle had also had all unnecessary items removed for as much rear ground clearance as possible. The axles are constructed from a high strength composite with an ultra-low flex rate, without the tendency to become brittle like glass reinforced plastics. The axles have a separate bolt on truss to distribute stress over a larger area and these trusses also incorporate the top 4-link mount for the alloy linkages.
It’s no secret that I’m a big fan of quad racing and FPV, I’m now also editing a Multirotor mag, and this genre of RC is growing at such a fast rate of knots’ that it was inevitable that it would spill over into the car world. The camera I used in the space where the winch normally sits on the bumper is derived from a 700TVL Sony CMOS CCTV boardcam unit, and has had the outer case removed, then the circuit board itself waterproofed with clear liquid electrical tape. It takes a wide variety of voltages from 5 to 14v and in this case is powered from the same 1300 3S pack I’m using to power the VTX (Video Transmitter). Now for ground based FPV this a budget this CMOS boardcam is an ideal solution, a CCD type would definitely perform better, with an improved dynamic range, light handling and colour characteristics, but can cost six times the price! If you find FPV is for you its east and simple to upgrade at a later date.
But why only 700TVL and not full HD? That’s a simple one to explain…Lag. The way the current breed of 5.8Ghz VTX transmit the analogue signal means that as you increase the resolution, you also increase the lag in milliseconds between what the camera sees real-time and what your eyes and therefore brain can comprehend. Lag is negligible using a 600TVL or 700TVL camera, but becomes worse as you hit 800TVL and 1000TVL. At the higher levels flying and fast ground based FPV becomes impossible, you’ve hit an object before you even realise and can react to it. In slower FPV applications like a multirotor filming platform or say a slow moving boat or scale vehicle it’s not so bad, but I always like to view a completely real-time image. If you shop around online or go to RC air shows you can often pick up a VTX and camera for under £40 for the pair. Brands like Boscam and Skyzone produce budget VTX units and Fatshark and TBS (Team Black Sheep) quality items.
WARNING: Now here we get into legal territory, as in the UK unless you have a specific licence, the 5.8GHz transmissions you are allowed to produce must be kept to 25mw or under ‘legally’.
Finding the right antennas can also be a minefield, and as with all RC electrics, better quality units can cost upwards of £70 a pair. Recently I’ve been using Fatshark Spironet and Aomway Four Lobe RHCP (right hand circular polarised) units on both my VTX and Headplay headset. The former cost about £40 a pair and the latter £20. The Fatsharks have the advantage of having protective covers over the lobes, but for a n application like the Spawn where the VTX is hidden inside the frame and the antenna not seen, the Aomway’s work a treat!
Now don’t go thinking you will get amazing range from any ground based FPV system, especially if you drive in in, near or through a built up area with lots of metal or objects to deplete the VTX signal. Wide open spaces are best, as is driving up an elevation if possible, that wat the signal will go much further. There are tricks like using a long VTX antenna mast combined with a antenna tracking base station, but that adds extra complication and cost to the setup. This is about having fun remember!
In use the Spawn handles just as I expected. And that’s important with any FPV vehicle. It took most obstacles I threw at it in its stride and was both capable and predictable. Driving it LOS (Line Of Sight again afterwards actually seemed weird, but that’s how I will be competed at the UK Scale Nationals and UK RECON G6 with it in 2016.
Placing the camera In the centre of the bumper was definitely the best position driving it by FPV as I could judge the distance between obstacles far better. Yes I had a few mishaps and the rig rolled over, or I got the undergrowth stuck around the axle and it tethered the rig to that spot until I (or a helper) could step in and released it, but that’s one of the quirks of this type of running!
I don’t think unless it was a very controlled environment I would risk running it by FPV on my own, but a group of us have been discussing making an FPV only trail section and running this as a separate class at the next RCCZ Nationals.
A huge shout goes out to Axial Racing for supplying the kit for me to review, and to the FPV Racing quad scene for inspiring me to add FPV to it in the first place. I will be experimenting further with antennas and different setups for both control and video…
Words & Images: Madpete: https://twitter.com/rrci_madpete
Manufacturer: Axial Racing USA (www.axialracing.com)