HOBBYMATE ASTEROID 3 INCH QUADCOPTER: Review

The Hobbymate Asteroid is a new 3 inch quadcopter that is available in kit, BNF or PNF formats that is available with motors and electronics suitable for 4s or 6s (!) operation. Following on from the awesome Hobbymate Comet (built here and reviewed here) this is another premium set of components at a spectacular price. It is available exclusively from HobbyCool.com here:
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http://hobbycool.com/asteroid-3-mini-fpv-racing-drone-kit/

In part 1 of this blog here I looked at the build and betaflight setup process in full. In this part 2 I'm taking a closer look at the components and review in general.

On the bench
From a specs standpoint this is a pretty special kit but that only tells half the story. I'll walk through the components and talk about their strong and or weak points

Hobbymate 1505 motors made by RCInpower. These are the stars for me. Like other modern RCInpower motors they are beautifully made: the single piece machined bell, the strong magnets with retention ring with an impossibly small air gap and the multistranded windings. Just as interesting is the size choice. 1505 is a wider stator but much shorter than usual. As a result it should have more turning force (torque) but potentially less top end and better efficiency as a result. Although it sounds like a large number the stator volume is not actually that big - see my comparison table below for some suprising comparisons.

1108	1306	1407	1408	1505	1506	1606
760	796	1077	1231	883	1060	1206

Comparison of common 3" motor stator volumes in cm^3

​Motors are available in 4300kV for 4s and 2700kV for 6s. Mine are 4300kV which I feel are a little high for 4s but more on that later.

iFlight SucceX F4. This is a pretty special unit from a specification standpoint, the most compact powerful flight stack to date:

• 35A BLHeli_32 ESC
• F4 flight control with 3 UARTS
• 25/100/200mW VTX

Like most modern iflight products it is nicely made and presented.

Asteroid 3"Frame. Well made but nothing particularly groundbreaking here although it does look durable and relatively light. Very stretched-x design, sandwich plate lower deck with 4mm thick (!) arms, 3 hole mounting for motors. It is unique in that it is designed for 14mm wide cameras only which up until recently was just the Caddx EOS 2 but now includes the more capable runcam racer nano as well. Frame weight is 35g

Caddx EOS2 FPV Camera. Based on my experience with the Eachine Trashcan I wasn't looking forward to using it again because of the awful vertical view in the 16:9 variant. I'm please to say the Asteroid 3 inch kit ships with the 4:3 variant instead which is much better and certainly passable as a budget (and lightweight) FPV camera.

Propellers are not included with this kit. I chose to use Gemfan 3052 and HQProp 3x4x4 V1s for testing.

Speed Measurement
After the build and setup here I maidened and have flown on both 3s and 4s. Given the current fascination with speed in 3 inch quads I decided to install a GPS unit - this Betian BN-180 unit in particular. I've chosen to use this only a a measure of speed my believe it to be more accurate than a radar gun which can be difficult to register these smaller quads on.

FPV performance
Easiest way to describe is to show my FPV feed using DVR as below. First of all I was pleasantly surprised that the 4:3 version of the EOS2 had an acceptible vertical field of view whereas the 16:9 version felt inadequate and made the Eachine Trashcan really uncomfortable for me to fly. The camera handled lights and darks pretty well and wasn't as oversaturated in red as I've seen some of these cameras even though it is autumn where I am with lots of red about.

​VTX performance was a little disappointing - although I like the mounting solution for the linear whip antenna I found I didn't like the performance and thought that matching a compact CP antenna like the Foxeer Lollipop 3 with UFL on the quad to a CP antenna on the goggle would be a big improvement. I'll plan to try this later and will report back on performance here.

3s Performance
A three-celled battery gave me suprisingly good performance and this is most likely do to the build quality and high kV of the motors however my admittedly crappy 3s 850mah betafpv batteries sagged badly under full throttle. Even then I still managed to get a top speed of 147kph (91mph). It genuinely felt quick too, covering a lot of ground quickly in a straight line. Since 3 cell batteries are relatively light it felt nimble and reactive in the maneuvers as well, enjoyable to fly. The tune as loaded in part 1 gave good performance, not noticeable oscillations and the motors came down cool

147kph on 3s = 91mph

4s Performance
I had big hopes for the speed using my CNHL Ministar 650mah batteries and I was not disappointed - 171kph (106mph) was my fastest measured speed as can be seen below. However like on 3s the batteries sagged badly but this time it was not because of the low quality battery but because I feel the kV on the motors are a bit too high. I prefer around 3600kV rather than 4300kV with a fairly aggressive prop like I've used here. This is easy enough to fix with a throttle limit as can be found in my article on betaflight throttle limits here. For reference to get an equivalent throttle limit to make a 4300kV motor perform like a 3600kV motor = 3600/4300x100 = 84% throttle limit. Note running a 3s on these 4300kV is like running a 75% throttle limit on 4s which is coincidentally where I like to run my throttle limit on 4s

Given the 4s 650mah battery is 87g compared to the betafpv 3s 850mah at 72g the quad felt like it carried more momentum in corners and maneuvers but not massively so. I feel like 4s 650mah is the right battery for this quad. You could get away with a 4s 550mah at a push but you would need to limit the throttle so as not to draw too much current and damage the battery.

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Current draw got up to 77A on this run (poor battery)

Durability so far
At this stage I've had a few minor tumbles in grass where I've done not much more than coat it in mud and bend some props but I have had one decent fall at speed onto a concrete path. It was an upside down landing and the impact was on the corner of the camera and front of the frame as you can see below. There was no significant damage to the frame but the camera lens got knocked back into the camera housing on and angle, cross-threading the lens. After some hard twisting I was able to remove the lens and then re-insert is square on the housing. After re-focusing the lens I was back in action no worse for wear other than a spec of dirt or dust on the inside of the lens that got in when re-seating it - my fault beacuse I was too impatient to wait for a cleaner environment to repair.

The arms seem to be very strong, one of the few times I've seen 4mm thick carbon used in a 3 inch quad so I'm hopeful these will stand the test of time.

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Summary and Recommendations
This is a well specified quad with and especially nice flight stack and nice motors. I've made little mention here of 6s capability because even though it is supported by the electronics and 2700kV motors that are available, I think it is unnecessary on 3 inch. That said the fact that the gear can handle it should bode well for reliability on more 'lowly' 4s.

This is a very fast quad on 4s or 3s but I think the kV of the motors is a little too high but easily solved with a throttle limit which I don't think will actually have much effect on the top speed.

The image from the Caddx EOS is satisfactory but I think the FPV signal would benefit from a CP antenna on the quad to match the CP on the goggles.

Overall I think it is excellent value for money at $140 for the kit as reviewed here. From a component standpoint it is superior to the more expensive HGLRC Arrow 3 inch. The Diatone GTR 349 is a firm contender for value but components are inferior to those on the Asteroid.

I've been a customer of HobbyCool for sometime as well as a review and can vouch for their customer service, I've always been well looked after and would like to think this is the same for all customers. The Asteroid 3" is exclusive to Hobbycool and is available here:

​http://hobbycool.com/asteroid-3-mini-fpv-racing-drone-kit/

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