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Old Aug 24, 2015, 07:40 PM
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XK INNOVATIONS K120 REVIEW - 2s brushless cp micro heli rtf - courtesy of banggood

INTRODUCTION

A week or so ago, Banggood asked if I would like to review the new XK BLAST K120 collective pitch micro heli and after a quick look at the specs list I jumped at the chance. Big thanks to FyreSG for the recommendation, I hope I can do your thorough reviews justice.

This is my first review but have been flying CP helis for just over 3 years and own a super cp, mini cp bl and double bl, v120 3 axis and 6 axis, a couple trex 150, an unflown preloved 180cf and a Trex 450 DFC so feel I have enough experience to give this heli a good solid test. Today it arrived and it's too dark to fly now so this may be a little picture heavy, all are under 1mb so hopefully not too much of a drag for slower connections. Questions more than welcome if anything is unclear of left out.

For anyone preferring to sit back and relax rather than scroll, here's a slide show with all the pics with some face noise from KRNFX
XK K120 RTF FROM BANGGOOD - UNBOXING AND SLIDESHOW (4 min 43 sec)


KRNFX for the audio - 100% noise from his face!
https://www.youtube.com/channel/UC8j...d8WKM7QCfN22WQ

The K120 is available for preorders as a RTF package at Banggood and is planned to be shipped from the 12th of September 2015.
http://www.banggood.com/XK-K120-Shut...-p-974730.html

XK are a fairly new RC company on the block but offer some interesting 3 and 4 blade micro helis like the K123 and K124 along with the K100 and K110 - a pair of 1 cell brushless micro helis and competitive bang for buck. This is their first 3D 2 cell offering however and along with the super thick looking carbon boom and tail motor cover, it has my firm interest.

XK Innovations Website:
http://www.xk-innovations.com/goods/52.html




The Specifications listed on the K120 page:
http://www.xk-innovations.com/goods/show-186.html

Rotor Diameter: 275 mm
Body Length: 260 mm
Height: 83mm
Flying weight: 78g
Battery: 7.4V 300mAh 25C
Flight time: About 5 minutes
Main Motor: Brushless 1106
Tail Motor: Brushed 8520
Control Distance: About 120m
Charging Time: About 30-60 Minutes
3D and 6G mode;3D aerobatics;Hovering flight;Small and big rudder setting.

Compatible with FUTABA S-FHSS

Features:

1.The all metal CNC rotor head without aileron design reference aerodynamic blade provides a strong driving force and body self stability.
2.1106 rotor brushless motor power is stronger, the 7.4v 300mAh 25C high rate battery
3.Transmitter supports switching between 3-axis & 6-axis gyro modes.Transmitter can switch from Mode 1 to Mode 2, vise versa.
4.3D Mode activates 3-axis gyro, enables aerobatics such as flips, rolls inverted flight, funnels and tick-tocks
5.6G use 6 axis gyro, flight performance and stability, easy operation, suitable for beginners to flight.
6.Standard 6 channel transmitter
7.With the balance charger


WHAT'S IN THE BOX?

Everything comes in a nice compact box measuring 31cm x 29cm x 10cm which was wrapped in a layer of foamy sheet and Banggood signature yellow tape.

There's 3 smaller black boxes snugly sitting in the main box, one with the heli, a second with the transmitter and one with some spare parts, tools, charger and psu. Everything arrived in good condition but the transmitter had shifted in transit and the pool noodle style foam protection on the antenna had slid down to allow the tx to poke out of its own and the outside box slightly. No damage apart from slight cosmetic scuff right on the tip and a slightly bent tail fin that bent back without issue.

































So, my first questions were/are:

Q. Does it have rotary servos, can we get gears?
A. Yes, unsure about gears or spares in general yet they are super dinky servos.

Q. Does it have piro compensation in 3G mode?
A. Unsure but likely if it has a 6G mode.

Q. Is it easy to work on?
A. Hell yeah, delightfully so. Easy access to everything, tail motor plug fis through boom and frame screws are large and not counter sunk with philips head with screwdriver provided.

Q. Does it look robust, will it take Throttle Hold over grass and keep flying?
A. Apart from the skids, there is very little torsional flex on the frame and the boards are well stuck down. I'd take a guess at yes.

Q. Does it need any immediate upgrades?
A. I predict plenty power and torque on 2s and the entire head and swash is aluminium.

Q. Does the tail hold when pushed hard in reverse flight and light wind?
A. For sure my most important factor in mcro heli is solid tail, we'll see.

Q. How stable/agile is it? Good for first CP and advanced pilots?
A. Tx is set up with dual rates and 2 flight modes for normal and 3d flight plus TH. Mechanical setup seems good.

Q. What is the lipo connector?
A. Trex 150 style 2s balance connector, awesome.

Q. Can it be flown with a Deviated TX?
A. Nope

Q. Is stock Tx and range any good and how low do the gimbal tensions go?
A. A quick feel up of this tx provides some smooth gimbals and to my surprise are not super tough to move like most entry level TX and have a fairly low tension out of the box I could easily fly with. Idle Up is on the back left switch and Throttle Hold is on back right switch. Opposite to what I use but shouldn't be a problem to swap over after the intial test. 6 X AA NIMH is the only power source offered, no space for a lipo without extensive modding but does have a charge port in the side and a 3.5mm trainer port on the back middle. Sticks are nice and spiky and the two part type so easy to adjust.

Q. Is it BL Heli on the esc or is it flashable?
A. No idea

Q. Does it have a gov?
A. Unsure

FIRST IMPRESSIONS

My immediate thoughts were this ticks all the boxes on paper and looks like a blend of a mini cp with it's coreless tail and geniuscp/mini cp type layout and Trex 150 2s power and metal main shaft, swash and head - so far so good. It looks stiff and flex free and I have no issue with a coreless tail providing they perform as well as a stock mini cp. Tail blade is also mini cp form factor and 45mm long. Last but not least we have that robust looking 5.20mm diameter carbon tube boom, a complete protective plastic housing for the the tail motor while still being accessible. The main gear feels stiff considering the massive cut outs and although the pinion/main gear spacing feels a touch close, I am confident that will wear in over a couple flights like the Trex 150 - I found the same spacing I used on the mini cp or V120 to strip due to torque on the 2s 150.

The lipo is 100% Trex 150 compatible and vice versa. It came sitting at just over 3.8v and after an initial charge on the supplied charger it showed a little over 4.2 on each cell and took 26 minutes. Standing voltage several hours later when I write this is 4.196V for cell 1 and 4.185V on cell 2.




K120 lipo - 17.14g
Trex 150 lipo - 16.38g
Nanotech Trex 150 lipo - 18.71g







*Canopy weighs 2.35g
*Single main blade weighs 3.2g each and are 18.82mm wide at the root and 16.65 at the tip
*Tail blade weighs 0.24g
*Walkera style/servo style motor connector
*Allen bolt mainblade bolts and swash balls, rest of the screws are philips.
* I measure heli as 86mm tall and 248mm long
*Heli with no lipo weighs 59.34g
-Trex 150 weighs 58.55g
-Mini CP BL weights 46.51g
-Super CP stock weighs 40.94g
-V120d02S weighs 84.09g
*8T Pinion and 64T main gear
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Old Aug 24, 2015, 07:41 PM
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ON WITH THE PICS!

XK SHUTTLE K120
















































































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Old Aug 24, 2015, 07:42 PM
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XK X6 TRANSMITTER















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Old Aug 24, 2015, 07:42 PM
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COMPARISON PICS




Maiden to follow shortly...
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Old Aug 24, 2015, 07:43 PM
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Maiden Flight

Maiden, stock lipo.
XK SHUTTLE K120 - MAIDEN - 6G, 3G and some 3D (6 min 36 sec)


Second flight, idle up, 3G and high rates from start. Trex 150 lipo
XK K120 RTF - 3D Flight (3 min 59 sec)



There was no need to bind the heli with the button on the board as per the manual so I presume this was flown before it got to me. Zero pitch was spot on and tracking good with tx setup ready to go for anyone from a new cp pilot coming from fixed pitch or fairly aggressive 3D flight. The blue power light on the TX is behind a small hole top center and shines very brightly directly in my eyes so added a couple small dabs of hot glue to diffuse the piercing glow. All TX settings can be changed but are stock so far.

6G - Limited bank angle makes it impossible to flip the heli and pirouette compensation keeps level and stable in slow smooth flight, faster forward flight produced an elevator bobble and the fbl fights you in the more aggressive coordinated turns.

3G - No limit on cyclic angles but still feels like piro comp is working to keep the heli level in piros but allows full collective hurricanes and piroflips without fighting.

D/R - Low and high rates available for both 3G and 6G mode, tail is faster in high rates.

FMOD - Normal mode has 80% max throttle and idle up 100% constant, there is no pitch jump when switching between modes and tail holds well punching out in both although punching back down in normal mode did spin the tail out as seen in the first video

START UP
Initialization of the fbl is around a second from plugging in the lipo if tx is powered on first and same if heli is powered first, both fly fine. It must be in normal mode or it will not spool up which is good as it does not have a slow spool up in idle up if you hit TH and then take of in idle up. Servos are super noisy as soon as powered on and noisier when throttle is moved from 0 but seem to perform well.

TAKE OFF
The tail spins up first and holds well when taking off although if gently lifting off in 6G mode it tends to lean slightly to the right until airborne. Spool up is slow if gentle feeding in collective in normal mode but gear mesh is a touch close and does produce a small wobble in the heli on initial blade movement. I haven't tried loosening the mesh yet as I would like to see if that changes with more flights but there is a plastic surround around the motor mount so unsure how much it can move and still run free.

SAFETY
Turning the TX off while heli is bound but sitting produces a red/blue board flashing light and is ready to fly again well within a second of turning it back on with solid light.

If TX is turned off while heli is being held and running in normal mode blades spinning it takes about 2 full seconds for the heli to reduce throttle and will hold any cyclic inputs it had before TX off. Turning TX back on provides the same, close to instant control so long as throttle is minimum or tx will just beep until you do.

If TX is turned off while running in idle up, again the heli takes about 2 full seconds to react and will hold throttle and cyclic inputs until then. Control to the heli is instant providing you are minimum throttle AND normal mode, nothing otherwise.

TH seems to work in all modes without delay both holding and releasing and pitch curves do not change from the mode you are in. Switching TH off while in idle up works and the only way to enter directly from standing to idle up.
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Old Aug 24, 2015, 10:05 PM
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K120 Manual

K120 Manual in PDF and JPEG format
https://drive.google.com/folderview?...2s&usp=sharing
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Old Aug 28, 2015, 05:34 AM
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nice review man, very well detailed and nice photos.
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Old Aug 28, 2015, 08:11 AM
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Interesting

What is the top most board? The gyro?

Curiouser and curiouser
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Old Aug 28, 2015, 09:20 AM
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What a professional review!

WOW! A very detailed review! Fantastic photos! I'd love to hear more about its 3D capabilities as I know you can push the XK K120 to its limits.
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Old Aug 28, 2015, 11:29 AM
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Quote:
Originally Posted by spykez View Post
Interesting

What is the top most board? The gyro?

Curiouser and curiouser
Yes, spot on according to the manual. It's stuck to piece of black spongy foam that seem just stiff enough to not move in relation to the main board. Manual added to post 6 in PDF and JPG format.

I tried a 3rd flight but used wrong switch as mine are set up different and had throttle on when skids in the grass and stripped a couple teeth on the main gear. Swapped it out but some vibrations were present enough to be pretty noisy, wiggle the lipo out and loosen the skid pins from the body. 51 seconds in you can hear the gear strip and heli twitch when it's hovering nose left so i'd guess one tooth stripped on the ground and the second in the air.
3rd lipo (1 min 15 sec)

Closer inspection last night showed me the feathering shaft was bent slightly which was rather surprising as I have literally never bent a feathering shaft on any heli below a 450 yet.


Looks like it's same thickness but shorter than the mini cp one. I will try to fit it later and see if it's still flyable.


The upgrade metal head on banggood for the K110 does look like this one so I took a chance and ordered a couple feathering shafts from them.
Metal head
http://www.banggood.com/XK-K110-Meta...-p-992559.html
K110 feathering shaft
http://www.banggood.com/XK-K100-K110...-p-992575.html
There's enough length on the TH and FMOD switches wiring that you can just swap the position of them so won't happen again.


Glue to prevent the blinding led


Unsure if any tx flashing can be in order on the ARM chip but the unused ports on the board the switches plug in and the rubber plugs covering holes switches can go in may mean it's possible in the future.



The lipos from trex 150 do fit and work but due to the plastic surround being every so slightly thicker, they get stuck and wedged on the frame and removing them seems to require removing the skids. The bit they plug into is a little too flexible for my liking too as its separate and supported by the front - stock lipo works and fits and removes perfect, I just only have 1. I think a slit in the bottom of the battery holder would fix it but didn't want to mess with it until I have spare skids.


Output fets

Thanks for the kind words guys
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Old Aug 28, 2015, 12:25 PM
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Very nice and detailed review ,thank you .
Looks to be a nice heli ,very promising , am i right in thinking it has a brushed tail ?
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Old Aug 28, 2015, 06:03 PM
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Quote:
Originally Posted by dadio View Post
Very nice and detailed review ,thank you .
Looks to be a nice heli ,very promising , am i right in thinking it has a brushed tail ?
Yep. brushed tail. Same size as the main motor in the HCP80
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Old Aug 28, 2015, 07:07 PM
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Thank you for posting the manual.
XK should use some initiative and make them available at or before the time their models go on sale.
Notice that servo holder is the same design as v977, but might not be same dimensions.
Don't know what to say about the quality of the electronics, other than the radio and the esc appear to be thrown together. Stand back and throw some components and solder and see if it sticks.
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Old Aug 28, 2015, 08:29 PM
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Quote:
Originally Posted by dadio View Post
Very nice and detailed review ,thank you .
Looks to be a nice heli ,very promising , am i right in thinking it has a brushed tail ?
Quote:
Originally Posted by NELICOPTER View Post
Yep. brushed tail. Same size as the main motor in the HCP80
Indeed, coreless. It measures 8.5mm wide and 20mm long. That 8520 they list it as makes more sense now

Quote:
Originally Posted by mono View Post
Thank you for posting the manual.
XK should use some initiative and make them available at or before the time their models go on sale.
Notice that servo holder is the same design as v977, but might not be same dimensions.
Don't know what to say about the quality of the electronics, other than the radio and the esc appear to be thrown together. Stand back and throw some components and solder and see if it sticks.
I was a little surprised no manuals were listed when one was in the box. There's a bunch of things that make me feel this has been touched by Walkera hands but apparently in some Chinese forums it is said to be WLTOYS.

So I played a little switcharoo and fitted the minicp feathering shaft and put the head back together but as expected there was too much slop. The philips screws on the K120 and the hex on the mini cp are same thread and interchangeable if needed though.

I wondered if adding both helis metal head spacers to the K120 would fit well and it did but had too much friction moving the swash up and down.


Then I thought the mini cp grips would sort that friction and indeed they do but the balls are too small for the K120 links on the grips and swash.

The main shaft is 2.48mm diameter on my cheap calipers and the mini cp swash fits perfectly so the hub will if the holes align height wise, turns out they do. So you could fit a mini complete head and swash if you had no feathering shaft spares which I do an was going to do until I tried bending the original feathering shaft back which worked good enough to get a hover that didn't sound evil and the skids weren't wobbling in a blur.


After that I was curious if the main gears were compatible and they both measure 32.42mm diameter and have 64 teeth. The center hub is about 1.3mm smaller on the mini cp gear and has 2 flat sides instead of one. You can mash it on to a stock mini/supercp and gear mesh is good when turning so i'd guess pinion is same too. A 9T would be interesting to try.


The pots in the tx are also the same form factor as Walkera which I had to go hunting for when I needed spares and were stupid hard to track down and came from Japan. If they do have the little center tab and flat section on the stem like Walkera ones and XK can make available spares that would be a smart move. Deviation crowd would be sorted and my sim tx could go on till the electronics die, not gimbals.
X6 pots


Walkera 8S pots


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Old Aug 30, 2015, 09:26 AM
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Looks very similar to a v120d02s except it's 2s and motor driven tail. I honestly think it would be better to buy a used v120d02s and convert it to 2s. Because then you get the torque tube tail and you'd also have the option of using a gy-280 gyro if you wanted.
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