KDS 550 V2 Build log + review

[Znybar]

Hey guys,

I'll be updating this regularly with my build log for the 550. It's all ready to go now, just have to (re)maiden it. I've got all the build log pics, I'll upload them soon.

Here are the electronics I've chosen for the build (so far):

3 RJX FS 0521HV servos for the cyclic
1 HK Mi digital high speed metal gear servo for the tail
YEP 150A ESC (2-6S) (it gets warm in Australia!)
Turnigy Dlux 10A BEC
Turnigy T600 1100kv motor
Spektrum AR7200bx + DSMX satellite

THE KIT:

The whole kit was in one small-ish box. All the parts were very well protected (especially the canopy + frame) and separated into different boxes. Parts themselves were in numbered bags that were referred to in the instructions. While the grouping of the items is not necessarily logical (i.e. the parts for whatever step during the build will come from various bags), at least it's easy to organise things as long as you keep parts in the bag until the kit is built. The frame comes pre-assembled, as well as the head and tail assembly. The build underlines the need to dis-assemble the parts and loctite them. There was no paper instruction manual, rather coming on a small CD in PDF format. This might be an issue for some, but worked fine for me. The instructions are also available on the KDS website.

Given that this is a HK brand, I was expecting poor instructions in chinglish. I was pleasantly surprised by how clear the instructions were. Not much wording, but very detailed schematics for a step-by-step build. There were only a few instances where they left me scratching my head because the 2D perspectives were a little hard to tell (i.e. the orientation of servos and such was sometimes difficult).

Quality-wise I was quite impressed. There were no defects that I could find in the kit. All the parts fit together as expected, and short of a few rough finishing touches near the head block (just metal scrapings left over), everything was cleanly machined. There are only a few niggling design issues that I'll point out during the build, but most manufacturers are guilty of the same sort of problems.

THE FRAME:

The first step in the build is to disassemble the frame that was pre-built and to put loctite on all metal parts. While the kit included no-name fastener, I chose to use proper Loctite because I know it works. No issues arose at this point, it was rather straightforward. Be careful not to install the bottom-most shaft bearing because it'll be necessary to take it out to easily get the main gear in.

The frame is very rigid, in part because of the design (aluminium blocks around the shaft) and the bracers and thick carbon fiber. Nice details such a slightly inclined battery tray, and the lack of a need to ground the tail because the frame includes metal links from the tail to the motor mount. To top it off, there are rubber holders at the front of the frame that make it easier to slip the canopy on as well as keeping it from moving around/vibrating in flight.



THE HEAD:

I went for the V2 DFC head because it looked nicer to me. All well-machined. There is just one SIGNIFICANT issue that I found while disassembling it to put loctite on the feathering shaft bolts: the thrust bearing holders were installed backwards! To all those who build KDS helis: make sure these are on the right way when you build your heli, otherwise your head will be unbalanced and you'll get a lot of wear on the thrust bearings.




MAIN SHAFT/GEAR AND TAIL BOOM:

Probably the most difficult part of the build, if only because most guys have large hands and this requires precision and control. A small pin has to be placed between the main gear and the one-way gear, and this is very hard without some needle-nose pliers. Aside from that it goes in very smoothly. Unfortunately the main gear are straight-cut, but this heli was released before slanted gears became so popular. At least it looks like good quality plastic, and the one-way gear is actually aluminium due to the V1 version's plastic failing in flight.

The tail booms on KDS are aluminium but oversized diameter, so very stiff. The stiffening rods require some epoxy to put the aluminium heads on. Make sure to press them in all the way or you'll have different lengths.



SWASH PLATE AND HEAD:

Probably the easiest part of the build, just slip on the swashplate and attach the head to it. Apparently the swashplate is oversized relative to a comparable Logo swashplate, but as far as I'm concerned there's no such thing as overkill for reliability.



TAIL ASSEMBLY:

A bit finicky because you have to tighten the nuts while keeping the belt under tension. One criticism that I have of this design is that the arm that's linked to the servo rod is made of plastic. I would have expected aluminium for such a crucial part of a heli. Aside from that, no qualms for quality and design.



ELECTRONICS:

I chose to install RJX servos for the cyclic, and will likely replace the tail servo with another RJX (seeing as in high voltage they get to 0.05 sec response). I am really impressed with these servos, the only criticism I have being that the servo arms supplied with the servos are slightly too thick to attach on the servos, meaning a washer has to be placed or the arms must be machined. Good thing about the KDS is the access to the servos is very good.

The battery tray easily fits 5000mah 6S lipos as opposed to the recommended 4500mah.

The gyro tray is actually deceptively small because the rear cyclic servo ends up taking up most of the space. My AR7200BX only just barely fit without touching the servo or the frame side. I used some 3m 1040 double-sided tape to install the gyro, and placed the satellite receiver on the opposite side of the beastx to get complete polarity (putting it on the same side would possible cause signal loss in certain orientations due to carbon fibre interference. I used the empty space next to the tail boom grips to hold excess wiring and ended up with a rather clean setup.



The ESC tray above the motor is of decent size, but there's no designated area to put a BEC, so I had to mount mine on the side of the frame. This doesn't really cause any issues, except that the YEP 150A has large capacitors that are a bit too exposed for my liking. This is more of an ESC issue though, and likely not present on the 700 that has a larger ESC tray. Space for the ESC wiring is also an issue, so I had to rout them over the ESC. This isn't ideal, but creates the minimum crimp in the motor wires and doesn't interfere with the batteries below. The canopy is quite large so it doesn't cause any issues in that department.



Heli good to go!

[Familyman67]

great!
can't wait to see the report.
go ahead! move it! move it!

[Znybar]

Updated!

[Kiwidan]

Nice build

[Familyman67]

What a great report, thanks for taking the time to document the build.
Have you maidened it yet?

Happy flyin'

[Znybar]

This weekend hopefully! The only lipo I had available died on me last weekend, so I had to postpone (even though the weather on Sunday was perfect).

[Familyman67]

Originally Posted by Znybar

even though the weather on Sunday was perfect.

My sincere condolences - that must have been tough!

[Ghostflyer1]

I would like to point out that the KDS Innova is not a HK brand... KDS is a brand of its own. Notice that HK lists it as a Pro class helicopter and that is becuase it is not the low grade stuff they normally sell... I won't even touch their batteries anymore.

[Znybar]

I have actually never had any problems with Hobbyking, out of everything I've bought the only thing I have to criticise is one bad lipo, and it was shipped from the AU warehouse.

What I meant was Hong Kong (if I'm not mistaken).

[Znybar]

Ok guys, I've got a problem and I need your help.

On spool up, I'm getting really bad vibrations that I'm pretty sure are coming from the head due to their frequency. Anyway, I took the head apart and checked it, put it back together, tightened it as much as I possibly could. There's no play in the blade grips. I then went on to check the whole main shaft, it is all straight. No play in it either.

I then switched the KDS blades for some Revolution ones. The KDS looked balanced from what I can tell but I double-checked with the Revolution ones, still the same problem. Only think I can think of are too loose/tight blades, but they look pretty dead on straight to me (and still present when close to take-off).

The vibes are the worst towards the end of the spool up, but are very visible as soon as the motor kicks in after the slow start sequence.

EDIT: I think I've fixed the issue. I removed the head and turned it 180 degrees (one of the LHS guys suggested it). Vibrations are much much lower now without the blades, only some minor transition vibrations. I'll try again with blades on tomorrow, wish me luck!

[Znybar]

So, I maidened it yesterday, managed to put three packs through it (all the packs I currently own).

Impressions: very positive. The first take-off was mostly adjusting blade tracking and gyro gain. The 1100kv motor I think is a little bit low for the heli, with the stock pinion I'm only hitting 2100rpm on the main rotor at 100% throttle. Ideally I'd get a similar figure at ~80% throttle so I can have the governor on and working effectively. So I think a pinion with about two more teeth should be in the future, or perhaps a higher KV motor.

Heli flew very stable out of the box, just loving the control over the 450. Sounds epic of course, and from the few pitch pumps I did it had plenty of power. The HK YEP ESC was barely warm after every flight I did, and same for the 10A BEC. Definitely not pushing the battery either, I'd be surprised if I was pulling more than 60A during the flight.

I will comment on the Beastx though, it seems to be a lot more finnicky to dial in than the Robird on my 450. The Robird, aside from the gyro gain required next to no in-flight setup, while this ar7200bx is requiring a fair bit more tweaking. I had the tail lock during fast forward flight (scary to say the least) and I'll have to go back and figure it out on the module.

[Familyman67]

Are you running your ESC in non-governed mode ? Or does it not have a governor ?
Else, I would not use a 100% throttle curve or you don't leave the ESC enough room to "govern"
80% is really the max I can do with my (stock) ESC and motor combo. If I go beyond then I face an rpm drop when I give full pitch. I do however think that I run at about 2200 rpm @ 80% governed throttle curve, but will recheck that.
btw. I am mostly flying on the 70% curve - much smoother and nicer sound and enough "ooomph" for me anyway. But I am not (yet) "smacking" the heli around with brutal TicTocs or other cool stuff - I am more the "smoothie" (loops, turns, slow piroflips, inverted flight etc.)

Talking about higher KV motor - you need to consider that a higher KV does not necessarily mean "more power" - often a higher KV comes with less power - so putting a bigger pinion in might be the better choice for you.

[Znybar]

I'm not running the ESC in govern mode yet, so yes I get rpm drops when I hit the pitch. I mostly want it to get more stable, which is why I'm aiming for the 2200 rpm. Any more than that I think is overkill for what I do with the heli.

Hopefully this weekend I'll get the beastx tuning sorted and I'll post a flight video or two!

[Familyman67]

I'd recommend you to switch on the governor function in the ESC or is there a reason why you shy away from that?
The governor will give you relatively constant rpm (as long as you keep your throttle flat-line at 80% or below). No need for a high headspeed in the beginning. I mostly fly with 60 or 70%.

On my DX8 I have programmed the following throttle "curves".
Flight mode 0: 0-60-60-60-60
Flight mode 1: 70 flat
Flight mode 2: 80 flat.

I did try it with 90 flat, but that caused the rpm to drop when I pitched hard.
As I said - I mainly take her off at 60% and then fly most of the time in flight mode 1 at 70%.

Looking forward to see the video - good luck with you heli.

[Znybar]

I don't want to go into governor mode when at 80% throttle I'm still below 2000 headspeed. For my tastes that was too low, the heli wasn't fully stable at that stage. Once I get a pinion with ~2 more teeth I'll definitely keep it in governor mode though.

I'm also going to change my normal mode throttle curve as right now it's too low with the current pinion.

Hopefully I'll be able to fix the beastx issues and get the video this weekend

[Znybar]

Ok so I've gotten a few more flights in now that I got a new BEC and replaced the HK tail servo with an ultra high speed Savox.

I am absolutely loving this thing.

Even though I'm running a pretty low headspeed (2100rpm) until I get a new pinion, it has a ton of power. It's very stable, and so nice and floaty compared to my 450.

[Familyman67]

sounds great! When can we see a video?

[Znybar]

I think I'll get one of the field dudes to take one next time she's in the air. Interesting thing happened on the last flight, one of the bolts holding the tail holder sheared in flight. Lucky I've got some replacements!

[Ghostflyer1]

EEEEPPPPPP That does not sound good

[Znybar]

I had a great and an interesting flight this weekend.

The first flight was just perfect, this machine is awesome. Second flight was shall we say interesting, video will be put up shortly...