yet another new build - needing some guidance

[si3po]

hi all,

new to the site having been recommended by numerous other forums as this being the place to come for advice on all things multirotor.

I've been around the R/C scene for some time and have sucessfully built and flown fixed wing a/c - i've had my BMFA 'A' Cert for about 18 months, i also fly micro (indoor) 4ch helis (i have 2x WL V911 & 1x T-Rex 100S) and a V929 quad, so not a total nooB by most standards.

Having had some time to see other club members DIY quads, i've decided i want to throw myself into the pool and get building one of my own. I've done a fair amount of research and drawn up a listing of the components i'd need, but would like some input as to whether they're going to be too under/overpowered for eachother....can anyone shed some light or point me in the direction of answers please??

You'll no doubt notice that all the components are from HobbyKing, purely for simplicity, price and stock holding (most everything in stock as i type) however i've no idea if they'll be suited to each other, or if the all up weight - coming in at about 1.5Kg going by weights provided by HK - will prove too much for the motors, but that's why i came here! If you feel that any of my components are mis-matched or suggest alternate options at the same/lower price-point, then i'd be more than happy to take the comments on board

HK X525 Frame
HK Power Dist Board
HK KK2.1 Flight Controller
Turnigy D2830-11 Motor
Turnigy Nano-Tech 4000mAh 3S 25C/50C
HK F-30A ESC
10x4.7 2-Blade props - 2x CW & 2x CCW
OrangeRX DSMX R620 6ch Rx (have this already)
Spektrum DX7 Tx (have this already)


any help offered is greatly welcomed....

Thanks,

Si

 

[jbrumberg]

Welcome Si. I saw a recent post here at MRF in one of the recent newbee builder's threads complaining about the HK PDB; basically I got the impression of poor QC, cheaply made. I believe a soldering contact separated during operation.

Do not forget the HK 10 pack of 10 cm 3 pin servo connectors to connect the Rx to the KK board.

 

[si3po]

Thanks jbrumberg, I've heard this too about the PDB on other sites, but figured I could reinforce the soldering when I get it. I'm not adverse to a bit of electronics in that manner.

What do you think to the other components? Are they well matched, or will I need to change anything?

Sent from my GT-I9305 using Tapatalk

 

[Motopreserve]

I did the same thing as you and ordered all my parts from HK to make sure it was easy and all arrived together (except my multiwii FC).


Sadly, I am the guy who crashed my quad due to the cheap HK power distro board. I'm sure there are people that have had success with them - but I of course would definitely not recommend it.


There are others out there for fairly cheap - and you want to make sure it's rated to handle the amperage. Or you could solder up a "squid" which will be custom for your quad - and you guarantee the quality control. The failure would not have been handled by reinforcing with solder. The failure was internal on the copper part of the board (I think). Those are not rated for the amperage draw either.


I would also warn you off the cheap props from HK. Mine arrived with several unusable due to not tracking correctly. And they're a PITA to balance. Worth spending a hair more and getting some decent APC, HQ or even Gemfan. Plenty of places stateside to grave them.

The reat of the components look pretty good. I haven't plugged them into eCalc - but that will give you an idea of how it will perform.


Good luck and have fun!

 

[jbrumberg]

I bought the HK breakout cable, instead of purchasing a PDF. It's heavy. I bet if I dissected it I would be very unhappy with the gauge of wiring and the splicing. Ignorance is bliss.:shame:

The list looks good. You are using components similar to what I am currently using.

Good Luck.

 

[Motopreserve]

Don't forget to grab the tools to flash the F-30A ESCs to Simonk firmware. HK sells them, but I think the last time I looked, they only had them in the International warehouse.

I build a squid for mine (probably similar to the one Jay bought), but it's made using 12AWG wire, and weighs 60 grams!!! Heavy - but of course I know it's solid because I did it myself. I ended up grabbing a good PDB from Witespy (2oz copper). You can check it out HERE.

The internet is filled with people b!*ching and moaning about the bad communication and slow shipping from Witespy - and most of it is warranted. But I have had good luck with him -as long as you are prepared for the wait (sometimes it's come in less than a week - this last one 3 weeks). He has ridiculous prices on things - and stock that is perfect for multirotors. Just takes a while sometimes...

I just plugged some numbers into eCalc. It looks like you could benefit from upping the battery to 5000mah (still 3S/25C), and could even step down to a 20A ESC. With 9" props that would give you decent flight times, but less lift. If you go up to 10" props, the flight times drop - but you get much more lift - in case you planned n trying out AV/P.

 

[si3po]

Thanks guys. Regards the breakout cable, I couldn't find this on HK. To be honest, id rather know the power is hard wired rather than going through a board due to the currents etc not suiting a low cost (probably lie quality) PCB...

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[jbrumberg]

http://www.hobbyking.com/hobbyking/...ullet_Multistar_ESC_Power_Breakout_Cable.html

Those breakout cables are located in the electronics section of the multirotor section of HK. Here is a link to the model that I have. They have different style connectors to accommodate the different style battery connectors.

 

[SoCal Blur]

I ended up grabbing a good PDB from Witespy (2oz copper). You can check it out HERE.

That board from RTFQ is definately unique in its design. They state 2oz of copper but don't give a current rating.

Here's the thing that drives me crazy in the RC world. People use solder as if it were a weld. Early on in my electronics training (6th grade, I think) I was taught, and to this day still believe, that other than soldering components to a PCB, if you solder wire to something that is likely to be subjected to stress, movement, vibration, etc., you need to make a good "mechanical" connection first and then solder it. Using the RTFQ board as an example, you drop the wire in the slot and then expect the solder to perform both the mechanical and electrical connection. That is BAD. A more reliable way, though not as slick looking, would be to just have a hole through the copper pad where you and insert enough bare wire to loop it through and twist it on itself, making a strong mecanical connection and then solder it to the board. This also applies if you are building a "squid." Be sure to make secure mechanical connections between all the wires first - even if you have to use a seperate, solid strand of bare wire to bind them all together, and then solder them together.

It takes just one "cold solder joint" to ruin your whole day. You have a much better chance of avoiding tragedy if you have a secure, mechanical connection backing up the solder joint. :02.47-tranquillity:

 

[si3po]

Thanks SoCal, having done some research, I think I'd be comfortable with using a breakout cable rather than another board that could fail. At least it's easier to repair/replace if/when things go Pete Tong!

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[Motopreserve]

I understand the value of the mechanical connection, although I'm not sure I understood your example with the RTFQ board.

I think the slots in the sides of the board are meant to hold the wire (maybe not as tight as you're talking about - but tighter than any others I've seen), and then the solder deals with the connection. If I get your drift - there could be some type of crimp on the board itself to secure the wire - then the solder goes on? The only concern I'd have with it this way would be vibes could stress the board (instead of the solder joint) causing cracks? Maybe I'm over thinking it.

The squid I made used solid copper strand to hold the group of wires together - and then I "soaked" it with solder, basically making it one giant solid piece made up of 4 individual wire ends. Not sure I'm describing it well, but I was pretty confident in the connection. Problem is: it's too damn heavy. My quad is bloated as-is, I didn't need the extra 60 grams.

 

[SoCal Blur]

I understand the value of the mechanical connection, although I'm not sure I understood your example with the RTFQ board.

I think the slots in the sides of the board are meant to hold the wire (maybe not as tight as you're talking about - but tighter than any others I've seen), and then the solder deals with the connection. If I get your drift - there could be some type of crimp on the board itself to secure the wire - then the solder goes on? The only concern I'd have with it this way would be vibes could stress the board (instead of the solder joint) causing cracks? Maybe I'm over thinking it.

The squid I made used solid copper strand to hold the group of wires together - and then I "soaked" it with solder, basically making it one giant solid piece made up of 4 individual wire ends. Not sure I'm describing it well, but I was pretty confident in the connection. Problem is: it's too damn heavy. My quad is bloated as-is, I didn't need the extra 60 grams.

The RTFQ board does somewhat hold the wire tighter in place but again, its relying on Solder as both the mechanical and electrical connection. Many people that build in the RC world are not expert solderers. They may not be able to recognize a cold solder joint. Even turning up the temp on their soldering irons too high could cause issues. If you can't descern a potential issue by the way the solder looks or behaves when you're soldering, you could be in for a rude awakening. I understand that a mechanical connection isn't always practical, but there is no substitution for it. In critical areas such as power distribution, its the best way to go.

The way you describe how you assembled your squid sound right. As long as that solid copper strand held the group of wires together securely on its own before you soldered them, you're good to go.

One thing to keep in mind, especially on the larger multirotors, a poor connection will generate heat. That heat can easily melt the solder and if there isn't a mechanical connection to back it up, the connection will separate. Even high current draw will generate heat if there is any resistance to speak of in the wires or the connections.

I only put this out there for people to consider and hopefully provide some helpful info. I know folks watch youtube videos on how to build some of this stuff. I watched one video where someone was building a squid and used nothing but a ton of solder to hold it together. If you don't know any better, you'll watch the video and think its the correct way to do it.

 

[Motopreserve]

Gotcha. Very good info.

I feel pretty confident in my soldering (as a recording engineer - I wired up FAR too many studios to count), but with this RC stuff, I always feel a little more nervous than I did with audio cables. Worst case in audio: the signal drops. Worst case in RC: the quad drops!

 

[SoCal Blur]

Gotcha. Very good info.

I feel pretty confident in my soldering (as a recording engineer - I wired up FAR too many studios to count), but with this RC stuff, I always feel a little more nervous than I did with audio cables. Worst case in audio: the signal drops. Worst case in RC: the quad drops!

I know exactly what you mean. I've wired a few Video/audio production suites in my time as well. I'm also a real-life helicopter pilot so maybe I'm a little extra paranoid when it comes to things potentially dropping out of the sky. :dread:

 

[si3po]

I just plugged some numbers into eCalc. It looks like you could benefit from upping the battery to 5000mah (still 3S/25C), and could even step down to a 20A ESC. With 9" props that would give you decent flight times, but less lift. If you go up to 10" props, the flight times drop - but you get much more lift - in case you planned n trying out AV/P.

Thanks motopreserve. I've looked at ecalc myself using the weights from hK (how accurate are they BTW?) and only get flight times of around 5-7 minutes using 1047 props.... is this considered 'decent'?

Also, you note that I can drop to 20A ESCs. How so? I ask as I've always been told to go by the maximum current draw of the motor (21A in this case, I think) and then add a 20% buffer to prevent burning out the ESC on full throttle.


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[Motopreserve]

The weights are usually pretty accurate. If you use "without drive" it will plug in the weights for you. You just need to enter the weight of the frame (which I got from the comments on the page - since HK didn't list it.

As far as ESC, I didn't look at the top draw on the numbers I used - but it didn't kick back an error. Keep in mind you probably won't be using full throttle very often (if at all) as long as the quad is set up well. Bursts maybe, but not running flat out.

The 30A ESC shouldn't hurt flight times by much. You should be able to work the data to get better than 5-7 minutes for sure. Shoot for up over 10 minutes for mixed flight time and over 15 for hover. It's a dance between battery and weight all the time.

 

[si3po]

The weights are usually pretty accurate. If you use "without drive" it will plug in the weights for you. You just need to enter the weight of the frame (which I got from the comments on the page - since HK didn't list it.

As far as ESC, I didn't look at the top draw on the numbers I used - but it didn't kick back an error. Keep in mind you probably won't be using full throttle very often (if at all) as long as the quad is set up well. Bursts maybe, but not running flat out.

The 30A ESC shouldn't hurt flight times by much. You should be able to work the data to get better than 5-7 minutes for sure. Shoot for up over 10 minutes for mixed flight time and over 15 for hover. It's a dance between battery and weight all the time.

Excellent info, thanks! I'll go back to HK and confirm the weights then before I go over to eCalc.

Which prop brand generally come out best for multi rotors? I've always used APC for my Nitro fixed wing gear and find the great, although a little more top end in terms of weight and cost...

 

[Motopreserve]

Honestly, after buying a bunch of cheap props (HK brand, Genfan) I would consider APC to be the low end of the prop spectrum. Going any cheaper just leads to junk props in the package, or endless balancing.

People really like the HQ which I've yet to try. And Graupners get good reviews, but they are a different characteristic than the typical APC slow fly (or copies).

I have a ton of HK on the bench that I keep going back to balance when I feel like I want to self-torture

You don't need any weights for eCalc except the frame - as long as you're using the without drive feature in top pane. It will calculate all the weights for you.

 

[si3po]

Honestly, after buying a bunch of cheap props (HK brand, Genfan) I would consider APC to be the low end of the prop spectrum. you.

Really? I'd only ever heard good things about the APC electric props...admittedly because I can get hold of them very easily.

Although I have used others before, including Graupner, I'd been told that they were too noisy for my club site (we have a noise limit imposed on us of 83dB for all modelsby the site owner) so I've stuck with the APCs which seem be much quieter....

 

[Motopreserve]

Sorry, I didn't articulate that well. I meant the APC should be the "cheap" props. Anything cheaper is not worth our time. There are much more expensive props out there that people love - but while I'm breaking props - APC it is! . I consider them cheap since buying the garbage props requires a few sets to get 1 usable set. Might as well buy quality from the get-go.

The minute I got my hands on the APC I started planning on how I could use the HK props for kindling!!! Maybe they'll come in handy since I need a fire if I'm going to fly around here in the freezing weather

In my opinion, the Gemfan I got are more usable than HK, but MUCH harder to balance than APC.