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Quad build

ikem

Senior Member
#1
I have a quad that i just got done building.

Turnigy SK3 920kv
Turnigy 3S 2200
450 Frame
Multiwii SE3 v2.2
40A ESC

What props would you guys recommend? I am running 10x4.7 right now because those are what I had available. Should I go smaller?
 

Craftydan

Hostage Taker of Quads
Moderator
Mentor
#2
ikem,

That motor should swing a 10x4.7 easily -- do you want to go smaller?

The only advantage I see of underpropping it is if the 10" prop is ovelapping the quad's body and a smaller one wouldn't, or you wanted shorter booms. A 450 quad frame, however, should easily accomidate the 10" props. Otherwise, if it's generating too much thrust, you can throttle back. you'll loose some of the resolution on your throttle control, but likely not enough you'd notice it.

The ESC is a bit overkill, but if you don't mind the extra weight/cost, it won't hurt anything.
 

kah00na

Senior Member
#3
I think you probably have the right size too. The smaller motors would need more throttle to get the same lift as the larger ones. Also, since the kv on your motors is less than 1,000, you should be fine. I'm using 10" props with my 980kv motors and I've been thinking about going to 11" to get faster responses out of it.
 

ikem

Senior Member
#4
So i had an esc die over the weekend.. One transistor on it got hit, but what ESC would you guys recommend? It is running 10x4.5 props (not 4.7s) and Turnigy SK3 920kv motors. I have basically had to rebuy motors, frame, and now escs already... gotten to fly it 4 times...

What brand/size would you guys recommend? would i be fine running Plush 18s?
 

Craftydan

Hostage Taker of Quads
Moderator
Mentor
#5
Plush 18's should be fine for the SK3, but mostly because the plush series is under spec'ed.

You might also want to check out the Q-brain 4x20A, I'm pleased with mine. So long as you don't try to burn out the sk3's, it'll work well and give you a nice clean build. It's also cheaper and lighter than 4 plush 18's + power board. If you're still paranoid (I understand), you can spring a few extra bucks and pick up the Qbrain 4x25.
 

Cyberdactyl

Misfit Multirotor Monkey
#6
Hi ikem. Yes craftydan is right, those 40's are massive overkill on a 450 pushing those motors and props. It seems there was a surge of comments in threads and blogs a few months back in forums, especially over at the mega-site rcgroups, to put huge ESCs on relatively small quads. I'm guessing, but it may have been because lots of folks were getting bored with 3S and experimenting with high-rate discharge 4S'.

I just finished a quad using HK's in-house 20A ESCs turning RcTimer 2808 1300 with 0947 CF props being powered from a 4S 90C, and the 20A ESCs DO get warm from a lot of 95% throttle, but in no way do they appear to be overworked. And that's with having the heat-sink plate covered entirely with fairly thick transparent shrink. I suppose in the the hot summer, I might be forced to cut a window in the shrink to expose the plate to unrestricted air, but for now they seem to handle it well. I think calculators, such a ECALC are assuming a constant 95-100% throttle, something you will never do unless you're someone like Warthox or attempting to lift a crazy load.
 

ikem

Senior Member
#7
how do those HK escs do? good response and performance? You say they do get warm with 9x4.7 and 1300kv, so it should be around the same with my 10x4.5 and 920kv.

I have also looked at the q brain, I have an integrated pcb on my quad, so single escs wouldnt be a wiring problem, but the cost and CG with the Qbrain is nice.

Anyone used multistars, non flashed?
 

Cyberdactyl

Misfit Multirotor Monkey
#8
The 20A and 30A HK UBEC work wonderfully. I'm on my forth set after 2 other quads and one tricopter. None have failed. I also learned 30A was unnecessary. But since the 30A weighs only 2g more and flashes the same way with simonK as the 20A, I can somewhat understand popping up to it just for the added feeling of security. But for a quad, it's an extra $12 for no real benefit to me. Sort of like running high octane in a family sedan.

Two great recommendations I got from David W on Flitetest was the dirt cheap HK ESCs and the awesome DT750s. Both have been flawless if treated right during the build.

The Q-Brain is a very nice system. And as you say, puts the mass in one spot. Worth it if looking for convenience and less complication. My only concerns, which are sort of minor, is designing the quad to allow the heat sink airflow, and if it fails, you're out the whole component instead of 1/4 the ESCs (although I haven't looked at the inside, you might be able to isolate the failed "ESC" and merely add a single if one fails, not sure just how integrated it all is)
 
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ikem

Senior Member
#9
from the look of it, it is very integrated.. and i do like the idea of changing only one out if it burns out.

How are the HKs non flashed?
 

Craftydan

Hostage Taker of Quads
Moderator
Mentor
#12
From what I've seen from those who have torn it apart, it's four independent ESCs with a shared power bus and switched BEC.

The common component failure on these are the FETs -- power transistors regulating/converting the AC current to the motors. which are independent of each other.

I will say it's heavy -- mostly due to a stout heat sink it's built on.

Frankly I agree with the repairability of single ESCs, but it was the economics that sold me on it. Doing cost comparisons, it would be cheaper for me to buy two complete Qbrain ESCs (one + spare) than a set of fair quality ESCs (4 + 1 spare) -- this would be true of any ESC over $12. All this and I don't need to buy a power distribution board either.

On the whole, unless I attach a bad motor/prop combo, it shouldn't burn out a non-defective ESC -- which is why I run my power systems though a watt meter to double check.
 

ikem

Senior Member
#13
I got it back together last night and took it back out. Much better, but still having some altitude problems, I'm just learning to deal with that though.

I have a gps module ordered for this, but does that enable alt hold mode? or do i need a bar for that?

All in all, i got through 3 batteries with some good practice (nothing broke!) and hope to get some more flight time this weekend.

BTW I got Multistar 20A ESCs. Cut the male bullet connectors off to solder it to the distribution board, but kept the other leads on and positioned them to break loose if the motor mount does snap again.