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new guy rolling his own Rotorbones H-quad, have some questions

slyp823

crash test dummy
#1
Hey guys, I'm planning to build my first quadcopter using the plans (and knuckle hubs) for the rotorbones H-quad as a bit of an ongoing project (meaning tons of questions as I collect parts) and I've got a few frame-related questions off the bat.

(1) I bought enough 1/2" square by 36" long poplar to build either 5 quads with 10" legs or 6 quads with 9" legs, but I'm honestly not sure which to go for. At $0.59/foot, material is cheap and I've got 18' of the stuff to work with so I'm not exactly wanting for material, but at the same time I can make more spares using 9" legs and not have any wasted material. would making the copter an inch shorter in width and length make it noticeably harder to fly, or have control boards gotten good enough in their ability to correct for airframe twitchiness that it wouldn't matter? obviously I'd have to stick to an 8.5" or smaller prop to keep from running the props into one another, but given that just starting out I'm not going to be doing FPV or carrying anything of any appreciable weight, I don't think the slight decrease in thrust from taking 0.5-1" off of the blades would be much of an issue, would it?

(2) I'm going to print out the .pdf plans for the frame and spray glue it to some material I have and cut it out either with a band saw or a scroll saw, depending on which I can get set up (I have access to both, but the scroll saw needs to be set up and bench space found for it, and the band saw quite desperately needs a new blade and some TLC), but I'm not sure which material would be best. I think I might have a bit of a material hoarding problem, as I currently have 6 8x10" sheets of 0.093" lexan/polycarbonate, 3 8x12 and 2 9x12 sheets of 0.125" kydex, all of which is basically in an as-bought state (uncut/undrilled, still has protective film where applicable), so I doubt I'll run out of material any time soon. Kydex is SOOOOO much nicer to work with than lexan when it comes to cutting (drilling is about even though, since I've got access to a drill press) but I've also noticed it's a bit more flexible than lexan, despite being thicker... but with the largest part only being 80mm/3.14" square and very well secured, would rigidity really be an issue? I've read with some h-quads that low torsional rigidity can cause REALLY nasty flight characteristics (as in flying 3-4 mistakes high might still be too low to prevent a crash) so I obviously don't want that to happen, but the design of the rotorbones quad seems to be more torsionally rigid, and from all of the shenanigans the FT crew has put the design through, if rigidity was an issue I think it would have reared its head by now, and with the potential for going an inch smaller, wouldn't the chance of flex be even less?

If you've made it this far, thanks for putting up with my late night ramblings, and thanks for any and all help! I'm sure I'll have a bunch more questions as I get into the more technical side of the build (motor/ESC/prop/flight control board selection and setup, and of course, pilot calibration :D ) so brace yourselves!
 

baddox

Senior Member
#2
I can't be of much use regarding the second point, but for number 1, I strongly suspect 9" booms with 8" props (probably 8045 slow flyers) will work fine with any well-reputed flight controller like a KK2. There should be plenty of clearance on the props, especially if you're using the rotor bones mounts which put the motor another half inch or so past the end of the boom. You would probably want 1000-1400 KV motors, and personally I would go 4S (I fly multirotors almost exclusively on 4S and 8045-9047 props, so I'm a bit biased there).
 
#3
i decreased the boom length in my bat bone from 13.7in to 12 so that I could cut an equal amount of booms.. I noticed no difference and that was more than the inch your considering..
I fly on some gold color hobby king motorshttp://www.hobbyking.com/mobile/viewproduct.asp?idproduct=12916&type=&idparentcat=520 using sf 8045 props.. on hk blues series 20amp esc.. no problems.. I use the hk multi rotor control board v3.

Even though it's not need I'd advise flashing simonk firmware on the esc..

You shouldn't have any problems getting lift with either material that you listed, and I cut my bat bone frame on a scroll saw.. worked amazingly
 

slyp823

crash test dummy
#4
thanks guys! hopefully I'll get my build started soon, or at least get a frame built so it can sit on my desk waiting for electronics...

EDIT: speaking of electronics, from a flight perspective, what's the best flight control board to use? I don't mind programming the board via PC (I'd almost prefer it, to be honest) but I absolutely do not want to have to do the whole "hold at half throttle and listen for three beeps, then rub your nose and do the rain dance" method of programming/configuring. the KK2 board looks really user-friendly and seems to fly quite well from what I've seen, and the program-via-LCD is pretty cool, but it seems to go out of stock VERY frequently. Any input?
 
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Craftydan

Hostage Taker of Quads
Moderator
Mentor
#5
Best is a relative term, mostly depending on budget, but a touch on taste.

The KK2 is a nice board, and better than most of the inexpensive boards sold at HK. The interface is very frendly, but expect to relfash it immediately. stock firmware is 1.2 which is passible, but nowhere near as nice as the 1.6 versions. the latest versions are fairly feature rich, but the processor is maxed out so we can't expect much more out of this board -- hopefully another version is in the works, but this one is very nice. There are also a few stores that resell it domestically -- some with reasonable markups, some price gouging. Had friends who've had good experience W/ GotHeli's store. I do recomend it, but it's the only one of the "Hobby King" branded boardsI would. that, and there are other fish in the sea.

Some of the higher end multi-wii boards are making great strides (GPS, barometric altitude, bluetooth programming), but the older ones should be avoided -- the sensors themselves are weak. Wish I could recomend on model but I'm not familiar with which is which among the multiwii.

If you've got the coin to drop, the Naza boards or APM boards are really nice and finished products with all the bells and whistles.

keep in mind, you don't really fly the quad -- the board does. You tell it "how to" in setup and "where to" in flight. The smarter the board, usually, the more it flies for you. Frankly many of the new RFT copters comming out don't appeal to me because *every* time I've seen them fly it's far too robotic and not as much a flying experience -- nice if you're filming, but way too synthetic when you're flying.

Naturally, YMMV.
 

xuzme720

Dedicated foam bender
Mentor
#6
keep in mind, you don't really fly the quad -- the board does. You tell it "how to" in setup and "where to" in flight. The smarter the board, usually, the more it flies for you.
Also, this can account for "the lost copter syndrome" a few members have experienced lately. Not sure I can completely trust the robots yet...
 

Craftydan

Hostage Taker of Quads
Moderator
Mentor
#7
At HHAEFI, this past weekend, had a guy showing off his DJI Phantom in one of its gps hold modes. Took it up to a ridiculous height set down the tx nad preceded to tell me the crazy things he's done with it. . . With the transmitter laying at his feet and the Phantom 500 ft in the air.

He then decides he wants to bring it down a little. Picks up the tx, holds the throttle down, and the copter starts to descend. For a few moments, he's chatting and Dead calm. Then he suddenly stops talking. Then he panics.

"I don't have control of it!!! "

He watches as it descends at about 0.5ft/s, and hit just 3ft from a guy who'd walked up to the flight line with his heli. The guy jumps back, the Phantom bounces and flips, senses it's upside-down, and shuts off.

The "pilot" rushes up to his copter, flips it over and beams as he shows no damage to the quad that almost hit someone.

"this is the best quad - It's indestructible and knows how to fix itself when I f*** up!"

After that display, I'll never recommend DJI's RTF copters.

There's something to be said about fool proofing. I believe it's "they'll just make better fools".
 
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slyp823

crash test dummy
#8
So for basic learning the ropes of quadcopters, a KK2 should be fine with the v1.6 firmware flash? For some reason I thought the KK2 was considerably more expensive than it is (REALLY wasn't expecting to see a $30 price tag on one of the most user-friendly flight control boards out there!) But upon seeing the price, assuming i can find a KK2 for sale somewhere I'm definitely snagging myself one. As far as motors/ESCs go, what's everyone's recommendations for a h-copter with ~9" booms? I've heard the suggestion for 1000-1400kv motors on 4s lipo, but which motors? At first its just going to be lifting the copter itself, but one day i might get crazy and strap my gopro to it and try not to crash, so I think I'd like a bit more available thrust than I'll need at first to account for my possible future shenanigans

EDIT: That bit about the foolproofing is spot on... the world will always evolve a more effective fool, usually about twice as fast as new foolproofing ideas come out! Thats a bit terrifying though, that heli pilot was lucky he didn't end up with a flying cuisinart hit him in the head! It also seems like a really good lesson on why you shouldn't trust the electronics to know what to do 100% of the time, nothing can replace intuition, skill or instinct.
 
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Cyberdactyl

Misfit Multirotor Monkey
#9
The KK2 really isn't that hard to grab at HK. The trick is to sign-up for a notification email once a new batch arrives. You'll find you only have to wait a few days to a week or so.
 

rcspaceflight

creator of virtual planes
#11
The KK2 really isn't that hard to grab at HK. The trick is to sign-up for a notification email once a new batch arrives. You'll find you only have to wait a few days to a week or so.
Is it just me or has Hobby King gotten a lot better about re-ordering backordered items? The batteries I wanted where out of stock, I checked again in a week and they had plenty of them.
 

Craftydan

Hostage Taker of Quads
Moderator
Mentor
#12
Is it just me or has Hobby King gotten a lot better about re-ordering backordered items? The batteries I wanted where out of stock, I checked again in a week and they had plenty of them.
It takes them a while to figure out what's popular -- a typical supply chain problem. They probably keep ordering XX% more than last time each time it sells out, and the OEM ramps up production for items that have growing orders. It does stabilize out for things that have long-term popularity, but that first batch or two of something really cool will always be a pain to get.
 

Tritium

Amateur Extra Class K5TWM
#13
You can always carry a small aluminum baseball bat to the flying field for protection against belligerent multicopters. Sometimes if they refuse to follow instructions they may need a QUICK firm "swat" for the protection of all parties nearby. ;)

Thurmond
 

cranialrectosis

Faster than a speeding faceplant!
Mentor
#14
I built the Anycopter with 10" booms (22" diagonal), then with 9" booms (20" diagonal). I still wanted to go smaller as I fly in my backyard. I built a knuckler H quad this weekend. It has 10" booms with 8" center beams. This puts rotors one and four 1/2" apart and rotors one and two 3" apart and gives it a 14" diagonal span.

Flight characteristics are remarkably different between the Anycopter (Flying Purple Squirrel Eater) with a 20" diagonal span and the BumblerBee with it's 14" diagonal span.

The FPSE is easier to fly. The H quad is more rugged and slightly more challenging to build. I used the same motors and escs on both and they weigh about the same. The BumblerBee requires slightly more throttle (I suppose due to more frame below the rotors) and is far less forgiving in the wind. Be careful reducing altitude and don't fly in your own wash. It is easier to do with the smaller copter.

Based on my experience, longer booms make a copter more stable, fragile, quieter, simpler to learn on and slightly more efficient.

I suppose more rigid materials make for better acrobats and less rigid make for better video copters. Wood naturally reduces vibration better than aluminum. With harder more rigid materials I would expect to need to take more drastic options to mitigate vibration. Others on this forum will have more experience here.

I like my BumblerBee. I plan to rebuild my FPSE with a MultiWii Pro and a different concept on booms. The FPSE is my experimenter and my camera copter. The BumblerBee is for whipping around the yard acrobatically.

This is video I shot today of me testing my new KK2 and transmitter settings as I trim this thing out.


Welcome to FT.
 

Craftydan

Hostage Taker of Quads
Moderator
Mentor
#15
You can always carry a small aluminum baseball bat to the flying field for protection against belligerent multicopters. Sometimes if they refuse to follow instructions they may need a QUICK firm "swat" for the protection of all parties nearby. ;)

Thurmond
And if it happens to contact the idiot pilot as well, just solved the problem more permanently.
 
#18
I use the hk multi rotor control board v3 and it works awesome. You re flash it just like the kk and the programming was super easy..

Look at the flitetest video on the multi rotor control programming.. you program it then forget about it.. I'm looking at the hk amp mega with gps next for its gps and advance features, but as a basic flight controller I have no regrets about buying the multi rotor control board.. just make sure you buy the programming cable.. I had to order mine from eBay