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Old Sep 24, 2012, 03:39 AM
We can rebuild it!
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I'm still waiting ony bits, glad I got these parts ordered, the V929 RTF I was promised for Christmas will be replaced with clothes because I need them more.

Thin is if I were to buy clothes nothing would be said about it, if I were to go and buy a helicopter that would be frowned upon Grrrrrr.
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Old Sep 24, 2012, 09:26 AM
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Originally Posted by jesolins View Post
Dave,
What glue is working for you to keep the UDI props on? I tried CA but that did not work on my U816. I fitted the Walkera micro props to it and those do not come off.
in post #1 step 10 i mentioned using straight pu to attach 1mm hub to .8mm shaft. i tried pu foam but it wasnt strong enough. straight ca failed to hold them on too. a similar method i referred to but didnt try was from experts in the indoor micro forum who swear by a combination of sewing thread and ca for big hub on little shaft.

to fix udi props which are not supposed to be loose i didnt try glue but instead galled the shaft with a pair of cable cutters. it seems to have worked because they have not come off again (knock on wood). i havent flown that much with the udi props since then so idk.

for me even walkera and wlt props have been known to shoot off into the ozone never to be seen again. simply cutting the tip off the shaft (again with cable cutter) after putting on props prevented them ffrom going away. it remains to be seen if it helps keep them from loosening and spinning on the shaft though.

ill experiment a lot more with this when the ali 1mm motors show up.
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Old Sep 24, 2012, 09:28 AM
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Grrrrrr.
grrrrrrrrrrr.... ruff!
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Old Sep 24, 2012, 04:56 PM
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ooops... i missed this 1st time through. those end of page posts are tricky. and it dont help that due to recent changes in rcg i dont have access on the weekend.

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Originally Posted by jesolins View Post
Hi Dave, Nice job again! Thanks for sharing.

You said the v939 works on a 30 and 60cm diameter quad too? I would not think that was possible with decent stability since the PID was optimized for the micro quad. The proportional values they coded for the micro quad would be higher than required for such a significantly larger one.
thanks again for the compliment. and yes, all three sizes. see this photo from post #1:



but im convinced its not pid. in my lowest cost itc3205 copter thread last year i tried all three popular algorithms and judging from behavior twisting by hand at half throttle it feels like tuned complementary filter or maybe even tbh. not so much pid. also ive noticed that there is slight oscillation with the big quads fc on a small frame but not the other way around. also indication of convergence instead of windup error. the unpopulated gain pot pads are a hint.

something else to note is its not size of the arms but more importantly their mass. in this case my whole quad weighs less than just one arm from the original quadcopters of similar size. so yeah, id also be surprised if kk type pid could perform in cases like this. specially considering these need no adjustments and work "out of the box". the wlt controllers opened up a whole new world of multicopter design for me.

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Originally Posted by jesolins View Post
Are you using the same motors and props when you did the 60cm test?
well i did use aliexpress motors and udi props on both smallest and biggest frames in this weekends tests. i dont think there is much difference between the 7mm pagers other than shaft which should not matter. they all have similar coil impedance. 6mm? thats a different story.

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Originally Posted by jesolins View Post
Do you have any videos of the 60cm version flying?
its difficult for me to put up any of considerable size due to phone line internet and flash is not an option either but i do have a collection of short test runs of the v939 on 60cm frame in my camera. like with the video in post #1 theres no flips or other wild behaviour. but if anybody is interested i can maybe pick out one or two from the 60cm lift/stability tests and upload to rcgroups. let me know.

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Originally Posted by jesolins View Post
What is the flying weight of the 60cm you tested this with?
as you can see in this pic flying weight of the 60cm is less than an ounce including battery. size may not matter but weight DEFINITELY does. if all you know is big multicopters and even micro quads like v929/v939 you actually have to fly one of these to understand what im talking about. i suspect it may even be possible to cut the frame weight almost in half again by using djs foam idea. but crash resistance may be a problem. idk.



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Originally Posted by jesolins View Post
Sounds like you did a brushless mod I am interested in your brushed to brushless solution too BTW
i wish. we have been talking about it though. heres a couple pics of the 4ch motor to servo pwm converter i did for somebody last year. this can probably be used to convert these v939/v929 clones to brushless using the hk 1s esc and 2gram motors. this was discussed earlier in this thread. at 0.15 grams its much smaller and lighter than TheSteve adapters and costs less too.
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Old Sep 24, 2012, 06:21 PM
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Originally Posted by dave1993 View Post
i wish. we have been talking about it though. heres a couple pics of the 4ch motor to servo pwm converter i did for somebody last year. im sure it could be used to convert these v939/v929 clones to brushless using the hk 1s esc and 2gram motors. this was discussed earlier. at 0.15 grams its much smaller and lighter than TheSteve adapters and sure costs less too.
What microcontroller is it ? An Attiny? Can you give us more informations on that ?
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Old Sep 24, 2012, 09:05 PM
Tri-Quad-Hexa-Octo-copters!!
United States, TX, San Antonio
Joined Feb 2007
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Hi Dave,
Thanks for your detailed response.
The 60cm quad has my curiosity up With the quads I normally fly with 10 inch and lager props, if you go larger than 70cm diameter, you lose most yaw authority unless you add some tilt to the motors on each axis in the direction of their gain thrust to induce yaw. How did yaw work for you with those tiny props? Yes a video would be nice if you find the time.
Thanks and Cheers,
Jim
Quadrocopter and Tricopter Info Mega Link Index

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Originally Posted by dave1993 View Post
ooops... i missed this 1st time through. those end of page posts are tricky. and it dont help that due to recent changes in rcg i dont have access on the weekend.
thanks again for the compliment. and yes, all three sizes. see this photo from post #1:...
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Old Sep 25, 2012, 10:03 AM
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What microcontroller is it ? An Attiny? Can you give us more informations on that ?
you guessed right. it is a tiny24. quickly became a favorite and im thinking of replacing my beloved tiny13. it is a more modern avr with not only 2x more memory and io but built-in temperature sensor and more advanced adc. also more stable internal oscillator set to 8mhz from the factory. most of all it actually cost less than the t13 due to sub-micron process.

in this application the 4 pwm timers (2x more than t13) come in very handy. you might be able to make out in the photo they are used to generate the esc signals. these run with no cpu intervention which makes coding a cinch. the other 4 wires are used to sense motor output pwm from the fc board.
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Old Sep 25, 2012, 10:21 AM
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Originally Posted by jesolins View Post
Hi Dave,
Thanks for your detailed response.
The 60cm quad has my curiosity up With the quads I normally fly with 10 inch and lager props, if you go larger than 70cm diameter, you lose most yaw authority unless you add some tilt to the motors on each axis in the direction of their gain thrust to induce yaw. How did yaw work for you with those tiny props? Yes a video would be nice if you find the time.
there is no doubt that larger frame affects ability to turn and pirouette. when i say it flies great i mean it dont go shooting off uncontrollably in random directions like my kk did at first. wlt engineers have definitely optimized v929/v939 algorithms for their respective quads. but these do seems to be far more tolerant of frame size than the "real" controllers i played with. and best of all no adjustments required.

ill go through the files in my camera and see if i can find some that give a hint of at least how stable it is. dont get your hopes up because theres no fancy flying here. i was basically just testing out the new aliexpress motors and trying to see if the somewhat lower thrust udi props showed on a test stand would affect real world performance. i was pleased to find both motors and props behaved pretty similar to their s107 and walkera counterparts.
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Old Sep 25, 2012, 11:57 AM
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Originally Posted by skitchen8
Well I've had this idea (in bits and pieces) floating around my head for awhile, and out of everyone I've talked to on the forums you're the best to ask. I love my 929 and the way it flies, buy it is too small and not powerful enough. I know someone (was it you? I can't remember) took the board and put on longer arms and I believe lost some stability. I was wondering with bigger motors if maybe it could make up for that.

So my question: since you have testing equipment I can't afford, can you record the signal before it goes into the speed control FETs? Or even barring that, do you know if it is PWM?

I'm thinking that building some h bridges is well within my abilities and if it is PWM coming off of the receiver I can run that through homemade h bridges for a reasonable price and get me some bigger motors to experiment.
multicopter motors dont need h-bridges. a simple transistor, preferably fet, will do since the motors turn only one way. maybe nerys 3d quad idea which does have reversing motors could use an h-bridge though. assuming we find a prop that performs adequately
in both directions.

the v929 board generates 150us pwm for the motors but not a clean square wave. they put a cap on the fets gate to slow down the edge for back emf and noise prevention. most put the cap across the motor but this novel approach wastes less energy. also interesting is the fact that it never turns off completely but maintains a small residual pulse. idk the reason for this. maybe an artifact of the output compare timer.

as far as maximum motor size ive attached 8.5mm pagers and even on the v939 board there was no sign of heat on the output transistors. so im guessing they can take a lot more. maybe even n20 or johnson 250s. with only 2 boards im not in a position to very atm. ive got a few on order so who knows...

anyway for real lifting brushless motors would be the solution. weve been discussing this but since theres no chance of meeting the low cost goal here it probably deserves a new thread. (ahhh... so many ideas... so little time... )
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Old Sep 25, 2012, 12:13 PM
Tri-Quad-Hexa-Octo-copters!!
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Dave,
Again thanks for the info. Since the FETs seem to run fairly cool another worthy mod would be an octo. Each "arm or fork or T or coaxial" with two motors wired in parallel. If the FETs ran too hot with that, we could solder another same FET pancake style. That would generate a few more lifties and some added flight redundancy. Fun!
Cheers,
Jim
Quadrocopter and Tricopter Info Mega Link Index
Quote:
Originally Posted by dave1993 View Post
multicopter motors dont need h-bridges. a simple transistor, preferably fet, will do since the motors turn only one way. maybe nerys 3d quad idea which does have reversing motors could use an h-bridge though. assuming we find a prop that performs adequately
in both directions.

the v929 board generates 150us pwm for the motors but not a clean square wave. they put a cap on the fets gate to slow down the edge for back emf and noise prevention. most put the cap across the motor but this novel approach wastes less energy. also interesting is the fact that it never turns off completely but maintains a small residual pulse. idk the reason for this. maybe an artifact of the output compare timer.

as far as maximum motor size ive attached 8.5mm pagers and even on the v939 board there was no sign of heat on the output transistors. so im guessing they can take a lot more. maybe even n20 or johnson 250s. with only 2 boards im not in a position to very atm. ive got a few on order so who knows...

anyway for real lifting brushless motors would be the solution. weve been discussing this but since theres no chance of meeting the low cost goal here it probably deserves a new thread. (ahhh... so many ideas... so little time... )
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Old Sep 25, 2012, 12:47 PM
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Originally Posted by dave1993 View Post
maybe nerys 3d quad idea which does have reversing motors could use an h-bridge though. assuming we find a prop that performs adequately in both directions.
You want a prop that works backwards nearly as well as forwards? Use the standard props. 87% efficiency in reverse - well, U816 props anyway. I know you bought some of those. LB props: probably slightly less so. Probably less effort than using heli-tail rotor blades unless you really want to.

Here's a little video demonstrating how these work great in reverse with the CW and CCW props swapped and the motors inverted. FC's a little freaked out with the Yaw being reversed and the CoG changed, but the quad certainly shows it can fly once the Yaw is adjusted for. Not stunt flying by any means, but proves the concept is sound.

For a scratchbuild, I'm sure you could work something out with the Yaw problem. Certainly illustrates you could make an Octocopter with two motors on each arm: one above and one below with standard blades and motors. Maybe running off the same connection. You wouldn't get the full 87% from the lower blade, as it's also in dirty air, but maybe 60-70% more lift would be useful.

Here's that video:
U816 inverted thrust and flight test (1 min 36 sec)
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Old Sep 26, 2012, 09:49 AM
We can rebuild it!
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Udi props have arrived

So my 2 sets of Udi props arrived yesterday, they were dispatched on the 8th but give how time zones workout against the time of dispatch I would guess that was a their Friday and my Saturday. 13 working days ain't too bad.

Here they are on the Foam Quad Frame, my V939 props were sent out 2 days later and the board the day after them so this time next week I should be airborn!
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Old Sep 26, 2012, 11:06 AM
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Worlds Lowest Cost Octocopter?

what with brandigan and jesolins talking about double motors and skitchens INCESSANT WHINING for more lift i came up with the octo frame shown below. no "dirty air" here. we will see how it performs when i get around to populating those holders and hub.



also a couple people asked to see video of the 60cm dquad. i really dont have anything atm except a few short test flights where i was checking out different motors and props. basically wanted to see if it would lift and be capable of some hint of control. the only place i have nearby is the 7 foot wide frat house driveway so no fancy flips or funnels. wind was a problem too. also because these are only test runs i didnt bother to change the camera from 10" macro used for the closeups so things are a little fuzzy (if not warm and...). heres one with aliexpress motors and udi props. by far the lowest cost setup.

http://www.rcgroups.com/forums/showt...0#post22839626

you can see that at least it has enough power to lift and dont go shooting off in random directions never to be seen again. when i get a chance ill replace it with a real video.
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Old Sep 26, 2012, 12:11 PM
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what with brandigan and jesolins talking about double motors and skitchens INCESSANT WHINING for more lift i came up with the octo frame shown below. no "dirty air" here. we will see how it performs when i get around to populating those holders and hub.
Ah, it's clear who's on top.of design. Might work, looks quite pretty, but I doubt it would fly well. Wouldn't the distance between the motors make control unnecessarily awkward? You'd have to supply proportionally larger control changes to the outer motors than the inner ones. Assuming you get a stable baseline to hover with.

Why don't you just put the motors really close together - like 1 prop blade distance apart and make sure that one motor is slightly more than one prop blade depth ( a few mm) higher than the other? Slight blade overlap would give a bit of turbulence, but less confusing for the FC. Works for a Chinook.


To make it even less confusing for the FC - although maybe heavier, maybe not - put a short 'Y' at the end of the arms and do the same thing: slightly overlapping blades, motors 1" apart.
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Old Sep 26, 2012, 12:21 PM
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Ah, it's clear who's on top.of design. Might work, looks quite pretty, but I doubt it would fly
lol! i love this guy. does anybody else love this guy? am i the only one? i really do love this guy.

thanks for the input brandigan. and the "inverted compliment". i have a theory that it just might fly. maybe even better than the original. assuming the fets like driving two motors. of course only time will tell.

btw pretty must be in the eye of the beholder. but i guess it might be true that "ugly is the new beautiful".

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To make it even less confusing for the FC - although maybe heavier, maybe not - put a short 'Y' at the end of the arms and do the same thing: slightly overlapping blades, motors 1" apart.
wayyyyyy too much work. at least for me. tacking on those other holders took literally less than 3 mniutes. i know this because my soft boiled eggs were done soon after i set it aside to foam up.
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Last edited by dave1993; Sep 26, 2012 at 12:45 PM. Reason: who else loves this guy?
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