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Old Feb 15, 2013, 11:22 AM
RC beginner
New York
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dont forget to take pictures! and show us the v911 project. if its a plane post in that thread over at the indoor forum. if heli show it off in the v911 thread in micro heli forum.
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Old Feb 16, 2013, 11:36 AM
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everything will be in my blog...The title is under my pro name..still waiting for parts and other things to arrive before i can start...not sure how long it will be..When i build a quad it will be in blog form as well...hope to see everyone there when i get started.

ill have pics and videos and tests and instructions...Will be a very in depth build from scratch on both the v911 and the quad.
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Old Feb 28, 2013, 12:58 AM
it WILL fly! someday....
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Slovakia
Joined Aug 2008
448 Posts
I got new 939 fc (from BG) and s107 motors from focalprice (came 7 black/white and 3 red/blue, in 10 pack) and built another quad. Seems trivial, but how to fix 939 props to those thin shafts? I used 2 strands of dental floss, so props fit tightly, but they are off-center, what causes really bad vibrations. Shaft are pretty loose in motor bushings, so this makes it ever worse. I balanced props as much as possible (some, but small vibrations felt when holding motor with fingers), but it still vibes, even gets into resonance. In the air fc freaks out. Shoots up, or even drops power intermittently, so quad almost falls down.

I think of epoxy drop on the shaft, filed down whit help of drill when hard. Is there anything less laborious? I cannot see how straightforward gluing props to shafts can be precise enough, so they are centered and perpendicular to the shafts.
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Old Feb 28, 2013, 09:58 AM
KlonWarz
Joined Dec 2012
454 Posts
I've been considering how to fit large hole props to a small shaft...
Cheap props/cheap method...

Center the prop in a small jig on the table of a drill press using a drill bit that fits well.
Raise spindle and replace with a larger bit that will fit some sort of plastic rod you have available. (perhaps a scrap from the tree of plastic model parts?)

Glue the rod in place.

Exchange drill bit for size that will fit you motor shaft.

Probably lube the cut with mineral oil???

Clean and balance.
Use a small drop of CA or other adhesive to affix upon motor shaft.

The question is... what will be the tolerance of your drill press spindle???
:-)
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Old Feb 28, 2013, 12:54 PM
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hi. after so much experimenting you must be able to answer the question: how length of booms matters if disregard other factors like weight?
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Old Feb 28, 2013, 01:13 PM
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United States, CA, Carlsbad
Joined May 2011
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Originally Posted by asanovrus View Post
hi. after so much experimenting you must be able to answer the question: how length of booms matters if disregard other factors like weight?
I ran some simulations on a simple axis and varied the arm length, then swept through PID values comparing the controllability of the axis and found some interesting stuff.

If you disregard weight (and even if you regard it), extended the booms actually makes the frame react quicker. This means more maneuverability. However, you are generally limited by the response time of your controller and ESCs. This means, as you move the props further from the CG, you eat up your sensitivity margins. Too far, and risk destabilizing your aircraft completely. On the flip side, moving your motors closer to the CG improves your sensitivity margins, making it easier to tune your PIDs to gain a stable aircraft. Larger sensitivity margins also mean the less sensitive your aircraft will be to changes in performance, weight, control delays, or whatever.
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Old Feb 28, 2013, 01:19 PM
KlonWarz
Joined Dec 2012
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Very good ilektron!
as an option, how abt tuning thrust with some sort of vector control?
rc
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Old Feb 28, 2013, 01:26 PM
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United States, CA, Carlsbad
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Originally Posted by rusty case View Post
Very good ilektron!
as an option, how abt tuning thrust with some sort of vector control?
rc
IMHO is why tricopters have such great yaw. A quick servo reacts quicker than spinning motors up and down.
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Old Feb 28, 2013, 01:39 PM
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Originally Posted by ilektron View Post
I ran some simulations on a simple axis and varied the arm length, then swept through PID values comparing the controllability of the axis and found some interesting stuff.

If you disregard weight (and even if you regard it), extended the booms actually makes the frame react quicker. This means more maneuverability. However, you are generally limited by the response time of your controller and ESCs. This means, as you move the props further from the CG, you eat up your sensitivity margins. Too far, and risk destabilizing your aircraft completely. On the flip side, moving your motors closer to the CG improves your sensitivity margins, making it easier to tune your PIDs to gain a stable aircraft. Larger sensitivity margins also mean the less sensitive your aircraft will be to changes in performance, weight, control delays, or whatever.
I agree..With a good aftermarket board you can tune for different variables like boom length and motors and weight and prop sizes etc...

With these pre programmed toy quad boards; were stuck with the parameters pre set from the factories..I wouldnt go farther than 1mm longer or shorter on boom size for a hybrid...id bet you can find the sweet spot somewhere within the length of boom the board was programmed for. Meaning within 1 mm shorter or longer at maximum
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Old Feb 28, 2013, 01:55 PM
RC beginner
New York
Joined Oct 2008
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Originally Posted by 6sharky9 View Post
I wouldnt go farther than 1mm longer or shorter on boom size for a hybrid...
i guess you havent read post #1 yet.

ive put v939 board on 60cm (2') frame. see video. and v929 fc on half size frame. there are advantages and disadvantages to various arm lengths but hard to say which is preferred. some like quick and frisky and other like slow and stable. i like both depending on mood and weather, indoor or outdoor. it is worth noting that the v929 fc on too small a frame will show minor oscillation and then theres the rebind issue for v939. pick your poison.
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Old Feb 28, 2013, 01:56 PM
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Quote:
Originally Posted by ilektron View Post
I ran some simulations on a simple axis and varied the arm length, then swept through PID values comparing the controllability of the axis and found some interesting stuff.

If you disregard weight (and even if you regard it), extended the booms actually makes the frame react quicker. This means more maneuverability. However, you are generally limited by the response time of your controller and ESCs. This means, as you move the props further from the CG, you eat up your sensitivity margins. Too far, and risk destabilizing your aircraft completely. On the flip side, moving your motors closer to the CG improves your sensitivity margins, making it easier to tune your PIDs to gain a stable aircraft. Larger sensitivity margins also mean the less sensitive your aircraft will be to changes in performance, weight, control delays, or whatever.
very interesting! if this principle is right then putting v959 board on v939 will make it even more stable then v959? another question I have: why they put gears on v929 etc? gear reduces speed but it could be achieved reducing size of props
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Old Feb 28, 2013, 01:58 PM
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New York
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Originally Posted by Richard_s View Post
how to fix 939 props to those thin shafts?
i guess you havent read post #1 yet.

a dap of polyurethane glue and eyeball the alignment it sets. if it ever does come off (unlikely) a touch of ca will keep it from ever coming off again. ever.
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Old Feb 28, 2013, 02:13 PM
RC beginner
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Originally Posted by asanovrus View Post
very interesting! if this principle is right then putting v959 board on v939 will make it even more stable then v959?
i dont have a v959 but if its similar in size probably little difference. i do know putting fc from big quad in smaller frame makes for faster response but risks the "shakes". other way around increases stability but slows response big time. i think this accounts for lots of the complaints in the v939/v949 thread. they get used to one and might not appreciate benefits of the new toy or may develop unrealistic expecttions.

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another question I have: why they put gears on v929 etc? gear reduces speed but it could be achieved reducing size of props
i have both and direct vs geared are completely different animals. the much heavier v929 has extreme lifting power compared to the smaller and quicker v939. just like in planes gearing is a way to allow use of bigger props with their increased efficiency and thrust. the different is not slight, sometimes an order of magnitude. for example putting a camera on stock v939 has dramatic effect on handling and flight time. not a positive effect either. and bigger battery also creates issues. my v929 pretty much ignores the 808 keycam stuck on there and lipo of 2x or 4x mah, no problemo.
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Old Feb 28, 2013, 02:25 PM
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do you think it's not board that makes difference in power? I thought gear cannot give power, but it can reduce it by friction (one of gears on my v959 has imperfection that I can't fix causing more friction). what's the difference b/n big prop rotating slower and smaller prop rotating faster?
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Old Feb 28, 2013, 02:27 PM
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United States, CA, Carlsbad
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Originally Posted by dave1993 View Post
i have both and direct vs geared are completely different animals. the much heavier v929 has extreme lifting power compared to the smaller and quicker v939. just like in planes gearing is a way to allow use of bigger props with their increased efficiency and thrust. the different is not slight, sometimes an order of magnitude. for example putting a camera on stock v939 has dramatic effect on handling and flight time. not a positive effect either. and bigger battery also creates issues. my v929 pretty much ignores the 808 keycam stuck on there and lipo of 2x or 4x mah, no problemo.
Yeah, given the same motor, a larger prop allows for more thrust per watt, which makes up for the difference in weight and reduction in efficiency of the gears.

Also, a big prop spinning slower can be more efficient than a little prop spinning fast.
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