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Old Sep 02, 2012, 08:47 AM
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Originally Posted by flying-llama View Post
By the way, I was using the term "braking" loosely in that to go from forward to reverse, the esc first has to stop the wheel from spinning forward (what I meant by brake in this situation) before it can start the wheel spinning in reverse.

Anyways, a second is a long time, but while not so pretty, height can compensate for that: from level flight, a quad (or other object) suddenly starting to go into free fall will lose about 16 ft (5m) in the first second. I lose about that height and more when I am not doing so well on a flip (I tend to start a flip from 30+ feet up).
Okay was wondering about that, most escs offer a braking feature which, if I understand correctly, shorts out the motor and effectively locks the coil in place. I actually think if you could program the esc to do it going from forward to brake to reverse might be faster than applying just reverse. My thinking is that going from forward to reverse directly would also be very taxing on the esc while it was overcoming momentum, similar to running a motor while a prop is being blocked from spinning. I could be totally wrong though, this isn't exactly my area of expertise.
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Old Sep 02, 2012, 08:52 AM
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Originally Posted by Brandigan View Post
These are both auto flips. No effort involved in recovery, the 100% stick version is like the v929, which is different to the Blade MQX, where you have to put a bit more effort in, feather the throttle when inverted and do the recovery yourself.

Also, to save having two posts, on the inverted props and braking propeller discussion, see these videos:
Variable pitch and inverted flight: http://www.youtube.com/watch?v=VIkqqVr_u9U

Earlier version of development of same: http://www.youtube.com/watch?v=Vy5Ky50eGJs

Recovering from a broken prop in midflight: http://www.youtube.com/watch?v=2GkDGpCSDbU

This is powering all 4 props off of one motor
Scroll forward a bit and the English text explains it all.
:http://www.youtube.com/watch?v=fkSx3fSz0tE
Nice videos. I think this will happen soon. A few years maybe and we'll start to see full 3D models reach the market. But there's some more work to be done before such models satisfy avid 3D pilots and FPV fanatics. Clearly, as seen in the videos, the servos are simply too slow to keep up. There's a lot of oscillation there. In other words, some good ESCs with fixed pitch props do a better job at keeping a craft stable. The response is quicker resulting in more stability. That said, variable pitch props on a quad is has huge potential and the technology required to make it work well is just around the corner, in my opinion.

Best,
Chris
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Old Sep 02, 2012, 08:59 AM
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Originally Posted by bobepine View Post
Clearly, as seen in the videos, the servos are simply too slow to keep up. There's a lot of oscillation there. In other words, some good ESCs with fixed pitch props do a better job at keeping a craft stable. The response is quicker resulting in more stability.
Where are you seeing that? In the first video, it specifically compares a variable pitch to a fixed pitch quad and the variable is a lot sharper at stopping.
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Old Sep 02, 2012, 09:01 AM
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Originally Posted by mystman View Post
Sorry, didn't get that $38 was "on sale". I like buying from BG but sometimes there prices changes like stocks.
Many online retailers do this, Amazon being the easiest example I can come up with. Also while looking for car insurance your quoted price will occasionally change based on what browser you are using. Whether fortunately or unfortunately the relationship between end price, supply, and demand can change constantly with the metrics available to online retailers.

I just recently designed an ecommerce site for my girlfriend, who makes jewelry. Though we don't have a large enough volume for it to become useful at this time between her site and Facebook metrics she can adjust prices based on demands for specific things (say necklaces are selling better than bracelets, offer a bracelet for x% off when purchased with a necklace to move inventory). For larger businesses the human element is totally removed, and algorithms take care of this three way relationship. I suspect BG likely uses a dual approach, where the algorithm suggests a price and when a predetermined difference between current price and projected price is hit a person can make the appropriate change. That is my theory, I could be wrong, but the underlying ability does exist and is not out of reach for a site with the sales volume that it seems BG has.
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Old Sep 02, 2012, 09:12 AM
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Brandigan thanks for the "Variable pitch and inverted flight:" videos.

Now we have to hope Walkera construct's one, and VL-toys or MJX makes a cheap clone of it.

The future is fantastic for RC lovers!
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Old Sep 02, 2012, 09:20 AM
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Originally Posted by Brandigan View Post
Where are you seeing that? In the first video, it specifically compares a variable pitch to a fixed pitch quad and the variable is a lot sharper at stopping.
Yes, it's faster to stop, of course, given the variable pitch commands on the blades via servos. Now look at that video again. The quad on the right doesn't stop as fast but it's rock stable. The one on the left stops quickly but look at it closely. It wobbles a lot more even a while after height stabilization. Not nearly as stable as the fixed pitch one on the right side.

Best,
Chris
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Old Sep 02, 2012, 09:21 AM
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Here's a video demonstrating manual flips with my x250.

Best,
Chris

X250 Tic-Tocs (5 min 49 sec)
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Old Sep 02, 2012, 10:01 AM
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Originally Posted by bobepine View Post
Yes, it's faster to stop, of course, given the variable pitch commands on the blades via servos. Now look at that video again. The quad on the right doesn't stop as fast but it's rock stable. The one on the left stops quickly but look at it closely. It wobbles a lot more even a while after height stabilization. Not nearly as stable as the fixed pitch one on the right side.
Weeeell, not a lot in it IMHO. Yes, I can see a bit of wobble, but can't tell if that's because the blades are inherently less efficient, due to being flat rather than curved, or the fact it effectively reverses the thrust to stop quickly rather than reducing thrust - which could produce other more general instabilities, like a minor amount of TBE, or something else entirely. I'd certainly trade that off against the other advantages. And who knows: maybe they'll invent variable flex blades that can also curve either way in flight.
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Old Sep 02, 2012, 10:08 AM
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I'd certainly trade that off against the other advantages
You have a good point, there. I just think this will be refined some more before it hits the market becayse FPV guys won't put up with wobbles. Them guys are after ultimate stability.

Best,
Chris
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Old Sep 02, 2012, 10:13 AM
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@ the MIT video. WOW! Just WOW! Amazing. Not just the variable pitch, but it's following a preprogrammed trajectory. This is what I should have studied in college. Some kind of engineering, I would have been so much better at that. I wasted my skill set. Many of you guys are young here. Take some advice. At your age you have no idea what your skill set is and what you are strong or weak at. I had no clue. I didn't even know to analyze this. What regrets. VALUE your college education! ANALYZE your strengths and personality type! Please don't end up like me...
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Old Sep 02, 2012, 01:05 PM
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after watching those vids it seems like variable pitch quads will no doubt contribute to the future of multirotors.

I could also see future multirotors going down two separate paths: the super stable fpv multirotor and the full 3d acrobatic multirotor
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Old Sep 02, 2012, 01:20 PM
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Originally Posted by beerassassin View Post
after watching those vids it seems like variable pitch quads will no doubt contribute to the future of multirotors.

I could also see future multirotors going down two separate paths: the super stable fpv multirotor and the full 3d acrobatic multirotor
The future for multi-rotors looks bright indeed...simply amazing technology!
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Old Sep 02, 2012, 01:51 PM
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Originally Posted by bobepine View Post
Here's a video demonstrating manual flips with my x250.

Best,
Chris

http://youtu.be/c4wGwjFTalM
Hey Chris, I don't understand your tic-toc demonstration. Isn't a tic-toc supposed to look like the pendulum on a clock (thus the name "tic-toc")? I was looking forward to your tic-toc demonstration because I couldn't see how it could be done on a quad, which doesn't have a collective pitch. Your tic-tocs looked like slow manual flips to me. Did I see correctly or am I misunderstanding something here?
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Old Sep 02, 2012, 02:12 PM
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Originally Posted by beerassassin View Post
after watching those vids it seems like variable pitch quads will no doubt contribute to the future of multirotors.

I could also see future multirotors going down two separate paths: the super stable fpv multirotor and the full 3d acrobatic multirotor
I see no reason for them to diverge. Just add more props and a larger frame - as is already done - to get more stability. My brother has a monster that has 8x motors with 14" props on it and is 1.2m in diameter from prop centre to prop centre for Aerial photography. Personally, I think he's gone a bit far, as I get great results with an X450 and a quick pass of deshaker on the results. With FPV for actual flying rather than hovering for Photography, don't think it matters all that much TBH.
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Old Sep 02, 2012, 03:11 PM
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Originally Posted by erdnuckel2 View Post
where do you draw the line between "auto flip" and "manual flip" chris? The mjx x100 will either do flips on pushing the button, or if you just push the stick all the way out if you are in PRO mode ... no matter what - so is this an auto flip or is it a manual flip? and if not, what defines a manual flip (also, the manual says that after doing a flip you will need to wait 2sec before initiating a new one ...)
Both of these are autoflips. With a manual flip, the quad, etc. keeps rotating as long as you keep the "cyclic" stick pushed in some direction and does not stop rotating until you put the cyclic stick back to neutral (or it hits the ground). There is no "recovery" period.
The hard part of this is that you need to time when to do the recovery and manually move the sticks accordingly.
The nice part is that you can then do multiple rotation flips, or try to do a 1/2 flip/roll in one direction and then a 1/2 flip/roll in another direction to get back right-side up, etc.
Also adding to the hardness of a manual flip: it is often best done with also manipulating the throttle at the same time as "cyclic".
For manual flips, it helps to have a lot of travel on "cyclic" (with the mQx, people often use over 100%).

An example of somebody who is good at manual flips (what I wish I could do):
http://www.rcgroups.com/forums/showthread.php?t=1428309
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