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Old Sep 25, 2012, 01:09 AM
Grrr :-)
nerys's Avatar
Levittown PA 19057
Joined Aug 2006
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really? where do you see "FLIP" anywhere in their? enlighten me.

his assertion was that I stated you could "flip" the propeller itself upside down to "reverse" its thrust. which is not something that ever came off this keyboard.

as for the airfoil comment your taking it out of context. I stated very clear that for the purpose of this discussion they are for all intents and purposes "flat plate" airfoils with shapes LE/TE

ie they would "function" reversed sufficient enough for flight.

you can keep quoting out of context all you want does not change reality. I stand by what I said.

and what do you know. ignoring the yaw spin HEY his drone DID In fact life "upside down" what do you know. I was right.

funny that.
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Old Sep 25, 2012, 02:12 AM
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Geez, guys....

Unsubsribed.

Chris
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Old Sep 25, 2012, 06:34 AM
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Originally Posted by jlcamp7 View Post
I keep hearing that these post have valuable information and while I don't disagree with that I do believe for the most part most if not all of this back and forth has extremely little to do with these cheap toy rtf quadcopters. I also have extremely valuable information regarding the Pythagorean thereom but I'm not going to go posting it because it doesn't really accomplish anything for the main discussion of this thread. I read through and appreciate both sides and I agree no one should be banned, however I have a feeling this is not going to end any time soon and would love to see this become a separate thread rather than filling the pages of this thread. Guaranteed anyone that comes reading/searching through this thread is not looking for this type of information.
^this post contains no valuable information that anyone looking through the thread would find useful. Define: irony

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Old Sep 25, 2012, 08:04 AM
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Originally Posted by dave1993 View Post
anyway we all more or less recognise (if not agree) these props are designed for thrust in one direction and upside down flight is not feasible.
Ah, Option 3: both. No 'projection' required.

Anyway, some factual information for those that want it.

The inverted/reversed props are easily capable of flight, as shown in the video. The FC doesn't like the CoG (at least) and it veers off after a few seconds and a few feet high, and in the limited space I was testing and videoing it I wasn't able - or willing - to see if I could fly it better.

Having read nerys theory about Yaw: you may well be right - the props are going the wrong way for the FC to compensate for Yaw drift - but as your original suggestion was that if the props could be made to reverse direction in flight quick enough the quad could stop, quickly flip upside down and fly inverted (and presumably do other cool stuff like tighter rolls/flips etc. with one prop pair going forward, the other backwards to flip faster), that's proven as potentially possible (only completely new FC software, quick reversing motors and neutral props required ), so I'm not bothered with testing further. Not stopping anyone else from doing it though. Post a video of your results.

Apologies to others who've been through this a few times, but these (short) quotes were what I based my experiment on and I put in a tiny bit of effort doing it:
Quote:
Originally Posted by nerys View Post
I am also wondering when someone is going to make one of these things fly inverted. the tiny direct drive units (u816 or ladybird) should be able to stop reverse and spin up the blades in reverse fast enough (tiny direct drive low inertia) fast enough to remain airborne and have all the controls "flip" in the TX so it flies like normal but "upside down"
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Originally Posted by dave1993 View Post
this is no more possible than getting a plane to fly backwards. reversing motor direction does not reverse thrust. you need variable pitch prop like on a 3d heli. not likely to ever happen either because you can buy several of these toy quads for the cost of just a single variable blade.
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Originally Posted by nerys View Post
your kidding right dave? if you reverse a fixed pitch prop you reverse its thrust.
yes normal props are "less efficient" reversed since they have an airfoil on them but these do not. they will spin and thrust in reverse JUST FINE either way.
don't believe me? swap your props and hold it upside down and "throttle up"
So it was obvious from the beginning that nerys was talking about the rotation of the props being reversed, not flipping them upside down and dave1993's reply showed he understood that (and later became 'confused'). The 'do not' above probably should have been "do not have much" to ward off 'confusion'. Nerys then suggested how swapping a CW with a CCW would demonstrate the 'reversing' effect. Some other knowledgeable person disagreed.

From my experiment and video we know it's possible, the quad flies - not well, but that's an FC issue, not props - so how much less efficient are the props when reversed?
I'll have a go at some rough maths:

Quad = 35g, Normal lift =24g (after zeroing quad weight on scales) , total lift capability = 59g
Quad = 35g, Reversed lift =12g (after zeroing quad weight on scales) , total lift capability= 47g

47/54*100 = 87% prop efficiency (U816 props) when reversed, or 13% less than with forward rotation. (Lots of other factors here, but close enough for illustration)

That's not too bad, and if the prop were neutrally pitched - like on the tail rotor blade of this heli I have here - maybe you could even that out to be 6.5% less efficient forwards and 6.5% more efficient backwards, leaving plenty of lift overhead for flight in either orientation. Then make the props 6.5% bigger to compensate and we're back to normal.

The LB and MJX X100 props were less flat and pitched for more lift in forward rotation. The LB ones required about 4% less throttle (according to the LCD, although that 4% is just a vague throttle value, not anything measurable in terms of lift/power) to hover the U816 quad when I fitted them on that, so they're more efficient going forwards. This would mean they would be less efficient in reverse. And the same with the MJX X100 blades - although as they are larger as well, there may be some compensation there and the remaining lift might be more than the 12g (+quad weight) that the U816 props give in reverse, but I've done enough experimenting for now.

OK, who's for trying out my other theory of putting two quads together - one semi-inverted and one normal to keep it steady - for an Octocopter that will be hard to launch and land? (Actually with a Starbuck's domed drinks cup lid as an upside down support under the battery, the lower quad could rest on that rather than the inverted props.... maybe I've not done experimenting after all.)
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Old Sep 25, 2012, 09:08 AM
The flightless bird
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Hey guys,
The RCGroups community is a welcoming and friendly group of people from all walks of life. Most of us have professions that have nothing to do with R/C... so there might be a knowledge gap depending on the person's occupation or time spent in this hobby. It is therefore important to be supportive on this forum and help others instead of attacking those who have a different opinion (regardless if they're right or wrong).

All of you who are involved in this argument are very important members on this thread and I've seen many of you go out of your way to explain and help others understand certain issues... so, as skitchen8 said....I also feel that if any of you were banned because of this argument, it would be a great loss to the RCGroups community.

If you feel that this discussion about inverted props and so on must continue in a heated manner as it is now, please make good use of the PM system or start another thread about the issue. Originally, my intentions were for people who own (or are interested in owning) these micro RTF quads to have a place where they can easily find information, share experiences and discuss issues they run into... I really don't want to see it degrade into a place where flame wars are held.

If this keeps going, I'm unsubscribing from my own thread!!!
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Old Sep 25, 2012, 09:18 AM
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Originally Posted by jameschen072 View Post
I really don't want to see it degrade into a place where flame wars are held.
If this keeps going, I'm unsubscribing from my own thread!!!
Great idea and as it is your thread, maybe you could chime in a bit more often when things get out of hand.
Some people's crocodile tears about who might get banned when they've been amongst the worst offenders is ironic to say the least.
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Old Sep 25, 2012, 09:24 AM
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Oh well...

There seems to be something in common in this thread and mine: http://www.rcgroups.com/forums/showthread.php?t=1680188 (Post #1878) onwards.) Sigh...
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Old Sep 25, 2012, 09:27 AM
The flightless bird
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Quote:
Originally Posted by Brandigan View Post
Great idea and as it is your thread, maybe you could chime in a bit more often when things get out of hand.
Some people's crocodile tears about who might get banned when they've been amongst the worst offenders is ironic to say the least.
I wish I could Brandigan, but I've been so busy lately that I've barely had time to check the forum. This is written at the end of a 36 hour shift...I am exhausted.
Anyways, back to the topic of micro RTF quads,
I have a one week holiday coming up... and I'm planning a trip to the largest aviation museum in China (Been there a couple of times and I have yet to see all of the aircraft on display...or mothballed, rather)...hope to get some footage and pics of my micros flying among Migs , C46s, the DeHavilland Otter, the DC8 and a few Russian clones of the B29... I can't wait!!!
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Old Sep 25, 2012, 09:28 AM
Fly Fast, Fly Hard, Fly Fun
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Canada, BC
Joined Apr 2012
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Quote:
Originally Posted by jameschen072 View Post
Hey guys,
The RCGroups community is a welcoming and friendly group of people from all walks of life. Most of us have professions that have nothing to do with R/C... so there might be a knowledge gap depending on the person's occupation or time spent in this hobby. It is therefore important to be supportive on this forum and help others instead of attacking those who have a different opinion (regardless if they're right or wrong).

All of you who are involved in this argument are very important members on this thread and I've seen many of you go out of your way to explain and help others understand certain issues... so, as skitchen8 said....I also feel that if any of you were banned because of this argument, it would be a great loss to the RCGroups community.

If you feel that this discussion about inverted props and so on must continue in a heated manner as it is now, please make good use of the PM system or start another thread about the issue. Originally, my intentions were for people who own (or are interested in owning) these micro RTF quads to have a place where they can easily find information, share experiences and discuss issues they run into... I really don't want to see it degrade into a place where flame wars are held.

If this keeps going, I'm unsubscribing from my own thread!!!
Well said. +1
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Old Sep 25, 2012, 09:29 AM
KDS450QS(ZYX4),V977,CX-20
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I've been to the Smithsonian in D.C. but when I was in Beijing, I didn't have the chance to visit the aviation museum because I didn't know it existed. Is it in Beijing?
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Old Sep 25, 2012, 10:04 AM
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Originally Posted by FyreSG View Post
There seems to be something in common in this thread and mine: http://www.rcgroups.com/forums/showthread.php?t=1680188 (Post #1878) onwards.) Sigh...
Phew, I thought that was a link to some of my posts, but it was Keyser Söze again. He was wrong there too.

Anyway, I'm done with the subject and will keep on topic in future. Although I probably will try joining two v929s together at the feet into an Octocopter and report on it unless that's considered too outré. . They too big? Maybe two U816s, then.

BTW, James and FyreSG, you do know that as starters/owners of your threads you can delete posts (assuming you have the time)?
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Old Sep 25, 2012, 10:24 AM
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Quote:
Originally Posted by jameschen072 View Post
hope to get some footage and pics of my micros flying among Migs , C46s, the DeHavilland Otter, the DC8 and a few Russian clones of the B29... I can't wait!!!
That will be awesome! Looking forward to the footage.
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Old Sep 25, 2012, 10:55 AM
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Quote:
Originally Posted by Brandigan View Post
Phew, I thought that was a link to some of my posts, but it was Keyser Söze again.

BTW, James and FyreSG, you do know that as starters/owners of your threads you can delete posts (assuming you have the time)?
like many of these theories i dont think this is true. you are confusing thread posts with blog entries.

imo nerys idea was one of the most innovative and interesting to come along in a while. i personally get a little bored reading about how long its taking banggood to get packages out and even repeated descriptions of how great these hover or how easy it is to get stuck on a neighbors roof start to wear thin. it was exciting when these things were new but less so for me lately. very little fresh info coming down the pike these days.

but being a "propellor head" the idea of reversing props and flying upside down fascinates me. so i think it would be a great idea to start a thread just for this subject. guys like nerys, brandigan, skitchen, et al, are obviously smarter than your average bear and if one of these guys dont start a new thread on it sometime soon then maybe i will.

meanwhile wake me up if anything really interesting happens around here. another cat fight for example.
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Old Sep 25, 2012, 11:15 AM
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Originally Posted by dave1993 View Post
i personally get a little bored reading about how long its taking banggood to get packages out and even repeated descriptions of how great these hover or how easy it is to get stuck on a neighbors roof start to wear thin.
This I can agree with, every time we start a topic and attempt to learn something new we get yelled at for taking it off the topic of repeating the same things over and over again. Never have I seen people so dead set on making sure that people don't learn or try new things.
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Old Sep 25, 2012, 11:42 AM
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So who wants a V1 LadyBird with a Hobby Grade Devo 2402D Tx for less than $70 shipped?

NitroPlanes is selling the v1 with the 2402D right now for $58.08!

I couldn't believe it but quickly placed my order as this is almost too good to be true. On top of that it you type in the code... pricepickle it gives you another 6% off. With shipping my total came to $68.72. The Tx alone sells for more than that!

So Merry Christmas as I didn't want to hog this opportunity. And also I have to give credit to dankar04 (hope you don't mind me sharing) who posted the pricing over in the favorite mini thread which made me go check it out.

Here you go:


NitroPlanes link
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