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Old Apr 28, 2011, 07:40 AM
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Zurich
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why the 5888 is SO cool and why it is capable of relatively fast flt >

1. this heli is relatively heavy (high disc loading) and has a lot of power for its size (rotorspan!).

2. thus the force that can be applied to fwd flt if it tilts fwd enough is much greater than lower powered lighter helis of the same rotorspan.

3. its relatively high inertial mass tends to make it more stable in slightly turbulent air.

4. the greater the coning angle the less stable: while it is not possible to greatly increase the coning angle of larger helis or ones with lower disc AND power loadings, the beauty of the 5888 is that one can in fact precisely increase the coning angles to get exactly the responsiveness vs stability that one wishes! [MY 5888s are adjusted to allow ca. 20 fwd AND ca. 20 sideways tilting ....!]


note the burst speeds -- measuring FRAME-by-FRAME -- in the below video starting at 3:00 min, and also note that the coning angles can be even further increased if desired
[pls click on the YELLOW address in the blue at the TOP of the box below to go to YouTube directly] >

4ch GT Mini-Flier 5888 (3 min 50 sec)
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Old Apr 28, 2011, 11:07 AM
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Originally Posted by xlcrlee View Post

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Originally Posted by xlcrlee View Post
You 2 "disbelievers" above obviously don't understand how to properly de-stabilize a small well powered 19 cm rotorspan coaxial heli and still leave it controllable, which involves adjusting the two coning angles, in addition to very good tuning. I do accept that you both have had no experience with such .... (if you read ALL my posts in this thread, you might learn some things of which you were not previously aware
in the below video starting at 3:00 min, and also note that the coning angles can be even further increased if desired [/I][/I][[B][COLOR="Blue"]

i saw the vid and it doesn't do anything more than most other 4ch coax, as a matter of fact my falcons can pitch even better and faster especially on rolls, reason i mention it cause its a comparative bird to the 5888 around the same size/weight and motor power.

regardless your vid does not prove anything per your claim a few posts back that it easily flies in 7mph winds and that claim is simply not true no matter how much tuning/coning you do on it... that is if we define flying as being able to move in all directions not just being able to hold hover while the wind blows... try to fly it outside against the slightest of wind like i have all winter and you'll see what i am talking about.
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Old Apr 29, 2011, 05:31 AM
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tested facts and personal opinions

First you apparently did not notice that it is not "my" video.

Next, since I am not only a physicist but also an engineer, I try very hard to be objective in technical and other matters, so I have now reconfirmed MY 5888's flying speed [OK, one of my FAST ones ....] >

In repeated flts diagonally across my livingroom, it traversed it in ca. 0.8 sec. Since that incl. starting and stopping (hover to hover), my professional estimate for the steady-state flt. (this is one of my business-occupations > some of my flying toy-designs have generated a half-billion USD [total, far from my share, sure]) is 3.5m in ca. 0.7 sec = 18 KPH or almost 11 mph.

I must add that this particular heli is set up to be barely stable and must be very delicately handled, almost as if it were an F1 racecar. > it actually whistles like a modern turbine-powered dental drill (although in a good way). At any rate, as so set up it is almost scary for me to fly if I am not careful.

I write the above NOT to attempt to convince you nor change your determined mind. Since you do not like this heli, it seems appropriate for you not to get even slightly involved with it. However, there are clearly others, like me, who DO enjoy it.

But this is a public forum in which all are invited to express their personal opinions, likes and dislikes. Thank you for sharing yours and for sharing your experience with the other helis you personally prefer.

Pax,
Lee
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Old Apr 29, 2011, 11:25 AM
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lee, it was not an attack on the 5888 at all, as a matter of fact i recommend it to others amongst other lower cost 4ch options in other threads but all i was giving you is my experience in flying outside in winds which i have done a lot thats all... flying sub micros in general in 7mph winds will not work especially going against the wind no chance (yet you stated that it can easily fly in such)... it does not work in 3-4mph winds either as it cannot pitch enough nor does it have enough power to easily fly against such winds.

as far as what you stated that it can reach 11mph, absolutely but in still air, however as soon as there is resistance from the breeze that speed falls off dramatically...

a couple of weekends ago i was flying one of my falcons 8913 that i tuned up for extreme pitch in the wind of 3-4mph and it had an extremely tough time against the wind as it just goes up and away, it was rocking and bouncing perpendicular to such wind and going with the wind i have caught a speed of 20+mph thanks to the tailwind... similar results to that you will find on the 5888 in such little wind as its relatively the same size, weight and with comparative motor power.
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Old Apr 30, 2011, 01:52 AM
Different fly 4 different guy
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Canada, BC, Salmon Arm
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Scorp - Does the 2.4 Ghz controller give more range than say a 27 mHz? I see some still advertised at 10m.
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Old Apr 30, 2011, 03:23 AM
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Zurich
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ToptoyExpress Delivered ....!

After some months delay (Swiss Post bureaucracy!), I finally recvd. a Jai Qi 8008 4-ch heli, a G.T. 5888-B and a mini-UFO.

The 8008 wasn't too hard to track & tune and flew surprisingly well …. for a toy. It's IR and has a "non-"hobby" “swashplate” function [i.e., it does not use normal hobby-like rotary OR linear servos]. While it IS a really nice toy (for a child or beginner), unfortunately the control delays & general (typical toy) imprecision (though it is generally quite stable!) made it too dangerous to fly around my precious birds, and anyway it isn't even close to the 5888 in performance or control. So I gave it to a friend for his birthday for him to enjoy!

This particular 5888 that I recvd. (gratis, so NO complaints!) was made at a time many months ago (I can tell by certain “rolling change” prdn. details) when G.T.'s QC left a lot to be desired (they corrected it after I pointed out the specifics [I also have an MBA in Prdn. Mgmnt.]). Anyway, I had to replace a defective motor.

It flew fine otherwise (MUCH better than the 8008, sure!), and after about 7 hours of “fun” work, which included changing parts, installing matching blades (stiffness, curvature and most importanly, equal weight!), I got it to fly really very well …. fast enough that I put away the extraI-hot 5888-B that I'd timed above (I'll save it for outdoor flying!) and replaced it with THIS one for daily indoor use.

To repeat, the toy 8008 flew nicely (although slowly, just poking along like most coax's …. except, of course, a well-tuned & tracked 5888), but the hobby-quality 5888 (which required some good hobby work on my part) flies & controls like a Ferrari vs the 8008 “Trabi” (not that “Trabis” are “bad”!).

The mini-UFO (a knock-off of a recent variation of one of my own ORIGINAL toy concepts [which did exceedingly well in the world marketplace] flies by itself, auto-hovering above the ground using an IR sensor, or above one's hand! It is exceedingly stupid … AND so really funny! I am definitely keeping it for silly humourous occasions. The birds at least enjoy me laughing at it!

Lee
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Old Apr 30, 2011, 03:27 AM
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addendum to above

The 8008 & mini-UFO were sent, unrequested, by http://www.toptoyexpress.com/ for me to evaluate but they have a coincidentally strange connection >

1.The 8008 uses heavily anhedralled rotors (NEGATIVE coning angles in flt.!) for stability (like the upper body of the UFO),

2.The 8008, the 5888, and in fact likely ALL the literally tons of tiny RTF R/C helis on the mkt. today largely owe their existence (on such a mass scale) to the immense popularity of the early PicooZ. And Alexander (who created the PicooZ) told me the PicooZs' self-stabilizing was inspired by, and used design elements from, the Vectron Ultralite UFO, which in turn was directly based on

3. MY original UFO design concept, which I made in the same factory, and which used design elements I borrowed from two toys I licensed to Galoob [Hasbro] & Kusan DECADES ago ….

4. which in turn used principles I found and which were clarified to me by none other than ....
Stan Hiller [ http://en.wikipedia.org/wiki/Stanley_Hiller ] in his California office way back when. I was there to discuss a totally new type of rotorcraft I invented (later in Newsweek magazine, etc.). Stan, who was divesting his controlling interest in his own Hiller Corp., Fairchild, Republic and Fokker Aviation to go into Ca. real estate (he did well!), told me to forget Aerospace, that he had a good connection to Mattel, and my “toy career” was thereby born ….



Lee
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Old Apr 30, 2011, 03:44 AM
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Originally Posted by gordonzo View Post
Scorp - Does the 2.4 Ghz controller give more range than say a 27 mHz? I see some still advertised at 10m.
I've flown several of my made-fast 5888s up high enough that I was barely able to see the orientation.. And despite Scorp's contrary experience with similar helis, my [modded? adjusted?] 5888 flying was often in active, breezy air .... in fact in bouncy thermals (I'm really a sailplane pilot, so I just couldn't help myself). But I will give Scorp right in insofar as while I could do 360 flying, I nonetheless had to carefully penetrate the occasional stronger gusts associated with the thermals .... as one would any "floater" glider.

Lee
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Old Apr 30, 2011, 10:36 AM
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Originally Posted by gordonzo View Post
Scorp - Does the 2.4 Ghz controller give more range than say a 27 mHz? I see some still advertised at 10m.
a few hundred feet when you are on 2.4ghz, on 27mhz probably around 60-90ft depending how many volts in the tx, i had one of mine thats 49mhz out about 150ft and didn't lose signal at that distance.
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Old May 01, 2011, 10:40 AM
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scorp, I was thinking about how to reconcile our differing observations re: the outdoor low-wind flyability of [different] tiny 4-ch coax's, and maybe found something >

The Wright Bros. used anhedralled wings on their successful Wright Flyer and preceding gliders. They had been slope-soaring on the dunes at Kitty Hawk, and maybe observed the gulls there, which also primarily slope-soar.

When one is sloping, the wind will blow a (positively) dihedralled aircraft INTO the slope.. Anhedralled wings, which gulls also coincidentally have, will turn into the WIND instead of being blown away by it and carried with it, and also keep plane/bird safely away from being smashed into the slope.

The airflow for helis is exactly opposite that of fixed-wing aircraft or soaring/gliding birds: the heli's airflow is from top to bottom, while a fixed-wing's flow, like that of a kite, is from bottom to top (OK, there's front to back and spanwise flows at the same time, in fwd flt. ...).

So a heavily "dihedralled" ROTOR (lots of "normal" positive coning angle) acts like an unstable or neutrally stable anhedralled gull's wing .... and turns INTO wind gusts, tending to fight gusts by penetrating them. And this physical action is much quicker than our visual R/C pilot reaction time or ability.

So maybe that's why my effectively over-powered 5888s, made so by my intense work-over (the factory chooses motors and driving voltage in the software/PCB to match the necessary fast prdn. line product, which has more aerodynamic and other resistance than mine: I estimate a 25 - 40% boost in "normal" effective power!), with lots of UNSTABLE coning angle/s, can more easily handle very slighty turbulent 7 mph "wind" (with an experienced sailplane pilot on the sticks).

Dunno, just hazarding a guess ....


Lee
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Old May 01, 2011, 11:48 AM
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those are some good points lee and the way blades are shaped will make a difference to a degree but we are still limited by the coaxial design of these birds with flybars that further just stabilize any constant required frontal pitch reducing momentum on forward flight and in wind even more so... i found that such a frustrating limitation with coaxes in general and to a degree with fixed pitch birds that it has forced me to look straight into cp designs as the best wind option.

but i am still curious how and to what degree did you cone or shape the 5888 blades relative to stock?
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Old May 02, 2011, 09:23 AM
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WINDingup/down ....

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Originally Posted by scorp View Post
those are some good points lee and the way blades are shaped will make a difference to a degree but we are still limited by the coaxial design of these birds with flybars that further just stabilize any constant required frontal pitch reducing momentum on forward flight and in wind even more so... i found that such a frustrating limitation with coaxes in general and to a degree with fixed pitch birds that it has forced me to look straight into cp designs as the best wind option.

but i am still curious how and to what degree did you cone or shape the 5888 blades relative to stock?
1. Of course I wasn't recommending the 5888 for wind-flight, just that its envelope can be pushed enough -- with lots of skill, work & luck -- to be OK in mild breezes (way less than 10 mph, but more than 2 mph).

2. I promise that I can aerodynamically destabilize a 5888 enough to make it totally un-funny to fly .... self-speeding up or spinning in (if I continue to hold the offending stick position steady), so I leave in some stability, but not much, for active maneuverability. THAT's the reason I really like this cheap, tiny heli > it allows lots of "re-adjustment" .....

3. I was messing around with the thicker blades of the G.T. 9008, warping with a hairdrier, but the 5888 blades are thinner and too heat-sensitive for that, so I leave the 5888 blades alone. Rather, I have actualy managed to collect almost 50 of them at this point (some new, some from damaged helis returned to Marcel) .... so I sift through them to find stiffer or softer or heavier or more elliptically dihedralled or straighter ones, depending on what I want for a particular 5888 (the helis AND blades all ALL different!), and to get a matched set! Then I bend and adjust the alu blade hinge plates and sometimes file away or add CA gel at the end of the blade root to get the exact "blade looseness" (tip-play/movement) I want. I have found that generally 4mm "tip-play" for the upper and 3mm for the lower blades works best for the 5888 (the upper & lower blades AND hinges are diff). This allows the upper rotor to incr. pitch more than the lower rotor w/incr. RPM, an effect necessitated by the diff Rn for the two rotors. The result is max efficiency as well as maneuverability/stability optimized for my taste.

4. To repeat: coax's ain't windy-weather machines, but my "souped-up" 5888s do fine (enough) in "wind" that will just barely manage to keep very light slow-flying delta kites up.


Lee
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Old May 02, 2011, 11:02 AM
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Originally Posted by xlcrlee View Post
I have found that generally 4mm "tip-play" for the upper and 3mm for the lower blades works best for the 5888 (the upper & lower blades AND hinges are diff). This allows the upper rotor to incr. pitch more than the lower rotor w/incr. RPM, an effect necessitated by the diff Rn for the two rotors. The result is max efficiency as well as maneuverability/stability optimized for my taste.
when you say tip-play you mean the outer tip part of the blade (opposite side of where its mounted in the grip) has the freeplay up and down of 3-4mm?

aren't the bottom blades the ones doing the pitching directly effected by servo/swash?
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Old May 03, 2011, 08:24 AM
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when you say tip-play you mean the outer tip part of the blade (opposite side of where its mounted in the grip) has the freeplay up and down of 3-4mm?

aren't the bottom blades the ones doing the pitching directly effected by servo/swash?
Yes, I refer to the tip's up & down movement when gently flexed by hand a bit outboard of the hinge..

[small technical detail > a "grip" is something that can firmly hold something, whereas these "blade-holders" on this and most R/C helis are actually hinges, allowing selected restricted movement with one to three degrees of freedom]

Yes, the bottom blades are drectly affected by the swashplate .... but I have noted earlier in this thread that BOTH rotors are interactive and respond to each other, aerodynamically and mechanically (through complex rotational inertia, etc., coupling). If you follow the aerodynamic (AIRFLOW!) precession effect initially caused by of the 45-offset stabilizing flybar, you can figure out why the LOWER rotor needs the swashplate inputs to be rotated 45 as well. Anyway, what the lower rotor does will affect the upper rotor (remember, too, that air is a viscous fluid).

The 4mm top and 3mm lower tip-play for the 5888 seems to generally allow max efficiency, LIFT-wise, of the two rotors, esp. also as they speed up from hover to max power. Adjusting the coning angles, absolutely and also relative to each other, allows tuning control-input response vs stability > incr. coning angle on the lower rotor further de-stabilizes it and allows greater control authority, while also destabilizing the entire heli. Incr. the upper coning angle destabilizes the heli and allows more effective control authority. The coning angle w.r.t. each other increases or decreases upper/lower rotor interaction.


Lee
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Old May 07, 2011, 04:36 PM
when is the wind stopping??
markkona's Avatar
Malta, Marsaskala
Joined Apr 2011
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Well guys yesterday I received the 5888 I ordered from focal price and I was amazed at the difference in speed from the IR model I was flying previously. today the wind almost dropped to zero and I tried flying it outside and the roof and it's really fast and the radio control is also very sharp I am flying this like a pro compared to the IR model what I also noticed is that the plastic parts fitted to the motors that turn the gears are slightly different and look more robust than the IR model as well lets hope they last longer since I have managed to grind the teeth of my first 5888's plastic gears. If the weather permits tomorrow I ll try flying it outside again and maybe take a small video as well since the one I took tonight only shows a green orb flying around!!
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