SMALL - espritmodel.com SMALL - Telemetry SMALL - Radio
Reply
Thread Tools
Old Mar 11, 2012, 07:54 AM
Registered User
Zurich
Joined Apr 2006
3,611 Posts
Quote:
Originally Posted by caall99 View Post
.... Granted soft aluminum is cheaper than plastic injection molding, but often you will notice that almost all the aluminum can be removed from these helis and the frame will still remain intact. With small tweaks a toy heli can become hobby grade, and it wouldn't even cost the factory much more money.
In point of fact, the price of the many metal parts is much greater than one-shot plastic molding .... and, far more significantly, every time a human touches something, the price goes up much more than the cost of those parts.

In this case, the manufacturing cost of screwing more than 60 [SIXTY!] tiny screws and bolts greatly exceeds the cost of using a few very cheap molded plastic parts. My long experience in and with factories, not just in China, reinforces what I've learned as a Physicist and Engineer with an MBA in Production Management.

You are exactly right: G.T. Model put a LOT into the looks of the 5888, which is a classic example of modern Chinese commercial design and which reflects the almost exclusive use of stainless steel in public places, etc.

And even though Blade makes higher quality products which don't normally require messing with, I personally find the look of their products, with the exception of the beginners' CX Hughes model, to be so unappealing and distasteful that I would never buy any of them at ANY price.

"To each his own ...."


Lee
xlcrlee is offline Find More Posts by xlcrlee
Reply With Quote
Sign up now
to remove ads between posts
Old Mar 13, 2012, 09:49 AM
Registered User
Zurich
Joined Apr 2006
3,611 Posts
optimal

I still love the repeatability of true science, within the real constraint of the uncertainty inherent in our exisitence in the stochastic real world [what can be considered the "Tao" [ http://en.wikipedia.org/wiki/The_Tao_of_Physics ].

One of these recent three 'destroyed' 5888s I got from Marcel, given a bad start when the factory shipped it to him with much-shortened rotor-shafts [allowing a ridiculous vibration and horrible inefficiency], became increasingly better as I continued to replace and then adjust almost all of the mechanical parts. Finally, after 2 weeks of trying 3 new motors and maybe 3 diff. blade sets (12 blades) and 3 LIPOs, among many other things, it is now the most PERFECT 5888 I have ever encountered. It is insanely:

> FAST [max, hover-neutral trim: 21+ KPH/ +mph]

> AGILE

> STABILE

> EASY

> EFFICIENT

> Smooth & Quiet



During this improvement process I of course tried many different rotor/blade settings [pitch & coning angles as determined only by the spacing and "dihedral" of each alu plate, but not "pitch-twisting" them].


And of course the visual edge-on "thickness" of the spinning upper rotor disc ~10% less than the lower! This corrects for the upper-rotor accelerated airflow and allows both rotors to spin at the same RPM for max efficiency.



The last problem to solve involved eliminating fore-aft rocking of the heli in very fast circles. This is caused by the lower control rotor and the upper stabilizer rotor not harmonizing but rather 'fighting' with each other, corrected by giving the upper rotor a maybe 1 or 2 greater coning angle than the lower, better spacing them.

The final "tip-play" settings which made everything work perfectly >


4 mm upper
3 mm lower



.... as I found many times before


Lee
xlcrlee is offline Find More Posts by xlcrlee
Reply With Quote
Old Mar 13, 2012, 10:24 AM
Registered User
Zurich
Joined Apr 2006
3,611 Posts
continued ....

I kept "out" the noisiest of those 3 renovated "dead" ones for daily play/fun. Using my standard practice, after "dialing-in" the rotor/servo system, of locking the main larger blade bolts w/CA gel on the underside. As the system settled in I had to continually re-adjust the thin inner bolts to optimize performance & handling.

Even though it started out differently, the final "tip-play" settings (also on the 3rd one) was exactly as the one in the above post [4mm, U; 3mm, L] and the coning anlges on all three such that the top surface angle is just barely positive (the MAC [mean aerodynamic chord] angle is greater), with the upper rotor 1 or 2 more positive than the lower. Many/most 5888s have more than enough servo throw [determined by the PCB!],so once 'liberated' per my posted "Tips" with LOTS more effective power, they need more stability and less control authority than a factory-shipped untuned & unadjusted one! Flattening the coning angles achieves this. Only in the occasional case with PCB-limited servo throw do the coning angles need to be "naturally" positive [these lightweight blades lift more than their centripetal force can keep them horizontal!].

Reminder: incr. coning angles = less stability & more control authority.
That's because the top-to-bottom airflow in a heli is reverse that of a fixed-wing aircraft [which is bottom-to-top, like for a kite].

And surprise: that noisiest one is now silky-smooth & ultra-quiet, as it gets sweetly & carefully "broken-in", not "broken-down" as I received them second-hand, which I am sure could have beed prevented if the users first chose to properly adjust them.


Happily, for me, they didn't ....,
happyLee
xlcrlee is offline Find More Posts by xlcrlee
Reply With Quote
Old Mar 14, 2012, 07:11 AM
Registered User
Zurich
Joined Apr 2006
3,611 Posts
extending motor life

A motor in a properly set-up & maintained 5888 can last up to 70 flts. (such a heli can have up to 4 motor changes, over 250 flts.).

1. Properly set-up & maintain your 5888!

2. Select, adjust and always lube pinions, etc. Hand-turned rotor, in reverse direction with heli inverted, should have barely more resistance than w/pinion disengaged!! If not, work on it! [Once I have a good pinion/main-gear match, I put that pinion in the same position in a replacement motor]

3. Stop to cool warm-feeling alu-cladding surrounding motor. Note: cladding does not touch motor, so motor temp is actually MUCH hotter > use lower lip, not fingers, to check cladding temperature.

4. LEFT alu motor cladding should feel slightly cooler than right side!

That doesn't necessarily mean that the left motor is cooler, since the left side aft of the rotor-shaft has more cooling counterclockwise lower rotorwash hitting the alu outer-spaced cladding. Anyway, consistently, whenever I allow the left motor cladding to be as hot or hotter than the right, the left motor soon dies! It is a double-check for correct "tip-play" set-up for the rotors > a cooler motor [cladding!] can get more pitch/tip-play and a hotter motor needs the tip-play reduced. This always works.



Lee
xlcrlee is offline Find More Posts by xlcrlee
Reply With Quote
Old Mar 14, 2012, 07:50 AM
Registered User
Zurich
Joined Apr 2006
3,611 Posts
use these photos as a guide

note the tightness of the alu blade-holders [hinges] > but go with 4mm upper tip-play, 3mm lower!

http://www.gt-model.cn/eng/Product_Show.asp?id=173


L
xlcrlee is offline Find More Posts by xlcrlee
Reply With Quote
Old Mar 15, 2012, 07:39 AM
Registered User
Zurich
Joined Apr 2006
3,611 Posts
blade adjustments

Not only can the black plastic piece sandwiched btwn the alu plates be filed for adjustment on one side, for ex., but also the blades' flat hub-attachment surface can also be filed OR thickened with a very thin layer of CA gel and then smooth filed [remove bushing first!], and/or the bushing itself can be filed to shorten it [EVERY piece of this heli is different from the next one].

What is desired is a tiny "rocking" up/down of the flat hub-attachment segment [allowing the blade tip to move up/down almost exactly 4mm/ upper rotor, 3mm/ lower rotor], with the microscopically raised ["higher"-than blade surface] bushing acting as the fulcrum and the alu-plates restricting the inner and outer ends of the flat blade hub-attachment section.

Lee
xlcrlee is offline Find More Posts by xlcrlee
Reply With Quote
Old Mar 20, 2012, 07:52 AM
Registered User
Joined Dec 2010
47 Posts
Still spinning anti-clockwise

Got my replacement motors from China today and have just fitted the one that powers the top rotor.

As I suspected, this has NOT cured the problem of my heli sitting on the ground spinning around.

Its like I can't trim it enough to stop this happening.

What do I try next ?

I've also managed to break off the small aerial that is connected to the PCD. Can someone supply a photo showing where it need to be soldered to ?

Thanks

Steve
gbjbasdw is offline Find More Posts by gbjbasdw
Reply With Quote
Old Mar 20, 2012, 11:01 AM
Registered User
Zurich
Joined Apr 2006
3,611 Posts
Quote:
Originally Posted by gbjbasdw View Post
Got my replacement motors from China today and have just fitted the one that powers the top rotor.

As I suspected, this has NOT cured the problem of my heli sitting on the ground spinning around.

Its like I can't trim it enough to stop this happening.

What do I try next ?

I've also managed to break off the small aerial that is connected to the PCD. Can someone supply a photo showing where it need to be soldered to ?

Thanks

Steve
Are your rotor blades tracked & properly pitched? The pitch and coning angles are mainly determined by the spacing and tightness of the alu blade hinge-plates. When properly adjusted the upper blades should allow 4mm "play" at the tips and the lower blades, 3 mm "play at their tips [gently flex up & down with your fingers].

If this is NOT the case, your heli will not work correctly.



When at flying RPM, the upper rotor DISC should appear to be about 10% thinner than the lower rotor.

If this is NOT the case, your heli will not work correctly.



Make sure the rotors have close to NO resistance when hand-turned in reverse with the heli inverted.


NO amount of electronic trimming will fix these issues.



If you use a stobe, or a fluorescent light or even a TV screen, BOTH rotors should be turning at the same speed .... with the lower rotor disc appearing 10% thicker than the upper.


If there is anything preventing ANY of the above from happening .... your heli will not work correctly.


If you do ALL of the above adjustments and the heli still spins, make a video and detailed pictures and post them here [or vid link].

---------------------------------------------------------------------------------------------------------------------------------------

The antenna is soldered to the PCB on the heli's right side, just above the small vertically elongated metal-box at the extreme right edge of the PCB. Depending on when yours was made, the wire is inserted from the rear in the first ones, later on the front side of the PCB.

If you look at the instruction page, in the parts list photo 023 "RECEIVER PLATE", the soldering point is just above where the right side edge sharply angles inward to the left. except attached from the front of the PCB in the newer models.

In this photo it is the 3rd, larger solder circle on the left, just "below" where the blue & red servo wires loop beyond the PCB [the two smaller ones on the right of it are the solder connections for the servo] >

http://www.goldenhobby.com/-p-729.html


Good Luck,
Lee
xlcrlee is offline Find More Posts by xlcrlee
Reply With Quote
Old Mar 21, 2012, 06:15 AM
Registered User
Zurich
Joined Apr 2006
3,611 Posts
clarification to above

When both rotors are turning at the optimally efficient same speed [except start-up and yaw-maneuvering] and the upper rotor disc appears slightly thinner [ca 10%] than the lower .... it means that the lower rotor has more pitch relative to the viewer. But relative to the airflow, they have the SAME pitch, since the lower rotor is actually in downward-accelerated air from the upper rotor > BOTH rotors have the same AoA w.r.t. the airflow!

L
xlcrlee is offline Find More Posts by xlcrlee
Reply With Quote
Old Mar 21, 2012, 06:26 AM
Registered User
Zurich
Joined Apr 2006
3,611 Posts
gears & motor (over)heating

That last used-killed, now-quiet 5888 started having the left motor get hotter than the right (the very BEST way to ruin a left motor!). The inverted lower rotor showed some slight resistance when hand-turned in reverse [should be almost ZERO!], and I discovered its main gear had a partially chipped tooth.

It took 4 diff. replacement main gears (both first and later style, from dead/used helis) and 3 diff. pinions (old style & new ones), EACH in diff. positions (incl. inversion) .... until I got a NO-resistance combo!

Right motor now properly slightly hotter than left, heli super.


L
xlcrlee is offline Find More Posts by xlcrlee
Reply With Quote
Old Mar 21, 2012, 06:41 AM
Registered User
Zurich
Joined Apr 2006
3,611 Posts
cool tracking/ coning-angle trick!

I just figured this out, tried it, and it seems to work:


If only ONE blade gets consistently loose(-r), slightly increase its coning angle (and/or decrease that of the other blade), keeping the same "tip-play" spacing.


This is assuming the threads are not stripped, in which case tighten with CA gel!

NOTE: esp. assuming the main blade bolts are CA-locked, REMOVE the thin inner bolts when carefully bending the blade + plates "unit" to avoid stripping!


The plates slide spanwise over the plastic piece, and are actually self-adjusting within a very limited range .... once PERFECTLY tracked. Of course, if not, and out of this narrow range, they are self-unadjusting!

So if one blade keeps getting loose, its often because that side is too low w.r.t. the other.


Lee
xlcrlee is offline Find More Posts by xlcrlee
Reply With Quote
Old Mar 21, 2012, 07:05 AM
Registered User
Zurich
Joined Apr 2006
3,611 Posts
air space

After finally (I do hope!) convincing my active young bird that micro 4-ch helis are not good for his health (and sure he also found out for himself), he's now found a smart way to fly "with" them >


He flies diametrically (180) opposite to them, as they circle, keeping a whole room's-width away, while flying thus in "formation" with them!



Clever, cool & funny ....!


Or, if the heli is zooming diagonally across the room on a high path, he flies on a low path, passing well clear underneath it in the opposite direction .... like fullsize AIR TRAFFIC rules!


He whistles with joy and says, "Go, Go!" as he so does.


With a 3-yr old human's understanding of my intentions & words ("Stay away from the heli! .... it's a 'Bad Boy' "), he has found a logical non-conflicting way (he is a Libra Rabbit w/a Horse [Go, Go!] asc.) to combine that with HIS "let's fly together" intention.

OK, his species has had 85 million years to work out socially & environmentally adaptive effective behavioural strategies ....

[Homo Sapiens may well not be around long enough to do similarly]


Lee
xlcrlee is offline Find More Posts by xlcrlee
Reply With Quote
Old Mar 29, 2012, 10:57 AM
Registered User
Joined Dec 2010
47 Posts
Firstly the spinning problem....

I have just been working on this and allowed the battery to run down, recharged it and then tried the heli again. When I tried it again the lower rotor was not spinning at all but the motor was running. On closer inspection I saw that the drive cog on the motor was missing.

So....
My problem was almost certainly caused by the cog slipping on the motor drive shaft ! I think lubricating the motor shaft was probably the cause because a small smount of the libricant could have slowly drained downwards onto the cog when the heli was left for a couple of months without use.
gbjbasdw is offline Find More Posts by gbjbasdw
Reply With Quote
Old Mar 29, 2012, 11:06 AM
Registered User
Joined Dec 2010
47 Posts
I mentioned before that my aerial had broken off while I was fitting a new motor.

Lee told me that it is connected to the top connection on the 3 on the right hand side of the PCD when viewed from the rear of the heli.

My aerial was attached to the other side of the PCB ( i.e. the side at the front of the heli).

I have removed some of the white silicon from the top of the rectangular component and taken a photo of where I believe I need to resolder the aerial. I think I am seeing the remains of the aerial wire there but can't be sure.

Can someone confirm that this is the correct place as there are 2/3 other small soldered connections very close by.

I could solder a wire to the rear of the PCB but I am unsure if the length of the wire is important. Again can anyone comment ?
gbjbasdw is offline Find More Posts by gbjbasdw
Reply With Quote
Old Mar 29, 2012, 02:45 PM
Registered User
Joined Apr 2011
11 Posts
29 mm is 1/4 wave at 2440 MHz, and that seems to agree whit the original antenna. However, I don't think that the round pad on the back of the pcb is the antenna contact, even though it is opposite the front antenna pad.
kydlt is offline Find More Posts by kydlt
Reply With Quote
Reply


Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
Discussion 4 CH Catalina Radio Remote Control Electric Twin Power RC Sea Plane butrflyblade Batteries and Chargers 4 Dec 27, 2009 02:49 PM
Discussion Opinions on Banana Hobby 4 CH Easy Fly 3D Aerobatic Radio Remote Control Electric RC 7rider Beginner Training Area (Aircraft-Electric) 14 Jun 01, 2009 09:46 AM
Discussion 2009 4 CH F-16 Fighter Jet 3D Remote Control Electric Ducted Fan RC RTF w/ 70mm EDF! rcheli146 Foamy EDFs 2 May 16, 2009 09:23 PM