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Old May 18, 2012, 06:50 AM
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Zurich
Joined Apr 2006
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broken LEDs and performance

If a wire comes off a fwd LED inside the cabin, it's easy to pry it out & re-solder. BUT, if an LED wire comes off at the PCB, it is extremely easy to overheat and kill the IC chip controlling the fwd/rev servo .... ruining the heli!

As I had previously managed to make this mistake before, when an LED wire came off at the PCB of yet another [VERY good] 5888, I instead removed ALL 3 LEDs, plus ALL their wires AND the translucent white cabin cheek cowls. That was a year ago and this heli is maybe the most fun to fly, with great performance and stability. It is a few grams lighter, has a bit less rotorwash resistance with the removed cheeks and a bit more available power for flight. Most of my other "HOT" tuned 5888s have even more power (for whatever reason), but also more weight: think of a lighter-than-air balloon, in which adding or substracting small amounts of weight induce climb or descent. They require somewhat more piloting skill & attention to deal with the power AND extra momentum when doing my typically much too FAST "wild & crazy" maneuvers.

However this unlit 5888 also happens to be SUPER-tuned and has an especially resistance-free drive-train! Since those factors more than override the LED, etc., removal, I don't recommend doing so just to get this boost. But if you dislike the LEDs or have a broken LED wire at the PCB .... try removing ALL the LEDs, their wires and the white cowl cheeks.


Lee


NOTE: this is why upon first opening/removing a 5888 cabin, I have since used gobs of CA gel to strengthen all of the wire solder joints! [a micro-gram of prevention]
.
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Old May 18, 2012, 09:42 AM
Sir Crashalot
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I removed the led wires at the front long ago because I didn't want the cabin attached to the board, it's hard enough to try to work on it as it is. I also removed the tailboom brace bars that do not seem to have any function other than to add weight.
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Old May 22, 2012, 07:22 AM
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Zurich
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Quote:
Originally Posted by stonecutter View Post
I removed the led wires at the front long ago because I didn't want the cabin attached to the board, it's hard enough to try to work on it as it is. I also removed the tailboom brace bars that do not seem to have any function other than to add weight.
It is the weight of all 3 LEDs and their wires that affect performance: LED current drain is actually generally negligable in these applications.

B.t.w., several of mine had fore/aft loose brace bars, one end of which I removed and tightened w/ CA gel, so now they DO function ....


L


both my bird & I still prefer operating WITH lights [he gets much more excited]
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Old May 23, 2012, 06:34 AM
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Zurich
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Exact Tuning: details explained

I just realized I may not have been previously explicit enough re: explaining my proven peak-performance set-up:

1. 4mm upper/ 3mm lower rotor "tip-play" [up/down movement by hand]

2. Flt.-RPM spinning upper rotor w/ slightly more positive coning angle relative to lower > actual amount of each varies w/user's taste for stability (lower angle) vs maneuverability (greater angle) and servo throw (varies w/each unit)

3. Upper rotor blades somewhat torsionally stiffer than lower


To get this, normally the upper rotor (bendable soft) alu (hub) plates must have a markedly negative coning angle [maybe neg. 2 - 3], and the lower rotor plates only a tiny neg. coning angle (since the upper blades are looser, they must be pushed down more!).

At low RPM the looser upper blades (fwd-swept!) self-twist in more pitch .... but as RPM increaes, the softer lower blades flex into more pitch, so that there is less pitch differential btwn. the rotors. [NOTE: the lower rotor must always have more pitch than the upper (it's in a downward accelerated airflow), but at higher RPM the lower rotor jumps into MUCH better Rn's, so it doesn't need so much of a pitch increase/differential].


The above is actually complex, and it took me a long time to understand the mechanics, but it is really what is going on with my "super"-tuned helis that fly like SRs half their weight (and with much greater stability and solidity than those lighter ones exactly because of the weight).


Lee
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Old May 23, 2012, 06:39 AM
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Zurich
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simple perfect-tuning check >

Assuming that the blades are balanced and the lower rotor has about 10% more pitch than the upper, if the spinning flybar shows a tiny vibration at its tips .... the rotors are NOT tuned!

The tips and entire length of a flt.-RPM spinning flybar will appear (viewed perpendicularly to its disc) rock-steady in a perfectly tuned rotor system ....

L
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Old May 23, 2012, 04:34 PM
Sir Crashalot
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Lee, when you say the blades form a negative coning angle you mean the tip of the blades point down towards the ground rather than straight outward? So that when spun up , the shape resembles more like an umbrella than a disc? What tools do you use to bend the alu plates.
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Old May 25, 2012, 07:39 AM
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Quote:
Originally Posted by stonecutter View Post
Lee, when you say the blades form a negative coning angle you mean the tip of the blades point down towards the ground rather than straight outward? So that when spun up , the shape resembles more like an umbrella than a disc? What tools do you use to bend the alu plates.
What I wrote was this >

To get this, normally the upper rotor (bendable soft) alu (hub) plates must have a markedly negative coning angle [maybe neg. 2 - 3], and the lower rotor plates only a tiny neg. coning angle (since the upper blades are looser, they must be pushed down more!).



In spinning, flt.-RPM operation, from 2. above >
upper rotor w/ slightly more positive coning angle relative to lower > actual amount of each varies w/user's taste for stability (lower angle) vs maneuverability (greater angle) and servo throw (varies w/each unit)


I.e.: BOTH rotors have positive coning angles, varying more/less with user taste .... but upper rotor has slightly more positive coning angle than lower.

Clear ?


AFTER first removing the thin inner bolts I use the blades themselves to bend the alu plates, OR instead I remove the thick outer bolts and use my fingers. In either case I carefully observe the bend before, during and after! [bolts MUST be removed to prevent stripping!!]



Lee
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Old May 25, 2012, 07:54 AM
Vroooom putta putta putta
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Did I miss a close-up photo that shows what the swash actuators look like?

Are they the "little motor and fan gear" or a more servo-like worm gear, or what?
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Old May 25, 2012, 09:41 AM
Sir Crashalot
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Quote:
Originally Posted by SubtleT View Post
Did I miss a close-up photo that shows what the swash actuators look like?

Are they the "little motor and fan gear" or a more servo-like worm gear, or what?
I would describe the 5888 servo as a "rack & pinion" type gearing, similar to the 9958. I don't have a convenient photo, but "worm-gear" is fairly accurate.
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Old May 25, 2012, 07:50 PM
Vroooom putta putta putta
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"Worm and traveller" isn't the same as "rack and pinion" at all really. The former seems more likely though.
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Old May 30, 2012, 01:57 PM
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Zurich
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5888 uses the same type of worm-gear servos as most of the micro fixed wing RTFs.
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Old May 30, 2012, 02:05 PM
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Zurich
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addendum to tuning details

I forgot to mention: if the heli is steady in a hover but yaws left when power is surged and if that annoys you .... make sure in that case that the lower rotor blades are softer than the upper so that the lower blades twist in compensating pitch to neutralize the yaw.

Lee
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Old Jun 19, 2012, 05:57 AM
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Zurich
Joined Apr 2006
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don't make this mistake!

While replacing a left servo [that is, one on the left side: both servos are the same!], I inadvertently put a servo screw in the hole under the proper servo-hole closest to the bottom PCB center, by the red LIPO-wire connection.

When I removed the screw and put it in the correct hole just above that one .... ther was no LIPO connection via the on/off switch! After unsuccessfully trying to solder over the damage I'd caused to the PCB, I finally had to cut down an extra servo screw and leave it permanently in the lower wrong hole in order for the switch to work!
[of course I put CA gel over that "repair-screw" and colored it black as a reminder during the next servo change]

So make sure to put that screw in the right hole ....!


Lee
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Old Jun 19, 2012, 06:02 AM
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Zurich
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important performance note!

The other day while flying one of my 5888s outside in a light wind, I found that this time it had a lot of trouble penetrating upwind. After a while I checked the spinning rotor discs, stopped it, and discovered that the lower rotor blades' "tip-play" had migrated to 2mm, instead of the proven-optimal 3mm.

When I corrected that, the airspeed almost DOUBLED!!


Lee
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Old Jun 22, 2012, 02:51 PM
Mike
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United States, TX, Dickinson
Joined Mar 2003
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I can't believe I found this thread! I have one of these I got to get used to the controls before trying my HDX450 again! I went through the linkages and tweaked them so it hovered still while the electronic trims were centered, much easier to control. Is there a post in this 60 page diatribe that explains all the tweaks to get this thing flying better than I have it (it actually flies very nice now!)?
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