View Full Version : Stinger6 Pro (Viper90 carbon+ali) observations
The details on my Stinger6 Pro are in this post here (http://www.ikarus-modellbau.de/forums/showthread.php?p=448590#post448590). Note the slope frame modification for mounting 4s 2500mAh under the hood.
To get the cyclic to come alive I had to remove flybar weights and swap the stock paddles (12g each) for Eolo 3D light paddles and 2mm ali mounts (6g each). Running a 4s setup at +2500 RPM is required to keep the 160mm CF tail rotor from blowing out at 12º/100% power demands. Then the performance is good enough for basic acro/3D otherwise at lower RPMs with stock paddles, the heli makes for a stable leisurely cruiser.
MS seem to have discontinued their canopy badged version which is worth having if you can pick one up very cheaply with all the upgrades. A plastic head version won't allow for safe operation at higher head speeds and therefore won't perform that well (tail and head RPM might be too low for harder acro moves).
Particularly a problem with the very stiff head damping of the ali head set. This heli seems to suffer a resonance issue with the frame and landing gear interaction with the rotor system, on a main shaft where the bearings are too close together. Any oscillation during spool down can get magnified very quickly and aggressively, sometimes very violently bending the relatively soft stock main shaft. I found that to reduce damage, as soon as you seen the onset of this problem immediately increase RPM or if spooling down, make sure to use a kill switch to spool down so that you can dump in a lot of pitch to load up the rotor and get out of the danger zone. To stay at 0º pitch is not advisable when spooling up/down.
In both the stock tail slider (brass/one way/plastic outer) and ali hop up (brass, dual bearing/ali outer) there is a design oversight. First I noticed my stock one way version start to lock up and get warm after a couple of hours of flights. Swapped in the ali version on bearings and noticed that to was getting hot and even though I left it with some play to move, not tight. The reason is that in both cases, the brass pitch slider and yoke at 10K rpm touch the stationary outer casing, generating heat and wear under tail pitch loading. I don't think many have tested this design much or they would have included some small stepper washers to engage the spinning components with the centre ball race and not contact the stationary outer race. I didn't have any correct sized washers to hand so I'm using a small rubber o-rings just pinched up (not too much or they will spread). More testing required...
Edit: This is not a good heli these days with so many other cheaper options, only if you want a light construction. With light construction comes problems with strength and resonance issues.
I had no tail trouble with this heli until I upgraded to Eolo 68mm tail blades (heavier and longer) and moved to a HS-82MG tail servo. I could not balance the blades (resonant zoned light weight construction materials), spooled up and the tail detonated. Replaced all the main components and still struggling to get a smooth tail at all RPMs, even with the standard length/weight MS CFc tail blades. Seems to resonate at +10,000 RPM on the tail rotor. Essentially the same as and Eco8 but not sure if anyone runs an Eco8 tail and +10K rpm? You don't have to with longer 205mm tail diameter, at 2K rpm the Eco8 is around 9K rpm on the tail (1:4.5 tail ratio I think), so may not be such an issue?
The rare time I find some one to operate a video camera and I have setup issues. Anyway you get to see a few 4s 500w punch outs, ranging from 2500rpm to 2700rpm (Axi 20º timing) as a reference guide. I'm may still be able to get more performance from this 4s 14.8v setup...
...MS-Stinger6-Pro_TailTroubleTesting.wmv (http://www.darkhorserc.com/Stinger6/video/DarkHorse-MS-Stinger6-Pro_TailTroubleTesting.wmv) 35MB 3.5mins 50fps WMV (slow server).
Still flys but now being dangerously stressed (for entertainment purposes) with a 19T pinion on Hyperion G3 VX-35C 2950mah ~340g 4s pack. +3000 RPM on the head and can only use ~9º of blade pitch (MS CFs are a relatively wide chord), the Spin log recorded 880w (14.7V x 59.8A peak). With a AUW of 1.2Kg it's pretty respectable performance now :D, goes well! Calculator estimates link (http://dhrc.rchomepage.com/calcAdvanced.htm?kv=1500&voltage=14.8&pinion=19&gearTeeth=120&drag=.90&MRdia2=860&mAh=2950&AUW=1180&packV2=14.80&MRdia=860&TRdia=160&MRchord=40&TRchord=22&MRblades=2&TRblades=2&boomlength=500&TRratio=4&The_modtype=1&profiledrage=0.0035&drain=.90&sliderThrottle=76.42&sliderPitch=2.14&motortype=0&outKv=1500&outRm=0.026&MaxIo=42&outMotoroz=151.1&outIo=3.3&esctype=42&Resc=0.0012&Amp=60&metric_escWt=56.7&celltype=0&outCellCap=2950&numofcells=4¶llel=1&Vcell=3.70&packV=14.80&outCellRes=0.0065&outCellWt=71.2&PackWt=284.8&metric_temper=12.15&metric_altit=1&metric_pressure=1013&AirDensity=1.236909&temper=53.9&altit=3&pressure=29.9&govRPM=2200&MRrpm=2903&Thr_P5=100&Thr_P4=85&Thr_P3=70&Pit_P5=100&Pit_P4=75&Pit_P3=50&PitchRangeHigh=10&PitchRangeLow=0&checkbox_mix=true&checkbox_gov=0&redButton=B-Restore2&checkbox_bal_thrust=0&checkbox_bal_power=0&LastItem=MRthrust3&), theoretically capable of ~90mph (300mph tips).
I don't think it will last long and won't be surprised if something goes bang, like the nylon gear train at those power levels. I was able to pull the main shaft bearing apart on the old setups power levels (15T pinion) which was vibrating a little whilst trying to land, so far so good...
'And now... you will die!' :D
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