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T-REX 550 › trying to solve torque problem
06-12-2013 04:12 AM  5 years agoPost 1
CF1

rrApprentice

Olympia, WA

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I installed a KDE 600 1100kv motor. The new motor gives me much better flight times over the stock motor. But this thing has crazy power. Under heavy collective the trail will torque around 180deg. I changed from the stock 85mm tail blades to 90mm and this helped some. I also set the torque setting on my ar7200bx to 100%. Again better but still not solved. I went to the V1 auto rotation gears because they have a higher gear ratio. That worked but they went strong enough and they broke in flight today. So back to the drawing broad. I'm thinking I can goto 95mm trail blades or put a 600 boom on. Any thoughts?

I'm running a 17t pinion with 170 main gear
Talon ESC in gov mode. 2100 rpm set motor timing 0 and gain at 30
Mavrikk G5 550mm mains
6s 45c batteries.

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06-12-2013 12:51 PM  5 years agoPost 2
VANHELI

rrVeteran

Omaha,Nebraska

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Have you taken the tail gain all the way up till the tail wagged and then backed it down a couple points? Could it just be too low of gain? How much collective pitch are you running? If you are using a standard 550 boom (not the new dfc), you can NOT run 95mm tail blades. Pretty sure 92mm will not work either.

I switched to the kbdd main blades on my 550 and started having tail blow outs without changing any settings. I went back to edge 553 blades and no more tail blowouts. I will probably stretch the boom and try the kbdd blades again someday.

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06-12-2013 12:53 PM  5 years agoPost 3
VANHELI

rrVeteran

Omaha,Nebraska

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...also, pretty sure the kbdd and maverick blades are very similar. 2100 rpm on a 550 is quite low as well.

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06-12-2013 01:40 PM  5 years agoPost 4
Richardmid1

rrProfessor

Leeds, England

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I agree that 2100 is very low on a trex 550 even with 550 blades and that there is your problem.

If you mean tail pre comp in the ar7200bx? then make sure its working the right way, from MID STICK to full stick the pitch slider should move left towards the tail box when viewed from behind.

If that is set correctly then up the head speed in the castle software to 2200 and ignore the warning.

Now turn the governor gain back down to 10 (low).

If that doesn't fix it you will need an 18 or 19T pinion and run 2300+ rpm. This is why you saw longer flight times than the stock setup.

60% of the time, it works every time!

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06-12-2013 06:25 PM  5 years agoPost 5
CF1

rrApprentice

Olympia, WA

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Tail gain is bleeding edge too high. In full collective inverted forward flight you can almost hear some flutter every now and then.

I'm not flying DFC just the original FBL head so I know the 95mm blades will work. Also I am running 11deg of pitch.

I usually fly a little lower head speed on my training helis so I learn to fly the move instead of power through them. Then when I put my Whiplash in the air I've got the moves down.

The tail pre comp on the ar7200bx is moving in the correct direction. It doesn't have as much deflection as my vbar offers to sole this. Maybe I need to pitch it and get a vbar....

I measured battery drain on the same ESC same head speed. Just updated the motor information in the ESC. I used to burn my batteries down to 25% on a 4.5min flight now they are only dropping down to about 43% in the same flight.

Richardmid1 are you thinking dropping the gov gain down will make it easier on the gears or not to whip as hard? I had been thinking of that but was trying to avoid the drop in head speed after the head over speeds.

I decided to move the the KDE main slant gear for the 700. Its beefy to handle the power and in 112T. I'll couple with a 12T pinion for 9.33 gear ratio. Will allow me to speed up the head a lot if I want.

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06-12-2013 06:40 PM  5 years agoPost 6
Richardmid1

rrProfessor

Leeds, England

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Well im not actually sure what 30 is on the new edge esc's but in the previous versions 30 would be very high and the default 10 works extremely well, it will stop quite so much power banging in so quickly when you hit the collective.

Im pretty sure your tail swinging problem is down to low head speed. The trex 550 was designed to run 2400+ rpm to get good tail authority with the stock 85mm tail blades.

60% of the time, it works every time!

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06-12-2013 06:49 PM  5 years agoPost 7
CF1

rrApprentice

Olympia, WA

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On the Talon 25 is the default gain and it did it also at that setting. I can fiddle with it and see if I see a difference.

I'm replacing my autorotation gear now and will go try it after and let you know if any changes make a difference.

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06-12-2013 06:56 PM  5 years agoPost 8
VANHELI

rrVeteran

Omaha,Nebraska

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I'm not flying DFC just the original FBL head so I know the 95mm blades will work
read my post again. The dfc 550 has a longer tail boom and might be able to run 95mm tail blades. If you are flying the original 550 version (shorter boom) 95mm tail blades will NOT work.

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06-12-2013 10:27 PM  5 years agoPost 9
jschenck

rrProfessor

La Vista, NE.

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On a completely unrelated platform but similar problem - my Trex 800 was swinging the tail pretty bad on full collective punches. turned out the way I had mounted the ball link on the tail servo was causing the linkage to bind against the tail servo. Ball link was on the back side of the servo horn. flipped the ball link over to the front of the servo arm so the servo can move it's full swing without mechanical binding and now no tail swing. I also changed the RX pack from a LiFe to LiPo since I have HV servos which I'm sure helps the tail servo performance - it was designed for straight LiPo voltage.

From what I've seen with the 550's they like the high headspeed. 2100 may be too low for the 550 with whatever gear ratio the tail is driven at. I haven't owned a 550 so I don't know for sure but have helped a few club member set theirs up. I haven't had tail swing problems even with a first release V1 550, flybar and somewhat 'soft' original motor and all.

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06-12-2013 11:54 PM  5 years agoPost 10
CF1

rrApprentice

Olympia, WA

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Do you have a part number for a longer boom? Align site only lists one boom h55031. Spot of guys are flying 95mm on the tails with no problem. I could see dfc being an issue but I won't fly dfc.

I flew the 95mm trails today. Inverted full pitch then full back elevator worked fine.

With the 95mm tail blades and the head speed bumped 50 rpms it has so far been able to not torque over. Need more flight time to tell if it's totally gone.

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06-13-2013 12:46 AM  5 years agoPost 11
VANHELI

rrVeteran

Omaha,Nebraska

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I saw in person an original 550 non dfc strike the tail blades on spool up. I run 85mm only. At a much higher rpm.

Dave V.

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06-13-2013 12:47 AM  5 years agoPost 12
VANHELI

rrVeteran

Omaha,Nebraska

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Apparently the booms are the same. The dfc sure looks longer though. Hope you get it figured out.

Dave V.

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06-15-2013 05:06 PM  5 years agoPost 13
ZS-JAF

rrVeteran

Nazareth, PA

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550 DFC has the 600 boom it says 600 on it. My 550E had the same problem with same head speed and blades. Head speed increase would be good.

I have a 3D heli, I don't understand why it doesn't do 3D.

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06-17-2013 05:46 PM  5 years agoPost 14
CF1

rrApprentice

Olympia, WA

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I switched to the KDE 112 slant main gear with a 12t pinion. I governed it to 2350. I also have the 95mm tail blades on. Finally I set the gov gain to a custom level between low and normal, 20 I think. Thing is a fright train now. Really moves and had no bog and unlimited power.

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07-13-2013 11:00 PM  5 years agoPost 15
helicoptermike

rrNovice

ontario,ca-usa

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Do you hear the motor bogging when you give full pitch? If so than that would also mean that you are loosing tail authority, which can cause the tail to let go. If this is not the problem,I would check to see if the ball link is binding on the servo end. If the ball link is not binding, take the ball link off of the pitch assembly and make sure that it is smooth as butter. You can do this by laying the heli on it's side (Tail blades up),and the move the pitch link by hand towards the tail blades. Let the pich slider go and it should fall towards the tail case on its own. If the pitch assembly is doesn't budge then maybe there is some binding in the pitch links or tail blade grips are too tight. If none of the above works, try another servo just to verify the servo is no bad. Note: Out of my experience, binding in the tail assembly causes me vibes, and tail blow outs have been due to gain too low or either a bad servo. I hope it works out for you.

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