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01-12-2006 07:03 AM  13 years ago
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majorsmackdown

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Portland, OR

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Help me roll please.
I have the tiger 50 with 3151's on the swash and a 401 gyro with the 9254 rudder servo, revloc governor. It seems to fly great, loops and flips are sweet and fast, but the rolls go crazy. it's happened to me 4 out of 4 rolls and it happens so fast and without witnesses I really can't say what's happening. I'll enter a roll up high and stationary, when the rotors are vertical I put in the negative pitch and she goes wild. by the time she's back upright the heli is far left from where the roll started and nose is pointing straight right (started tail toward me). the swash plate stays level throughout the pitch range on the bench, the gyro is holding great until this move. the balance is just about dead on level without fuel. no binding in the head. the phase is as I think it should be , and phase is locked in. these rolls are attempted in idle1, -5.5, 5.5, 11, with fiberglass rotors. It just befuddles me. This is my 5th chopper I've built and I've never had one react this way before at all. I'm at a total loss as to WTF. Any ideas ? Thanks.
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01-12-2006 01:49 PM  13 years ago
Atlas321

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Bridgewater, New Jersey

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Have you tried a little expo on the controls as they are a bit touchy in CCPM......? You are possilbly adding a little too much negative at the wrong time and are giving a little tail input as you come down and up with the collective.....Possibly....?AMA # 760459 Hyper Evo 50 / Trex SE
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01-12-2006 04:44 PM  13 years ago
majorsmackdown

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Portland, OR

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I do have some expo programmed in the cyclic and rudder, and i think my timing on the sticks close enough I shouldn't have the problem. I do have the standard paddles without weights by the way. I have a very touchy trex already so I have some experience with a jumpy heli. What makes it mysterious to me is that I have a sceadu evo with a similar setup - rpm and pitch curves and I can roll it just fine and very predictably. The tiger flips and loops very similarly to the evo so I was expecting the rolls to be similar as well, but I'm not finding that to be the case. Also I have tried the rolls with a much reduced swash afr on cyclic the same thing occurs. And as far as I understand that would really numb the controls? Thanks for your input.
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01-13-2006 07:54 AM  13 years ago
rocketScientist

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So Cal

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rolz
You have your timing wrong. Begin a roll..

When the main blades are vertical, you should be at zero pitch - NOT full negative pitch.

When the blades are upside down, be at "hover" negative pitch.

When they get vertical on the other side again, zero pitch.

Back to upright,upright "hover" pitch.
The sky is NOT the limit. The Ground is.
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01-13-2006 09:18 AM  13 years ago
majorsmackdown

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Portland, OR

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I hear ya, I'm not at full negatvie pitch when the rotors are vertical, that's just when I start adding it. Like I said, the sceadu is rolling for me very nicely and predictibly. I'm really leaning toward the notion that I need stronger servos, or I have a defective servo. Tell me if I'm wrong, a flip and a roll are very much the same right ? - just in a different direction. ? The flips and loops look great. My timing is the same for the flips and loops as I've tried in the rolls. I'll report back in, I'm going to give it one more try then I'm going to see if stronger servos do the trick.
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01-13-2006 06:34 PM  13 years ago
darkfa8

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Brick, NJ - USA

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it's possible that you have a bad servo. The 3151's areplenty strong and give a cumilative torque of 120oz. on the swash.

you could also apply some pressure to your servo's output horn while operating on the ground to to see if it slips, grinds or exhibits any other poor operation.
- Dan Goldstein
Team Revolectrix
Lynx Heli Innovations
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01-13-2006 06:40 PM  13 years ago
majorsmackdown

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Portland, OR

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ok on the torque, I need to determine if I have a bad servo. I've put some finger pressure on the swash as I move my stick around, and I hear nothing funny, but the servos don't really press against my finger very energetically, and it's easy to stall them. on my other heli I have 9252's and the swash moves with the stick totally regardless of a finger trying to obstruct. thanks for the input
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01-13-2006 07:08 PM  13 years ago
Rafael23cc

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Junction City, KS

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I suggest that you try flying rolls instead of stationary ones, they feel a whole lot easier.

Start by flying forward at a comfortable speed, and start the roll. as mentioned before, you need to be at 0 degrees when the head is vertical, and be close to "hover" pitch while inverted. The rest is the same but on the other side.

If you have timing problems they will show up in sideway movement. If you have cyclic / tail interaction problems, they will show up by not having a straight flight line.

For my very first loop, my heli ended up flying close to 90 degrees from the intended flight path. I had a buddy observe my hands while I did the roll and he told me I was oulling a little elevator while appliying aileron. Tha made my heli take off in another direction and make all kinds of weird maneuvers.

Rafael
Keep your feet on the ground, but your eyes on the sky.
Team Heliproz.com
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01-13-2006 07:17 PM  13 years ago
Raffy

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Chicago, Illinois

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Different brand models do have their own flying charactheristics.
This is why it is important to own one particular brand and get used to flying it. Owning different models will throw off your desire to perfect a flying routine.

Even if you own the same brand model but different power band(50 size and 90 size)alternating them to practice a routine will not give you good results.
Imagine you becoming a good Jockey with a fast and athletic horse and using a donkey to practice on!
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01-14-2006 10:16 AM  13 years ago
majorsmackdown

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Portland, OR

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10-4, I just didn't expect this much difference. amazing how similar my trex and sceadu fly. and the tiger was very similar until this roll issue. I'm suspecting a bad servo, I have another set of servos with more torque just in case. But I'm going to giv'r another try setup as is with an observer before swapping out gear. thanks for the input.
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01-15-2006 03:51 AM  13 years ago
majorsmackdown

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Portland, OR

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ok, problem solved, solution unknown. The swash setup asks for 20mm for the 2 rear ccpm servos, and 23mm for the forward servo for lenghts of the servo horns. I didn't have the exact lenghts but kept the correct ratio of 1 to 1.15. my horns were approx 22 and 25 mm. I errored long, but decided to swap the horns back to error short. 19mm and 22mm. I also reduced my max pitch from +/- 11 to +/- 9. I don't think that made the difference since my first bad rolls were only going to -5.5 degrees. but it was part of the changes. All I can figure is that longer horns on the relatively weak servos (3151's) had too much leverage on them. shortening these arms I think made the difference. ya, I know they called for 20 mm to begin with - I just didn't suspect such seemingly small difference would be such a big differnce - but I guess it's the difference between a servo holding or not holding and not holding is no good. thanks for all the ideas in trying to help me solve this problem.
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01-15-2006 04:25 AM  13 years ago
Jeeum

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Orange County,NY

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Here's one for ya. At first when I started flying the tiger I was taking it easy, just forward flight. Then started adding loops,rolls then eventually flips. Last time I took it out I really started beating on it. As the day went, I started to get more and more upset with how sluggish the cyclic rate is(all stock).

Then I let my brother fly it. All of a sudden it sounds like it's losing head speed in the turns and he says it's ballooning in forward flight like a fixed pitch heli. He lands it and I start going through the heli, expecting some major problems. I found out that the right and left side servos had both broken their mounting lugs at one end of the servo. So basically everytime you would give a input, the servo would float in and out of the mount. You can imagine what that would do to your flight characteristics.

These were MPI 870mg servos. I'd used them for awhile with great results in other applications, but the cheap plastic they use for the case just began crumbling. So now I'm waiting on some 9001's and my 3d Flybar/paddles. I'm really looking forward to how this thing is gonna fly now.
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01-16-2006 11:09 AM  13 years ago
majorsmackdown

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Portland, OR

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thanks for the scoop - I checked my servos and they were working their screws loose a little, there might be a call for nut and bolting the works together, or some ca or plastic loctite. thanks for the heads up.
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01-17-2006 02:26 PM  13 years ago
jvanscoyk

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Tucson, AZ

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I used a lttle RTV underneath the servo grommets on all the servos. It seems a little easier to replace the bosses in case you should strip one of them out. The servos are now rock solid with no movement in the side frames.


Jim
must go faster, must go faster.........
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01-17-2006 02:46 PM  13 years ago
majorsmackdown

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Portland, OR

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right on, good idea. I was thinking I'd have some major disassembly to nut and bolt it all up.
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01-17-2006 07:42 PM  13 years ago
djMidnight

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Petaluma, California

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jvanscoyk: I used a lttle RTV underneath the servo grommets on all the servos.
Forgive my acronym ignorance, but what is RTV?

Jason
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01-17-2006 07:59 PM  13 years ago
coolhandluke

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Collins, MS

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RTV
Room Temperature Vulcanizing (RTV) silicones
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01-17-2006 08:01 PM  13 years ago
coolhandluke

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Collins, MS

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rtv
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01-17-2006 08:02 PM  13 years ago
majorsmackdown

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Portland, OR

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Room Temp. Vulcanization. Vulcanization is a technique for strengthening, stiffening, deoderizing rubber by adding chemicals or compunds and heat typically... so this is RTV. Room Temp. Vulcanization. I'm not sure if it's really the correct use of the term or not, but it's Permatex's marketing at least. Permatex has a whole line of RTV silicones in tubes, for different heats, oil resistance, etc.. (I should be getting paid for this). a ehaheha
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01-17-2006 08:58 PM  13 years ago
FLYINFOOL

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Cudahy, WI

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Most RTV silicones use an acid to cure. That is why they have a viniger smell.
The fumes from that acid are very bad for electronics.
There are grades of electronics safe RTV available and that is what should be used anywhere near your electronics.
Jeff Borowski
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