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Next-D › My Rave is drifting right and forward after a flip or inverted
01-14-2009 02:43 AM  9 years agoPost 1
ke6d

rrApprentice

San Jose, CA

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My Rave is flying quite well, but it has an odd behavior. I can take off, trim it so that it would hover hand off for a few seconds then slowly drifting off as any CP helicopter would do. I can fff in any direction without any problem, but as soon as perform a flip (forward or backward) or go into inverted hovering. The heli is consistently drifting right and forward (that requires several left and back trim clicks to get it hover hand off again) If I was to trim the heli to get it level, then I have to "untrim" at some point during the flight because it would drift left and backward after a few fast circuits with the new trim.

If it is drifting right and forward after the flip/inverted, I can also perform a right roll after going back right side up to cancel the drift without resorting to trim to get it level.

I have check the swashplate, all the links/balls, sizing all ball links, and servo arm to make sure that there were nothing loose/stuck anywhere, but this odd drifting behavior still persists even after 8 shake out flights.

At first, I thought the brand new Hitec 5065MG servos were not centering well after the flip, but I tested the servo motion and observed the swashplate/servo arms on the ground many times. The swashplate is always level, arms at 90 degrees after the stick sequence.

I am now leaning toward something mechanical that was stuck as the heli went inverted which required a left roll to straighten it out, but I could not pinpoint the problem component.

Any advice on where to look?

Thanks,

Dan

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01-14-2009 02:54 AM  9 years agoPost 2
CUheli

rrNovice

Kansas City

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First, are you adding these trims in your stunt mode or just in normal mode? and did you use a swash level of some kind to set up the heli?

If you have a level swash and add some trim to counteract forces on the heli (in upright hover) then when you flip it inverted you will have to counteract that trim.

To avoid this you can set up the heli to hover hands off w/ trim in normal mode and leave the trims at center for stunt modes. This is what I have learned, if anything is incorrect im sure someone will chime in.

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01-14-2009 05:43 AM  9 years agoPost 3
ke6d

rrApprentice

San Jose, CA

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I am using the swashplate leveler to set up the swashplate. When taking off for the first time, I usually only has to do 1 or 2 clicks on the trim to get the heli hover hand off.

What I am saying is that my heli is hovering hand off then if I did a flip or went into inverted, then when I get back to up right, my heli now drifts right and forward.

Now it is drifting - without doing any trimming, if I roll the heli left one time, the drift went away and the heli is hovering hand off again.

It is very repeatable.

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01-14-2009 05:54 AM  9 years agoPost 4
CUheli

rrNovice

Kansas City

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Ok, I see. I misunderstood the problem.

You could check if the paddles are aligned. or they might be moving in flight.

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01-14-2009 10:00 AM  9 years agoPost 5
hootowl

rrProfessor

Garnet Valley, Pa.

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Could be tight ball links. Disconnect your links from the servos and move the swash by hand feeling for tightness. Also make sure the links aren't tight on the swash balls. Use a resizer if they are tight.

Wolves don't lose sleep over the opinions of sheep

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01-14-2009 02:40 PM  9 years agoPost 6
ke6d

rrApprentice

San Jose, CA

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Resizing the ball links was the first thing I did but it did not help.

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01-14-2009 03:45 PM  9 years agoPost 7
inkspot1967

rrProfessor

Cranston Ri

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what servos are you using? whats your setup?

sounds like the servos are not centering to good

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01-14-2009 06:08 PM  9 years agoPost 8
ke6d

rrApprentice

San Jose, CA

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My setup is:

Cyclic: Brand new Hi-tec 5065MGs
Gyro: JR770-3D
Tail servo: Futaba 9257
ESC: CC 45HV
Motor: Scorpion-8 motor
BEC: Hobbywing 3A

At first I thought the problem was from the new servos, but I let the heli sit on the table with the motor wires disconnected, then exercise the servo a lot. The arms always comeback to 90 deg positions afterward.

I can fly my heli in fast circuits for several minutes without any problem, but as soon as I go inverted then go back to upright, the drifting problem shows up. Something about going inverted that messes it up.

I will be taking out the head and rebuild it this weekend to see if it helps.

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01-14-2009 06:14 PM  9 years agoPost 9
inkspot1967

rrProfessor

Cranston Ri

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the only other thing i can think of is the whole head geometry could be off like having different deg of cyclics on ail or elv or paddles not strait.

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01-14-2009 06:59 PM  9 years agoPost 10
Sky Dancer

rrVeteran

Bryan, Texas

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Ked6,

The first thing I would try is to put a pitch gauge (or paddle gauge)on one of the paddles and level it up with the main blades. Then align the main blades with the tailboom. Now, watch the pitch gauge and give forward cyclic and release. Does the paddle gauge return to its original position? Now, give rear cyclic and see if it returns as before.

If you see a difference in the paddles returning to center, either you have too much drag in your linkages or a servo problem. I found, if you remove the cyclic linkages from the servos and move the swash by hand, you'll probably be surprised at the drag caused by tight linkages. If this is the case, just resize the links again until you can move the swash easily. This can make a significant difference in the ease of flying.

One final thing, which paddles are you using? Try hovering in different headings (N-S-E-W) to see if your trims seem to change. I've also seen trim changes here depending on my blade/paddle combination.

Let us know what you find, ok?

Don C

Keep up your rotor speed !

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01-14-2009 07:33 PM  9 years agoPost 11
ke6d

rrApprentice

San Jose, CA

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I have been building at least 10 CP helis in the last 2 years, this is one of a few problems that get me scratching my head

I did the pitch measurement when I built this things a couple weeks ago. Using the pitch gauge, I set/measured the collective pitch is +/- 11 degrees (my preference) Aileron and Elevator pitch is +/- 7 degrees.

The paddle is set to be leveled (using a water bubble) then tested the cyclic movement. Everything seems to be normal.

The paddle I am using the the light weight set.

May be I should hold the heli upside down and yank on the head, then follow by some cyclic movements, then measure to see if anything did not return to normal position.

I will pull the head off and rebuild to see if I spot anything was missed this weekend.

Will post what I found.

Thanks,

Dan

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