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HelicopterRadio - Servo - Gyro - Gov - Batt › G7703D Gain Values?
07-11-2008 03:05 PM  9 years agoPost 1
kcass518

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Manhasset, NY - USA

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Just put the G770 3D and the 8900 servo on my Evo 50, DX7, AR7000. The tail hunts a bit, and when I'm in a sharp right turn it really oscillates in the turn then calms down when straightened out. I set it up according to the RC Heli article - 50% expo, 150% ATV, 60% dual rate, and I started with 30% gain using the Gear ATV. I dropped it to 20%, and still it's hunting. Tail servo ball link is 17 mm from center per Evo instructions. If I move it in closer to the center, I get binding. Everything in the tail is smooth as silk. It all worked fine with my GY401. I have the 770 mounted with Zeal tape which should minimize the vibration, but it doesn't seem to be working. The twitch I get seems to be caused by normal vibration or too much gain.

What gain value are you using with this setup? I'm thinking of moving the gyro to the back platform and sticking it with my usual servo tape which has always worked for me before, but I would think that would increase the vibration rather than lessen it. Nothing is pushing on the wires (I removed the canopy for testing when I thought it was pushing the wires a bit - no improvement).

Any suggestions?

BTW, the wires around the gyro you see are not touching it at all. Maybe they're giving some electrical interference, though?

Oh, I did set it up by initializing in HH, then mechanically getting it to hover straight in Rate Hold, so that, in a hover, when I switch between HH and Rate Hold, the tail stays still.

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07-11-2008 03:19 PM  9 years agoPost 2
AltecLansing

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North Carolina

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Sounds like you got the rate mode set up properly. I have the same set up but my gyro is on the back. I'm even using the zeal tape, also, (great stuff). My gain is just under 20 percent. I had the oscillation in turns also, but turning down the gain got rid of it. I also moved the ball closer to the center on the servo arm. How are you getting binding? When you move the ball closer to center, the range of movement should have gotten smaller, so there shouldn't be any binding.

Man, I miss the eighties.

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07-11-2008 03:47 PM  9 years agoPost 3
kcass518

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Manhasset, NY - USA

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Thanks, Altec. 'Binding' is probably a bit of an overstatement, but it bends the tail pushrod more than it should when at the extremes. I'll move it in as a last resort. It's good to know that you're under 20% though. I think I'm going to move the gyro to the back, mount with Zeal, put a piece of tape over the top of the gyro to keep oil out of the switches, etc, and turn down my gain. I might also replace my ball links with ones that aren't quite so sloppy. They were fine before, but there is a tiny bit of play in them, and maybe it's enough to be a problem. After that, I'll move the ball link and see what happens. This thing is really sensitive!

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07-11-2008 03:59 PM  9 years agoPost 4
AltecLansing

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North Carolina

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There is also a servo travel pot on the gyro you can use for adjusting travel.

And the manual says to use 11 mm length on the servo arm for the 600n which is a 50 size heli.

Man, I miss the eighties.

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07-11-2008 04:14 PM  9 years agoPost 5
kcass518

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Are you at 11mm? I can get there, but as I said, it will make the pushrod bend at that first pushrod guide which I'm not crazy about.

I have the travel pot on the gyro a little low because of the longer servo arm, but I didn't think it would cause the hunting. I know they say to start it at 80 - 90%, and I'm probably at 60 - 70%. I'll check it out further tonight. I will say that the plastic screwdriver they gave me didn't fit the pot very well. My old Futaba one works better.

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07-11-2008 04:32 PM  9 years agoPost 6
AltecLansing

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do you have a pic? I'm going to mic my servo arm now.

Man, I miss the eighties.

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07-11-2008 04:35 PM  9 years agoPost 7
AltecLansing

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North Carolina

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my ball is set on the 3rd hole out on the arm that came with the 8900 g servo.

Man, I miss the eighties.

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07-11-2008 05:07 PM  9 years agoPost 8
kcass518

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Manhasset, NY - USA

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Mine too, which is where they have it in the photo in that RC Heli article. I measure it to be about 17 mm. Here's my photo:

PS - the 8900 didn't fit very well in the bracket, and I now see that I ended up using different holes on one side. I don't think it will make much of a difference though.

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07-11-2008 06:50 PM  9 years agoPost 9
AltecLansing

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North Carolina

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adjust the travel limits on the gyro and turn down the gain. If you bring the ball in some, you should be able to have more leadway in gain adjustments.

Man, I miss the eighties.

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07-11-2008 06:59 PM  9 years agoPost 10
kcass518

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I agree that bringing the ball in will allow a higher travel limit and a higher gain, but isn't mine exactly where yours is? Do you know about what % your travel is on the gyro pot?

I'm also curious - with the Zeal tape, do you use two strips per the instructions, or one full square? Do you have a safety strap covering the gyro?

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07-12-2008 03:03 PM  9 years agoPost 11
kcass518

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Okay, for anyone else reading, I moved the gyro to the back, used a full square of Zeal tape, put a safety strap on it and lowered my gain to 19 and viola, no more problems. It tracks like a champ. I don't know if the safety strap is helping or hindering, but since it works I'm going to leave it. Unless someone can say that it's unnecessary. I never lost a gyro when using good servo tape, but two guys at my field lost their gyros three or four times in the last six months, so I'm being cautious. Here's the photo:

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07-12-2008 03:08 PM  9 years agoPost 12
AltecLansing

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North Carolina

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I'm glad its working for you. I don't use a strap and don't find it necessary. Just tug on it from time to time to make sure the tape is good. I've had the zeal tape on for over half a year now and have had no problems with it so far. You probably did more for the wags through the turns by turning down the gain. I am at 18 or 19 myself. You did get rid of all the binding right? Also, how fast is your piro? Does it look fast?

Man, I miss the eighties.

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07-12-2008 03:19 PM  9 years agoPost 13
kcass518

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Hi,

I should try it without the strap to see if there's any difference, but since it's working I'm inclined to leave it alone - at least until I get used to it.

No binding because I left the ball link on the third hole out. The pushrod bends a little in a full left turn, but it doesn't seem to affect the performance - at least I can't tell yet. I'll keep an eye on it.

Piro looks scary fast. I didn't push it all the way yet, but it really moves.

Are you using two strips of Zeal, or one full square? Do you know where your travel is on the gyro pot?

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07-12-2008 03:32 PM  9 years agoPost 14
AltecLansing

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North Carolina

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I'm using one square of zeal tape. I think two would have been too much. I can't really tell what my pot is set at. Its basically a plus sign and I don't remember how much I turned it from the starting point. I'm thinking of turning the pot more to increase the travel limit a little bit as I don't have an extremely fast piro. Also, adjusting the travel limit on the rudder channel will change the piro rate. I need to check it one more time in rate mode and make any necessary tweaks. Other than that, I'm satisfied with the flying of the heli. I don't do 3d and I only do a little aerobatics at this time. But as time progresses, I will need a more aggressive response from the gyro.

Man, I miss the eighties.

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07-12-2008 04:12 PM  9 years agoPost 15
kcass518

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When I said two strips, I meant that in the instructions, they suggest using two strips of Zeal, each about 1/4 or 3/8" wide, placed under the gyro with space between them. I did this with my 401 and it worked fine, but I was just curious if everyone did that or not. The guys at my field use a 1" square and leave it at that.

To adjust the travel limit, I started with the pot turned down, pegged my rudder stick all the way to the right, and then slowly turned the pot clockwise until I heard a little servo buzz. Then I backed it off until the buzz went away. My Rudder ATVs in the DX7 are at 150/150, and, per that article, I adjust my piro rate by raising or lowering the Dual Rate for Rudder. I made sure that I adjusted the Dual Rate the same for when the switch is up and down, because otherwise the tail might do strange things when clicking into throttle hold. Right now, Dual Rate is at 60%, and it's enough for me. I don't want to break my tail off! Expo is at 45%.

I can't call what I do '3D', but I'm creeping up on it. My high point was three back flips in a row, but that ain't 3D. I'm mostly doing flips, rolls, loops and I'm sneaking up on autos by practising approaches in NOR. It is nice to have a tail that is this snappy, though. I think it will help me progress faster.

I tested my hover in rate mode this morning, and it seemed fine, but it seemed to drift right one time and left the next. The heli was downwind from me, so I presume the wind caused the drift. I'll know more tomorrow, but I'm happy for now.

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10-02-2008 03:35 AM  8 years agoPost 16
helisin

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Calgary, Canada

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I've read this thread and got some good info from it but I'm looking for this article on the 770 3D / 8900 set-up that someone referred to.

I'm thinking abut getting the combo for my big Intrepid EB gasser and would like some reference and recommendations for values etc. My radio is a 9303.

Thanks in advance.

Rob.

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10-02-2008 01:45 PM  8 years agoPost 17
kcass518

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Manhasset, NY - USA

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Hi Helisin.

This was from a while ago, and I don't have the info readily at hand, but I think the article referred to was in RC Heli, maybe the January 08 issue. I can look harder when I get home and repost tomorrow, but I think that was it. I also think there was a blurb about the article on the cover, but I checked 'back issues' online and couldn't find it.

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10-02-2008 03:55 PM  8 years agoPost 18
helisin

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Calgary, Canada

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This was from a while ago, and I don't have the info readily at hand, but I think the article referred to was in RC Heli, maybe the January 08 issue. I can look harder when I get home and repost tomorrow, but I think that was it. I also think there was a blurb about the article on the cover, but I checked 'back issues' online and couldn't find it.
Thanks kcass518. I pulled the 770 manual from on-line. Seems to be pretty good set-up instructions with good starting values. JR manuals seem to be a bit better than what I remember the Futaba manuals as far as setup hints and instructions go. Don't go searching too hard because I think the manual may do it for me. Thanks again.

Rob.

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10-03-2008 03:00 PM  8 years agoPost 19
kcass518

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Manhasset, NY - USA

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So, we're having our 40th High School reunion this weekend, and my best friend from elementary school and his wife arrived last night at 6:30 to spend the weekend. He lives in Newfoundland. He had requested that I find some Ballantine's Ale, for some reason, and I had to go to a number of beer distributors before I could find any. I made it under the wire, picked them up at the train station, and off we went. When we got to my house, of course, we opened the Ale. I completely forgot to look for the article and even forgot to look in my Palm to see the note I had left for myself. Tasty it is.

Glad you found the instructions. I'll still look for the article, but I might not get to it for a few days - party party party.

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10-03-2008 04:00 PM  8 years agoPost 20
helisin

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Calgary, Canada

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Completely understandable!

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HelicopterRadio - Servo - Gyro - Gov - Batt › G7703D Gain Values?
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