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Midland Helicopters . HeliProz . ZoomsHobbies

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Beginners Corner > how much gain is too much?
 
 
nmrs
Senior Heliman
Location: Austin, TX

Results from latest test flight. First, I put the esc (standard align esc) in governor mode with straight 90% throttle (well 0 at low stick in normal, but everything else 90). I'm still just hovering tail in, but I am getting more comfortable at jamming collective up and down to see how tail holds on climbout. Governor mode did seem to help some: tail was still blowing out on climbout, but didn't seem to be drifting left on descent like before. I will probably have to compare governor mode vs throttle curves again as my flying progresses. I had gain at 50 (using gear channel endpoints) and was still seeing tail blowout some (3 - 4 inches) to the right on hard climbout. As before, blowout corrected itself once I leveled off the collective. I landed it and raised gain to 60. No wag and blowout on hard climbout was still there but was minimized -- now maybe 3 inches. Landed and upped gain to 70. Still no wag, blowout minimized more (about 2 inches now) but still there. Can/should I keep trying to raise gain? Or am I getting into dangerous territory for the health of my servo? I'm still not seeing any wag, but don't know if I am still getting too high. I'd feel much more comfortable running in the 50 - 60 range. Based on HeliSmith's comment, maybe I just won't get wag:

Quote 
The adjust until tail wag method doesn't always work. Sometimes it just doesn't wag and no two setups are ever the same even using the same parts.

One other thing, I am using the stock plastic tail blades, and they have a few small dings from landing in grass (St. Augustine is pretty tough grass). I was reading an older thread (http://www.runryder.com/helicopter/...?top=1208339653) where someone recommended different tail blades. Should I try the CF tail blades?

For my current flying ability, I doubt this slight blowout during climbout will really impact me at all. It's just annoying that things aren't working perfectly .
05-30-2008 04:13 PM
 
 
nmrs
Senior Heliman
Location: Austin, TX

Forgot to ask about the servo horn. As I said before, I have the ball about 9.5mm from the center screw. So far there have been conflicting opinions about where to mount it.

From KCass18:

Quote 
Has anyone addressed the point that 9mm from the center of the servo to the ball link might be a bit much? I don't have my TRex with me, but my memory tells me that I'm at about 5.5 or 6.5, and that this distance was pretty critical. Sorry if my memory is weak, but since you've spent so much time on this I didn't want it to wait until I got home to double check it. Does anyone else have their ball link at 9mm? Hope this helps.

PS I think this is what Zaneman meant in Point #2 - move the ball link closer to the center screw. I actually drilled a hole in my servo wheel because none of the stock holes was close enough - I do remember that!

HeliMatt seems to have the opposite opinion:

Quote 
1. My 9257 worked best (on a MiniTitan, not trex, haven't tried it there yet) with the ball further out on the arm, not closest in. Sorry, don't have the exact distance. When I tried it furthest in, I had the gain to 100% (futaba radio) and it didn't hold super well, and no wag. Putting the ball further out on the arm INCREASES MECHANICAL GAIN. I then turned the transmitter gain down, and got a good hold. Higher gain could make it wag.

What is the general consensus on on how far out to mount the ball on a 9257. When I look at how I have it mounted, its close to 90, but not exact. Would probably need to be a bit further out to be 90.



I guess I can get out one of the star horns with multiple holes at various distances, trim it so it doesn't hit the boom (thanks BladeMaster), and try a couple of different ball positions...
05-30-2008 04:31 PM
 
 
nmrs
Senior Heliman
Location: Austin, TX

Results of servo arm test

Since there were several suggestions earlier in the thread for increasing mechanical gain (via moving ball out from center) and only one tentative suggestion (because he wasn't looking at his heli and was trying to remember) for moving it in, I decided to start with moving it out:



As you can see, at center it is now less than 90. Before with the round horn, it was more than 90:



But it is approximately 90 for most of its travel now:



With the horn in this position, I did start to see wag with increased gain (wasn't seeing any wag before), and was able to reduce the gain down to 43. Above that and the tail started wagging. Blowout on climbout is still present (argh!), but minimized further still now -- now only blowing out about 1 inch or so.
05-30-2008 05:46 PM
 
 
kcass518
Veteran
Location: Manhasset, NY - USA

NMRS,

Since you're still having issues, I'll measure my ball link tonight and post the real distance tomorrow morning around 10 when I get in to work. I don't want to be giving you inaccurate information. Looking at your photo, I'm pretty sure my ball is closer to the center. I'll try to post a photo. I'm not saying that this is the right answer, but the guy who set up my TRex is an incredible heli pilot and was the heli-guy at our LHS for years. I think that moving the ball closer to the center allows you to increase the LIMIT pot which gives you higher resolution - it allows you to use more of the servo throw for the same result.

One other thing to check (academic, but I'm not sure if it was covered) is your REVO MIX screen. All values must be at ZERO. REVO causes the heli to drift in one direction when going up, and the other direction when dropping down. Also, are you jamming the throttle stick to full when lifting off? I've found that when I push full throttle quickly that my TRex will twist a little in one direction, but it's very brief and just caused by the sudden acceleration, so I ignore it.
05-30-2008 05:55 PM
 
 
nmrs
Senior Heliman
Location: Austin, TX

Quote 
One other thing to check (academic, but I'm not sure if it was covered) is your REVO MIX screen. All values must be at ZERO. REVO causes the heli to drift in one direction when going up, and the other direction when dropping down.

REVO mix is at zero. Thanks for the suggestion though.

Quote 
Also, are you jamming the throttle stick to full when lifting off? I've found that when I push full throttle quickly that my TRex will twist a little in one direction, but it's very brief and just caused by the sudden acceleration, so I ignore it.

This sounds exactly like what I am seeing (I'm not jamming collective on liftoff, but from steady hover). At first it was twisting out 3 - 4 inches. With the current setup, its twisting about an inch. As soon as I reduce the acceleration it pops back to where it was before I jammed the collective, so gyro seems to be doing its job -- it knows where its supposed to be and gets it back there as soon as the acceleration is removed. Maybe I am being too nitpicky. Maybe what I am seeing is standard behavior. I haven't held a sustained ascent (keeping throttle all the way up) to see if it restores itself in the middle of the climb as right I'm too scared to let the heli get that far away from me. So the longest I have held a full pitch climbout is 3 or 4 secs.
05-30-2008 06:06 PM
 
 
Blade_Master1
Key Veteran
Location: Canada

The top picture the servo arm looks good
if you want to use the round servo use one of the offset holes you can get a perfect 90*
plug the servo directly into the RX with 0 trim and center the horn

I prefer Finless bobs way of set-up but to each his own
I don't fly scale and I don't fly in rate mode always in HH

for that 1" of travel raise your gain a little more you should be able to get it under a 1/2" on my trex450 it is actually 78% on my Raven I have it set to 94% and it holds well in a climb out and while doing loops

get away from using throtle curves on an electric use a flat line

set your governor to soft start
enable throtle hold
when you land (touch ground) hit the throtle hold it will be your start stop switch
set normal mode for 85% ESC will get very warm battery will be somewhat warm
Idle1 up1 for 90 - 95% less hot ESC battery very warm
idle up 2 set 100% throtle luke warm but battery hot

IMO just do it the Finless way

JM2C's :)
05-30-2008 06:33 PM
 
 
kcass518
Veteran
Location: Manhasset, NY - USA

Hmmm... To me, a drift means that the heli is rotating very slowly in one direction and doesn't come back unless I give it opposite rudder. I've had that problem on my Evo 50. If you're just getting a momentary shift when popping the throttle, it indicates to me that the tail rotor servo or gyro isn't keeping up with the throttle. Mine does that too, but I ignore it. I don't go from a dead-stop to full throttle in normal forward flight, so I don't think it affects my flying. It is possible that you're expecting too much precision, although these machines are pretty accurate. I'll be interested to know your conclusion. Oh, also (again, if it hasn't been mentioned) make sure your tail slider and pushrod move very freely, and that there is no slop in the pushrod, the ball links, or anywhere else. With my 450, the instructions showed setting up the tail pushrod with Z bends instead of ball links, and I can imagine what problems that would have caused.

As an aside, for my bigger nitro heli I use the method of mechanically getting the tail to hold in Rate Mode, and then setting the Limit, etc. But, for the TRex 450 I center the tail slider with all arms at 90*, and adjust the Limit so that I get full travel to right and left. They're different animals.
05-30-2008 07:00 PM
 
 
nmrs
Senior Heliman
Location: Austin, TX

Quote 
on my trex450 it is actually 78% on my Raven I have it set to 94% and it holds well in a climb out and while doing loops

Are you using endpoints to set gain, or is this the gyro sense menu? I was paranoid to go much above 60% gain (endpoints which I think pretty much equate to actual gain percentages), but maybe I should just relax.

Quote 
if you want to use the round servo use one of the offset holes you can get a perfect 90*
plug the servo directly into the RX with 0 trim and center the horn

I'll give that a try. I've redone my whole tail setup about 6 times in the past few days. What's another go?

Quote 
IMO just do it the Finless way
I think I pretty much am, but will go back and watch the video again to see if I am missing something.

Quote 
Oh, also (again, if it hasn't been mentioned) make sure your tail slider and pushrod move very freely, and that there is no slop in the pushrod, the ball links, or anywhere else.

Yes, everything looks good from this perspective.

Quote 
It is possible that you're expecting too much precision, although these machines are pretty accurate.

This is probably right on. I was definitely having real problems before with actual drifting as you define it:

Quote 
To me, a drift means that the heli is rotating very slowly in one direction and doesn't come back unless I give it opposite rudder.

With all the great advice I've received in this thread, I've eliminated that drift. Now just seeing the tail kick out on climbout, then recover when the throttle is reduced. I'm gonna give Blade's suggestion a try, and try one of the offset holes on the round horn and compare that to what I have now. If it's worse, I'll go back to what I have. If it's better, great. In either case, I'm heading out to the flying field tomorrow, so I can have one of the more experienced guys look at it and tell me if I am just expecting too much precision and should just leave it alone.
05-30-2008 07:44 PM
 
 
Blade_Master1
Key Veteran
Location: Canada

good call going to the field live help usualy clears up things more

I use the gyro sense menu

when you use the offset hole just center it like I mentioned by plugging directly to the rx and center the tail slider adjust the servo travel using your gyro you should be in the 90% range.

your gyro gain can go very high keep raising till it starts hunting
then back it down maybe 3-5%

bring to a hover "check" no hunting land
raise 5% bring to a hover "check" no hunting land
kepp doing this till its starts hunting
bring to a hover, starting to hunt, land lower 2%

gyro hunting looks like a short fast wag

.

JM2C's :)
05-30-2008 09:50 PM
 
 
nmrs
Senior Heliman
Location: Austin, TX

Blade, I did just as you said. Used offset hole and it lines the bar up pretty much perfectly at 90. Gyro limit is now just under 100 -- reaches to each end to almost binding but not quite. One thing -- when the servo is centered, the ball isn't centered over the middle of the servo hub anymore when using the offset hole. It's a little to the left, or if I try and rotate the horn to the next notch, it's too much to the right. I could use subtrim to center it, but I don't think you're supposed to use subtrim with a gyro. Is that correct? Or is it just trim you don't want?

It's a little windy right now, so I can't really tell if the tail is hunting or being blown by the wind and correcting. I'll try again tomorrow morning at the field with help from one of the other guys. Maybe they can distinguish between hunting and wind (I can't seem to).

The tail is not drifting anymore as long as I have the gain above 50. If I drop it to 40 it starts drifting left again. I'm not sure if this is from the wind or not, but if I raise it to 50 it stops drifting. No matter what I set the gain to (well I tried a few values between 40 and 65) I am seeing the same slight wag (as I mentioned, I can't distinguish between gain induced wag and wind induced wag).

I did put new plastic tail blades on and couldn't tell any difference before or after, so I guess the dings weren't making a difference. Haven't tried CF tail blades, so not sure if they make things better.
05-30-2008 11:31 PM
 
 
Blade_Master1
Key Veteran
Location: Canada

no sub trim and no trim or it will cause drifting

when your gyro is working well wind will not cause it to wag

servo horn and tail slider both have to be centered together
adjust long rod accordingly

plug directly into RX to do this (easier)

raise gain the wind should not affect tail

put nose of heli into the wind this will help

don't fly in strong wind till you are comfortable

JM2C's :)
05-30-2008 11:55 PM
 
 
nmrs
Senior Heliman
Location: Austin, TX

Quote 
servo horn and tail slider both have to be centered together
adjust long rod accordingly

Even with the rod disconnected, when the servo is centered there is no way to get the ball centered above the servo since the horn wheel is notched. One notch is too far left, next notch is too far right. Is it just the offset wheel I chose (left side hole above the 1). Should I try the right hole or the ones above 2, 3, or 4? Which offset hole do you use Blade?
05-31-2008 01:17 AM
 
 
Blade_Master1
Key Veteran
Location: Canada

just keep moving the servo horn around one of the off centered holes will line up there are 8 holes one of them will



.

JM2C's :)
05-31-2008 01:34 AM
 
 
nmrs
Senior Heliman
Location: Austin, TX

Found a hole that lined up perfectly. Everything looks mechanically good now. Long arm to ball to servo center looks to be exactly 90*. Now to get a little help fine tuning the gain tomorrow morning and I should be all set.
05-31-2008 03:16 AM
 
 
Blade_Master1
Key Veteran
Location: Canada

I don't know if you are aware
don't lengthen the tail rod too much, you can also slide the servo back on the tail



ps ignore the dates i didn't bother setting up camera

JM2C's :)
05-31-2008 03:31 AM
 
 
Blade_Master1
Key Veteran
Location: Canada

use your gyro menu keep it simple



JM2C's :)
05-31-2008 04:02 AM
 
 
kcass518
Veteran
Location: Manhasset, NY - USA

Yup, each quadrant of the servo wheel is slightly different. You did the right thing there.

Per my posts yesterday, here are photos showing my tail servo - the ball is only 6 mm out from center which is what our local pro set it to. It may or may not be the right thing to do considering the different opinions here, but I do know that the distance the ball is from the center also affects the amount of gain you need. I use the GEAR/GEAR channel, not the gyro sense menu, and my gain is at 60%. I could probably increase it, but have never tried because it works fine the way it is and my time is limited when at the field. I hope this helps. I'm also interested in hearing about your results. My feeling is that all these helis are made the same, and if they have the same gyro, servo, radio, etc, the setting should be the same, too, but I guess that with so many variables there is a lot of room for differing strategies. One thing I will say is that on the DX7 you are able to have different trim settings in each flight mode, and that bit me once. I had inadvertently moved the trim in Idle Up 1 once, and every time I flew, the gyro would drift and I couldn't figure out why. When trims were the same in all three flight modes (all centered), everything was fine again.

05-31-2008 03:31 PM
 
 
nmrs
Senior Heliman
Location: Austin, TX

Took it out to the flying field to day and got everything flying well. Was wagging at 50 and felt a little loose at 45, so now its at 48 and seems nice (using gear channel, not gyro sense). Heli is still in the car, but I'll get out the calipers when I bring it back in and measure the distance from servo center to the ball.
05-31-2008 07:14 PM
 
 
kcass518
Veteran
Location: Manhasset, NY - USA

Great! If it works, that's the answer. I would like to know if it's true that my ball link is too close to the center, but I'll do my own testing by increasing the gain some time soon and will let you know what I find out.
05-31-2008 09:17 PM
 
 
rexxigpilot
Senior Heliman
Location: florida

I gained 20 lbs last year, It was too much
06-01-2008 12:33 AM
 
 
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HeliHobby . Ron’s HeliProz South . Century Helicopter

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Beginners Corner > how much gain is too much?
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