View Full Version : FB Atom 500 - Asymmetrical Pitch values
06-16-2011, 09:41 PM
For some of you here in this forum, my dilemma is probably a no-brainer. But, for me, it's been a challenge, a head scratcher. Using the AFR values for aileron, pitch, elevator, Mixing Arms positioned downward 5 degrees, the basic linkage lengths listed in the last version of the assembly manual, and, with no subtrim on Futaba S9650 servos, I get +12, 0, -14 for the pitch range.
I've tried raising and lowering the swash to see if I could get symmetry, with no result. Currently the base of the swash is at 11 mm from the bearing block. When I did get a +13, -13 pitch value, the value at mid stick, with a linear pitch curve, was +3.. Turning the pitch link on the grip to achieve 0 degrees at mid stick, only resulted in lowering the positive pitch and increasing the negative.
Can anyone advise on what I may be doing wrong?
Thank you for your consideration
06-16-2011, 10:27 PM
you are on the right track I think you just did not do things in the right order.
try re-centering the swash
then re-set 0 pitch at mid stick
then take your pitch measurements
make sure the pitch curve you are using for set up is 0-25-50-75-100.
some guys run 0-50-50-50-100 for set up as you are at mid stick(for 0 pitch)everywhere but the extreme ends.
double check your radio for no mixes,trims or anything out of the ordinary
dont worry we'll get this straightened out:)
06-16-2011, 10:54 PM
Thank you for your swift offer to help. The are no mixes, trims, expo, nor subtrim. During setup I did use the 50, 50, 50 to check at mid stick, but used a linear pitch curve when checking the range.
Forgive my ignorance, but when you say, "try re-centering the swash", what do you mean?
06-17-2011, 11:13 PM
Ok, "fenderstrat"... I centered the swash anti-rotation pin in the anti-rotation guide using a 50% pitch curve all around. Result? Same as before: +12, 0, -14, using a linear pitch curve.
Not wanting to spend much more of my "Golden Years' trying to find a solution to a problem which Atom owners don't seem to have, I went on to make the pitch symmetrical, +12, 0, -12 using the Pitch AFR and an altered pitch curve.
Thanks for your initial help.
06-17-2011, 11:16 PM
Are the links attached to the upper mixer arms at a 90 degree angle to the arms?
06-18-2011, 12:07 AM
'Not wanting to spend much more of my "Golden Years' trying to find a solution to a problem which Atom owners don't seem to have, I went on to make the pitch symmetrical, +12, 0, -12 using the Pitch AFR and an altered pitch curve."
No dont do that that that will cause problems later
when I say "adjust the swash" I mean change the distance from the servos to the swash by adjusting the 3 links from servo to swash.you will not need too many turns.then reset 0 at midstick and procede from there.
You are not wasting anyones time.I would much rather see your heli set up CORRECTLY,then covering up the issue using your radio
06-18-2011, 12:12 AM
This is how the link looks at mid stick, 0 degrees, after the change to the AFR pitch and altered pitch curve. No, it's not quite 90.
06-18-2011, 12:18 AM
The upper mixer arms are down at too sharp of an angle. Try setting them so that the links connected to them are at 90 degrees to them and check pitch again.
06-18-2011, 12:19 AM
cool a picture really helps,now we are on the right track:)
06-18-2011, 12:21 AM
Thank you for your support, but, I have raised and lowered the swash by turning the 3 links, more times than I can remember..(on second thought I have the notes) LOL At one point I couldn't go lower because I couldn't turn the pitch servo link in any more. The results were all the same- uneven pitch.
06-18-2011, 12:25 AM
Man, I'm behind your responses...
@Bum...I'll start all over again tomorrow to make sure of the 90 degrees and report back.
@fenderstrat..."A pic is worth 1000 words". Cell phone pic - Evo 4G
06-18-2011, 12:28 AM
@ Bum and fenderstrat
Do I get to 0 degrees at mid with the mixing arm linkage or the grip pitch link?
06-18-2011, 08:27 AM
@ Bum and fenderstrat
Do I get to 0 degrees at mid with the mixing arm linkage or the grip pitch link?
If you can, use the grip linkage to maintain that 90 degree geometry of the links relative to the mixer arm. If not, it's OK to use the other link.
06-18-2011, 09:52 AM
just a thought but are your EPA's all at 100 for both directions of travel?
also when you were raising and lowering the swash did you re-set 0 pitch each time then check your range??
just so we are on the same page,even if you only move the swash links 1 turn you have to re-set 0 pitch at mid stick THEN take your blade pitch measurements.
you cant adjust the links then measure pitch.if its NOT this.we will have to start looking elsewhere.Stuff like this drives me nuts and its not even my heli..LOL..we WILL get this
06-18-2011, 12:12 PM
As Alan said your mixer arms are on a too sharp angle. Make sure when you are at midstick that the bottom side of the mixer arms is approximately level with the flybar, as mentionned in the manual.
06-18-2011, 07:06 PM
"Bum", fenderstrat, DFlyer... Sorry for the delay, but I have been "piddleing" with the 500 for about 5 hrs, and, I continue to scratch my head.. My nose has been so buried in this heli (because of your support) that the wife got ticked that I was focusing solely on this, so she marched off to gamble at the casinos in Atlantic City.
Thank you again for your keen observation and suggestion that I manage the geometry. Before redoing the geometry to get the 90 degrees @linkage to mixing arm, I set servo to swash linkage lengths and swash AFR percentages for Aile, Elev, Pitch, as per manual.
I tried everything combination of Mixing Arm linkage length to Grip pitch linkage length to arrive at the 90 degree geometry. Each combination mysteriously resulted in +12, 0, -14. After depleting both my Tx and Rx battery and, replacing them, I tried one more time. Result - + 13.7, +1.5, - 12.2. (see pic). My experience has been that if I now bring the grip down to zero by turning the pitch link in, that will result in bringing the pitch at full stick down.
Yup....EPA's are at 100 in both directions. And, yes, I did reset for zero pitch at mid. Each time I did that, I lost positive pitch at full. If this is driving you nuts, then, you better join my wife in Atlantic city. LOL
Thank you for sharing your expertise.. I tried doing as per the bum's suggestion. I hope I didn't go way past the 90. If I did, blame it on my eyesight.
To all.... I have been reading your instructive posts, along with AhClem's for over a year in this forum. I want to doubly thank all of you for the time that you are investing in this matter. HAPPY FATHER'S DAY!
06-18-2011, 08:54 PM
if you were losing positive pitch at full,did you then adjust the links the other way?I am assuming yes
so if your epa's are 100,your pitch curve is 0-50-100,the pitch setting in the swash menu is allowing for full travel.and the head is set up right,what are we not seeing?????HHHMMMM,this one is a head scratcher.
one time I was having a set up issue and it was because I was thinking that my normal curve was 0-100 but I was setting up in throttle hold which had a different pitch curve.LOL I wasted a bit of time on that one.
I'm really out of ideas on this one.
Don't give me any excuses to go to AC, its only 90 min from me and some blackjack sounds like fun right now
06-18-2011, 09:11 PM
Out of ideas? Not a problem.... If I set up the mixing arm geometry at 90 by the means I mentioned before, I invariably got more positive pitch than negative. That was good, but, to get to zero at mid stick with a linear pitch curve, I would have to lower the grip (turn in on the link), resulting in loss of the positive pitch, i.e., +12, 0, -14.
Right now I'm at +13.7, +1.5, -12.2 after a combination of 1/2 turns on the links....LOL I may just have to go back to the Finless Bob work around for uneven pitch range
06-18-2011, 09:28 PM
I still think we are talking about 2 different things here.
if you say you have +12 0 and -14 then you adjust the links FROM SERVO TO SWASH,in the negative(sorry had to fix it) direction 1 deg then reset 0 pitch at mid you should get +/- 13.
the fact that you are off by even ammounts tells me that the set up is correct,its your 0 point of the swash that needs adjusting,am I making sense?
if you have say 26 deg total.if the swash is correctly in the middle you get 13 and 13.if the swash is one deg either way you get 12 and 14.again the total movement is correct and remains the same only the 0 point of the swash is different.If you were getting say -5 0 and 11 then there would be something off.but your travels seem even
06-18-2011, 09:49 PM
"the fact that you are off by even ammounts tells me that the set up is correct,its your 0 point of the swash that needs adjusting,am I making sense?"
Ok.. I understand what you're saying. And, no, I didn't want to move the swash up or down to keep one variable consistent. At +13.7, +1.5, -12.2, you've given me something to work on. I'll report back.
06-19-2011, 04:15 AM
From left field...just make sure if you have a hover pitch trim on the Tx it is set to zero.
PS Make sure when you are checking your pitches the flybar is at right angles to the mainshaft.
06-19-2011, 09:39 AM
You really mean from "Down Under", not from left field. LOL Thank you for your input. "Hover pitch" at zero - check. "Flybar" at right angle to shaft - check. My 66 yr old brain is fried "piddleing with this heli. I'm putting this to the side, and, trying gardening to get back some self-esteem.
At 4:00 am this morning I changed to a new "Spindle shaft. Then, I dropped the swash, turning the servo links one full turn in. Result: LF grip (+12.7, +1, -13.2), RT grip (+12, 0, -14). Subsequently, I went one full turn in on the left grip, Mixing arm linkage. I have again arrived at (+12, 0, -14) for both sides, with no cigar.
Perhaps it's the fault of my Align Pitch Gauge, or, maybe, my geriatric eyes. It could be that the Atom 500 "is just not that in to me". I'll go visit my daughter for a change of pace.
06-19-2011, 11:02 AM
now you really have me confused,you should be getting the same readings on both grips,something is not right
If you are moving the swash and re setting 0 pitch at midstick,your values HAVE to change one way or another.I dont see how you are moving the swash and still getting 12 and 14
06-19-2011, 05:45 PM
Hang in there yank, I'm 69 and looking after the grand kids at present. Do I need a rest!
You can cheat and change your endpoints until you can start again.
I have always found the level of the mixing arms at mid stick to be the critical thing. Get those spot on and everything falls into place and hang on, I feel a senior moment coming on. Just one more thought. The servo arms angle to the links needs to be 90 deg. When I first set up my Atom I set the servo arms parallel to the servo body (horizontal) but then I saw that in fact they needed to be pointing down slightly to get a 90 deg angle to the link to the swash. If they are not correct you will get a different swash movement above and below mid stick.
I'm on a roll. Have you checked you swash for level at high and low stick?
Must go and lie down for a while.
PS Had another look at the photo and your servo arms do not look right particularly your elevator.
06-19-2011, 10:23 PM
Keep at it Roy,
Sorry the PM's did not help!
I suspect when you find whatever is causing the problem it will be something simple that was overlooked.