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HelicopterThunder TigerOther › R50 Pitchy in FFF
05-03-2005 08:01 PM  12 years agoPost 1
ChristianM

rrVeteran

Oslo, Norway

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Hi

I have been struggling with pitchiness on my Raptor 50 for a while. In FFF it wants to pitch nose down. Likewise, if I let it drop in a knife edge or death spiral it will tend to roll inverted. The problem becomes more pronounced the faster I fly. Anybody else have this issue? I have tried various flybar paddles and I am currently using the stock paddles drilled out so they weigh 20 grams (same weight as the TT lime green paddles). I love the cyclic rate that they give me and they are less pitchy than the KSJ paddles but the pitching is getting old. I have removed almost all slop from the head so the control linkage is very stiff. Has anybody any tricks or solutions to sort this out?

My setup is as follows:
R50 with OS50 SX-H, MP2 and RevLock governor
Quick UK R50V2 metal head with blue dampers
Quick UK swash plate
TT 600mm carbon blades
Metal blade grips
Stock paddles Dremmeled out to reduce weight (20 grams each)
Head speed: Normal=1600rpm, Idle-up1=1850rpm, Idle-up2=1950rpm
Pitch: ±10 degrees
Futaba S9252 servos on the cyclic and collective



Thanks,
Christian

Burn fuel, be happy

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05-03-2005 08:45 PM  12 years agoPost 2
Wa11banger

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Huntsville, Al

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My model seems to go in and out of this scenario between crashes lol.. But I just received an email from a friend today about this very subject. I do not know who the author is but kudo's to them/him/her for the findings, it is something I am going to try for this weekend on both of my 50's
have finally solved my pitchyness with my white MinAir 20g paddles on my R50V2 (this may also affect R30V2's too as I believe the mechanics are the same in this area).

The problem was not the paddles at all, although because they are more 'powerful' they tend to show the issue more than the stock paddles do.

The root issue was that I had the length of the 'elevator idler rod' a bit too short. The manual calls for it to be 66mm, ball center to ball center. I think it should be closer to 67mm ball center to ball center.

By the 'elevator idler rod' I mean the rod which goes between the elevator arm (pitch arm) and the elevator idler arm (which is the arm at the collective tray pivot point, between your elevator servo and the elevator arm).

I carefully measured the distance between the bearing of the idler arm pivot point and the center of the pitch arm pivot point and came closer to 67mm on my R50V2. The manual calls for the rod to be 66mm here. By using 66mm (or anything shorter), the geometry is not correct and you will induce tiny pitch changes to the swash plate at full positive and negative collective. This is what causes the pitchyness when doing fast forward flight!

If this rod is too long, you may get a similar but opposite affect that I did. My R50V2 pitched down with full collective fast forward flight.

By making the elevator idler pushrod dimension 67mm from ball center to ball center, all of my pitchyness in fast forward flight has gone away and my R50V2 is much nicer to fly now!

FYI, the stock paddles show this problem also, but since they make the heli more stable, they are simply much slower to react to the problem, so many pilots may have this geometry problem and not even know it. Unless they were 'smarter' in setting up their mechanics than I was!

The white MinAir 20G paddles are much more aggressive and and show this issue quickly!

So shame on me for not checking this dimension earlier! The difference between 66mm and 67mm is not really noticable by eye in the geometry of the mechanics (or at least me eye ). However the difference in flight responce is dramatic IMHO.

I found this problem when a friend loaned me his paddle pitch guages which happen to have bubble levels on them. I noticed that my paddles where changing elevator pitch (for/aft cyclic) ever so slightly when I changed my collective from starting at zero pitch (centered) and going to full positive or full negative collective.

Check your geometry on this rod to ensure that your R50V2 (and probably the R30V2 also) to be sure that you're not missing out on some better rappy flight performance.

I don't know if this dimension is the same on the V1 machines as I don't have one to check right now.
Hope it helps
Rick

Proud member of the Quick UK, Duralite Flight Systems, V-Blade, & KBDD team

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05-03-2005 09:50 PM  12 years agoPost 3
ChristianM

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Oslo, Norway

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Rick, thanks for forwarding the e-mail. I will check the length of the link referred to in the mail. However, the fix you describe in you post should only affect forward and backward flight and since these symptoms are also showing up when flying sideways (knife edge drop) then I suspect that there is another issue going on also. I believe the flybar is too powerful so it overcompensates. I would like to experiment with the flybar ratio but that's not so simple with out access to a machine shop.

TT Helis
The picture is a bit old and I have since changed out the auto hub in the picture with the white one from TT.

Thanks, keep your suggestions coming.

Christian

Burn fuel, be happy

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05-03-2005 10:29 PM  12 years agoPost 4
Jose AB

rrApprentice

Miami,Florida, USA and Dominican. Rep

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What paddles are you using ?

how high exponencials do you have?

Jose

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05-03-2005 10:57 PM  12 years agoPost 5
ChristianM

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Oslo, Norway

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Jose AB

I am using the original Raptor paddles drilled out such that they weigh 20 grams (same weight as the TT lime green paddles) and covered with shrink wrap. I am using 25% expo, but it is not a sensitivity issue on the stick. I have to pull back on the cyclic in FFF to maintain level flight.

Christian

Burn fuel, be happy

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05-03-2005 11:05 PM  12 years agoPost 6
Jose AB

rrApprentice

Miami,Florida, USA and Dominican. Rep

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I had the same prob with one of my raptor 30 and I just put it away for a wail. Then changed paddles, blades , washout, hub, and a couple of parts.
Then took it out last week and everything was ok. I really Don t know what part did it .

Jose

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05-04-2005 12:13 AM  12 years agoPost 7
hornet dave

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Cedar Rapids, IA USA

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paddles out of alignment would do exactly what you describe.

I got a fever! The only prescription is MORE 6HV

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05-04-2005 01:49 AM  12 years agoPost 8
drdot

rrElite Veteran

So. California, Orange County.

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HI..

Hornetdave hit it..

Paddle alignment is the #1 reason Raptors get a bad "rap" for weird and pitchy behaviour...I set mine with bubble levels attached to X-acto plastic modeling clamps...Get them within a 1/4 bubble of level and all the problems go away. (assuming you do not have geometry issues...)

John.

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05-04-2005 01:51 AM  12 years agoPost 9
Ted Toth

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Myrtle Beach S.C.

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drdot great idea very cool I like simple
do you shim the level due to the pitch of the paddle?

.

You don't stop laughing because you grow old, you grow old because you stopped laughing.

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05-04-2005 04:04 AM  12 years agoPost 10
ChristianM

rrVeteran

Oslo, Norway

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Wa11banger,
I measured the 'elevator idler rod' with digital calipers and I too determined that it needed to be 67mm and not 66mm. I measured the rod and it was almost the right length (luck I guess). It only needed one turn of a link to bring it exactly to 67mm.

drdot and Ted,
I did check my paddles and they were slightly off. I used my pitch gage sighting against the flybar arms and noticed that one of the paddles was maybe 1 degree off. I hope that this does the trick. I don't think I will have the time to fly before the weekend but I will report back then on how she behaves.

Thanks for the help.

Christian

Burn fuel, be happy

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05-04-2005 04:54 AM  12 years agoPost 11
Wa11banger

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Huntsville, Al

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I hope any or all the ideas brought out in this post help.. I too am investigating them.. My paddles are spot on, so no worries there but I have not checked the travel or change at full range with my idler link at 66mm

Proud member of the Quick UK, Duralite Flight Systems, V-Blade, & KBDD team

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05-04-2005 05:34 AM  12 years agoPost 12
TurboStew

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Ft Collins, CO

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Let me tell you about this. I do not want to start a long debate about bell-hiller ratios but, I have played alot with this on R50 heads, both big-blocked 690s bladed R50 heads and stock heads with 600s and my conclusion is as follows.

The reason for the pitching down is a flybarless head wants to pitch up because the advancing blade gets more lift than the retreating blade, and because the lifting effect happens 90 degrees later, the heli pitches up. A flybar counters this. Because the flybar has no "collective pitch", the advancing paddle hits the air in FFF with "negative pitch" (relative to the wind) driving it down. This cancels out the pitching up of the main rotor. This is a good thing until you get a flybar system with too much sensitivity, which overpowers the main rotor in FFF causing pitching down. The R50 has a 1-1 bell-hiller ratio, which is on the high side (most helis have less hiller). The trick is too move the top mixing arms in 3.5mm on the see-saw lowering the hiller ratio. You must drill and tap the flybar see-saw to do this. I have suggested this to several local people and all pitch down problems have been cured. You can also use heavier paddles, but at the expense of cyclic rate.

Just an observation,

8.5 pound 90 birds Rock!

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05-04-2005 05:38 AM  12 years agoPost 13
Wa11banger

rrElite Veteran

Huntsville, Al

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I do agree with what you are saying and somewhat understand it. I have seen helis with this mod fly and they do fly well.. But there are 4 rappy 50s at our field all built and rigged out with bling basically the same.. 1 of mine pitches down.. 1 does not.. one of the other guys pitches down.. the other guys does not.. I believe that your conclusion will help but it is not the root cause.. If I have 50% that do and 50% that dont.. all with the same hiller ratio, the ratio mod can be a aid but is not why it is doing it

Just my .02
Rick

Proud member of the Quick UK, Duralite Flight Systems, V-Blade, & KBDD team

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05-04-2005 02:46 PM  12 years agoPost 14
ZZ3Astro

rrVeteran

Panama City, Fl

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I posted about this problem some time ago.. What I've found is the combination of TT Carbon blades and stock paddles seem to do this. I also had mine drilled out to lighten and I think for some reason it amplifies a problem with the CG of the stock paddles. Solution? Green paddles... my greens are about 3 grams lighter than the drilled ones and no pitching down like before. Also I moved the drilled paddles to my second Raptor 50v2 with V2 VBlades and I don't see much if any pitch down tendency .. so it seems to be the combo above that does it the most. Still, I ordered a second set of the greens and will be retiring the drilled pair. Greens work fine with the VBlades too but I prefer the TT blades.

steve

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05-04-2005 04:43 PM  12 years agoPost 15
KYLE 05

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Houston,Tx - USA

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ChristianM
I have run into the same problem as you have.Solution was go to V-paddles and watch allignment.This was the best balance of fff and quick cyclic responce.I usually run Sab's or TT mains and also make sure everything is trimed in idle-up,etc,etc.KSJ's were way to pitchey and stock paddles were not quick enough(even modified paddles)Well thats my 2 cents,for what its worth,but try the V-paddles I think you will like them.

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05-04-2005 11:51 PM  12 years agoPost 16
PietervA

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New Zealand

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I moved from stock black TT paddles, to KSJ, then MA. Worst pitchiness with KSJ, but even present with MA. Now have slime greens on both machines, and smooth as!

Stock 50V2 head, btw. But obsessively ensured I have minimal play.

Ciao

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05-05-2005 02:43 AM  12 years agoPost 17
ChristianM

rrVeteran

Oslo, Norway

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Thanks for your help guys.

As luck would have it I just received a shipment from Heliproz with green paddles and an OS 50 Hyper I will fly it this weekend first with the modified original paddles I have been using, only aligned again and then with the green paddles so I can test the difference. Hopefully this will resolve the issue. If not then I will try the V-paddles or modify the flybar carrier to reduce the flybar ratio as TurboStew suggested. I read somewhere that Allan Szabo was using this mod also. I will report back on how it works out.

Christian

Burn fuel, be happy

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05-11-2005 06:24 PM  12 years agoPost 18
ChristianM

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Oslo, Norway

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Progress
I finally had a chance to fly yesterday. First I flew the original modified paddles and the tracking has improved noticeably . When I did the knife edge fall it no longer tried to roll inverted so it tracks a lot better now. Then I changed to the green TT paddles but I did not notice any difference between them and my modified original paddles. They are the same weight and geometry so I guess I'm not surprised. You can see the template (PDF file) that I used to cut out the paddles at the bottom of my gallery.

However, I am still not quite satisfied with how it flies. The heli is perfectly trimmed out when there is no wind, but when I hover with the nose into the wind then the heli rolls to the left. With the tail towards the wind then it rolls to the right. I found this tread (Always falls left of oncoming wind) where this issue is discussed. I will try to modify my flybar carrier to reduce the flybar ratio and also play with the delta offset. Thanks for all your help.

Christian

Burn fuel, be happy

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05-16-2005 03:24 AM  12 years agoPost 19
kaptkaos

rrKey Veteran

Miami FL

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As far as that 66 MM linkage....are you sure the other one was 86 MM?

If you give a Chimp a gun, and the Chimp shoots, DONT BLAME THE CHIMP!!!!

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05-16-2005 03:52 AM  12 years agoPost 20
kaptkaos

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Miami FL

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Im getting elevator pitchyness myself.

I check my linkages, and the one you mentioned is at 66 MM but the one going to the servo is 82 MM instead of 86 MM. Does anyone think this will make a difference?

I also have my linkages on the outside ball on the see-saw arms.

I read on Raptor Technique that a rearward CG will cause pitchyness in FF, but I have a forward CG.

I have the TT White paddles on it. I have had this pitchiness with TT CF 600 and TT Woods.

If you give a Chimp a gun, and the Chimp shoots, DONT BLAME THE CHIMP!!!!

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HelicopterThunder TigerOther › R50 Pitchy in FFF
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