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HelicopterMain Discussion › Adjusting Pitch
09-10-2007 01:59 PM  10 years agoPost 1
ddavison

rrVeteran

Brownsville, Pennsylvania

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A discussion came up yesterday about adjusting blade pitch. The question was , when you adjust blade pitch do you do your adjusting on the two long rods up from the swashplate to mixing arms or on the two short links from the mixers to the flybar or blade grips ? Or does it depend on the brand of heli ? Lets hear the opinions and reasoning out there. Dave

DaveDavison,GasGob,WhiplashGas,Spectra,JRXG11MV,12X

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09-10-2007 03:15 PM  10 years agoPost 2
BarracudaHockey

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Jacksonville FL

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It depends and the answer is you can usually do either. The important thing is to make sure the long rods are the same length. I usually do course adjustements with the short rods, fine adjustments with the long ones.

Andy
AMA 77227
http://www.jaxrc.com

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09-10-2007 04:46 PM  10 years agoPost 3
Bugdozer

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Los Angeles, CA

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Adjusting the long rods has half the effect as the short due to the mixing arms. Use the short rods to get close and the long to fine tune. I find myself using the long rods to get blade tracking dead-on as the short may have too much effect on pitch.

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09-10-2007 05:21 PM  10 years agoPost 4
Hughes500Pilot

rrKey Veteran

Anaheim, CA

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I use the short rod only... Because the long rods must be the exact same length... But, I use a turnbuckle to make the adjustment to the small rod. By using a turnbuckle, I can make exact adjustments without going too much or too little.

-Steve

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09-10-2007 06:34 PM  10 years agoPost 5
kangarooster

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Orlando Fl-USA

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Hughes500Pilot,
Where did you get the turnbuckles ?
I had to make my last set and it turned out to be more work than
I intended, but definitely worth the effort.

Ben

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09-10-2007 06:44 PM  10 years agoPost 6
trilerian

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Niles, MI USA

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Where did you get the turnbuckles ?
I am curious to that as well.

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09-12-2007 09:20 PM  10 years agoPost 7
AceBird

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Utica, NY USA

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Adjusting the long rods has half the effect as the short due to the mixing arms.
I don’t see this logic holding true for the Predator. If the bell / hiller mixing ratio is 1:1 then it doesn’t make any difference they both have the same effect.

It is a matter of geometry. When I initially set up my linkages I use a clamp collar that insures that the swash is perpendicular to the mast. Setting one blade level and rotating the mast 360 degrees without the bubble moving will prove perpendicularity. If for some reason tracking is off you should look at both blades and their links and decide what link to move that would improve the bell / hiller mixing link parallelism. For instance suppose that you had to increase the pitch of one blade. Lengthen the link on the side that would make the bell / hiller link more parallel. If you have to lengthen the link more than one turn for tracking than move both links so the bell / hiller link stays parallel.

The direction and ratios may be different for other heads but the key is to keep the parallel and perpendicular relationships on the linkages. Symmetry must be maintained in order to prevent coupling.

Ace
What could be more fun?

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09-12-2007 09:24 PM  10 years agoPost 8
BarracudaHockey

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Jacksonville FL

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Its not the mixing ratio its the arm length from the pivot point.

Andy
AMA 77227
http://www.jaxrc.com

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09-13-2007 02:41 AM  10 years agoPost 9
tlankford01

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Amarillo, TX 79110

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I usually adjust within the radio or the longer arms. Make sure that you turn both equally assuming that you already made sure they were the same length in your original build. I only adjust the short arms if my blades are not tracking properly. You can make fine adjustments with either side that way and they may be minor differences in length of the short arms if that is what is required for tracking.

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09-13-2007 11:16 AM  10 years agoPost 10
Morris

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Hong Kong

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Same as bulldozer, I use the short one to get close and long one to fine tune. I see some of us concerns the length of long ones to be exactly the same. I do not see this a big issue. Step by step, get close by adjusting the short rod, then fine tune the long rod, then check the blade track and adjust the long rod to match. This should be good enough

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09-13-2007 05:41 PM  10 years agoPost 11
AceBird

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Utica, NY USA

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Got me confused

None of the latter posts make sense to me. All the links should be symmetrical. For every link on one blade there should be an equal length link on the other. If you have a good set of carbon blades they will track when symmetry is maintained. The problem is if you are using your eye to maintain the swash and the flybar level you start off with an error. Use something that will make both perpendicular to the mast and you will find setups to be straight forward with almost no need to track the blades.

Ace
What could be more fun?

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09-13-2007 06:48 PM  10 years agoPost 12
Bugdozer

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Los Angeles, CA

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I use a swash leveling tool and a digital micrometer on all my links. With the old Align carbons, tracking is WAY off. Using 325 woodies, tracking in not bad but still requires some adjustments. I don't have any high end carbons but I have never had a pair of blades track perfectly on a symmetrical head.

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09-14-2007 01:18 AM  10 years agoPost 13
skydude

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Gainesville, Florida, USA

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Hughs500pilot???

Hughs500pilot???

--

Watch out all you moles!!! (Vae, puto deus fio)

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09-14-2007 01:39 AM  10 years agoPost 14
oldboldpilot

rrKey Veteran

Southern California

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Hi all,

The long rod from swash to mixing arm is adjusted to set the mixing arms level when the swash is level, the washout control arms are level, and the pitch stick is in mid-position.

The short arms up to the blades are called "pitch rods," and they are used to set blade pitches.

Helis are Man's Defiance of the Laws of Nature - OCHC

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09-14-2007 05:30 PM  10 years agoPost 15
d_wheel

rrVeteran

Deep in the heart of Texas.

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Can anyone show mathematically or graphically where it really matters which one is used? I have tried both ways and can't see any difference...

Later;

D.W.

Gettin old aint for sissies!

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09-14-2007 05:52 PM  10 years agoPost 16
AceBird

rrElite Veteran

Utica, NY USA

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Can anyone show mathematically or graphically where it really matters which one is used? I have tried both ways and can't see any difference...
On the Predator there isn't any, mathmatically or graphically when the ratio is one to one. It varies a little when the ratio is slightly off 1:1.

Oldboldpilot, heads are different on different ships. The predator has the long rods going between the mixer and the swash and short between the flybar and the mixer

Ace
What could be more fun?

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