suzonka

My Feedback: (7)

setting CG with different hang angle masts, does it matter if the mast is tilted more on one model than on others as far as setting the cg about 2 degrees nose down? some masts are straight up 90 degrees and others are titled 15 to 20 degrees back from the nose. so when you pick up the rotor shaft how should you check the cg say if the tail is pointed way up in the rear if you have an angled back mast where as a 90 degree mast will not have the tail going upwards

floridagyro

The CG for autogyros is referred to as hang angle. The mast tilt does not affect the hang angle. When you suspend the the gyro by the rotor blade attach point the gyro should tilt down about 10 degrees. However, the rotor head should be positive, tilt back, somewhere between 4 and 10 degrees. Also, the engine should have a down thrust of at least 5 degrees.

Phil

mnowell129

I ignore the fuselage. My method is to make the
rotor mast hang vertically plus 2 more degrees nose down
from that. I don't even look at the fuse.
mickey

suzonka

My Feedback: (7)

Thanks Gys for the information, Ill email you a short note .

robobart

Ok, I am still trying to figure out the "CG" for autos. The Mfgr said "12-14 degrees hang angle". In the airplane world, the "Neutral Line" is usually through the CG, and close to parallel with the elevator-engine (Exc. "T" tails) line.
I was expecting the plane of the rotor to be tilted up by the "Hang Angle", but I am beginning to question this presumption, maybe the "Neutral Line" is down by this amount when the rotor hangs level?????

Then the engine thrustline is down from the N.L. by the downthrust spec??

Excuse My Confusion, but I suspect herein lies the key to the major differences between Helis and planes vs. Autos......?????
I boil it down to, What is the referance line for autos?????
Since the elevator is the largest fixed flying surface (Exc for the huge profile fuse of the 2D), it would seem to be the best common referance line to use????
Robobart

floridagyro

Hi Robobart,

To determine the hang angle for the 2D without the print can be a little confusing because of the fuselage shape. The directions are to tape the full size drawing to the wall and suspend the gyro by the rotor shaft and it should match the drawing.

If you don't have the drawing, you can draw an imaginary line just under and parallel to the bottom of the windows. This line should pitch down approximately 12 degrees with the gyro suspended by the rotor shaft.

Hope that helps.

Phil

robobart

Thanks for the good information, Phil!!!!!!
My windows appear to be stickers, and the line below is not very straight. So, I averaged it out with a straightedge, and my averaged line was within 2 degrees of the elevator chordline!!
The result? When I took the battery off the elevator and positioned it under the throttle servo, Voila!! 14 degrees nose down from horizontal!!!
Per your suggestion, I've ordered blade stock from aerobalsa (SP).
Balancing is old hat, but I am wondering about tip weight?? do you have a spec for how much is added? or, the resultant CG of the blade??
I have been reading about the rotor testing that occurred, and am contemplating making a set of Pitch Shims for testing various angles (Blade pitch relative to plane of rotation).
Being a heli guy, I am resisting the urge to just put a collective servo on..LOL

suzonka

My Feedback: (7)

sounds your on the track, I in the begining had questions,it will all come together ,its a ot different than a heli or airplane.LOL SUZONKA[&:]

ALbert.S

The instructions on my Kellet said the same thing about taping the plans to the wall UGH!!!!
I measured the angle of the top of the pylon on the plans from the horizontal line on the top of the plans and it looked to be -3 degrees The rotor bearing is mounted on the top of the pylon so I just hung the whole thing up by the rotor shaft and put my incidence meter on the top of the pylon and adjusted the weight and balance until I got -3 degrees. Then I took it out and flew. The I added more nose weight and moved rotor mounting until I got -6 to 8 degrees. This is where I have been flying This is my "Hang Angle" The motor has downthrust also probably about 6 degrees

robobart

Ok, I am still hoping for some kind of standard referance line. My "Pylon" is curved, although there is the lateral pivot axis.
How does the pylon line compare to the elevator chord line?
Maybe it's my airplane fixation, but it seems the the elevator chord line should be the common aerodynamic element if there is one?
I would like to think that one could easily get a consistant setup if certain common elements were always used, Ele. chord, rotor disk plane, mast line, engine thrust line, and rotor pivot axis for example. Somehow, it seems the CG point ( Both lenghtwise and vertical) should be significant too.

OK, Feel free to tell me "Shut up and fly the thing" if I am over analyzing the setup. It just seems like if all the elements were measurable, then setup and troubleshooting would be MUCH easier.
Robobart

mnowell129

I'm in a different camp altogether. I put the cg on the mainshaft. I.E. if you hold
by the rotor, the mainshaft hangs straight down, just like a heli.
mickey

ALbert.S

I just took down the plans for the Kellet I will agree if you hang the machine by the rotor shaft the "Hang angle " is the CG. The way mine measures out Hanging by the rotor The center line of fuse and stab is pointing nose down around 14 degrees. I measure from the top of the pylon since the center line of fuse is hard to determine and the pylon is flat and the incidence meter sits there very nice. So if you level the center line of the fuse and stab the rotor will have positive incidence about 12--15 degrees Right??? On the Kellet you can move the rotor bearing assembly back and forth to achieve balance. I moved the servos forward and the batteries and servos and gas tank are all behind the firewall to get the proper balance without adding weight. The motor has about 6 degrees of downthrust also These setting have worked for me My Kellet flies very much like a fixed wing aircraft I get the rotor up to speed with an electric drill and throttle up head straight into the wind and it lifts off and climbs out very nice Landing is much like a fixed wing I do put in some downtrim so when I cut the throttle the nose goes down,Keep the rotor turning, and keep enough throttle to keep the air flowing over the tail so you don't loose control it sets down and then I hit the retract switch which tilts the rotor forward so there is no more lift.

floridagyro

Robobart,

If you use the SG6042 profile blades, you don't need any shims. Mount them flat and they will spin up OK and you don't need any tip weights or you don't need to worry about balancing the blades cordwise. I haven't done that to my blades for years. However, do balance the blades lengthwise.

For your first flight have plenty of down angle when you suspend the gyro by the rotor shaft. It's the same with airplanes, nose heavy fly tomorrow, tail heavy rebuild. Gyros don't have any control if the engine quits and it's tail heavy. Also, if you have a lot of power and the gyro is tail heavy it will ground loop real fast, and I also like to set some down trim on the first flight and retrim after it's flying.

Phil

robobart

EXCELLENT!! Y'all are wonderful!!
I MIGHT try the factory blades once the MDS is broken in, IF the SG have not arrived, and unless you recommend against it??
But aqll the setup seems to be making sense now.
Thanks again!!