Variable Pitch goes BIG!!

[SleepyC]

Ok.. I was trying to make this all slick for MAX on the home page, but I can see there in no time.
Heres the shots, I'm hoping KIWI will step in here and explain things.

[Biff]

I think the cat is out of the bag before it really should have been! The actuator assembly is really quite simple. Believe it or not the three blade system works a bunch better, One of the problems with VP is you have to use flat blades. Flat blades like flat wing are not very efficient.

Obviously a wing on a plane would never see high sub-sonic speeds. A prop on the other hand does. The dynamic load of this spinning mass is trying to throw bades in the arc they are spinning. Thatis straight and level flight. Think of a simple 90 degree pull to vert. The load on the system HATES doing that. Much like spinning a bicycle hweel and trying to turn it.

Most of that issue was solved with cromo-poly impregnated Titanium. So the P-factor and progressional loads are within limits. Now for the blade in-efficiency. Keeping a flat blade was almost a given. Enter Emo Krigel. Emo came up with the idea of using blades of a semi sym. construction. With this method,transferring flight loads in the forward flight realm is a far more efficient means. He concentrated on FORWARD flight because reverse is only used momentarily.

Emo was the first guy to grasp the concept that reverse is only used for brief periods of the flight,so he needed to mostly concentrate on forward flight efficiency. As long as the system can handle the momentary shock of a down line stop and sustained invert hover it would work!!! BRAVO all who made this project a reality!!

[flyingklown]

Yeah right....You wished! No way.....I don't believe it!

K L O W N

	Quote: Originally Posted by LeadingEdge
	Variable Pitch goes BIG!! article by: Jeremy "Toro" Billeaudeaux For the first time, a giant scale variable pitch application has been successfully designed, built and flown by a group of modelers from South America. Hailing from Santiago Chile, these engineers have accomplished what was previously thought of as impossible – giant scale variable pitch flight. Pilot, Mario DeSantos states in his thick Spanish accent “ I can’t believe this backward propeller idea actually work”. As a group they were motivated to continue an experiment that had been forgotten some years ago with the new advent of the VPP systems being offered by Hobby-Lobby, and other manufacturers. “Witnessing the foamy do flips around itself was out of my mind” De Santos stated, “We need to do that with glow plane, but how?” That’s where Armand Manillo stepped in. A Mechanical engineer by trade, Armand, already had a design in his head having recently been bitten by the heli-bug. That’s where the brains popped in taking the basic design of a raptor 90-tail rotor system, putting it on steroids and beefing it up for OS 1.40 use. The mechanism itself looks almost identical to the raptor setup, Manillo stated. The exception being the actuator coming off the side and activating the slider via bell-crank instead of a linear system like the raptor setup, also an adaptor to prevent the slider from hanging up on the threads of the Shaft on the O.S. was constructed. Propeller use comes from a custom built fully symmetrical design that obtains +10 and –10 degrees pitch at full deflection. Now for you non-heli guys, a heli hovers at around 6 positive with a whole lot less RPM’s than a 1.40. The whole unit is machined out of T6 aluminum. The 2 machinists that created this masterpiece also have a place in the modeling community. The first an RC car enthusiast has built several custom pieces for his racers, the second a friend of Armand’s is a fellow heli-guru that operates at the same club as Armand. Both of these guys wanted to witness something spectacular to be the cutting edge of the RC world. They poured many, many hours after work machining the parts to make this project come to light. When asked about their failures that they had, they said “ too many to list” “We had so many my boss get angry with us for using up all the stock we have.” When faced with these difficult challenges it only drove the urge further for this team to succeed. Faced with countless unsuccessful test flights, the group would re-group, re-gather, and re-build so many airframes time after time. Discouragement set in, but one small success lit the fire underneath the group some months ago. The test bed was an old Hanno Prettner pattern ship that had been handed down so many times it had hangar rash from ¾ of the RC pilots in Chile. I even think KIWI had his hands on this one once. They fashioned a rather unfashionable exterior setup on the bird that they were able to get consistent runs with. They were able to taxi, and ground handle backwards, but up in the air was a different story. From forward flight they would have so much aerodynamic force on the propeller they were constantly breaking components. Until finally they found a system to institute the pitch change more slowly much like a servo saver on an RC car. This was the group’s first success. They were able to stop the airplane in mid air, and allow it to fly backwards for 20 feet or so before it would fall out. With more practice eventually timing was learned and they were able to stop the airplane, put it in a nose down attitude, and through several pitch changes able to keep the airplane upright for several seconds. Eventually they figured out how to back the airplane up with more thrust application and arrived to the point you see here. I must say impressive!!! So where do we go from here? Will we be seeing this on a 40 % soon? Will it become standard issue in the 3D world, or will the next Shootout freestyle be done with VPP? Who knows? But I have my speculation. It was only a matter of time this was accomplished. Having seen leaps and bounds in the electric market, I knew it was only a matter of time to see this on a glow plane. These Chileans have truly set the bar to a new level. Will we be seeing a unit mass-produced soon, perhaps, but unlikely. I would venture to see more testing done on this, and expect to see it in the states in April of 2007. All I know is that this is amazing. Good job Mario, Armand, Caesar, and Carlos. You guys are over the top, and we at the Giants think this deserves a giant tip of the hat. While all of this is coming in is second hand, our friends down south promise to send us more images of exactally how they made this happen. The video below was caught during a recent airshow in Santiago during a noon time VPP demo. Remember where you saw it first... A FlyingGiants exclusive!

[youngflyer]

dude does anyone want to fix the vidd?

[Kiwi]

Guys,

Second time around here on this one. I dont understand the problems with the video link, mine is working perfectly. Marcelo de Huevon has had only the last two weeks perfecting this setup.

He told me in the vertical down line to hover the setup is still a little twitchy and takes some mixing because the torque reaction reverses when you go from + to - pitch.

Biff is also very astute when he picked up the difficulty the boys had with the prop design. Sorry I cannot show you what is actually on that plane in the photo as I have been sworn to secrecy on it.

However I can tell you the blade form changes significantly across the span and is not entirely unlike the VESS design. Of course the other big problem in this design was to get the center of load as close to the center of the prop so the actuator has sufficient force to move it through the +10 to - 10 degrees of pitch.

Again our Techy guru Biff picked up on this early on and was actually a motivating factor in the cross sectional design of the blade. Not being a super techy guy myself it is difficult to explain but in basic english if the c of G of the blade is too far forward the prop wants to increase pitch under load by itself. If the c of G is too far back the prop wants to feather. The forces at say 2000 rpm are managable but at 7000 rpm or so not even the largest RC servo at 3300oz can hold it.

Thus the guys had to compromise a lot with prop efficiency as opposed to effectiveness.

It has been a fine line between success and disaster and of course there has been a fair amount of community service done perfecting this.

Guys trust me on this one. Checks in the mail;!!!

Kiwi

[Disciple]

lol i'm so confused........at least i know this thing exists...whoo hooo....it's almost like the reverse pitch props on small turbo prop aircraft.

[Guillermito]

The photos seem published, the one that appears flying is Marcelo Colombo and the video is of 2 monkeys! ??????

[Kiwi]

Guillermito,

I strongly suspect your computer has the April 1st virus.

Kiwi

[cjbravo]

Kiwi:

Que es eso compadre una foto de marcelo con MI GENESIS volando al reves que Honda LOCO, se que es el dia de los inocentes, pero como tanto y en nuestro evento.......

[Kiwi]

Compadre Cristian.

Una gran abraso y por fin bienvenido a nuestra club virtual.

Que buena los chistes y camaradaria tenemos aqui. Su avione es algo famoso ahora no???

Kiwi

[ShortBus]

You sure thats not a picture of radio lock out??? hehe

[Dennis C]

You guy's are full of ****