V22 Osprey build

[BQuick]

I'm experimenting with building an Osprey. I'll share my build with you guys here and let you know how it flies.

I'm building it around two 14-7 three bladed props (master airscrew). I plan to fly it on 3S 2600 lipos with a total amp draw of less than 20 amps.

I'm not using variable pitch blades. The lift will be controlled by motor speed.

Most of the constuction is from 2" pink foam.

I'm going to have 2" of wing rotate with each motor so that I can use them as ailerons in forward flight.

I'd love to hear your comments.

- Brad


This is the main wing with the parts for the motor tilting mechanism:

[BQuick]

This is the wing with the motor rotation parts glued in place:

[BQuick]

These are the fuselage part:

[BQuick]

This is where I currently am in the project. The main wing is glued permanently to the upper half of the fuselage. Tonight I hope to install the servos to move the motors.

[v22chap]

Hey ,,that is starting to look like a V-22 :D Good work looking good ,,keep the pix coming .
The wing /ailerons moving with the motor pods should work fine ,but probably not needed unless you have a system to get the pods to go all the way into airplane mode ,,and then if you do ,,you have to worry about the aileron stick controlling the motors as (yaw) in airplane mode (which is needed with the motors that far out on the wing tips ) And the same stick controlling the regular ailerons (roll ) in airplane mode.There is a little conflict going on there .Now you can probably put some radion mixes in there to disconnect the controls some but it will have to be thought out a little more.
Joe Orlando is working on a TH-2 mixer controll unit for those of us that are into VTOL's and we hope to have this auto change deal in the unit.I will let you know as soon as we find out what it can do .
Good luck on the project
Larry

[BQuick]

Larry,

Thanks for the comments. I'll start off with hovering, just to keep it simple, but I do plan on transitioning to forward flight. I'm hoping I can do all of the mixing in my transmitter, using a switch to switch modes. I do have a V-tail in-the-plane mixer for use with a gyro for roll if necessary.

- Brad

[v22chap]

Brad
I like the pink foam idea ..should be really light and that is the name of the VTOL game
If you do the pod servo linkage right you can do up to 45 degree tilt into airplane mode and have a lot of fun without going all the way over .. Vtolman has proved that .I makes you hover at 2/3 back elevator stick ,,but it can be done.
What radio do you have??
Larry

[BQuick]

I got the pod servos installed tonight. It's tough to get more than 90 degrees of throw so that they can be operated at both positions, but I think I have enough. I'm using full sized servos, so I have lots of torque, so I should be able to yank the pods around without any problem. How much do I need to be able to tilt back from 90 degrees vertical?

I've got a Hitec Eclipse, but I think I'm going to try it on my new Polk transmitter. It has a pile of mixers that can be programmed and activated by switches. It will be able to handle hovering without any problem, but I haven't tried to figure out just how the transition will work.

One thing that will be tricky is that this thing has very little wing area, so I won't be able to "harrier" it (high alpha). I think it will have to fly at fairly high speed in heli mode before it can be switched to airplane mode. The thing that scares me is how to get it back into heli mode?

Well, that's what makes this a fun project.

I try to upload some pictures of the servos installed tomorrow.


- Brad

[v22chap]

tilt back from 90 degrees vertical
Brad ,,I am guessing here as it has been quite awhile since I did my engine vector test bed.. but you're probably going to need 15 to 20 degrees to be able to have yaw and pitch control in a hover and also transition back from 60 degree forward flight .Once you get to this 60 degree forward flight point ,,I have another idea for you to be able to get the rest of the forward tilt for full airplane mode.

Getting back to heli mode is simple ,,nose down 1st ,slow down throttle for a little bit and hit the tilt switch, then power back up to gain hover .it actually is easier than the transition forward .
Yes it has to be fast forward heli mode to gain lift over the wing first.Again start out with nose down, full power heli flight and then hit the tilt switch and adjust elevator to gain level flight again.If the plane CG is to far back it will tend to nose up a lot and still need down elevator.The last one that I show the video of ,,was very nose heavy in airplane mode and didn't need hardly any down elevator ,,matter of fact I thought I wasn't going to be able to pull up enough to get level again.
With that said ,,the other birds could start airplane transition from a 15 ' high hover.Drop the nose 10 degrees hit the 60 degree tilt switch and full throttle climb out and it would level of into a slight nose high climb with in about 100 '
Good luck and have fun Brad
Larry

[BQuick]

I didn't get very far last night. I starting working with my transmitter to see if I could program it. The transmitter has seven cusomizable mixers and I've used four of them already just to control the pod servos. It's beginning to look like I won't be able to do forward flight and hovering both at once without a lot of further thought.

The other problem I ran into was that with all of the mixing, I couldn't avoid having one servo rotate to the point where my linkage went "over center" on the arm that controls the pod. I may change it to a pull-pull sytem that rotates a drum on the end of the pod pivot rod.

Just a small bump in the road.

- Brad

[BQuick]

Here is my latest progress.

The first photo shows how I had the pod rotation set up with pushrods on the servos.

The second photo shows how I converted it to a drum system using kevlar thread.

I've also shown shots of the motor, tail section, and an overall shot.

My dad made me the motor parts and the motors can each develop 20 oz of thrust at 8 amps using the three bladed props.

The all up weight of the plane is a whopping 1 lb, 11 oz. It's a real pig, but the motors should have enough to hover it without any problem.

I got the radio programmed for hover only. I tried to lift off, but I couldn't get it under control. Unfortunately, my drum system isn't quite stiff enough. It would get just to where it was going to lift off, I would make a small correction, and it would spin out of control.

I'm considering cutting it apart and putting the pod rotation servos out at the ends of the wing, then mounting the pods directly to the servos. I'll think about it for a few hours before I go ahead and hack it apart.

- Brad

[BQuick]

OK,

I moved the servos to the ends of the wing and I have liftoff!

I first tried without using a gyro on roll, but quickly determined that I needed one. I installed the gyro, but now I have problems with pitch. I have it balanced at the pivot point. I tried lowering the COG by making the fuse 2" taller, but it didn't help.

It just wants to tip forward or backward.

I've been using some 11-6 props instead of the 14-7 triples.

Any thoughts?

- Brad

[fhhuber506771]

Well... 4-blade props would be scale for an Osprey wouldn't they? GWS makes some nice LIGHT 4-blades. That takes weight off the top in hover-vto mode. (its an idea... not sure if you can get a pair in opposed rotations)

Add the stub wing sections that pivot with the motors. You'll have better thrust vectoring for the pitch axis control You'll also unload the servos controlling the motor pivot a bit if the pivot line is appx 25% chord of the section that moves. This might or might not help your pitch control... but its worth trying.

Got much heli flying experience? You may be simply seeing the inherant instability of a heli hovering in ground effect. Support a barbeque grill's grate a couple of feet off the ground and try barely lifting from that. It should have you out of ground effect. (how to cheat a bit at learning to fly a heli. ;) )

The full scale Osprey has all sorts of computer stabilization assistance...

[BQuick]

Every picture I've seen of an Osprey has 3 bladed props.

I could try the stub wings, but I'm not sure that it will help much.

Yes, I fly a heli that I built from scratch, so I know how it's supposed to work.

Thanks for the comments.

- brad

[v22chap]

Brad,,sorry ,,been away from the house a couple nights ..
Yes the scale bird has 3 blades not 4
I really think part of your problem is the high motor pods.
You will also need a slow older type piezo gyro on the pitch to control it. Vtolman had to find a gyro that would ,,as you rotate it around and around ,,would make the servo move 90 degrees or more and stay there as long as you were rotating it. As the newer gyros will just move it and then right back to the original position . Pitch axis is the hard one to control as you only have small blades and a large moment to control in the length of the fuse.
Larry

[BQuick]

Larry,

Thanks for the reply. I was trying to do it without a gyro for pitch control. I re-read the long thread in muiti-rotors and now I realize I need a second gyro. This is the question I posted in the other thread:

I'm trying to get my mind wrapped around the gyro. When you grab the machine and tip the nose down, which way does the gyro tilt the motors. I would think that it would have to tip the motors forward so that it pushes against the inertia of the props to straighten out the fuselage. Is this correct?

If so, when I push the stick forward, the motors rotate forward. The counteracting force rotates the fuselage back. The gyro doesn't like the fuselage tipping back, so it dampens my original input. Is this correct?


Thanks.

- Brad

[v22chap]

No ,when you tip the model nose down the gyro is suppose to counter it so it would move both motor pods back to keep the bird from wandering off into forward flight.
With such a small rotor area (and even my large rotors )..you really don't have much counteracting forces from moving the pods back and forth. The motors just move back and forth and the fuse tilts very little ,but the control of the motors moving back and forth stabilize the bird or make it move forward into flight or back into a hover or reverse flight about like a heli would look doing the same movements .The only time you are going to see the fuse tilt a lot is when you start to transition really fast ,then you will see it move nose up a lot if you are not already feeding in some down elevator . ... if you have the balance between heli and airplane done right. My first several birds all tilted nose up a lot when I started transition ,but this last one I moved the heli CG back 3/8" and extended the fuse nose by 3 " and it just put its nose down and stayed down,,,I had to counter it with a lot of up elevator to keep from smacking the ground ....if you notice my last vid ...it looks like I almost did ,,, :eek:

If so, when I push the stick forward, the motors rotate forward. The counteracting force rotates the fuselage back
No ,, if you push the elevator stick forward the motors rotate forward and so does the fuse ,,just like a helicopter would do.The gyro will try to counter that ,,but since you have feed in stick control it will ignore it for a little ...this is why you need a gyro that is slow acting and not a Heading hold fast acting return one ,,as it will fight the stick movement to much and make it dance back and forth ,,,much like it does now with out a gyro.
You really just have to play around with the controls as they are hard to figure out on paper or even on the bench. But this is the way I set it up and the way Vtolman did it.
You will also notice that he has his motors mounted right to the pivot tube ,,,no up pod at all and he said he wanted to lower them some way if he could.
Hope this helps ,,if not pm me and we can talk more
Larry

[BQuick]

I still can't see how tilting the pods forward can make the fuselage want to tilt forward. It seems that all of the forces would want to top it backward.

- Brad

[BQuick]

I verified what you said. I fired up the plane and held it in my hand with the blades turning. Yes, when I tilt the pods forward, the fuselage also goes forward. I can't explain exactly why. Probably because the thrust line is now above the cog, creating a moment about the cog.

So it looks like I need another mixer so that I can put the gyro before the mixer. At least that may free up one of my mixes on the transmitter, so I may be able to do the mixes for forward flight as well. But first I have to hover.

- Brad

[v22chap]

You are talking about a VTOL ,,,all rules of aeronautical engineering are null and void ;) :p :rolleyes:
Yes another mixer would be the way to go .
You also need to use expotentail on your pitch and yaw axis and really keep the movement of the pitch axis especially small around center .I would say it should move less than 1/16" back or forward to control it in a hover.Which if you are moving it more than that may explain why it wasn't able to be controlled on the pitch axis at all. You also need to have the plane balanced precisely on the pitch axis.

[BQuick]

Ok, Thanks for the advice. If I am correct that getting the thrust line above the cog is what rotates the fuselage, then getting the pivot point higher would help. I may have to experiment with putting my servos on top of the wing rather than underneath it.

- Brad

[BigS]

Larry, where did your osprey balance when you flew it with props on it in aeroplane mode?

Shannon.

[BQuick]

I got my second v-tail mixer and installed a second gyro. It does seem more stable, but I broke off one of my pods and chopped the plane up a little. It's a good opportunity to move my pivot to above the wing.

By the time I get this one flying, I'm going to have to build another one. This one's looking pretty rough.

- Brad

[v22chap]

Hey,,glad to hear that you feel it is making progress and have gotten another mixer .. and yes they do get beat up during the research period

[aghaei]

we see your interest project about VTUAV i pleased to have more information about the build plan of it i look forward to hearing from you.

[aghaei]

Hi dear
we see your interest project about VTUAV i pleased to have more information about the build plan of it i look forward to hearing from you.
respectfully

[v22chap]

Aghaei
Sent you an email ,,, but my bird is 18 yrs of trial and error and is all scratch built from ideas running around in my head ,,, no real plans have ever been made of it .
I have a website that shows more pictures and explains some more about it and other guys VTOL's also :
Welcome to R/C VTOL's (http://www.geocities.com/v22chap/vtol)

It is an old free site that will shut down after so much bandwidth has been used ( usually about 1 hour ) then it will come back up in 4 or 5 hrs .

There also is a video of the last attempt at transition ,,,that ended up in mechanicall problem causing a crash .

At present I am working on another test bed and this one will use two electric motors not the gas ones that the other one used .

[lphan]

Have you seen this . Pitch instability for a V-22 with non-helicopter rotors.

http://www.youtube.com/watch?v=vduXzKXHk_o

[v22chap]

Yep ,,seen that too ... he is getting there though ... just needs more time .