rcav8tr

Eddie has a point regarding reaction time on the puffer nozzles. The best way to overcome this would be an onboard controller. that way it can react to pitch, yaw and rotational moments much faster than anyone of us could. The controller would have to have a PID control loop on each axis in order to maintain stability. The real trick would be transitioning from assisted hover to stable, unassisted flight and then back.

Pegasus, your definitely on the right track.

Ed

Pegasus

There are some good heading lock gyros out there that may be usable to stabilize the Harrier in the hover. It will take a bit of experimenting to get the puffer jets just right to make it respond properly and quickly, I don't think I would want to fly it in a serious cross wind! The transition to forward flight will be the hard part, as the throttle, nozzles and elevator have to be perfectly time to do so. Not to mention the usual corrections needed to keep the plane straight and level.
Ed, I hope you right about being on the right track.

Doug Cronkhite

My Feedback: (34)

I would highly recommend against using the heading lock function gyros. Standard rate gyros will do just fine. Heading lock gyros were tried in airplanes at Horizon with some nearly disastrous results.

Doug Cronkhite
Team JR

RampRat

So what happened?

Doug Cronkhite

My Feedback: (34)

They just fight the natural flight characteristics of airplanes and take control as opposed to stabilizing things. Rate mode works great, but heading lock is bad mmkay..

RampRat

mmkay...

EddieWeeks

During the development of the Rig, I had to turn the
gain down on the roll gyro, (Simple rate gyro) and
found out this just about made the plane impossible
to fly. I fixed the problem and turned the gain
back to %100 and it flew great.

This made me think, if I got top of the line heading
hold gyro it would be that much better. I borrowed
3 from a friend and hung the Rig on the strap and
tested it.... Man what a pain in the *$$... All the
linkages had to be reset so 1.5ms was in trim.
And I almost got one axis working but I was
very unhappy with it because it keep drifting
and it acted like it had a mind of its own. I heard it
could be done, but it was way to much trouble.

I found a simple JR400 works great. The key to
make something hover is.

1: thrust of the control system
2: reaction time

A tail rotor, like I use, turning 9000 rpms can put out 5 lbs
of thrust for ~0.5 sec and then maintain ~2 lbs.

I think servos are plenty fast enough.

Also... I found it very important to be able to test all the
control systems with running the turbine. Hours and hours
of testing, hanging on the strap were very important.

Hope this helps..

Eddie Weeks
http://www.corpcomp.com/weeks1/

nate10588

Pegasus,
about the reaction control system, using compressed gas at higher psi might be what you need. Should not weigh too much as you only need it in hover and as you could build your own turbine eingine, you might be able to make an in-flight pressurization system. About that engine, this thing is going to be spinning at 150,000 rpm at least, right? And this engine is going to produce around 70 lbs of thrust, right? Well, how are you going to get it by AMA whose regulations state that a turbine aircraft can only produce 35 lbs of thrust per engine. So, you are going to have to make two engines or some how get AMA to let you do this. Also, this is a very dangerous aspect of the sport and even factory turbines explode periodically, so you are going to have to put like a 1/4 in steel ring around the cassing and stand a couple hundred feet back. Doubtless you have come across these problems already and I would like to know hoe you plan to over come them as I would like to try a VTOL project in the future.

rcav8tr

Hi Nate 10588

I don't know about an inflight pressurized system, but you could certainly try a ground pressurized system. Trick would be not running out of gas/pressure at the wrong time.

A 150000 rpm for these turbines is not exceeding high. Most turbines you see out there now idle at 50-60000 and produce max thrust at 120-125000(17-30 lbs) and 155000(12 lbers). All the ngvs I've seen have at most a 1/8" ss ring if not a 3/32" or 1/16" ss ring. Turbine blades in these turbines have very low inertial mass and do not require extreme containment measures. Haven't heard of any turbine wheels exploding lately.

I'm not sure how you'd deal with the AMA issue, but you could try arguing that it is a special turbo prop, just with a ducted fan attached instead. If not, you'd have to campaign for a new turbine category.

As Pegasus knows, I can hardly wait.

And I agree with Doug about the heading hold gyro. Gyros are definitely required. I think the best way to do hover and transition is by using an onboard controller. The controller's purpose is to maintain the aircraft in a stable, stationary hover. It would then take control inputs from the receiver and convert those to control movements on the aircraft, to move the aircraft around. The biggest trick is transitioning from r/c flight control to computer hover control and back again. Who takes over when?!

Ed

EddieWeeks

You can't be serious.. ! You want to put a 1/4 in steel ring
around a turbine on a VTOL.


EddieWeeks

EmptyHead

Wow Dude....that thing is the ****! I want one...heck I want two!

What a trip you must be on. Amazing for something built at home! Keep rocking man!

FLY V/STOL

My Feedback: (7)

Pegasus,

As a fledgling Harrier pilot, and avid RC'er all I can say is Holy Crap! That is one unbelievable piece of work. I've been toying with the idea of building a STOL version vice a true V/STOL due to power problems. If there is any help I can give you please let me know I am very interested in the success of this project.

Pegasus

Please PM me your email address.


Thanks EmptyHead

Nate10588,
A high pressure system will be a bit difficult to do as you cannot take it from the core turbine.
The core spins at 100k and the fan at 32k, it produces 40 pounds of thrust after all the losses. After the Harrier is complete and works well I may have to move to Canada to fly it!

Guybo

This AMA situation in the US sounds like a real pain in the ass!!.

I hope all the do gooders don't spoil the fun over here!!.

Pegasus you are more then welcome to run her up over here anytime.

Doc Watson

I've heard of a british turbine being developed for a harrier, maybe an urban myth......

Why not try the harrier replacement www.awatson1.fsnet.co.uk

I am.......

Also listen to Eddie, he is in a very small club of people who have hovered and not gassed about doing it (like me).

Doc

Guybo

Finally I managed to get to a computer terminal with Braud Band, which is rare in the country side over here!!, and down loaded Eddie's videos of his VTOL rig. Amazing is the answer, unbelievable, most incredible well done. If anyone is interested in model VTOL aircraft then check Eddies site out, which the address is posted earlier in this Thread.

Regarding the Puffer jets. I noticed that Eddie is using Helli tail rotor units, powered by electric motors, for his lateral control, were I believe correct me if I'm wrong you are varying the pitch, whilst running the motors at a constant rpm. This is a nice solution to the problem, as Mass flow as opposed to velocity flow in this case is more easily achieved, and probably more effective. To achieve working high pressure nozzles would be very difficult, as there is no source for this, as a model gas turbine can only really achieve a max of 2 bar case pressure, which would not produce enough flow in my view regardless to the loss in engine performance!. Pegasus turbo fan produces 40lb of thrust including duct losses, is that including all ducting to the puffer jets?, as if so you are probably onto a winner if that is the case.

Finally I would like to wish Doc Watson all the best for his flight trails on his EDF VTOL JSF, which is also another incredible project, and I am looking forward to hearing the out come!.

Jackjet

My Feedback: (1)

Pegasus,

just bring it out to Rabbit dry lake when your are ready to fly it .

Rabbit Dry Lake - the jet modelers Area 51 ........fly WHATEVER you like .


Jackjet

Pegasus

Jack,
I would love to be flying out there with you guys again.
I guess that is the place to fly it.
Yes,,, AMA is a pain in the butt.

tinsink

Hey Pegasus,

Where are you getting your bleed air from?
I assume you only have a centrifigal impeller
in your engine. Do you bleed it before the diffuser?

Pegasus

I am getting the bleed air off the fan
You can not take it from the core turbine, it must be left untouched

SigKavalier

Thats pretty cool. Though I want to see a Yak-141 Freestyle hover! Ah the first supersonic VTOL aircraft.

tinsink

Thanks for the info Pegasus.

Just to let you know, when I worked at Avco Lycoming all of the
turbines, including turbofans, turboprops and turboshafts had
both "bleed bands" and "customer air" in the compressor
sections. The bleed band opened the compressor to atmosphere
at the 5th axial stage for idle purposes and the customer
air was taken from a fitting the 6th stage axial. They never
touched the air near the centrifigal impeller either.

Pegasus

The amount of air the full size takes from the compressor is also a much smaller percentage than I would need to take from the model sized motor.
The full scale harrier takes the bleed air of the 5th stage (I believe)compressor for the reaction control system.

Pegasus

I took some video of the turbo fan running but have no place to post it, there 3 megs each, one of start up and the other of it running.

Anyone have some free space to post these?

EddieWeeks

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