THRUST VECTORING
 

I am looking for some ideas on mechanical design for thrust vectoring.... anyone have any design ideas?

RE: THRUST VECTORING
 

First of all what type of power unit are you going to use. There are a couple of ways to do this with a turbine you can mount the engine on gimbals or pivots, or you can mount the tube in a manner so it can be moved to vector the thrust (like a harrier jump jet). With a prop aircraft you can do it like a Osprey by pivoting the engine, or putting vanes behind it to direct the thrust.

RE: THRUST VECTORING
 

[link]http://www.parkjets.com/X-31.html[/link] Check this out. I made one of these a few months ago. Very fun little park plane. The thrust vectoring is very simple but very effective. You can really do alot of crazy stuff with thrust vectoring. Ever made a U turn?

RE: THRUST VECTORING
 

OK; before going ahead you have to decide what type of control are to be mounted on your plane... i.e.: Do you want to use the thrust as elevator or as a plus for elevator control? This can be critic for your design...

RE: THRUST VECTORING
 

vector thrust mount

RE: THRUST VECTORING
 

OK; assuming that this is an electric engine with a propeller, you'd better think on a nice servo for tilting since it has to win against gyroscopic torque of the propeller... otherwise you'll need a counter rotative propeller on a rigid shaft. Another possibility: change tha propeller by a fan; think that the smallest the massive rotative diameter, the smallest the torque according to: T=K*rpm*R^2 (where K=constant; rpm=rpm; R= propeller/fan diameter).
Keep in touch

RE: THRUST VECTORING
 

guille2006


What axis does this formula apply to…? Is it the for/aft axis or the rotational axis?

Regards

RE: THRUST VECTORING
 

I tried a side to side pivot with a ST .15 engine on a flying wing. The engine mount knuckle has to be tight enough to eliminate vibration and loose enough for the servo and onboard battery to actuate it. I had to settle for loose enough to pivot, and the vibration killed a standard servo on the first flight. The engine could be pivoted 35 degrees from center. If done during forward flight, the model would just mainly crab. If pivoted during a spin or a tumble, then the vectored thrust did enhance the planes' antics. Now I can say, "been there, done that". Any future attempts will be tried with an electric motor. A U-joint with a pair of servos is what I might try.

RE: THRUST VECTORING
 

Combatpig,
I can see how a gas/glow motor would kill a servo.

The power pulse from the motor must of played hell on the servo.

Thanks for the info.

The setup I am interested in is single axis (pitch axis) at this time, I can see an improvement in 2 axis control if one was to mounted the motor on gimbals & tied the servos into the elevator/elivons
Mass balance of course...

RE: THRUST VECTORING
 

Being able to tilt the motor up and down should prove to be a lot of fun with a high performing model!

RE: THRUST VECTORING
 

I'm doing reference to the "tilt" axis... I can suggest you to make a easy-quick test: hold a running electric engine with your hand and try to move it emulating your idea. With this you'll get an idea of the forces envolved on your problem. If you can do the same with a EDF you'll see some differences. Keep on!!!
Guille

RE: THRUST VECTORING
 

Don't try this with a motor mounting a propeller.

RE: THRUST VECTORING
 

Rigth... you can hurt yourself. It was just an idea...

RE: THRUST VECTORING
 

It only hurts for a few minutes… just kidding…

Safety is always highest on the priority list.

A control rod would be my most likely way of doing the proof of concept

RE: THRUST VECTORING
 

Now it's getting shape... move that rod with your hand (from a few miles of distance) so you can feel how hard can it be for a servo. You can also measure the force with elastic bands or springs in order to choose the proper servo for this.

RE: THRUST VECTORING
 

I built a Zagi type flying wing, larger than a Zagi. Mounted the motors in the middle of the ailerons as part of the ail. Half an ail. on either side. Up elev., both motors pointed up, etc. Two ESCs programmed into the rudder channel for differential throttles. Actual rudders were fixed. Flew OK.

RE: THRUST VECTORING
 

Gord; do you have a photo of it? Post it!!!!

RE: THRUST VECTORING
 

This was quite a few yrs ago when brush motors were more common. I still have the wing but no electrics in it. The motors were held with two straps like this -^- -v- One on top and one one the bottom. The straps are thin sheet metal. The ails. were sandwiched between the flanges with 4/40 screws. I'll try to make a pic but I'm not good with the computer end of it. These were speed 400 motors with Zagi, Gunther props.

RE: THRUST VECTORING
 

All,
Keep in mind the environment that the vectored thrust mechanism is operating in is a dynamic one.

It is great that some posts have pointed out some math but the math does not address the dynamic condition/s that & mechanism must operate in.

P-effect in pitch, how does the math solve for this condition. Is it working for me or against me?
How does the airframes pitch change affect the situation, my thought are such that it helps the situation?
Visualize what the airframe is doing in pitch in your head & one can draw some sound conclusions.

I am not a big math guru (trial & error works well) if anyone is willing to comment please do

Example:
From experience I know that canard equipped aircraft must have an elevator on the main wing because the canard does not provide enough pitch authority for aerobatics (pusher). Ok… you can put a huge canard on the aircraft but why bother.
One only needs to look at the X-29 with vectored thrust build (suffered the same lethargic control authority issues). Lessons hard learned...
Canards make good speed brakes

Take a look at the thread
"is it possible to make a rc plane like this???" authored by "speedbrake" #103

Seeing as the zagi with motors attached to the elevons worked, I feel my idea/design is superior in servo use, as it is far more mass balanced than a motor on a unbalanced control surface.

Flypaper 2 has the data point on vectored thrust working on an unbalanced control surface

Enjoy

RE: THRUST VECTORING
 

Hi HO; I really have to disagree with you in the following points; and please, understand that I want to help!!:


Currently, I'm working as aeronautical engineer in a VTOL UAV which uses the principle of thrust vectoring for maneuvering and, believe me you cannot do the "try and error" work without a previous (and long we agree) math work. In fact, you'll be surprised how many workshop time and money you can save with this hard work (not to mention that failing in a project can carry a big bitter dissapointment). And please; don't you give up against math; it's being done from the ancient grecia and there are a nice bunch of books and information that you can read to make your stuff easier... I can suggest some if you want; just tell me. Current math's and phisics allowed to make astounding planes such the russian Sukhoi Su-27 developed on early 70's so; why to stop on our beloved model RC ones?
Now:

False; If you just have a look at several (and most) aeronautical authors, you'll see that it's all a matter of "arranging" things; there is not a configuration better than other: ones are better for some applications where other are worst.
Another anecdotic thing: we cannot compare our RC planes (stables) with an static unstable and computer FBW controlled airplane such the X-29. This experimental failed on computers but taught a lot to US engineers at early 80's.

Well my frined; my apologies for my english and feel free to ask for help as much as I can...
Keep in touch
Guille

RE: THRUST VECTORING
 

On the Zagi, the wing has a notch cut out and the motor housing is ahead of the hinge line to balance the aileron. Didn't like all that weight hanging out on the ail. either.:D

RE: THRUST VECTORING
 

I played around with thrust vectoring a few years ago, using multiple airfoils whose incidence could be controlled through about 90 degrees, as well as their camber - sort of like a venetian blind behind the propeller. I wanted to turn the propwash through nearly 90 degrees for VTOL. The scheme worked, but turning the propwash through such a large angle produced a thrust loss of about 40 percent, making a gimballed motor look more inviting. Due to the rather poor results, I never proceeded beyond a simple tethered mockup.

RE: THRUST VECTORING
 

Rotaryphile
You said the thrust loss with the blinds type of set up was on 40% at 90 degrees for VTOL...
The setup I am working on is similar to yours although I am not looking for VTOL, I am more interested in STOL performance mostly.
So I would assume that if I where looking at 45 degrees max the thrust loss will be a lot less than that. Thanks for sharing the results of your testing.

RE: THRUST VECTORING
 

Gillle2006,
Remember, this is a hobby & it is all about tinkering & experimenting with new/rediscovering ideas.
Trial & error does work… Just look at Orville & Wilber Wright.
Orville & Wilber did not have to do anything fancy to figure out if an idea worked or not, they just did it brother...
I think you will find that most of the significant technology breakthroughs are not mathematically understood at the time of discovery & the math & science come later to explain them.
Ask yourself, did Orville & Wilber Wright need to know why one airfoil performed better than another in there wind tunnel tests?
One only has to play with an idea long enough to figure out what works & what doesn't, isn't that why we tinker?
It's great that you play with UAVs but they are $$$ driven projects, most of the time $$$ driven projects have strings attached.
Don't get me wrong, I like to do my planning/basic math but it's good old fashion tinkering/brainstorming I like to do

Build something crazy & see if you can make it work, or build something you know works & make it crazy.


Enjoy

RE: THRUST VECTORING
 

HO-229
It will never fly...LOL
Who cares as long as we can have fun trying