RC Groups

RC Groups
    VTOLs
        Discussion Tilt Wing Project

#1 jyothibasu1k Feb 02, 2013 09:04 PM

Tilt Wing Project
 
1 Attachment(s)
hi,

i am almost done and all setup is ready for tilt wing RC aircraft. but during hovering due to vibrations of the motor the propeller is oscillating. how to rectify it.

can any one help me

#2 leadfeather Feb 02, 2013 09:59 PM

1) Make sure the props are balanced.

2) If the airframe structure is not stiff or strong enough it may cause vibration.

Best of luck!

#3 jyothibasu1k Feb 02, 2013 10:42 PM

the two things which you told was okey. we have moderate stiffness in the wing frame. due to throttle vibrations the propeller is oscillating.

what to do now

#4 leadfeather Feb 02, 2013 10:46 PM

Quote:

Originally Posted by jyothibasu1k (Post 24016811)
the two things which you told was okey. we have moderate stiffness in the wing frame. due to throttle vibrations the propeller is oscillating.

what to do now

Can you post a video to help us understand what you are trying to describe?

#5 jyothibasu1k Feb 02, 2013 11:03 PM

sure, but i need time

#6 jyothibasu1k Feb 03, 2013 07:30 AM

here are the testing videos

Check 1 (0 min 29 sec)


Check 2 (1 min 5 sec)


Check 3 (1 min 20 sec)


Check 4 (1 min 18 sec)


Check 5 (1 min 50 sec)

#7 leadfeather Feb 03, 2013 08:35 AM

I've watched the videos. Below are my observations and comments:

1) The vibration you mentioned in your first post is coming from (for the most part) ground effect. There is a lot of turbulance very near the ground and this will cause the craft to buffet and vibrate. In video #4, when the plane is being held higher off the ground it appears to be operating much smoother.

2) It appears you have no stabilization in any axis. I don't think you will have any success hovering without gyro assistance.

3) Your plane is very tail heavy in hover. The mass must balance in line with the thrust line of the propellers while in hover.

4) It appears you are using tilt to try to control pitch in hover. I think you will have much more control authority if you use the ailerons to control pitch as well as yaw in hover.

5) You vertical tail fins are tiny. You may find that your plane will not be stable in forward flight and will spiral left or right.

6) To transition to forward flight, the tilt should be slower or in 2 steps (1/2 tilt and then full tilt) to allow the wing to gain some forward speed to make the transition.

Good luck. :)

#8 jyothibasu1k Feb 03, 2013 10:56 AM

so the 1st point can be over come by changing the location/surfaces. :)

2nd can be over come by using a gyro... (can we over come with single gyro or it is manditory to use two)

#9 leadfeather Feb 03, 2013 12:39 PM

Quote:

Originally Posted by jyothibasu1k (Post 24020709)
so the 1st point can be over come by changing the location/surfaces. :)

2nd can be over come by using a gyro... (can we over come with single gyro or it is manditory to use two)

On the first point, the vibration will greatly reduce once you are hovering a little higher.

On the 2nd point, yes a gyro can only controls one axis; you must use another gyro for each axis you want to stabilize (pitch axis, roll axis and yaw axis). You can also use a flight control board which will have 3 gyros included.

fixed wing flight control board

#10 bz1mcr Feb 03, 2013 03:04 PM

I watched the videos and did not see or hear any indication of motor vibration or "oscillating". The motors appeared to be running smooth and consistant.

What I see appears to be a an unstable aircraft and a pilot who does not know how to control it. Unfortunately I have no experience with aircraft of this type, so I can not help much with proven experience.

However as an engineer and experienced RC pilot I offer these things to think about:
I would think the CG needs to be directly under the props during hover.
I would think you want the wing angle to be absolutly fixed (very securely locked) in a near vertical position. Control of pitch and forward or backward should be by "Flaps".
I would think you will need differential motor speed to level the wing in hover.
If you have opposite rotation props then yaw should been very minimum, but a small amont can be controlled with differential flap action. (like normal aleiron function when the wing is normal flying position.

One final thought....what you are trying to do is very difficult. It has been attempted many times. And, the results speak for themselves.

#11 jyothibasu1k Feb 03, 2013 10:14 PM

i hope that, roll and pitch needs gyro.but the yaw can be controlled by rudder effectively with out a gryo. what do u say abt it.


Quote:

Originally Posted by leadfeather (Post 24021699)
On the first point, the vibration will greatly reduce once you are hovering a little higher.

On the 2nd point, yes a gyro can only controls one axis; you must use another gyro for each axis you want to stabilize (pitch axis, roll axis and yaw axis). You can also use a flight control board which will have 3 gyros included.

fixed wing flight control board


#12 leadfeather Feb 03, 2013 10:56 PM

Quote:

Originally Posted by jyothibasu1k (Post 24026745)
i hope that, roll and pitch needs gyro.but the yaw can be controlled by rudder effectively with out a gryo. what do u say abt it.

You might be OK with out a gyro on yaw, but it would be easier to hover with yaw gyro. With your low level of flying experience I would reccomend the all three gyros.

If you used counter rotating props, yaw would be more inherently more stable while hovering.

One more thing to consider is that when you go from hover to forward flight, the yaw and roll control change. The ailerons control yaw (and pitch) in hover but control roll in forward flight. The motor speeds control roll in hover , but control yaw in forward flight.

It gets complicated in a hurry. That's why the flight control boards are a big help in making VTOL practical.

A simple "no gyro" approach might be to have flybar stabilized rotors. F&T had some success with this approach as did the AirHogs toy VTOL. The problem is that there doesn't seem to be any suitable, eaily available, readily adaptable flybar rotors for our VTOLS.

As I have told you in the emails; VTOL is one of the most difficult things you can do in RC. Realistically, with your limited experience and limited resources, your chances of success with VTOL in the near term aren't very good. I'm not trying to be pessimistic, but I don't want you to have false hope or expect success to be easy at all.

#13 jyothibasu1k Feb 03, 2013 11:59 PM

we are using counter rotating props.

as u said earlier that we need to increase rudder area.
what we did here is two small rudder area = one full large area.
(one large rudder is splited in to two half's)

we are not using rudder's here but instead we are using bank and yaw system
for changing yaw moment



Quote:

Originally Posted by leadfeather (Post 24027096)
You might be OK with out a gyro on yaw, but it would be easier to hover with yaw gyro. With your low level of flying experience I would reccomend the all three gyros.

If you used counter rotating props, yaw would be more inherently more stable while hovering.

One more thing to consider is that when you go from hover to forward flight, the yaw and roll control change. The ailerons control yaw (and pitch) in hover but control roll in forward flight. The motor speeds control roll in hover , but control yaw in forward flight.

It gets complicated in a hurry. That's why the flight control boards are a big help in making VTOL practical.

A simple "no gyro" approach might be to have flybar stabilized rotors. F&T had some success with this approach as did the AirHogs toy VTOL. The problem is that there doesn't seem to be any suitable, eaily available, readily adaptable flybar rotors for our VTOLS.

As I have told you in the emails; VTOL is one of the most difficult things you can do in RC. Realistically, with your limited experience and limited resources, your chances of success with VTOL in the near term aren't very good. I'm not trying to be pessimistic, but I don't want you to have false hope or expect success to be easy at all.


#14 leadfeather Feb 04, 2013 06:54 AM

Jyo,

Here is a video showing F&T's flybar stabilzed VTOL. I think this idea has some potential if the right stabilized rotors can be found. In his case, it look like F&T used rotors from a Blade CX helicopter which he modified quite a bit to get to work.

The flight of this plane does not look as stable as his later gyro stabilized craft, but with enough R&D it might be possible to get a good rotor designed and built for VTOL applications. AirHog did this on their toy VTOL.

#15 bz1mcr Feb 04, 2013 07:26 AM

Quote:

Originally Posted by jyothibasu1k (Post 24026745)
i hope that, roll and pitch needs gyro.but the yaw can be controlled by rudder effectively with out a gryo. what do u say abt it.

Rudder can control yaw in normal flight, but in hover it is not effective at all. There is just no air flow over the rudder in hover. Yaw in hover must be controled by differential flap which is like aleiron.


All times are GMT -5. The time now is 07:16 PM.