Tractor Gyro Dynamic Rudder Stability Test

TimMoses

Junior Member
Joined
Sep 26, 2005
Messages
45
Location
Monroe, NC
Aircraft
Quicksilver GT-500
Total Flight Time
1800+ Many more hours unlogged)
Some concern was expressed at Mentone about the stability of the rudders on my new design due to the large counter balance. So I decided to make a simple 1/4 scale test rig to magnetically stick down to the hood of my car. After the rig blew off the first run (?!@%!$%), I duct taped the repaired unit on and proceeded to test the model at 60 mph down the runway. There was no instability or flutter at all, in spite of the model being made of rather flimsy cardboard. The model is 100% statically balanced at the hinge point with pennies and has approximately 25% of the rudder area ahead of the hinge line. The gas to drive up and down the runway probably cost more than the model test rig. If there is still concern, I may mount the whole tail on the front of the car.
 

Attachments

  • T_Rudder test.jpg
    T_Rudder test.jpg
    95.4 KB · Views: 0
  • T_tractorgyro 002.jpg
    T_tractorgyro 002.jpg
    136.3 KB · Views: 0
  • T_tractorgyro 003.jpg
    T_tractorgyro 003.jpg
    114.2 KB · Views: 0
Last edited:
They look nice to me Tim and it looks like you have plenty of volume.

Control balance and flutter are often not a design priority.

What does the upper link on the landing gear do?

Thank you, Vance
 
The upper link on the landing gear just keeps the wheels vertical throught their 15" vertical stroke.
 
Thank you Tim, I can see where the wheel remaining vertical is a good thing.

How do you manage the brake torque?

It all looks very nicely done.

Thank you for sharing your innovation and your pragmatic approach, Vance
 
The upper arm is more rigidly mounted in the fore and aft direction than it might appear in the picture. Also, the axle is on the centerline of the lower tubes and imparts torsion loads to them. Between the 3 tubes the braking loads are controlled. The main braking load would be trying to hold the gyro still during prerotation as opposed to landing as with an airplane.
 
Tim,

Good show ole man! Have you any drop test information for your gear? The last time we spoke you were working on your struts...looks like you worked it out OK.
 
Well...about all I have done so far is jump up and down on the keel tube with my 230 lbs. The rates on the shocks are adjustable so I should be able to tune them better during flight tests.
 
I wonder who will be the test pilot on that there tractor gyro thingamagiggy? :)
 
I don't know...I guess some fool will be unable to resist flying it.
 
you guys ought to see it in person, Tim is very detailed and the gyro is first class! Hopefully he will post more pictures and details of it as he has time. I practically begged him to bring it to Mentone, but he wants it to be ready to fly first. Maybe he will have it done by Bensen Days....
 
looks great Tim, Ercoupe never had any problems with the same design. happy flying.
 
Some concern was expressed at Mentone about the stability of the rudders on my new design. So I decided to make a simple 1/4 scale test rig to magnetically stick down to the hood of my car.

Tim, if you are concerned about flutter testing, that should be done with the real thing to be conclusive. The scale model can easily exhibit totally different vibrational and torsional modes. So your not seeing any sign of flutter on the 1/4 scale model shouldn't set your mind apeace.

-- Chris.
 
This test was not to check for flutter. The original concern expressed was that the rudder could reverse due to the large aerodynamic counterbalance ahead of the hinge line. The rudder outline is very similiar to a Piper Cub with areas and moments from the hinge line that are also similiar. The rudder is torsionally very stiff being made of foam and fiberglass with reinforcements at the hinge, counterbalance and control horn. The gyro will probably never go fast enough to be prone to flutter.
 
I already have a hydraulic prerotator, but I was thinking of installing an electric prerotator that is dual voltage, ie. 12 vdc for starting the prerotation and 24 vdc for finishing the prerotation.
 
Top