Off-set rotorhead gymbal

[Jetson]

Hello everyone,

I'm checking out the design on an Autogyro MTO, and noticed that the rotorhead gymbal is offset to the right (image shows how the rotorhead looks from the front) . I understand that the offset helps to provide stability but would appreciate if someone could go into greater detail as to how it provided that stability. Let me clear this out of my ignorance zone.

Thanks for your help!!

 

[MikeBoyette]

They use this to counteract the induced torque of the engine. It uses the offset thrust of the flying rotor to offset the torque of the engine. This is another way of doing it without having to use a full span tail.

 

[okikuma]

Just one of many methods to offset the torque of the engine/prop.

If one is standing behind and looking at the prop of the MTO gyroplane, the prop rotation is counter-clockwise. Newton's law of equal and opposite reaction, The fuselage will roll to the right side. If the lift vector of the rotor is slightly right of center of the thrust vector line of the prop, this will constantly counter the torque roll to the right.

Wayne

 

[Mayfield]

As with most engineering solutions, there is a "yeahbut." Since rotor thrust is fairly constant in unaccelerated flight, there is often a pronounced rolling moment with a reduction in engine thrust. Not unpleasant, but it can be felt.

Jim

 

[okikuma]

As with most engineering solutions, there is a "yeahbut." Since rotor thrust is fairly constant in unaccelerated flight, there is often a pronounced rolling moment with a reduction in engine thrust. Not unpleasant, but it can be felt.

Jim

Jim,

Not a perfect solution. Other solutions were an adjusted left tilt of the rotor head by adjusting the push-rods, or just holding slight left cyclic. Differential deflection of horizontal stabilizer within the prop wash was another method. All equally not perfect.

Wayne

 

[Loren Jones]

As with most engineering solutions, there is a "yeahbut." Since rotor thrust is fairly constant in unaccelerated flight, there is often a pronounced rolling moment with a reduction in engine thrust. Not unpleasant, but it can be felt.

Jim

Good point. I suspect the only "perfect" solution would be some sort of fly-by-wire system that dynamically adds or subtracts bias from the system based on current power output and other factors. I'm doubtful we'll ever see such a system in gyros anytime soon.

 

[MikeBoyette]

Good point. I suspect the only "perfect" solution would be some sort of fly-by-wire system that dynamically adds or subtracts bias from the system based on current power output and other factors. I'm doubtful we'll ever see such a system in gyros anytime soon.

Well sir,
I would be surprised if your machine is not almost perfect with the tail you have. My Dominator would almost fly with no input from me even with moderate power changes. I could (with no wind) take off, fly the pattern, and land without touching the rudder. With a 670 I had very little torque felt in the airframe. Tall Tails are an amazing aerodynamic device that most people view as ugly. I prefer function over fashion.

 

[Loren Jones]

Well sir,
I would be surprised if your machine is not almost perfect with the tail you have. My Dominator would almost fly with no input from me even with moderate power changes. I could (with no wind) take off, fly the pattern, and land without touching the rudder. With a 670 I had very little torque felt in the airframe. Tall Tails are an amazing aerodynamic device that most people view as ugly. I prefer function over fashion.

I'll have to agree....I think my machine is pretty close to perfect! The only change I anticipate is adding trim capability for the longer straight-and-level flights.

 

[Aerofoam]

Good point. I suspect the only "perfect" solution would be some sort of fly-by-wire system that dynamically adds or subtracts bias from the system based on current power output and other factors. I'm doubtful we'll ever see such a system in gyros anytime soon.

This would easily be accomplished, along with auto pilot gps, and a glass cockpit, map position, etc. with a simple UAV "Cube" autopilot.
Integrating it with servos and trim tabs, or parallel control through the push rods.
Probably could happen for less than $1k including monitor, servos and wiring....

 

[Georgi]

This would easily be accomplished, along with auto pilot gps, and a glass cockpit, map position, etc. with a simple UAV "Cube" autopilot.
Integrating it with servos and trim tabs, or parallel control through the push rods.
Probably could happen for less than $1k including monitor, servos and wiring....

Are we going to the Moon? Pretty scary! Where did "flying" go?
P.S. Sorry, got distracted: spent almost 8 hrs. and still was not able to connect a "round" autopilot to my new toilet

 

[WaspAir]

This would easily be accomplished, along with auto pilot gps, and a glass cockpit, map position, etc. with a simple UAV "Cube" autopilot.
Integrating it with servos and trim tabs, or parallel control through the push rods.
Probably could happen for less than $1k including monitor, servos and wiring....

. . . and everyone tells me that an articulated rotor is too complex and unnecessary!

 

[MikeBoyette]

I'll have to agree....I think my machine is pretty close to perfect! The only change I anticipate is adding trim capability for the longer straight-and-level flights.

Dad used an electrically actuated trim that pulled on a spring attached to the rear of the torque tube of the rotor head.

 

[Loren Jones]

Dad used an electrically actuated trim that pulled on a spring attached to the rear of the torque tube of the rotor head.

That's exactly what we're looking at. We already have the electric actuator. Just figuring out which grip I want to accommodate multiple switches.

 

[Sv.grainne]

I have to chime in even with my limited experience.

Flew a Tango 2 first. Had to use rudder to counteract engine rpm changes. Then flew a Magni, same but opposite.

Now flying my Aviomania, no noticeable change in yaw with engine speed!

Nice!

 

[Doug Riley]

No stabilizing scheme that employs rotor thrust to counter an airframe moment is optimal. In some cases, this approach is lethally ineffective. Why?

As Jim Mayfield points out, rotor thrust in unaccelerated flight is pretty constant. Trouble is, flight isn't unaccelerated all the time. A turn is accelerated flight. A zoom climb is accelerated flight. The moment created by the lateral offset will, in these cases (as well as in a throttle reduction) will be in the wrong amount. You'll get an uncommanded rolling tendency.

Most seriously, a pushover or entry to a downdraft is accelerated flight. In these cases, there will be much less stabilizing moment, because rotor thrust is reduced. With a very torque-y powerplant, the resulting roll can be very serious. It has happened.

We should use forces other than the (highly variable) rotor thrust to stabilize our airframes. The force needs to one that doesn't quit on us at the wrong time (such as low G flight). If the force happens to change in tandem with the torque, so much the better.

Of course, this notion applies equally to stabilizing the frame against drag-over or power pushover. Don't count on rotor thrust to save your bacon.

 

[Jetson]

Just one of many methods to offset the torque of the engine/prop.

If one is standing behind and looking at the prop of the MTO gyroplane, the prop rotation is counter-clockwise. Newton's law of equal and opposite reaction, The fuselage will roll to the right side. If the lift vector of the rotor is slightly right of center of the thrust vector line of the prop, this will constantly counter the torque roll to the right.

Wayne

Thanks Wayne, I had to stop for a moment and visualize this but it makes sense. Good explanation.