[ray]

I have just invented Lobsta's Law "On any flying related internet forum, as a discussion grows longer, the probability of the thread descending into a discussion of ipads and Skydemon approaches 1". (With apologies to Godwin)

And while some posts are simply trying to be helpful and are related to the topic, others are just folks trying to be clever and failing

[lobstaboy]

Well I really am most terribly sorry, Ray. Would you like me to PM you all my future posts in advance so that you can assess them for their suitability for the forum?

Or why don't you just put me on your ignore list?

[Flintstone]

Nice try though ray, we appreciate your effort.

[Mutley]

From Skydemon to handbags in just 6 posts - Mornington Crescent?

[Flintstone]

Point of order Mr Chairman, five posts. ray clearly swung her handbag at lobstaboy first.

[hatzflyer]

I wish there was summat interesting on here to read, It's getting a bit like watching emerdale.

[MercianMarcus]

Try an av8 ipad kneepad holder, works a treat with a mini ipad and Skydemon

The other issue besides space is gloves. Normal flying gloves work ok with an iPad, padded motorcycle gloves don't work at all.

[ray]

I struggle with bare fingers already lol

[masterofnone]

Have newer gyrocopters managed to somehow overcome the problem of bunting then? Or made it much harder to achieve?

The short answer is yes. The main factor to improve stability which the research identified is the vertical location of the thrust line relative to the aircraft's CofG.

Simplistically, you have two main sources of force affecting gyro stability. The rotor, which provides lift and stability as a consequence of its angular momentum, and the thrust from the engine prop. In the absence of a rotor, if the prop is displaced from the vertical CofG, it will create an unbalanced moment about the CofG, causing the fuselage to rotate anti clockwise (if situated above) or clockwise (below CofG) - that is...it will bunt.

With the rotor in place, it's angular momentum balances the engines thrust moment, so long as it is spinning fast enough. The displacement of the thrust line effectively acts as an amplifier for any discrepancy in the forces between the prop and rotor.

The problem with many designs before the Glasgow study would have thrust lines located significantly higher than the CofG. This was invariably to accommodate clearance between the prop and the rear fuselage/empennage. And consequently this would create less stable aircraft, that were more sensitive to changes in power and rotor speed.

More modern designs invariably include a bent/displaced rear fuselage, which allows for the prop to be mounted lower, resulting in a thrust line much closer to the CofG (= more stable aircraft).

GtE will be along in a minute to tell you I just made that up

[Dave W]

Do all current gyros have a teetering head? If so, must they for an insurmountable engineering reason?

[MercianMarcus]

Do all current gyros have a teetering head? If so, must they for an insurmountable engineering reason?

AFIK all gyrocopters have teetering blades, it is the magic that makes them gyros.

Ignoring any wind component to keep things simple, the advancing blade will be travelling faster (speed of rotation plus forward speed) than the retreating blade (speed of rotation less forward speed). As the blades are wings, the advancing blade would have more lift if it were not for the teetering arrangement. The advancing blade moves up, reducing the angle of attack (less lift) the retreating blade moves down, increasing the angle of attack (more left) until lift form both blades is equal.

[Dave W]

Nah, that's what flapping hinges on non-teetering blades are for. An autorotating helicopter's disc is acting in the same way as a gyrocopter's.

[MercianMarcus]

Nah, that's what flapping hinges on non-teetering blades are for. An autorotating helicopter's disc is acting in the same way as a gyrocopter's.

At PPL(G) theory level (no idea about more advanced) teeter and flap (but not "blade flap") are interchangeable. The text says: "the rotors teeter or flap" and also "called the teeter bolt or flapping hinge".

EDIT: Dave, based on a very quick google, I'd say the difference between the gyro and the heli is that on the heli the blades flap independently, whereas on the gyro they teeter as a fixed unit (like a see-saw.)

M

[Dave W]

Well, that was my question really: Do gyro blades need to teeter, or is it simply that most current gyros happen to do so as it is the least complex and cheapest dolution to achieve the aim.

I think it's the latter, but I'm more familiar with helicopter so am not sure if there is an engineering reason I can't see at first view.

[Mutley]

Gyro rotor blades need a mechanism to equalise the lift on the advancing and retreating blades. Teetering is the simplest, lightest, most cost-effective way of meeting that requirement.