Gyro Pics

[kolibri282]

Someone compiled a nice collection of autogyro pictures, amongst other things a C-30 with a teetering rotor (G-ACWF about half way down the page).
http://nhungdoicanh.blogspot.com/2009/05/cierva-c-30.html
and some Kellet pictures as well:
http://nhungdoicanh.blogspot.com/2010/09/kellett-kd-1.html
a rare french beast:
http://nhungdoicanh.blogspot.com/2009/05/sud-ouest-so1310-farfadet.html

Have fun!

[WHY]

Hi Juergen

Some great photos with some fine detail of design

Tony

[WHY]

Juergen

It appears that even though the two blade rotor is used in that one model it still uses variable pitch and has the pre-rotor set up. It would sure be interesting to know the results of that experiment. I am guessing something was not to good since they did not continue with the two blade set up , again it would be interesting to know what they did not like.

Tony

[kolibri282]

...again it would be interesting to know what they did not like.

I immediately thought of your question about a two bladed rotor in the Spacwalker thread when I saw the picture, Tony and it would be great if someone with more knowledge of Ciervas gyros had an answer to the questions. The best way to learn is from the mistakes *others* have already made...;-)

[Alan_Cheatham]

Peter W Brooks book Cierva Autogiros gives details on G-ACWF and tests of it's two bladed "Autodynamic" rotor head. High vibration and ground resonance were some of the reasons for abandonment and Cierva's system didn't use collective pitch for the blades.

.

[WHY]

Hi Alan

Thanks ever so much for that information on the G-ACWF gyro, as I said in another post information is more valuable than gold when you are experimenting. I thought there would be a reason they did not persue the two blade set up further I also realized now that Cierva 's system did not use collective, I assume just overspeed for short take off.

I was thinking that the bigger the rotor the more severe the "2 per pulse" with the rotor, however I would not have guessed ground reasonance as a problem.

I am guessing that if one were to persue a tractor gyro much larger than the Little Wing you will need to think along the lines of a articulated rotor head like a helio and probably different blade profiles ??

Even with all the design changes that would be necessary I think if I were looking to bring a new gyro to the market place today, it would not be another Xenon class or a Genesis class gyro since these style and class of gyro's have now been very effectively fulfilled and would be hard pressed to compete with for market share, but would instead go for the "enclosed fuselage open cockpit single place/two place tandem" style of tractor. I think this would be a very limited market with only a very small percent of "plans built units" but rather a "kit"built or ready to fly market and probably a expensive market. Maybe this is because having flown in the Stearman and a Waco with the radial engines and open cockpit, for me this becomes the "benchmark" for ultimate flying. The throb of that radial is a real "real heart throb". Also this catagory of gyro would be in the operational class of the Xenon type class which can provide some uses beyond fun but you sure would have to increase the price of the "hundred dollar hamburger"

Tony

[karlbamforth]

I was trying to upload a few articles about the jumpers using the autodynamic head but they exceed the forum limit.

In "Jumping to it" a comment is made that the 2 blade system was a proof of concept and that they were very happy with the results and would proceed with development. They also mentioned that a lot of vibration was present but that it was due to an error on the drawing board in that something was manufactured out of tolerence. The vibration was expected to reduce after corrections.

BTW the head was not "overspeeded" as such, they used a "delta" type drag hinge that allowed the blade pitch to reduce when the prerotator was engaged and increase again when released, causing the gyro to jump.

In the second article "Direct take-off" they describe and show a picture of a development 3 blade autodynamic head, it has changed in that it now only has one drag damper for all three blades instead of the more usual 1 per blade. The reason is because 3 drag dampers would need to be matched/tuned to each other, any discrepency would cause the blades to drag and change pitch at different rates. This would cause the problems of vibration and ground resonance. A single drag damper would seem to be a good way to reduce the problems, so it looks like they continued to develop their ideas.

Designing a 2 blade head with delta type drag hinges shouldn't be too difficult and tying the 2 blades together to ensure equal drag rates should be doable. The 2 main difficulties I see is in plane stiffness may be reduced which is not good and delta type hinges can generate a pitch/roll couple.

Errrrmmmmmm maybe we should go to a dedicated thread for this.
I'm not sure how to load the articles, they are PDF and exceed the forum upload limits. If you are interested PM me and maybe I can make them available.

[Alan_Cheatham]

Cierva's philosophy on design was to keep his engineering solutions as simple as possible but this also caused his company to lag behind development compared to others such as Pitcairn. Since you need to feather the blades anyway for jump capability I see no reason why one would not choose collective blade control such as seen in more recent and successful jump systems.

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[Brent_Brown]

The R22 has a dalta head

[karlbamforth]

Cierva's philosophy on design was to keep his engineering solutions as simple as possible but this also caused his company to lag behind development compared to others such as Pitcairn. Since you need to feather the blades anyway for jump capability I see no reason why one would not choose collective blade control such as seen in more recent and successful jump systems..

The delta type drag hinges do collectively pitch but it is done automaticly, making it simpler to use. Flying with both collective and cyclic control is far from easy.

[Alan_Cheatham]

Let me restate then.

By collective I don't mean manually controlled but jump collective that is engineered to operate automatically such as the system on Carter Copters jump demonstrator.

Do a little research, Cierva and Pitcairn were at odd as to how they saw the implementation of jump technology, Pitcairn's was was the better and after Cierva died his company dropped development of the Autodynamic head.

Using direct control of blade pitch for jump allows the elimination of, or proper design of, the lead lag hinges/dampening and not to compromise them for the sake of jump feathering.

.

[karlbamforth]

No arguments from me Alan, just pointing out the the autodynamic system was a form of automatic collective.

I would love to learn more about Cierva and Pitcairn, if you have any references or documents it would be great to see them.

Not sure I agree with your statement about the "more recent and sucsessful jump systems" most if not all are in the prototype stage, non that I know of are in production or planning to be in production. Although they look fantastic and I want one I have heard that they can be difficult to operate, with little room for error.

One other consideration is that in Europe collective is not allowed on gyro's, if it was automatic and only able to be used on the ground it may be possible to argue that in flight it operates as a conventional gyro.