FW189 spinners?

[Charge]

Does anybody remember what was the name of these curious spinners seen on FW189 and if they served some purpose by their strange design?

Why not just a plain smooth spinner?

http://en.wikipedia.org/wiki/Image:Argus_AS_410.jpg

http://www.warbirdfinders.co.uk/aircraft_FW189_V7+1H.htm

http://the-72world.web.infoseek.co.jp/page159.html

-C+

[Krusty]

I built the airfix kit in the last link.

I figured they HAD to have a purpose.

Best guess I can make is they actually disturb airflow. Those were very simple air-cooled engines as far as I understand. Cheap, low powered engines. They're right under the props, as well. Maybe the normal airflow around the prop had a chance to bounce outside of the air scoop on the engine, so this "stirred" the air to better let the turbulence flow through the engine.

Best guess I could make, I'm afraid.

[straffo]

I think it's for the constant speed mechanism, the me108 taifun as a similar spinner .

[Krusty]

Why would it need spinning radiator fins to run a constant speed mechanism?

[MiloMorai]

Think you are right Straffo. Photo with the spinner tip removed.

http://bp2.blogger.com/_CbwnjooteyI/SFgXCo7K2lI/AAAAAAAAQe0/zp9tg-K8M6A/s1600-h/30.jpg

[Krusty]

I'm still not sure why that needs fins. A larger spinner, sure, to house the stuff, but why the fins?

[straffo]

Why would it need spinning radiator fins to run a constant speed mechanism?

don't know either perhaps it's just for aesthetic ?

[Charge]

"The powerplant was a couple Argus Ar 410 12 cylinder inverted-vee air cooled engines providing 430 hp for take-off and driving two-bladed automatic pitch propellers with pitch control vanes such as those mounted on the Me 108"

http://www.baermann.biz/pauke/index.php?itemid=70&catid=6

By that logic the propeller would adjust to more "coarse" setting as the speed increased as the increasing forward velocity would slow down the spinners rotation.

Here is a link to Bf 108 model where the alternative spinner was mentioned:

http://www.kitreview.com/reviews/bf108reviewbg_1.htm

But no mention of which is which and from pictures you see that the other is vaned and the other is a smooth one.

-C+

[MiloMorai]

The vanes act, like the small prop on the Me163, as a generator.

Charge, does a windmill slow down if the wind blows harder?

[Charge]

No, but if the forward part likes to turn with same speed as the propeller the forward speed would try to slow it down because of the vanes, and that would happen in high speed (or as high as that engine would allow...) and it is not a problem to gear it so that it would work either way. But how could it have enough momentum to alter the angle of blades?

-C+

[MiloMorai]

But the tip part of the spinner will not turn at the same speed as the prop. It will turn at what ever speed the air stream will turn it at.

I would say the centre part in the photo I linked to, is the coils of a generator. An electrical current is produced which runs an electric motor which changes the prop angle.

[Krusty]

But the tip part of the spinner will not turn at the same speed as the prop. It will turn at what ever speed the air stream will turn it at.

The vanes are static. They have no pitch. There are more efficient designs for power generators than this.

[Lusche]

The vanes are indeed responsible for maintining prop pitch. They do not generate electricity, they do work mechanically/hydraulic.
I do remember that from a certain airspeed on, they induced a rotation of the spinner relative to prop hub movement, induced by dynamic airflow. This movement is driving the pitch control mechanism. I'm not shure at the moment if it's by mechanical or hydraulic means. I scanned my tiny library but unfortunately I didn't find any illustrations yet

I'm sure someone will soon dig up some details, if not I'll try to have alook at my university's library in the next few days.

BTW, the lead developer for variable pitch propeller mechanisms for Argus from 1935-1938 was Hans Jacob Reissner, who emigrated to the States and was working at the Illinois Institue of Technology.

[Captfish]

The vanes are part of the constant speed feature of the propeller. The fins are attached to the spinner and is free to spin,the spinner is attached to a small oil pump. The oil pressure adjusts propeller pitch, if the load on the propeller increases ie during climpb, the pressure falls and the pitch is decreased.

I'm trying to find a diagram of this, but I'm having little luck, But i havent given up yet.

[Wolfala]

My first thought when seeing it: it's gotta be a high speed Orange Juicer.