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ashontz
Joined: 27 Dec 2006
Posts: 723
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 Posted: Wed Feb 28, 2007 9:20 am Post subject: Interesting airplane history - off topic |
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I remember reading about this in an old EAA experimenter magazine before they went gloss and all advertizememts.
Single Blade propeller
http://notplanejane.com/everel.htm#everel7
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craig(at)craigandjean.com
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| Posted: Wed Feb 28, 2007 10:39 am Post subject: Interesting airplane history - off topic |
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| Quote: | > Single Blade propeller
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I looked around and couldn't see why they stopped making the Everel single
blade prop after about 1945. The only negative things I could find were that
they were expensive and needed frequent readjustment of the counterweight.
But I did have fun reading about the US WWII cruise missiles:
www.stagone.org/ns.html
-- Craig
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ashontz
Joined: 27 Dec 2006
Posts: 723
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| Posted: Wed Feb 28, 2007 10:43 am Post subject: Re: Interesting airplane history - off topic |
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| craig(at)craigandjean.com wrote: | | Quote: | > Single Blade propeller
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I looked around and couldn't see why they stopped making the Everel single
blade prop after about 1945. The only negative things I could find were that
they were expensive and needed frequent readjustment of the counterweight.
But I did have fun reading about the US WWII cruise missiles:
www.stagone.org/ns.html
-- Craig |
Probably needed frequent adjustments because it was made of wood and humidity and expansion caused the out of balance conditions. Betcha an aluminum prop would rarely if ever need adjusting.
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ihab.awad(at)gmail.com
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| Posted: Wed Feb 28, 2007 10:47 am Post subject: Interesting airplane history - off topic |
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On 2/28/07, Craig Payne <craig(at)craigandjean.com> wrote:
| Quote: | >> Single Blade propeller
I looked around and couldn't see why they stopped making the Everel single
blade prop after about 1945. The only negative things I could find were that
they were expensive and needed frequent readjustment of the counterweight.
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It seems that the "single blade" and "flapping" issues are
independent. A single blade prop is used on at least one motorglider
I'm aware of in order to make it more stowable. But the real
innovation here seems to be allowing the blade to "flap", similar to a
helicopter rotor, thus reducing or eliminating various propeller
asymmetries due to an off-axis airstream. This could easily be
accomplished with a 2- or n-blade propeller by giving each blade a
flapping hinge.
Ihab
--
Ihab A.B. Awad, Palo Alto, CA
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ashontz
Joined: 27 Dec 2006
Posts: 723
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| Posted: Wed Feb 28, 2007 10:56 am Post subject: Re: Interesting airplane history - off topic |
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| ihab.awad(at)gmail.com wrote: | On 2/28/07, Craig Payne <craig> wrote:
| Quote: | >> Single Blade propeller
I looked around and couldn't see why they stopped making the Everel single
blade prop after about 1945. The only negative things I could find were that
they were expensive and needed frequent readjustment of the counterweight.
|
It seems that the "single blade" and "flapping" issues are
independent. A single blade prop is used on at least one motorglider
I'm aware of in order to make it more stowable. But the real
innovation here seems to be allowing the blade to "flap", similar to a
helicopter rotor, thus reducing or eliminating various propeller
asymmetries due to an off-axis airstream. This could easily be
accomplished with a 2- or n-blade propeller by giving each blade a
flapping hinge.
Ihab
--
Ihab A.B. Awad, Palo Alto, CA |
It wasn't mean to flap, but it does move back and forth a few degrees depending on engine RPM and airspeed. The movement is designed to change the pitch of the prop, not eliminate asymetries. The hinge it pivots on is on a slight angle to perpendicular, so that when it moves forward or back the pitch of the prop changes. It moves forward or back depending on air pressure on the blade and balanced against the counterweight on the other side which is also dependent on rotational speed. A two blded prop could be built with opposable weights like this, but there's actually an advantage to one blade, namely more time for dissapation of the wake, so the blade isn't trying to cut into turbulent air. So effectively one blade in clean air is actually more effiecient than two blades cutting into each others turbulent air.
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ihab.awad(at)gmail.com
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| Posted: Wed Feb 28, 2007 11:12 am Post subject: Interesting airplane history - off topic |
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On 2/28/07, ashontz <ashontz(at)nbme.org> wrote:
| Quote: | It wasn't mean to flap, but it does move back and forth a few degrees
depending on engine RPM and airspeed.
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Ah I see ... thanks for clarifying! -- I
--
Ihab A.B. Awad, Palo Alto, CA
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