6 Egypt Silk Mill 2pi wind turbine ; revisions 4 ; 25 June 2011 .

These figures explore an alternative design for the core housing(s) of individual turbine elements .

In doing so, the depart from those of 22 March and 4, 14 & 15 April .

In those previous posts, (particularly of the 4th and 22nd), the core housing was an annular design, holding the wings inside of it .

Two drawbacks to such an approach would be the high number of parts involved,

(increasing the statistical chance one would break and take a core off-line, or cause it harm) ;

and the need for the housing to maintain almost perfect roundness in order for the wings to turn freely,

(something which would become more difficult as the cores became larger,

and which could greatly complicate their integration with the arch ––

as this would need to have some flex) .

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Here, the core housing is of the hub-type,

with the wings turning together with the housing's nose-cone .

The perimeter ring joining the wings' tips is remodeled as a neutral-lift airfoil ;

(the points where the wingtips meet this ring are filleted for increased strength, though it is not obvious at this scale) .

The ring has three basic purposes :

to strengthen the wing assembly ;

to suppress or eliminate wingtip vortices ;

and, possibly, to allow the development of more complicated wings .

To meet these needs, a heavier ring may be required, (depending in part upon materials) ;

however, i prefer to begin from the minimal side, as it is also non-lift-producing turning weight and surface area .

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The core's wingspan has been increased as a proportion of the space available .

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The core's (torpedo-shaped) machine housing is linked to the arch by a bridge

which is swept leeward in a modified cosine curve, (seen from above) .

This should reduce the bridge's bow wave interference with airflow past the faster turning, (more productive), parts of the wing .

When seen from the front or back, the bridge describes a very shallow ellipse

which would bring its cross-sectional line to perpendicularity with the curve of the arch,

(were the bridge to extend to the arch-center instead of being trimmed to meet the arch's inner surfaces) .

An object of this elliptical curvature is to allow the bridge to flex slightly with the arch .

The bridge supports the core from below, allowing service to be performed from above .

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The two full views are shown with only one core, (the lowest), of about five possible .

Ideally, the first core would be the highest .