Ветряные мельницы, страница 4

The Whed,  —Undoubtedly the most interesting part of  the undertaking is the wind-wheel.  The f raming (see Fig.

67,  % and /) consists of  an inner and outer ring of  2 f t.  and 4 f t.  diameter respectively,  and four double arms with

cross stays and diagonals; the whole being made of  1-in.  by ^in.  steel,  preferably galvanized.  This section is

largely used for making brackets for roof  guttering,  so shovdd be easily obtained f rom a builders' ironmonger.

The ends of  the arms should butt tightly against the bcu^k nuts which secure the hub f langes.  A wheelwright

could very quickly form the rings in his tyre-bending rolls,  if  any dif iSculty be experienced.  In bending the arms,

care should be taken to avoid too sharp a radius,  so as not to crack the material; and it would be well to arrange

that the arms should require to be slightly sprung

forward in order to insert the f ront f lange bolts,  that they may be put in tension and stif fen the wheel against

wind pressure.

Vanes,  —^There are twelve vanes,  of  which details are given in Fig.  67.  These vanes should be formed of

galvanized sheet steel (about 22 S.W.G.) or,  failing this,  stout sheet ''tin." To stif fen them,  the vanes must be

curved to a radius.  This can be done by bending them over a shaped block of  wood,  or by recourse to the

tinsmith's rolls.  The connection to the inner ring is made by leaving ears on the smaller end which are

af terwards turned at alternate right angles.  It would be as well to leave these ears rather long,  and to trim them

in siiu.  The attachment to the outer ring is by a bracket,  seen at Fig.  67,  o,  which may be made f rom the same

material as the vanes.  As it is bent to two radii—^those of  the vane and of  the outer ring—some curved hard

wood vice clamps will be found necessary for shaping it.

Strictly speaking,  the angle of  the chord of  the vane should be greater at the inner end than at the

circumference,  but a uniform angle of  about 25 degrees (with the plane of  motion) will give nearly as good

results and is more easy of  attainment.

If  gearing be dispensed with,  and the pump driven direct,  the speed of  the wheel should be as slow as possible;

in this case an angle of  about 40 degrees would be suitable.

218 THINGS WORTH MAKING.

The wheel is shown with the vanes set to revolve it oounter-clookwise,  in accordance with the invariable custom

of  the older millwrights; but as in the present case this might impart a tendency to turn the wheel into the wind,

and therefore to counteract the ef fect of  the governing arrangements,  the reader is advised to reverse the

direction of  rotation.  It will be noticed that care has been taken to reduce edge resistance to the lowest quantity,

and if  the wheel be built as shown,  better results will be obtained than are possible with wooden arms and

vanes.

The fact that the wheel is built up of  galvanized material will not entirely ensure it against corrosion,  as the cut

edges will be unprotected; it ought therefore to be painted.  If  it be desired to retain the galvanized appearance,

aluminium paint can be used.  Before applying paint,  however,  the surface of  the zinc had better be cleansed by

going over it f irst with a weak solution of  vinegar and then with clean water,  and af terwards thoroughly drying

it.

Pump8.~The pumping power of  the mill will be somewhat a matter of  experimenting with dif ferent lengths of

pump stroke,  as a good deal depends upon whether the mill is " well blown ** or not,  and the excellence,  or

otherwise,  of  the workmanship will also enter into the question; but the following table gives about what should