Ветряные мельницы, страница 3

In BO small a mill some form of  reducing gear is almost a necessity,  as a speed of  100 to 160 r.p.m.  IB too fast

for a pump ; hence a spur-wheel and pinion giving a ratio of  not less than 3 to 1 will be required.  The pinion

should be at least 2^ in.  diameter at the pitch circle,  for it has to be bored to f it the wind-wheel shaf t,  f rom

which it follows that the spur-wheel will be of  about 7 in.  diameter.  Probably some gear-wheels f rom a lawnmower would be available or,  at least,  could be used as patterns; failing this,  cycle sprocket wheels and chain

would prove a very fair substitute.

The pump and its connections will be referred to later,  as we have now to consider the tail vane and the

governing arrangements for controlling the speed of  the wind-wheel.

It will be noticed that the axis of  the wind-wheel lies to one side of  the centre line of  the head,  the centre lines

being 1^ in.  apart,  and that the arm which carries the tail vane is hinged to the head.  This want of  balance

creates a tendency for the wheel to turn out of  the wind,  but this is counteracted by the action of  the spiral

spring (see Fig.  66,  /).  If  the wind be light,  the tail vane,  which acts,  of  course,  as a weathercock,  will keep the

wheel normal—^that is,  at right angles to the

214 THINGS WORTH MAKING.

direction of  the wind—^in which position the wheel will develop its full power.  If ,  however,  the wind pressure

increases suf f iciently to overcome the resistance of  the spring,  the head will alter its relative position to the tail

vane,  with the result that the wheel will turn more or less obliquely to the wind €knd receive its force with

diminished ef fect.  To stop the mill,  the spring is extended by an external agency—^namely,  the wire cord seen in

Fig.  66,  d and—^which causes the wheel to turn parallel to the vane,  so that it presents only its edge to the wind.

The Tail.  —^An enlarged view of  the tail V€wie is given at Fig.  65,  6.  The arms are of  l^-in.  by l^in.  stuf f ,  tapered

to the outer end.  A f ine saw cut is run up to a distance of  2 f t.  6 in.  f rom the outer end to receive the vane,  which

may be of  galvanized sheet steel of  about 20 S.W.G.  The cross-piece,  shown at Fig.  66,  c,  is to act as a stop when

the vane is pulled parallel to the wheel.  The inner end of  the vane is stif fened by a l^-in.  by ^in.  strip at each

side where the steel wire cord and the spring are attached.  The last may be a large-sized bell spring,  but some

experimenting will be needed to obtain the requisite adjustment.

The cord passes over two pulleys and down the turn-table tube.  It will be necessary to attach the end of  the cord

to a short cylinder of  hard wood or metal,  say,  f rom 2 in.  to 3 in.  in

*t TO owe rooT

f—••-. .^

Fig.  67.—DetaUf l of  windmilL (i,  j) Frame; f ront and aida ▼lews,  {k^ Q Axle of  wheeL (m) Attaohment of  inner

end of  vane to inner ring of  f rame,  (n) Vane on rings,  (o) Attachment of  vane to outer braokets by bracket {p),

S15

216 THINGS WORTH MAKING.

diameter {x in Pig.  66,  a),  which revolves with the turn-table,  but can be slid up or down.  The easiest plan is to

cut a hole through the axis of  the cylinder to f it the (square) pump rod.  If  a groove be now cut in the

circumference of  the cylinder,  and two pieces of  iron be bent into the shape of  eccentric straps and placed in the

groove,  cords can be taken f rom the two bolts which unite the straps.  These two cords should be joined to

another which is taken to a reel or a lever,  y (Fig.  66,  a),  at the base of  the tower.  In this way the position of  the

tail vane can be regulated f rom a stationary point.