918
THEORY AND PRACTICE OF ENGINEERING.
Book II.
When the cylindrical shafts are hollow, the diameter must be multiplied by 1 *05, andwhen the shafts are laid horizontally, something should be added to what is given in theforegoing tables, as they are calculated for vertical shafts.
When the shaft is of wrought-iron, multiply the diameter found by 0 963, if of oak by2-238, when of fir by 2*06.
In the following table is given the dimensions of several shafts, subject to torsion andlateral pressure, and which have been found to work well in practice.
Horse-
power.
Revolutions
per
Minute.
Diameter ofJournals inInches.
Length
of
Shaft.
Sectionof theMiddle.
Diameters
of
Journals.
Cast-iron lying shaft
20
20
6
11
73
7-368
—
18
22
5»
11
7
6-889
—
16
22
5J
10-6
7
6 621
14
» 24
5
10
63
6 153
—
12
25
5
9 6
6
5*768
—
10
25
4 ’
9
63
5-428
—
8
27
4
9
6
4 904
—
6
28
-H
8-6
53
4-414
—
5
30
31
8-6
C|
4-061
—
4
32
33
8
43
3-484
3
34
3J
8
4
1 -203
—
2
36
23
8
3
2-802
—
1
40
2
8
3 i
2-151
Malleable iron lying shaft
6
28
3
8-6
—
5
30
3 i
8
• —
4
32
2
8
! _
3
34
2
8
i _
2
36
13
8
, —
1
40
1
7-6
The cross-tailed gudgeon, which is made ofeast-iron, must be turned very true; it consistsof four leaves, which form a cross, and which arelet into the end of a wooden shaft; the front.edge of each leaf is made thinner than the back,so that when it is inserted, and a pair of stronghoops are driven tight upon the end of the shaft,the wood is closed all round the cross and holdsit fast: screws are occasionally added to securethe cross.
An octangular wooden shaft is generally usedfor a water-wheel, made of a sufficient length toreach across the pit in which the wheel works;the gudgeon at each end supports it, and allowsit to revolve upon its proper bearings. A cast-iron box in this case is fitted upon the end of theshaft and tightly wedged ; this prevents the shaftfrom splitting as effectually as hooping. Uponthe end of this iron box is a projecting flaneli, onthe face of which are four grooves or notches,into which the arms of the iron cross enter; thisis also part of the gudgeon on which the shaftrevolves.
The best shape for cast-iron shafts is tubularor hollow cylindrical; and care should be takerthat at each extremity the metal should bethicker; the gudgeon should have three armscast or wrought on it, so that it can be attachedto the end of the shaft by screws or bolts.
The end of the wooden shaft is sometimesfitted into a cross piece and box, for the purposeof more readily putting on a new gudgeon whenrequired; by simply taking out the screw-boltsthis is easily performed.
Fig. 1297.
Fig. 1298.
Fig. 1299.