A Treatise on the Construction and Operation of Wood-working Machines ... by John Richards

Author:John Richards
Language: eng
Format: epub
Publisher: E. & F. N. Spon
Published: 1872-03-25T05:00:00+00:00

Edge thickness of rim E = | 2 ' | an increasing progression, A = 8j^, B = i, N = D.

Too

Centre „ „ „ C = -OSP + E.

Number of arms N; when D> 12, N = 5; D>30, N = 6.

Breadth of arm at rim B = ^- ==— ^ —, increasing to hub 1" in 16".

Thickness of arm T = -^, parallel from rim to hub.

♦ O

I—I o Ex] I ^

Q «5

I

n u

3

■s

Hubs.

ParaUelogram of web P = -^D + F,fihown in Fig. (^^^^)

Web of hnb W = P + T, M shown in Fig. Shaffc to be uBed S.

A^D-j-F P

End diameter of bub H = ^ ^^ f- S, or j^ -f- S, increasing 1" in 16" to web.

p Metal thickness of hub M = -—when selHscrew bosses are used; for splhie add ^ to M.

F

Versed sine of facial curvature = wj for high faces.

64 •

EECIPEOCATING MOTION IN WOOP-WOEKING MACHINES.

Before entering into any remarks upon sawing machinery we will devote some attention to reciprocating machines in general.

That reciprocating motion is very imperfectly understood is a fact that no one with an experience among the makers of machines will dispute. There is, of course, nothing involved in it that is not fully comprehended in the known laws of physical science, and it is, in that sense, well understood; our meaning is, that such knowledge has not heen sufficiently elucidated in text-hooks, or has failed to be appreciated and understood by those who are practically concerned in its application to construction.

Science in its researches has left but few nooks in the industrial arts unexplored; every detail of shop manipulation, every conceivable application of mechanical forces, has, with but few exceptions, passed through the ordeal of scientific criticism and investigation. Even the most simple matters have become the subject of abstruse mathematical calculation, and are demonstrated in formulas that are a- hundredfold more complicated than the operations themselves. This 25eal to apply mathematics to our shop manipulation, or rather to all matters pertaining to mechanics, has, no doubt, in a large

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measure, to be imputed to a receut realization of the fact that they are intimately connected. But now that experience has proved that the mechanics who rely upon scientific data, and who follow the principles of construction as laid down from the deductions of scientific men, are the only ones to succeed, it has not only awakened an interest but a pride in the amount of such knowledge possessed in our shops. This zeal to study theoretical mechanics is sufficiently attested in the number of polytechnic and other scientific institutions of learning of this kind that have recently sprung up.

The discovery of the mechanical equivalent of heat has done much to restore confidence in the theoretical laws of mechanics. Without this philosophy a link in the chain was wanting; there was a stopping point to theoretical deductions about forces; much that could not be explained in a manner sufficiently rational to gain the confidence of mechanics when they had

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