Essay on the shafts of mills also an introductory account of the progress and improvement of millwork

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Printed for J. Taylor, 1814 - Mills and mill-work - 156 pages
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Page 133 - Muschenbroek has given a very minute detail of the experiments on the ash and the walnut, stating the weights which were required to tear asunder slips taken from the four sides of the tree, and on each side, in a regular progression from the centre to the circumference. The numbers of this table corresponding to these two timbers may therefore be conVOL.
Page 133 - ... the weights which were required to tear asunder slips taken from the four sides of the tree, and on each side in a regular progression from the centre to the circumference. The numbers of this table corresponding to these two timbers may therefore be considered as the average of more than 50 trials made of each, and he says that all the others were made with the same care.
Page 132 - All woods are more tenacious while green, and lose very considerably by drying after the trees are felled The only author who has put it in our power to judge of the propriety of his experiments is Muschenbroek. He has described his method of trial minutely, and it seems unexceptionable. The woods were all formed into slips fit for his apparatus, and part of the slip was cut away to a parallelepiped of one fifth of an inch square, and therefore one twenty-fifth of a square inch in section. The absolute...
Page 38 - RULE II. < For wooden water-wheels, multiply the diameter in feet by the width also in feet, to which add the square of half of the diameter. The cube root of the sum will be nearly equal to the diameter of the gudgeon in inches.
Page 136 - Emerson's is very different from what we find in Muschenbroek's. But precise measures must not be expected in this matter. It is wonderful that in a matter of such unquestionable importance the public has not enabled some persons of judgment to make proper trials.
Page 134 - It may be said in general that two thirds of these weights will sensibly impair the strength after a considerable while; and that one half is the utmost that can remain suspended at them, without risk, for ever; and it is this last allotment that the engineer should reckon upon in his constructions. There is however a considerable difference in this respect. Woods of a very straight fibre, such as fir, will be less impaired by any load which is not sufficient to break them immediately.
Page 135 - He gives us a practical rule, that a cylinder whose diameter is d inches, loaded to one fourth of its absolute strength, will carry as follows: cwt.
Page 137 - The strongest wood of each tree is neither at the centre nor at the circumference, but in the middle between both ; and in Europe it is generally thicker and firmer on the south-east side of the tree. Although iron is much stronger than wood, yet it is more liable to accidental imperfections ; and when it fails, it gives no warning of its approaching fracture. The equable quality of steel may be ascertained by corrosion in an acid ; but there is...
Page 137 - ... teak wood, the tectona grandis, is said to be still stronger than oak. " The strength of different materials in resisting compression, is liable to great variation. In steel and in willow wood, the cohesive and repulsive strength appear to be nearly equal. Oak will suspend much more than fir, but fir will support twice as much as oak, probably on account of the curvature of the fibres of oak.
Page 92 - therefore the strength of the tube is 64, subtracted from 125, is equal to 61, but the strength of the solid axle of the same quantity of matter, and three inches diameter is expressed by the cube of 3 or 27, which is not half of that of the tube. (En. Brit. art. Strength of Materials, 124.)* 190.

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