Practical and descriptive essays on the art of weaving by Duncan John

Author:Duncan, John
Language: eng
Format: epub, pdf
Tags: Weaving
Publisher: Glasgow : Printed for James and Andrew Duncan
Published: 1807-03-25T05:00:00+00:00

of the tail is made fast, and the other sustains all the weights attached to the harness. The simples which are pulled down to raise the harness are connected to the tail, between the end which is fast and the pullies. Consequently, the simples act in the same ratio, as a weight fixed to a moving pully, suspended by a rope passing through the pully, and of which rope one end is made fast. It has been often demonstrated, that a weight, say of 2 lbs. in this situation, will be balanced by another of only 1 lb. suspended from the other end of the rope, after passing over a fixed pully. Hence the weight, or the power, which is the same thing, applied to the simples to pull them down, must be somewhat more than double the sum of all the weights, attached to that part of the harness which is to be raised. See Emerson's Mechanics, Prop. 27, or almost any elementary treatise.

But in the case of the patent loom, the harness is raised perpendicularly by the comb; consequently, no more power is required than will overcome the sum of the weights to be raised; and if the lever, at the end of which the comb is fixed, be divided into three equal parts, and the centres, or pivots, placed at the distance of one of these parts from the comb, the power will be again doubled: Emerson, Prop. 19. From these calculations, we may deduce, that the power required to raise the harness of the patent loom, v/ill be only about one fourth of that required for the other.

But in every species of complicated mechanism, many deficiencies and objections, which may not be obvious to the eye of a transient spectator, frequently become apparent upon practical experience. For this reason, I was at pains to collect from those who were daily employed in working them, their opinions of the comparative merits of the two plans.

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