PLANING-MILL MACHINERY. ITS SELECTION, ARRANGEMENT AND CARE. In times when business must be done on small margins, and when the most lively competition presses all branches of trade and manufacture, a new significance is given to the aphorism that "economy is wealth." Though not its derivative signification, economy really means "wellordered arrangement," and the benefits to be derived from such a system as will produce the best and greatest results with the least expenditure, are perhaps more marked in the manufacture of wood into its various forms of use than in any other line of industry. Often the same firm will own the pine land, cut the logs, haul them to streams controlled by themselves, drive them to their saw-mills, saw them, convey the mill product in their own vessels to the manufacturing and wholesale points, unload at their private docks, kiln-dry, and manufacture at their own planingmills into the many forms demanded by the trade, thence shipping directly to the retail markets; thus bringing under one management all the various stages of production, manufacture and transportation that, in most lines, are divided among many parties. This concentration of such various and far-extended lines of operation calls for the highest executive ability and the keenest insight into detail, lest the advantage to be gained by leading into one channel so many streams of industry should be lost by the friction and leakage thereby likely to result. Perhaps at no point in this chain of operations is the need of the personal oversight of the owner greater than at the mills, and there it is often most lacking. For this reason, the man of small means who simply owns or runs a mill, but who applies practical and scientific knowledge in its constant, personal oversight, can successfully compete with the great firms whose immense affairs cannot be conducted with such absolute economy as rules in his smaller establishment. The object of these pages is to offer a statement of facts and some suggestions, based on the experience of practical mill men and professional engineers, in regard to the best and most economical construction and arrangement of planingmill machinery. In studying this subject, the first thing that comes under consideration is the character and amount of power required, and as steam power is almost entirely used in planing-mills the discussion of water-power will be omitted and steam power will be alone considered. In very few lines of manufacture are such varying and sudden demands made upon the power as in a planing-mill. The sudden starting of heavy planers and saws strains an engine to its utmost, and if it is not strong enough, costly repairs and delays draw heavily upon the profits of the business. The work to be done should be accurately calculated, and the engine and boilers adapted to this result, making them powerful enough to drive all the machinery intended to be put in, even if all started at once. If the boilers have too limited steam room, excessively hot fires must be kept up in order to generate steam of sufficiently high temperature and pressure to supply the demand, and the result is that there is danger of burning the boiler, and unequal expansions and contractions cause leakage, fractures, etc., and drawing more steam from a boiler than it was calculated to supply, often causes pulsation which soon tears it to pieces. The kinds of boilers and engines required for various mills depend so much on local conditions that no one form can be recommended as applicable to all of them. Proprietors and managers and engineers have their preferences, and can profit by the experience of other mills in similar localities. A few years ago furnaces were built with a view to consuming all the fuel possible for the purpose of getting rid of the shavings; but a change has taken place, and now economy in fuel is a nesessity. There is no doubt that the more simple the construction of a boiler the less likely it is to get out of order, and the less care and skill is required on the part of the fireman or engineer; and where economy of fuel is a secondary matter, the plain cylinder boiler is the safest and most easily cared for and repaired. Where proper attention and skill can be given to the care of a boiler, experience has shown that the tubular gives the best results; the flue boiler is, however, very extensively used in planingmills, as a practical and valuable compromise between the cylinder and tubular forms. But whatever form is determined upon, if the engineer has not a thorough technical knowledge of the subject, a responsible firm should be selected to build it, and to them, having been informed of the kind and amount of work required, should be intrusted the proportions. But some principles can be profitably laid down for the guidance of the purchaser, The size of the water and steam room of a boiler should be determined, partly, by the character of the fuel. It is evident that in a fire fed by shavings and mill refuse there cannot be maintained a steady heat, and with a small quantity of water the temperature would change with every change of the fire, while a larger amount of water would retain heat for a longer time, and the amount of steam given off would not be sensibly affected in so short a time. Many of the best authorities disparage the value of the dome. It adds but very little to the steam capacity, while it weakens the boiler to a disproportionate extent. A steam dome of ordinary size will add but about one-tenth to the steam capacity of the boiler. It would act as an antiprimer, and would supply drier steam if the metal of which it is made were kept at the same, or higher, temperature as the other part of the boiler; but, as the dome is usually exposed to the action of the air, it is kept at a lower temperature than the main part of the boiler, and cools the steam coming in contact with it, producing partial condensation; and thus it happens that steam taken from a dome is often more wet than that in any other part of the boiler. While the steam room should be ample to meet sudden demands from the engine, the reservoir of power is mainly in the heated water. With a working pressure of 60 pounds, each cubic foot of steam in the boiler will produce only 4.65 cubic feet of steam at atmospheric pressure; but one cubic foot of water in the boiler will produce nearly 35 times that amount, as at 60 pounds pressure the temperature of the water is 307.5°, or 95.5° above the boiling point at atmospheric pressure; and as every degree of heat added to water already at 212° may be taken as competent to generate 1.7 cubic feet of steam, 95.5° will produce 162.35 cubic feet, or nearly 35 times as much as one cubic foot of steam at 60 pounds pressure. In general, according to the best authorities, water should occupy three fourths of the boiler room, and, within limits, the larger the boiler, the more economical will be the use of fuel. The following table may be of value, it is given by Roper, and can be relied upon as being as accurate as any that can be obtained: Table Showing the Proper Diameter and Height of Chimney for any Kind of Fuel. "For stationary boilers, the area of the chimney should be one-fifth greater than the combined area of all the flues or tubes. In boilers provided with any other means of draught, such as a steam-jet or a fanblower, the size of the chimney is not so important as it is in cases where the draught is produced solely by the chimney. Rule for finding the Required Area of Chimney for any Boiler.-Multiply the nominal horse-power of the boiler by 112, and divide the product by the square root of the height of the chimney in feet. The quotient will be the required area in square inches. According to the experiments of Mr. Isherwood, the best proportion for the draught area is one-eighth of the area of the grate. Many constructors, however, make it greater, amounting in some cases to one-seventh and one-sixth. Others make it less, one-tenth being not uncommon. But experience has shown one-eighth to be the most practical proportion, and the one capable of producing the most satisfactory results." It is unnecessary here to give figures as to the number and size of the flues, amount of heating surface, size of fire-box, ash-pit, etc., which are furnished by the engineer in charge. The boiler room should either be located at a distance from the mill, or should be so protected by brick or iron-covered walls that there will be no danger of a fire starting there communicating with the main building. The engine room should also be entirely separated from the mill, but, in this case, for protection to the engine, as the dust which abounds in a planing-mill should be kept from the engine as far as possible. For planing-mill use an engine is to be recommended that has as little brass and bright work as possible, as, in spite of all precautions, it cannot be kept clean without being continually wiped off, and engineers soon tire of this, the consequence of which is it goes about half clean, when it looks worse than the wrought iron painted, as this can be wiped once a day and look comparatively clean. It is well to repeat what has been mentioned as to the power of engines. The engine should be large enough to drive, easily, all the machinery at once, that is intended to be put in, and a little extra power will be an advantage in the long run. To insure steady motion the driving pulley should be as large as expedient and of a weight of 600 pounds to the inch of cylinder diameter, and the piston should have a speed of from 350 to 400 feet per minute. To find the horse-power of an engine, multiply the area of the piston in square inches, by the speed of the piston in feet per minute, and divide the product by 33,000. The result is the horse-power value of one pound mean effective pressure, and if multiplied by the whole mean effective pressure, will give the indicated horse-power. Another nearly correct method, easy to remember and correct enough for ordinary purposes, is as follows: Multiply together the square of the diameter of the cylinder in inches, the length of the stroke in inches, the number of revolutions per minute, and the steam pressure; multiply the product by four and cut off six figures at the right. Not infrequently is it the case that a person wishes to approximately determine the transmitting power of a given size without the trouble of making a calculation, and to assist this class the following table is given: Cylinder. 7x12 in..10 horse-power Cylinder.12 x20 in..30 horse-power 12 " x24 x20" 14 x24" 66 8 x15 12 35 66 14 The amount of power necessary to drive a planing-mill can easily be calculated from the figures given below: 30 inch surfacer, 1 side. 8 horse-power. .10 66 with 2 cylinders. 7 moulding machine, 4 sides 66 4 66 Circular saws, for each inch of cut above table.. 1 These figures are mostly from J. E. Richard's calculations, and are as nearly correct as can be made. SHAFTING AND PULLEYS. Following the subject of power will appropriately come the consideration of the methods by which the power is transferred from the engine to the machinery; viz.: shafting, with the accompanying bearings, hangers, pulleys, etc., and the modes of erecting them. Tables of strength of materials show that cold rolled shafting is much superior to the hot rolled for whatever purpose it is used. Its resistance to torsion. or twisting, is 30 per cent. greater than that of the latter. Hangers for line shafting in planing-mills should be of sufficient strength to tear asunder the belts which are carried upon the shaft they support, without breaking; otherwise serious accidents from winding belts may occur, in consequence of the width and strength of such belting as it is necessary to use. A "cored section" for a hanger, is the only kind which should be used in such mills. These are made of sufficient strength by the best manufacturers, and it is therefore unnecessary to give here any figures as to their proper size or weight. They should be placed at a distance apart not to exceed 10 feet; 8 feet |