March 10, 1921 



HARDWOOD RECORD 



17 



'By Allan E. Hall, Milwaukee, Wis. 



Fig. 1 — Filing Room, with 



The lumher-manujacturing plant 

 includes forest equipment and mill 

 CQuiptnent, only the latter, ho-werer, 

 being considered in this paper. A 

 general statement is given of power 

 consumption, and the method of 

 measuring sairmill production. Saie 

 mills hare been driren by motors for 

 about fifteen years, and the system 

 is gaining. 



A motor-driven mill will produce 

 lumber at a lower poicer consump- 

 tion, and will sare on various items 

 of operating expense. The economti 

 of motor driving depends on the life 

 of the operation, size of plant, and 

 the addition of by-product factories; 

 very rarely on fuel consumption. 

 Fuel generally costs nothing, and 

 under this condition, the sawmill 

 operator can install his own steam- 

 electric plant and genci'ate current 



ehraper than he can buy it. The advantage of unit driring is modified 

 hp the fact that each piece of lumber passes through a chnin of machines. 



The motor-driven mill reduces cost of boilers, power-plant buildings, 

 mechanical transmission machinery, belting and instalUition ; but cost of 

 motors and wiring must be added. Induction motors are practically uni- 

 versal. In a small mill the electric drive will be hit/her in first cost; in 

 a larf/c mill it will be lower. 



Certain log-handling machines, and the earriage feed, arc steam-actuated. 

 The other machines may be motor-driren, generally by individual divect- 

 eonnceted motors. Anxiliary machinery is group-driven. The load factor 

 averages about GO per cent of the motor rating. .1 list of machines with 

 appropriate motor sizes is given. 



The complete modern plant for the manufacture of lumber in- 

 cludes everything required to transform the growing tree into 

 finished lumber ready for the builder; and this plant naturally 

 divides into forest equipment and mill equipment. The forest 

 equipment, which includes logging machinery and railroad and 

 water transportation of the logs to the mill, is not considered in the 

 present paper. The mill equipment, to which attention will be 

 given, reduces tlie log to lumber, dries it, finishes the surface of the 

 lumber if desired, and so converts the log into a marketable product. 



i The mill equipment includes the sawmill proper, the dry 

 kilns, the planing mill, the necessary storage sheds for kiln-dried 

 lumber rough and finished, and a storage yard for part of the lumber 

 which is stacked outdoors for air drying. The sawmill breaks down 

 the log into rough-surfaced pieces of various sizes. Part of this 

 lumber may be shipped "green" from the saw, but most of it is 

 either air-dried or kiln-dried. Part of the dry lumber is also shipped 

 fough, but the higher grades are generally surfaced in the planing 

 mill and made into flooring, siding, ceiling, and numerous other 

 special forms. 



3 It is economical to build the parts of the plant as close to- 

 gether as insurance regulations will permit, and the common rule 

 is that roofed mill buildings must be 200 ft. or more apart at their 

 nearest points. The storage yard should also be 200 ft. or more 

 from the nearest roofed building. Three separate boiler plants 

 may be erected, for sawmill, kilns (which are almost always steam- 

 heated), and planing mill, but this is uncommon. Generally the 

 sawmill boiler plant feeds the kilns. When the planing mill is belt- 

 driven, a separate boiler plant is often built for it. In other cases 

 steam is piped from the sawmill boiler plant to a belted engine in 

 the planing mill. 



4 The capacity of a sawmill is regularly given in thousands of 

 feet board measure per day of 10 hours. The power required for 



^ Allis-Chalmcvs Manufacturing Company. 



Motor Direct-Connected 

 Sharpener 



Automatic Band 



Presented at the Annual Meeting, New York, Dec, 1920, of The American 

 ,^ociety of Mechanical Engineers, 29 West S9th .'Street, New York. 



sawmill alone varies from 4^^ to 

 8 hp. per 1,000 ft. of lumber per 

 day; e.g., a sawmill of 100,000 ft. 

 daily capacity will require from 

 450 to 800 hp. The lower figure 

 is for mills cutting small and 

 medium pine logs; the higher 

 figure for Pacific Coast mills 

 working the heaviest timber, or 

 mills sawing hardwood. 



.5 The planing mill will require 

 from 2 to SVa hp. per 1,000 ft. 

 on the same basis. The total 

 power for milling is therefore 

 from eVa to 111/2 hp. per 1,000 ft. 

 board measure of lumber sawed 

 per 10 hours. 



6 Two things should be kept 

 in mind in estimating and comparing power used in different saw- 

 mills: First, two sawmills rated at 100,000 ft. board measure per 

 day each may deliver this 100,000 ft. in very different forms. The 

 first may be a "board mill" and the entire day's cut may be lin. 

 boards. The second may be a "timber mill" making .50 to 60 per 

 cent of the logs it handles into timbers or large dimension pieces. 

 It is obvious that one 12-in. by 12-in. by 16-ft. timber will add just 

 as many board feet to the day's tally as 12 boards 1 in. by 12 in. by 

 16 ft., but the latter will have consumed much more power. Second, 

 it consumes more power to saw hard, dense wood than to saw soft, 

 light wood. Some mills work hardwood or softwood exclusively; 

 others juust cut various kinds just as they come, owing to the 

 timber supply being of mixed varieties. 



7 Two similar flour mills or cement mills or steel mills, turning 

 out a stream of uniform product, may be compared with consider- 

 able accuracy. Two sawmills both rated at 100,000 ft. capacity 

 may differ widely in power consumption. In this paper an effort 

 has been made to consider average mills cutting a mixture of boards 

 and heavy dimension pieces, the average being possibly 7o per cent 

 of lin. and 2in. lumber and 25 per cent of larger pieces. 



^ Few attempts at driving sawmills electrically were made 

 until after the use of induction motors became common. The 

 earlier efforts to apply direct-current motors to woodworking ma- 

 chinery were few and unimportant. About 1906 the problem of 

 equipping complete sawmills with motor drive began to attract 

 attention, and at least one successful installation was made in that 

 year, at the Oregon Lumber Co., Dee, Ore. During the next three 

 years several new mills were built on this system, and a few were 

 changed from shaft drive to motor drive in the Northwest with 

 striking success. The Pacific Coast states have led in the adoption 

 of the system until it has become almost universal practice in new 

 mills of medium and large size. Until about seven years ago the 

 South and East were behind the Northwest in recognizing the 

 advantas;es of electric driving, but since that time an increas- 

 ing nun ber of plants in the eastern half of the country have 

 adopted it. 



9 Planing mills introduced motors first, as the application was 

 easy and the advantages obvious. Complete sawmills followed, 

 overcom ng skepticism by lumbermen, who were unfamiliar with 

 electrira machinery and afraid of it. Progress has been con- 

 tinuous :lrom the fijst, and no instance is known where a sawmill 

 has changed its driving system from motors back to lineshafting. 

 The illustrations in this paper show clearly the trend toward motor- 

 driven maehinerv. 



