April 10, 1921 



HARDWOOD RECORD 



51 i 



HIGH HUMIDITY 

 DRY KILN 



"A" — automatic con 

 trots for regulating temper- _ 



iiti-re and lunnuiity. Note that the air 

 trai-cis across only 3^ feet of boards where 

 upon it is reconditioned. This is your giiaraiit, 

 hoard is dry every board is dry. 



'The Kiln With the Circulation 1'om Can Understand" 



B. F. STURTEVANT CO., Hyde Park, Boston, Mass. 



ATLANTA, GA. 

 PHILADELPHIA, PA 



BOSTON, MASS. 

 ROCHESTER, N. Y. 



CHICAGO, ILL. 

 SEATTLE, WASH. 



NEW YORK, N. Y. 

 SAN FRANCISCO, CALIF. 



Coast log turner, which does the same work as the "nigger" in a 

 different way. 



37 Sometimes an overhead log "canter" is used for turning 

 logs, supplementary to the "nigger." It turns the logs by a hook 

 attached to a chain wound on a drum and may be motor-driven. 



38 Jump saws for cross-cutting boards and timbers, hinged 

 transfer skids, the mechanism for raising press rolls on edges and 

 gangs, and for raising saws on a trimmer, are moved by direct 

 steam or compressed-air cylinders. 



39 The carriage which holds the log while being sawed is 

 almost alway.s reciprocated by a steam engine through a wire rope 

 or by a steam cylinder directly connected to the carriage itself. 

 No electrical control system which is simple and sensitive enough 

 has been developed. 



40 All these steam-actuated devices are so simple and positive 

 in action that there is no apparent advantage in developing elec- 

 trical methods as a substitute. 



41 The other principal machines are connected to the motors 

 through flexible couplings, except band mills, band resaws and 

 gangs. The band mills may be so driven, but there are certain 

 objections which should be considered: the motor cuts partly 

 through the mill floor, is inconvenient for inspection, and in the 

 way of workmen; and motor speeds do not always match the 

 speeds of the band mills, requiring a speed-changing device coupled 

 between motor and band-mill arbor. Log band saw mills are built 

 with wheels 6, 7, 8, 9, 10 and 11 feet in diameter. Irrespective of 

 wheel diameter, the saws, and hence the wheel rims, are run at 

 speeds up to 10,500 feet per minute — plain cast iron wheels at 

 twice the ordinary limiting speed of engine flywheel pulleys. 

 Another condition sometimes weighing against connecting a con- 

 stant-speed motor directly to a band-wheel arbor, is that in north- 

 ern hardwood mills the saws may be run at different speeds in 

 winter and in summer. If much frozen tit/oer reaches the saw. 



operators prefer to reduce the speed 1,000 or even 2,000 feet per 

 minute below that used when logs are clear of ice. 



42 Gang mills run at such a low speed and require so' much 

 power that direct-connected motors of sufficient size woul* be 

 very expensive, and standard practice up to the present has been 

 to belt from a higher-speed motor. 



43 The lumber-transporting equipment, including live rolls, 

 chain transfers, chain and belt conveyors, is most conveniently 

 and cheaply group-driven, though there is now a tendency to go 

 farther in the use of individual small motors than there was a few 

 years ago. 



44 The filing-room machines for sharpening saws require little 

 power and are arranged for mounting individual motors directly 

 on the frame in most cases. 



45 When specifying sizes for sawmill motors it must be remem- 

 bered that very great and sudden peak loads are encountered, and 

 the ratings must be larger on this account. In general, it is found 

 that the load factor on an entire sa^vmill is about 60 per cent of 

 the total nameplate rating of the motors. 



46 A condensed list of the machines found in the ordinary saw- 

 mill follows, the sizes of motors suitable therefor being stated in 

 each case. 



Machines Motor Sizes 



Log jack, for hauling logs into the sawmill 25 to 50 hp. 



Circular log cut-off saw, for dividing long logs after 



being drawn into the mill 25 to 50 hp. 



Drag saw, for cutting off logs too large for the circu- 

 lar saw above mentioned 15 to 40 hp. 



Overhead log canter, for turning large logs lying on 



the log storage deck or on the carriage 10 to 20 hp. 



Band mill, for ripping the logs which are moved back 



and forth in front of it on the carriage 100 to 300 hp. 



Circular head saw, sometimes used instead of band 



mill 100 to 400 hp. 



