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Early in 1886 Mr. Charles Esplin, of the Pray Manufacturing Co., of Minneapolis, Minn., built a Band Mill upon an entirely new principle, and one of them was operated that year by the Superior Lumber Co., of Ashland, Wis. It was illustrated and advertised in 1887 as “the only perfect Band Mill in use.” It transpired, however, that the analysis of band saw troubles and their causes as published by Mr. Esplin was truly perfect, but the Band Mill built by him to correct the troubles was imperfect to the extreme, as will be seen; and the wonder is that he did not see it himself, when clearly on the right track.
Band Saw Mill of Charles Esplin
To understand this construction it is proper to state that the attempt is made to apply an exceedingly sensitive and automatic strain to the band saw; a strain instantly responsive to any change in the run of the saw, whether due to expansion or slippage; no matter what might happen the strain would always be uniform, and perfect lumber with lots of it would be the continual result.
The top wheel with its shaft was mounted in fixed boxes, adjustable only in order to change saws. But the heavy lower wheel with its large shaft and belt pulley was mounted in boxes integral with an iron rocker or tightener frame to which was attached a long weighted lever like an old fashioned safety valve lever; and the wheel thus equipped was placed in the saw. Thus it will be seen that the weight of the wheel with its shaft and the rocker frame, lever, weight and pulley, was employed to strain that saw downward automatically; and it was designed that this wheel acting through gravity should respond instantly to changes which might occur to the saw, whereby all slack would be taken up and a perfectly uniform tension be maintained.
This kind of talk was certainly catchy with lumbermen for it also sounded good. There was, however, just one thing Mr. Esplin and others overlooked, namely, if an adjustment is at all necessary to meet changing conditions in a band saw running from 9,000 to 10,000 feet in a minute, then that adjustment must of necessity take place almost like a flash of lightning, and that automatically.
Mr. Esplin’s lower wheel, boxing, shaft, belt pulley, rocker frame, lever and weight probably weighed four tons. Such a weight cannot move like a flash, and goes too far when it does move, and broken saws or snakey lumber were the logical result. The inertia of such a mass prevents quick action.
This mill was a failure like the rest, and the designers of Band Saw Mills for sawing logs were left groping in darkness. To be sure, Band Mills to some extent were in use though largely under protest because of the poor lumber they made, the small quantities produced, and the troubles experienced with cracked and broken saws.
