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R. S. BELCHER, Chairman; W. E. BURKHALTER, ANDREW Gibson, J. F.
PINSON, B. H. PRATER, J. H. WATERMAN, Sub-Committee
Your Sub-Committee was requested to make final report, if practicable, on the preservative treatment of Douglas Fir. Our report will be confined to the treatment of Douglas Fir ties, for the reason that the treatment of fir lumber and fir piling are large subjects of themselves, and we would recommend that a Sub-Committee on fir treatment be appointed next year and a special study made of the treatment of fir lumber and piling as now practiced, and recommendations made as to Standard practice.
General Requirements for Douglas Fir Tie Treatment
Your Sub-Committee believes that the preparation of Douglas Fir
Perforating or Incising
The Douglas Fir log having such a small percentage of sapwood,
pendicular to the fibre, yet the preservative penetrates the heartwood readily parallel to the fibre from any point where the fibre has been cut.
Perforation of the ties not only aids the preservative to effect an entrance into the wood, and enables a more uniform penetration of preservative to be obtained, but also reduces materially the period of time necessary to season fir ties for treatment, and reduces surface checking of the ties to a great extent.
The Perforating Machine There are only two perforating machines in this country, to the knowledge of your Sub-Committee. One of them, owned by the St. Helens Creosoting Company, St. Helens, Oregon, is briefly described as follows:
The cut on the following page shows the machine photographed from different angles. The picture in the lower left-hand corner shows the outgoing side of the machine and the vertical perforating cylinders, also the tension springs which supply sufficient pressure so that the entire length of the tooth which protrudes from the cylinder, enters the wood. The machine has two vertical and two horizontal perforating cylinders and four surfaces of the ties are perforated at one time. Nine eight-foot ties per minute may be perforated when fed into the machine as fast as it will handle them. A fifteen horse power motor drives the machine and is mounted on frame of the machine as shown in upper right-hand picture.
The Perforations The cut on the next page shows the shape of the perforations at the surface of the tie, and their arrangement. A cut of one of the teeth is also shown.
The tooth enters the surface of the tie at an angle of approximately 60 degrees to the surface of the tie. As the perforating cylinder revolves the tooth is forced into the wood, the tooth becoming perpendicular, of course, when its entire length has penetrated the wood, and the sharp edge of the tooth parting the fibres as the tooth is again forced to an angle in leaving the wood.
The perforations shown in the illustration are two inches apart lengthwise of the tie, one and one-quarter inches across the tie and offset one-quarter inch. The tooth is one-eighth inch thick. This arrangement requires that the preservative penetrate five inches each way from the perforation with the fibre, but only requires one-sixteenth inch penetration across the fibre to make impregnation of surface of the tie complete to the depth of the perforations, which are three-quarters of an inch in depth.
As development of perforation of Douglas Fir ties goes on it is probable that the spacing of the perforations will be improved, and it is probable, also, that the shape of the teeth will be improved. It is recommended that Sub-Committee on this subject next year continue the study of the spacing and type of tooth with a view to improvement of both.
Treatment of Douglas Fir Ties With Zinc Chloride Your Sub-Committee recommends that the treatment for Douglas Fir ties with Zinc Chloride be in accordance with the specification for the "Preservative Treatment of Wood with Zinc Chloride” as already approved by this Association.
Experimental Treatments of Douglas Fir Ties With Zinc Chloride
Your Sub-Committee has carried on some experimental treatments on thoroughly seasoned Douglas Fir ties, both perforated and non-perforated. This work was done in a small experimental treating cylinder in which ten ties are treated at one time. A summary of results of
these experimental treatments is attached hereto. In this summary the treatment given each group of runs is indicated and under this is given the average absorption in volume per cent for each run, also the average absorption in volume per cent for the group. It will be noted that the perforated ties, given the same treatment as the non-perforated, in general, show a much higher absorption in volume per cent. This is due to perforations permitting solution to penetrate the sides of the ties as shown in the following illustration of un-perforated and perforated ties.
In these photographs the potassium ferrocyanide uranium acetate visual test has been applied, the dark portions indicate that portion of the wood to which the zinc chloride solution has not penetrated. The immense improvement in the treatment of Douglas Fir due to perforations may be seen by referring to the following photographs.
It appears from our experimental treatments that seasoned perforated fir ties were treated to refusal when the pressure, gradually increased to 175 pounds in 1 hour and 30 minutes, had been held 4 hours, and non-perforated ties, when the pressure, increased to 175 pounds, in 1 hour and 30 minutes, had been held 5 hours.