Table 15 . --Comparative screen analyses of disk flakes (hammermilled) and ring flakes 

 from unsound forest residue species. Ring flakes are derived from spiral 

 or drum chipper fingerlings ; disk flakes from split chunks. (Logs flaked 

 when green except where noted. ) 





: Percentage of 



material passing 





: through 1/32- 



inch mesh screen 







: Disk flakes 



Spec i es 



: Ring flakes 



: (hammermil led) 





FROM SPIRAL CHIPPER 





FINGERLINGS 





Aspen 



36 



14 



Paper birch 



40 





Western larch 



24 



14 



Lodgepole pine 



23 



10 



Lodgepole pine--dry logs 



33 



16 



Douglas-fir 



10 



11 





FROM DRUM CHIPPER 







FINGERLINGS 





Douglas-fir (58 percent) -- 







Western hemlock (42 percent) 



30 



21 



Douglas-fir 



39 



21 



Fingerling Chips for Flakes 



Many of the experimental panels produced for evaluation in table 14 included ring 

 flakes generated from hand-cut fingerlings. In order to assess the quality of flakes 

 derived from "chipper" fingerlings, experiments were conducted employing partially 

 decayed forest residues (Heebink and Chern; 2 Heebink, and others, in press). 



Included species were Douglas-fir, western hemlock, lodgepole pine, western larch, 

 aspen, and paper birch. Fingerlings from the spiral chipper and Arasmith drum chipper 

 were flaked in a Pallmann ring flaker. Hand-cut chunks of similar material were disk- 

 flaked and then hammermilled . Homogeneous panels were prepared from each furnish 

 retained on 1/32-inch mesh screen. The percentages of fines passing through a 1/32-inch 

 screen are given in table 15. Fines for the ring-flaked material were twice the hammer- 

 milled, disk-flaked material. Normally, for sound wood, the proportion of fines in 

 hammermilled, disk-flaked material passing a 1/32-inch screen is about 3 to 5 percent. 

 The nearly 2 to 4 times the amount of fines generated here reflects the presence of 

 barky or decayed wood and the influence of hammermil ling. 



Flaking decayed material produces proportionately smaller pieces than does flaking 

 sound material, with the proportion of smaller flakes increasing with decreasing residue 

 size. With sound wood (table 16), flake uniformity from disk and ring flakers is notably 

 different. About 93 percent of disk-cut flakes are retained on a >l/4-inch screen, 

 while only 56 percent of ring flakes from hand-cut fingerlings are retained (Lehmann 

 and Geimer 1974) . 



2 Heebink, B. G., and J. Chern. 1975. The "Spiral Chipper": evaluation of an 

 initial reduction device to convert forest residues for structural particleboard . 

 (Unpubl. FPL Off. Rep.) 



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