Trials with Laminated Crossarms

Due to the increasing cost and limited supply of clear timber crossarms and the high degree of waste and drying degrade involved in their production, the Bell System is considering the use of laminated crossarms. Early tests showed that arms laminated with Douglas-fir lumber and a resorcinol resin glue tended to be as strong as or stronger than solid crossarms of the same species. Specimens loaded with ten 60-lb. blocks and exposed for 3-l/2 years showed no delamination and less surface and end checking than standard creosoted southern pine solid arms. Later tests showed that dead-end arms made from laminated kiln-dried southern pine lumber were about 30 percent lighter and considerably stronger than the standard green, steamed, solid southern pine dead-end arms. Laminated jack pine crossarms check and warp less than solid jack pine arms but do not show any apparent difference in strength. Current Bell specifications for crossarm manufacture are outlined.

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