. Electric railway journal . [Vol. XLIX, No. 23 safety of two, as is conceded in the National Bureau ofStandards new safety rules to be sufficient for pins. Under these conditions the bottom petticoat of theinsulator is 2 in. above the iron cross arm. As 500 voltswill not jump 1 in., and as the poles are not absolutegrounds, it seemed to be quite safe to make this distancebetween insulator and arm 1 in., as in an actual casethe bottom of the insulator had been only % in. abovethe iron arm at a corner pin for eleven years withoutproducing failure. With the pin thus shortened the load at the sid
. Electric railway journal . [Vol. XLIX, No. 23 safety of two, as is conceded in the National Bureau ofStandards new safety rules to be sufficient for pins. Under these conditions the bottom petticoat of theinsulator is 2 in. above the iron cross arm. As 500 voltswill not jump 1 in., and as the poles are not absolutegrounds, it seemed to be quite safe to make this distancebetween insulator and arm 1 in., as in an actual casethe bottom of the insulator had been only % in. abovethe iron arm at a corner pin for eleven years withoutproducing failure. With the pin thus shortened the load at the side scoreof the corner insulator was brought to within 3 in. ofthe iron cross arm and the safe load on the pin wasmade 3300 lb. with a factor of safety of two. That this strength is ample is shown by the fact thatthe pressure against the side of the corner insulator ata 90-deg. turn, provided with two symmetrically ar-ranged poles, each at the apex of an angle of 135 by the feeder, is as follows for the different. LIGNUM VITAE CABLE INSULATOR serves equally well for both feeder-cable uses, straightline and corners. These lignum vitse insulators had a severe fire test inthe 1906 San Francisco conflagration where great cop-per cables were melted off and standard-pipe iron tubu-lar poles were heated till they bent over the wood insulators, though scorched and in a few casescharred, were ready for service after the ordeal, while
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