Show the J P karns heading machine CORNELS CORNELL civil ENGINEER there has recently been developed a new machine for use in tunnel driving known as the J P karns heading machine it is essentially a large air drill similar in its action to the ordinary air drill so generally used in tunnel work of the present day it is capable of drilling a hole twelve inches in diameter in hard rock to any depth not exceeding fifteen feet the machine is intended to be used in connection with the small air drill the twelve inch diameter hole is not loaded but is used as a relief taking the place of the usual cut shot which is necessary for the advancement of a heading in the ordinary method of tunnel or heading driving the machine is twenty five feet long over all twenty four inches high above the rail eighteen inches wide and weighs pounds it is mounted on two four wheeled trucks for convenience of transportation and operation resting on the trucks and attached thereto by a kingbolt king bolt through each truck is a structural and cast steel frame supporting the drill which is the important part of the machine the trucks and frame need no further description but it may be well to give a description of the drill proper this has three main features the air cylinder through which the machine gets its power the cutting head and shaft at the right and the feed screw at the left of the cylinder the head and shaft are in one piece being a steel forging and are connected to the piston rod of the air cylinder by a universal joint surrounding the shaft and piston and bolted to the end of the cylinder is a steel casting which forms the support tor for the head and shaft the shell conceals the piston rod universal joint and the shaft attached to the end of the cylinder opposite the head by means of a ball joint is the feed screw which operates in a feed nut it is by means of this screw that the machine is advanced when in operation the only moving parts when operating are the head and shaft the cylinder and the feed screw all other parts of the machine are stationary the head is ten and one half inches in diameter and f fitted to receive removable reamers and cutters which are so designed that they cut a twelve inch diameter hole the two reamers are of the striking type they are hung off center and when they hit the face of the hole are forced outward chipping the outside of the hole and keeping its diameter to gauge the cutters are held rigidly in place by hook bolts extending through the head and secured by wedges on the back the shaft which is forged with the head in a single piece is made of vanadium or nickel steel four inches in diameter ten feet long and supported in the cast steel shell on ball bearings the shaft is so designed that it has the reciprocating and rotating motions of the small air drill the rotation taking place on the back stroke striking a straight blow on the forward motion under the front end of the shell are two pairs of small wheels placed at an angle of 43 degrees with the vertical which support the front end of the drill the wheels are so designed that as the machine advances in the hole they engage the sides of the hole and keep the alignment the only other support is a single wheel underneath the other end of the cylinder which rests U the J P karns heading machine on a forming the bottom of the carriage the air cylinder is a standard five and a half inch rand provided with a standard piston and piston rod except that the chuck of the piston rod is designed to receive and is a part of the universal joint which connects the piston rod and shaft the feed screw is seven feet long and works through the feed nut which slides in grooves in each side of the carriage when the machine has advanced the length of the screw the feed nut which is divided longitudinally in a vertical plane is separated moved forward again clamped on the nut secured in its new position by four pins two on either side and the machine is ready to resume operations to drill a fifteen foot hole the nut has to be moved up twice note recent operations of the karns heading machine in utah on an exhibition run at the old maxfield mine in big cottonwood canyon near salt lake city which property is now being opened up by the boston development company under the management of fred H vahrenkamp demonstrated its wonderful possibilities by boring a one foot diameter hole for easing the ground a distance of fifteen feet in five hours or an average running time of three feet per hour the formation is a hard white limestone after this heading had been run eight small drill holes were used in breaking the seven by nine foot face with ninety pounds of powder with results which were almost unbelievable when compared with the old methods of blasting the test demonstrated that this new method of tun nelling will increase the speed approximately per cent and decrease the cost at least one half there is every evidence that the karns heading machine is now a commercial success and wonderful possibilities were freely predicted by everyone who witnessed the operation of the machine and the shooting of the heading |