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RECOIL MECHANISM-----15-POTTNDER GUN NO. 12.
Recoil Mechanism of Driggs-Seaburt 15-Poundf.r Gun No. 12.
The attachments used in making■ the tests consisted of two eyebars engaging the trunnions, a breech plug with a 3-inch stem extending beyond the breech of ,the gun, and three filling pieces fitted to the bore of the recoil cylinder. These were secured to the testing machine by gripping the eyebars at points beyond the muzzle of the gun, while at the other end the stem of the breech plug was gripped in the opposite hydraulic jaws of the machine. The springs in the recoil cylinder were removed and three special filling pieces were substituted therefor. When the gun was tested in firing position all three filling pieces were used; in recoil position only one piece was in place in the cylinder.
Tensile stresses were applied in an axial ־ direction to the gun by !lulling on the attachments, the reaction being taken up by the recoil mechanism.
Photographs show the gun in the testing machine, and on these prints are sketched the location of the gauged lengths on which observations were made.
The tests began with a series of loadings up to 40,000 pounds, after which the loads were increased to a maximum of 60,000 pounds, the gun being in firing position at the time. These loadings were followed by observations made with the gun in recoil position.
In the first test, the gun being in tiring position as regards the relative positions of the oscillating slide and the sleeve, but bottom side up on account of gaining access to the parts under examination, the observations on gauged length A were made upon the longitudinal movement of the gun with reference to a point on the bottom of the lug of the sleeve at its rear end. As shown by the details, the movement of this part of the sleeve lug was ".0235 under a load of 40,000 pounds tension.
These measurements on gauged length A were followed by measurements of the extension of the piston rod, measured over all on gauged length B. Measurements on other gauged lengths followed in the order in which they appear in the details of the tests.
Photograph No. 1 shows the extensometer in position on gauged length D. On gauged points E to K the micrometer employed was secured to a bar mounted over and supported by steel blocks clamped to the gun.
The tabular details show that a movement of point E on the front end of the oscillating slide lug occurred in a direction from the axis of the gun, while at point F, at the rear end of the same lug, the movement was toward the axis of the gun. Similarly, on gauged points G and H the sleeve lug showed an overturning movement, point H moving away from the gun, point G toward it.
After measurements on gauged length K were completed the gun was rotated 180 degrees, and thus brought right side up. Measurements across from cheek to cheek of the oscillating slide at three places—gauged lengths L, M, and N—were now taken. At L and M the cheeks moved outward when loads were applied, whereas at N the movement was toward the gun, the slides closing inward. Longitu-