Hinge Load Test


Load Testing the "Vi Kapler Style" Hinge

created December 21, 2014

Here's the setup that I used to load-test the cast aluminum tail hinges that are used on the Pietenpol Air Camper and several other amateur-built aircraft. The pair of hinges is at the far right of the load beam, with the two-tab half of the hinge screwed to the bench and the single-tab half of the hinge screwed to the underside of the load beam. An AN-3 bolt is used as the hinge pin for testing purposes. A section of 3/4" electrical metallic tubing (EMT) is used as the lever pivot for the wooden 2x4 load beam. The hinges are placed 4" to the right of the lever pivot and the load is placed 30" to the left, giving the load a 7.5:1 mechanical advantage. A galvanized steel pail is used to hold the load, which was wet sand in this test. The vise in the foreground plays no part in the test.

A view of the underside of the load beam showing the EMT pivot tube and the arrangement of the two hinge halves in the jig. Incidentally, the workbench that was used for the test was used by Corky Corbett to assemble the fuselage sides of his second Air Camper, NX42CC, and has traveled nearly 3000 miles from Shreveport, LA to San Antonio, TX and then to Medford, OR.

The test rig under load. The load beam is just about to touch the edge of the bench and the pail could hold no more sand, so the test was stopped here and the load was weighed. The load beam is clearly deflecting and the workbench made a few creaking complaints as the load had been added, but nothing broke or failed. The load at this point was determined to be just over 121 lbs., which means that the hinges were bearing over 900 lbs. of load. This is almost 30% more than the hinge that Vi Kapler load tested to failure, so the test was discontinued and I called it good enough.

I disassembled the test rig and inspected all components. The only apparent change was plastic deformation of the base of the test article as seen above. No such deformation was noted in the test article that Vi sent me from his load test; see image below of Vi's test article and his handwritten notes.


In memory of Vitalis Kapler; May 14, 1927 - December 11, 2014.