Testing

As a proof of concept of the final design, a prototype was assembled out of 1018 cold rolled steel plate and ½ inch grade 8 hex bolts, nuts and washers to simulate the pins.

With the need for a mechanical advantage in mind the MK II was created using a compact bench-mount lever press. The arbor press chosen has a maximum force of 2000 lbs and provides approximately a 18:1 mechanical advantage when the user applies a force to the very end of the handle. To measure this force a hanging scale is attached and pulled perpendicular to the handle to clamp the hose between the jaws. The output force on the hose is then calculated from the measured force and on the scale using the calculated mechanical advantage.

The high pressure test was conducted at CAL Fire Station 21. This test was conducted under static conditions with the valve at the end of two sticks or 200ft of hose using the MK II testing device. The pressure of the hose was varied using the station truck with a range from 50psi to 300psi. The pressure was measured at increments of 50psi.

The force required to clamp a fire hose is related to both the internal water pressure as well as the magnitude of the deformation of the hose. During the action of clamping the hose the force required can be related to internal water pressure and the stresses present in the hose itself. The model below depicts the force body diagram developed during this project.