Prototype Clamp

Prototype - Clamping Bar

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Step-by-step demonstration of how to use the final design to clamp the fire hose.

Analysis to Justify Design Decisions

In order to test the original design concept and to know if it was a design worth pursuing a rapid prototype was constructed using 80/20 T-Slot aluminum strut and 3 ¼-inch grade 3 bolts with stainless steel sleeves secured with wingnuts and a washer for a lock on pin 3.

The 80/20 strut allowed for quick adjustment of pin location to optimize the restriction of the flow during a low pressure test of 52psi. The final pin locations that resulted in the most flow restriction can be seen in Figure 1, with the residual flow shown in Figure 2.

Figure 1. Side view of clamping bar prototype; bolts and wingnut placement simulates pins on final design.

Figure 2. Water flow result from prototype.

Prototype Simulation Performance

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. 1018 cold rolled and grade 8 steel was selected for the prototype material based on loading calculations for user safety. Von Mises stress and factor of safety plots were calculated at the estimated forces associated with 150 psi operating pressure to check for safety and durability of the prototype in Figure 3 and Figure 4. At 150 psi, the maximum Von Mises stress is felt at the bottom of the second pin at 50.51 ksi.

At that same area the factor of safety is at a minimum of 1.235. Although low, the simulation shows that the prototype will not yield when the water pressure in the hose is 150 psi.

Figure 3. Von Mises stress analysis on prototype at 150psi water flow.

Figure 4. Factor of Safety analysis on prototype at 150psi water flow.

Prototype - Screwing Around

Figure 5. Annotated CAD model of prototype.

Theoretical Predictions

Mechanical advantage from screw =2RL
- R stands for handle radius and L stands for screw lead.
Mechanical advantage from the arm =Force on L1Force on L2
Leverage=L1L2

Analysis

The total mechanical advantage of this design is 1:168. For every one pound force applied, the resulting force is equal to 168.
To clamp a hose at 300 psi, a force of 908 lbs is required.
With an applied force of 5 lb, this design would be able to clamp a hose at 300 psi.
It would only take 9 revolutions to fully clamp the hose.
Height of the hose is 1.5 in. The height between jaws is 1.86 in.
Width of the hose is 2.6 in. Width of the jaws is 3.14 in.
Weight of the clamp if made out of plain carbon steel is 3.49 lbs.

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