Pssa  Penn State Seat Attenuator Design Team

                                                 Bryan Kraus                            Zac Chapell                    Mike Reedy                            Joe Recanatini

                                            bmk194@psu.edu                    zac102@psu.edu            msr199@psu.edu                    jur123@psu.edu

 

Project Description:

    We were commissioned by ARCCA, Inc. to design a new CCOPS seat for the High Mobility Multi-purpose Wheeled Vehicles (HMMWV).  The previous seat was unable to prevent soldier injuries sustained from the sudden acceleration of land mines and IED (improvised explosive devices).  With the addition of an energy attenuator, the vertical acceleration levels will be greatly reduced ensuring no serious spinal injuries to a well restrained and seated occupant.

 

Benchmark Design:

   

Mine Blast/Slam Down Injury Analysis Graph:

 

Our Proposed Design:

    The design concept that we will base our mock-up on is the slider-trigger design. The slider-trigger design builds off the four-bar linkage design from the plane crash survival guide.  The difference is that there is an attenuator system that is allowed to slide during the first impulse but becomes rigidly connected to the seat in the second landing impulse to create two separate systems.  In the first impulse, the compression attenuators resist the collapsing motion from the seat linkage system. During this collapsing motion, the second attenuator system is allowed to move along a slider joint in the upper part of the seat.  After the first phase is complete, the seat is airborne.  At this time, a spring system will allow the linkage to return to its original upright position, but actually travel a little bit farther than the original position to engage the second attenuator system.  The second system will be engaged by a trigger slot at the point past the original position which makes the second attenuator system rigidly connected to the seat.  During the landing impulse, the second attenuator system dissipates the energy and leaves the soldier unharmed. The following pictures show the progression of the four bar mechanism.

     

Ratchet Mechanism:

    The ratchet mechanism progression is depicted in the following four pictures. Picture 1 shows the mechanism at rest. Picture 2 shows the mechanism when the first impulse occurs and the seat is moving forward. The yellow pin is moving back along with the ratchet teeth. Picture 3 shows when zero gravity occurs and the seat is moving back upright. You can see that when the yellow pin moves forward, it takes the green pin along with it. Picture 4 shows the green pin has become disconnected with the blue tooth, which springs down and locks into place when the second impulse occurs.

Material and Fabrication:

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Our mock-up consisted of numerous fabrication processes. The top and bottom frame consisted of welded steel tubing. The water jet was used to construct the dog bone links, rack of teeth, ratchet tooth, and parts of the box for the ratchet tooth. The CNC machine was used to fabricate the groves in the ratchet tooth, as well as, the box. This machine was used to ensure precision. The mill was used for the slots in the “L” brackets so the ratchet tooth box can slide along it. A hollow steel tube and a solid aluminum cylinder was used to mimic the compression of the first attenuator. A rigid piece of steel is used to pose as the tension attenuator (We only needed to proof of concept so we didn’t something to mimic the tension). The toggles were fabricated using the mill. Linear springs are used to mimic the torsional springs for the four bar system, as well as, the toggles.  Some complications we ran into during fabrication were machining the small intricate parts. It took the team a lot of time to complete those parts, but feel that a company well versed in machining will not run into as many obstacles.

 

Coming Soon: Pictures of the mock-up upon completion.

 

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