Detachable Litter Base
Neo-Natal Intensive Care Air Transport Equipment
Progress Report, March 15, 2006
Contributing Members (PSU Mechanical Engineering Students)
Clay Hammond (503)-705-3803
Nick Kuzmenko (503)-679-6422
David Searls (503)-651- 3811
Kathryn Kling (971)-533-2576
Academic Advisor (Boeing & PSU Faculty)
Marshall Smith(503)-833-2736
Sponsor & Industry Advisor (Fleigen Works Inc.)
Micah H. Hamley (503)-221-4001
Executive Summary
When a critically ill infant must be transported, every second counts. Therefore, the equipment used to transfer these tiny patients must be simple, lightweight, rugged, and easy to use. Fleigen Works, a company that provides engineering solutions to aeronautical problems, has taken on the task of redesigning a system used by Legacy Emanuel Hospital for emergency air transport of newborn infants.
The support sled for the current system is a modified adult stretcher. The high weight of this sled contributes to an excessive overall system weight that has led to injuries to the EMT staff that use it. Lower weight results not only in greater safety but also a system that can be loaded and unloaded more quickly, saving valuable seconds.
The current locking system that secures the sled to air transport is also in need of redesign. It can take up to 45 seconds to secure the locking pins with the current configuration. Even with the pins secured there is no visual cues to the pilot to let them know it is secured. Our team has been tasked to include this safety feature in a redesigned locking system.
While there have been some setbacks in the design process, the project is adhering closely enough to the timeline to predict completion on schedule. Our analysis has shown that the design criteria are reasonable. At this point, even allowing for unforeseen difficulties, we should have a working prototype by June.
Table of Contents
INTRODUCTION……………………………………………………………1
MISSION STATEMENT………………………………………….…………2
PROJECT PLANNING……………………………………………………..2
PRODUCT DESIGN SPECIFICATIONS…………………………..……..3
EXTERNAL SEARCH……………………………………….……………..3
INTERNAL SEARCH………………………………………………………5
TOP-LEVEL FINAL DESIGN…………………………………………….8
PROGRESS ON FINAL DESIGN…………………………………….…..9
CONCLUSION AND RECOMMENDATION…………………………..9
APPENDICES……………………………………………………………..11
Introduction and Background
While in transport, premature babies require a collection of life support and monitoring equipment. This comes in the form of an incubator, oxygen tanks, monitors, power supply, etc. For ease of transport and timeliness, the best way to carry all of this is in one assembly, locating all of the components onto some form of a structural platform. The down side to this is the combined weight of all the components, which exceeds 300 pounds. Because of this, it is not entirely uncommon for the Emergency Medical Technicians (EMT’s) to develop back injuries, lifting such a collection in and out of the transporting aircraft. The support base currently utilized by Legacy Emanuel Hospital is a modified stretcher produced by Life Port, Inc. Made primarily almost exclusively of steel, this support base weighs in at approximately 37 lbs.
One of the tasks at hand is to design and engineer a suitable platform, able to carry all necessary equipment, while weighing at least thirty percent less. The final design has to be able to endure guidelines as established by the FAA. This includes ultimate emergency landing loads upward, forward, sideward, downward and rearward of 4.0, 18.0, 8.0, 20 and 1.5 g’s respectively. An additional requirement of the FAA is the validation requirement before allowing such a device to be used, which means subjecting the final design to the above-prescribed loads. The other task is the design of a latching mechanism, which secures the platform to the aircraft for which it is being transported within. Such a mechanism needs to be backward compatible with the existing system or as a stand alone, without introducing interference to other devices such as stretchers that will continue to utilize the existing system. It should be noted that both the support structure and the latching mechanism are allowed to deform, but not fail, in the event of an emergency landing.
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Mission Statement
Design a lightweight support sled for attaching neo-natal intensive care equipment to standard air-transport restraint fixtures. This will replace the existing base and reduce the weight by 30% while conforming to all relevant FAA regulations. A new locking mechanism must also be design that can be locked in half the time as well as having a visual cue that will let the pilots know it is locked. A prototype, complete drawings and a Bill of Materials will be completed by June of 2006.
Project Planning
As can bee seen from the Gantt chart below we have hit the major mile stones need to complete ME 492. The biggest mile stones we still need to hit are testing, prototyping, and the final report for 493.
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Product Design Specifications (PDS)
There are several design constraints for this project, the biggest being weight. Since the main goal is to reduce the weight of the sled to 28 lb this is going to constrain what materials we can use. We also must meet the FAA safety regulations for crash supports; the sled must survive 20Gs in vertical, 18Gs in horizontal. The rest of our product design specifications can be found in appendix (A.1)
External Search
Currently we found only two companies that make neo-natal intensive car air transport units. The first is Life Port Inc, which is what Legacy Emanuel hospital is currently using. As can be seen in figure1, the base sled of the unit is a modified adult stretcher witch adds weight to the unit.
Figure 1 – Example of current system used at Legacy Emanuel hospital
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The other direct competition is from a company named Ferno Aviation Inc, figure 2. While there system is lighter, it is harder to install and carry. It is also another modified adult stretcher.
Figure 2 – Example of Ferno Aviation unit
We found that most of the excess weight in these sleds comes from the fact that these are modified adult stretchers. Design of a sled for the sole use of neo-natal care will cut much weight.
For the lock search we found came up with several products. First we thought about the latching mechanisms of car doors and car seats. These are proven locks that easily available. Another product we thought of using was a pull action latch clamp, figure 3. These would have the benefit of being highly visible to those in the aircraft as to if the lock was engaged or not.
Figure 3: Jergens pull action latch clamp, part number 70558.
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Internal Search
A first design iteration we had was of a folded base sled as can be seen in the figure to the right. The sheet metal base would be folded to give strength and support the equipment attached to it.
Figure 4: sheet metal sled idea
Another design we came up with was a pair of aluminum I-beams to be the spine of the sled with aluminum tubing as hand rails, see figure below.
Figure 5: I-beam sled design
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Our final design for the sled had two iterations, first was instead of I-beams to use hollow rectangle bars to save weight, figure 6. The second iterations have the handle railings attach to the sled’s spine at an angle to provide more strength for the welds, see figure 7.
Figure 6, first iteration of rectangle beams
Figure 7, second
iteration of rectangle
beams with lower handles
For the lock design we first thought about using the current pin receiving blocks on the aircraft by having two pins extruding out of feet blocks on one side of the sled, then using pull action latches to secure the other side.
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The second lock design would use all four of the current pin receiving blocks. As in the design mention above, there would be two extruding pins on one side of the feet blocks. The other two feet blocks would have pins that would be engaged by pull action handles. These would also serve as visual cues to the aircraft personnel that the locks were engaged, figure 8.
Figure 8: Side pin with handle configuration
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Top Level Final Design
For the final selection of our design we used two design matrixes, one for the sled and one for the locks. The categories were weighted for importance base off the PDS requirements, with 1 being the lowest and 5 being the highest.
Design Matrix for locking mechanisms
Cost / Weight / Visibility / Ease of Use / Reliability / TotalCategory Weight (1-5) / 1 / 5 / 3 / 5 / 4
Car door lock, on gurney / 1 / 2 / 1 / 5 / 3.5 / 53
Car seat lock, on gurney / 1 / 2 / 1 / 5 / 4 / 55
Side pins on half, clamp on other half / 1 / 3 / 4 / 3 / 2 / 51
Side pins on half, handle pins on half / 2 / 3 / 4 / 4 / 4 / 65
Design Matrix for sled
Cost / Weight / Strength / Ergonomics / TotalCategory Weight (1-5) / 2 / 5 / 3 / 4
Folded base / 3 / 3 / 2 / 3 / 39
I-beam Base / 2 / 2 / 5 / 2 / 37
Rectangle Base / 3 / 4 / 3.5 / 3 / 48.5
Rectangular beam, fold down handle / 2.5 / 3 / 4 / 4 / 48
As can be seen from the above sled design matrix the rectangle beam base and the rectangle beam base with the lower handles scored the highest with only ½ a point difference. Due to this small difference we will develop these designs further to see which one will in fact be the lightest.
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Progress on Design
Last week, our group was finally able to coordinate a trip to see the actual helicopters and airplanes that carry the neon-natal care equipment. From that visit we came to the realization that our locking mechanism ideas are not practical for the airplane transport. Given that the pin receiving blocks are not in the same potion on every aircraft we came to the conclusion that the current system of spring-activated pins will be the path we should explore.
Conclusion and Recommendations
Much has been learned by the progress that has been made thus far in the project. The work completed and the knowledge gained bode well for a successful completion of the project by early June. The finalization of the frame design can be made soon once a few further analyses have been made. The two frame models that have been created must be analyzed to find necessary wall thicknesses to meet strength and rigidity constraints. Once these analyses are complete the resulting weights can be compared and the lightest frame chosen.
The most challenging aspect of the project has proven to be the design of the latching mechanism. This portion of the project has been hampered by the logistical difficulty of seeing how the pilots and EMTs currently use the sled in the existing aircraft. Our original understanding was that the installation of the sled could be most satisfactorily accomplished by a system that allowed placement and locking to occur as discrete steps. According to feedback from the end user’s, however, a sled that automatically locks in place once it reaches the correct position is more desirable, so long as it has a positive engagement indicator. Having now learned this, we are in a better position to finalize this aspect of the sled with a design similar to the current configuration but with increased reliability and decreased weight, a task that should not prove too difficult.
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It is therefore recommended that the project proceed according to schedule mindful of the time lost due to latch design difficulties. We are planning on continuing work on the project through spring break in order to not lose time or momentum. The design goals have proven to be reasonable and attainable and we anticipate the completion of a sled that will contribute to a neo-natal transport system that is significantly lighter and easier to use than current system.
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Appendices - A.1
The following is our final PDS that shows all of the requirement for our sled and lock design.
Elements / Customer / Requirements / Importance / Metric / TargetWeight / EMTs / Reduce Weight / High / lb / 28lb
Applicable codes / Safety / FAA / Must meet FAA Regulations in crash support / High / Force / 18Gs in vertical, 20Gs in horizontal
Testing / FAA / Passes FAA tests / High / Y/n / Yes
Cost of Production / Fliegen / Do not exceed budget / High / Dollars / $3000 to $6000
Size and Shape / EMTs / Be able to fit in helicopter and through doors / High / Inches / 18 1/2 width
Performance / EMT / Locks secured faster / High / time / 22.5 sec
Aesthetics / Aircraft personal / Visual confirmation of lock / High / Y/n / Yes
Ergonomics / EMTs / Is comfortable to handle / Med / Y/n / Yes
Environment / EMTs / Withstand exposure to weather / Med / Degrees F / -30 to 130
Life in service / EMTs / Last as long as support equipment / Med / Years / 10-20 years
Materials / EMTs / Can't produce toxic fumes, non-flammable / Med / Y/n / Yes
Documentation / FAA / Must provide needed FAA documentation / Low / Y/n / Yes
Legal / Fliegen / Does not infringe on any other patented items / Low / Y/n / Yes
Timelines / PSU Faculty / Follows ME 492 and 493 time lines / Low / Y/n / Yes
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