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Homework Help: Inflatable seatbelt

  1. Jan 12, 2015 #1
    I am making a project on inflatable seat belt ()

    I need some help with calculations
    I will be working with a air cylinder with compressed air in it, a solenoid valve (electro pneumatic), and seatbelt made out of airbag fabric.

    how do i determine how much pressure i need in air cylinder( previously ive built the same project with 85psi but did not take care of specifics and performance, and 85 was just an arbitrary value which i could attain max that time ,and i don't have access to that project anymore)

    how how do i calculate optimum pressure required,aslo what kind of valve should be used on the cylinder before the solenoid valve is attached, as this time i need things to be more specific

    if more data is required please ask me, am badly in need of help
    Last edited by a moderator: Jan 12, 2015
  2. jcsd
  3. Jan 12, 2015 #2

    Stephen Tashi

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    Science Advisor

    You'd have to say what you mean by "optimum" first and this may not be simple. What is being optimized?

    It may be a compromise between several objectives. Is the objective to inflate the belt as quickly as possible to some given pressure in the belt? Is this belt reusable after it inflates? Must the cylinder hold enough pressurized air for several uses? - or is it for a single use, like an air bag ?
  4. Jan 12, 2015 #3
    By optimum i mean what minimum pressure is sufficient to inflate it quickly(as i said previously i kept pressure 85psi,is 85 psi really required)

    And yes it needs to inflate real quick and if required two cylinders and valves may be used

    And yes it should hold pressure in bag but not for long as soon as it inflates it also starts to deflate as in airbag

    Yes it can be reused unlike airbag, and a container should contain air for more than 1 inflation(but thats not mandatory)
  5. Jan 12, 2015 #4


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    Education Advisor
    Gold Member

    By "real quick" I assume you mean 37 days. This is "real quick" for purposes of getting a document back from the government.

    What? It needs to be faster than that? Ok, you need to send me the cash to pay my Mind Reading Bill. Or you need to put in a number for how quick is "real quick."

    As to "what sort of valve" you need, I'm guessing "real quick." You could Google up some valve makers and their products, and see what opening characteristics they have.
  6. Jan 12, 2015 #5


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    Staff: Mentor

    @sdawkins -- can you tell us how a regular airbag inflates/deflates? What is used? And how is your design going to differ from that?
  7. Jan 12, 2015 #6
    Ford claims its system works in 40milliseconds
    So that is the desired result but for me i can go upto 80milliseconds

    A regular airbag inflates using chemical reactions,generating gases required for inflation.as soon as the air bag inflates the gases starts to escape from small pores of the airbags.

    In my project cold compressed gas is used for inflation, for ease of calculation deflation may be ignored
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