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  1. JonnyRotten

    Child car seat safety feature

    Thanks for your reply Brian, I'm thinking that I won't use it.
  2. JonnyRotten

    Child car seat safety feature

    Hi Folks, I'm not sure if i am posting this in the correct place so apologies if I'm not. I have recently purchased a Cybex Aton Q infant car seat as per the attached photo. It has a safety feature that I just can't quite get on board with. You are supposed to extend the telescopic rod (Or...
  3. JonnyRotten

    Thermal Expansion of a trapped fluid with a piston and air chamber

    I was hoping to set my limit to approximately 5,000psi (which should be a very small volume in the air chamber). The air compression should be relatively slow - as fast as the oil can expand due to temperature - so the heat should dissipate before it reaches the crazy temperatures that the...
  4. JonnyRotten

    Thermal Expansion of a trapped fluid with a piston and air chamber

    At the moment, I am calculating the volume expansion of the fluid due to temperature and then putting that in as a volume decrease in the air chamber and working out the P rise caused by that, using P1V1/T1=P2V2/T2. Then I am just assuming that the oil chamber will be at this pressure. But I...
  5. JonnyRotten

    Thermal Expansion of a trapped fluid with a piston and air chamber

    Ah I see. The cylinder will have a constant outside temper of 121 degC in a constantly moving fluid so should dissipate some of the heat. Initial pressure will be atmospheric and temp will be ambient.
  6. JonnyRotten

    Thermal Expansion of a trapped fluid with a piston and air chamber

    My final temperature is 121 degC. I want to ensure that the pressure in my Oil chamber builds to 5,000psi. Obviously the air chamber pressure will be the same as I have a floating piston separating the two. So using the equations for gases that you have given me, I still need to equate these to...
  7. JonnyRotten

    Thermal Expansion of a trapped fluid with a piston and air chamber

    Ok thanks, Could anyone point me in the direction of a set of equations that would allow me to calculate what piston stroke and initial air chamber volume required to ensure that the pressure builds up to 5,000psi? This is obviously a function of initial oil volume.
  8. JonnyRotten

    Thermal Expansion of a trapped fluid with a piston and air chamber

    Thanks for your replies. The liquid expansion is significant. If it was fully trapped, it would reach 10,000psi. I want to add enough of an air chamber so that it only reaches 5,000psi at 121 degreesC. Would P1V1/T1=P2V2/T2 be accurate enough? I was using this for the air chamber.
  9. JonnyRotten

    Thermal Expansion of a trapped fluid with a piston and air chamber

    hi Folks, I was hoping for some help in a calculation. I have a cylinder with closed ends and a floating piston in the middle. On one side of the piston I have a fluid and on the other side I have air. I will be heating up the cylinder and I would like to calculate how far the piston would...
  10. JonnyRotten

    basic opposing springs question

    Yeah I understand that - but ultimately I have doubled the spring rate. If i had a single spring with a rate of 1Lb/in, for every extra 1Lb added then it would compress 1". But with the 2 spring arrangement that I have described above then it only compresses 1/2" for every extra 1Lb added.
  11. JonnyRotten

    basic opposing springs question

    israelkk, can you explain why the double rate is trivial please? Thanks
  12. JonnyRotten

    basic opposing springs question

    Hi folks, I'm sure this is a simple question but here goes. I have a plate with 2 coil springs, 1 pushing from each side of the plate. Each with a force of 5Lbs. So the plate is at equilibrium. For argumments sake, lets say each spring is identical with a spring rate of 1Lb/in. If i then add an...
  13. JonnyRotten

    second moment of area

    Is it possible to calculate the second moment of area of a shape with autocad LT 2006?
  14. JonnyRotten

    Calculating the second moment of area

    Hi, Basically i am trying to calculate the load required to deflect the finger of a collet. Its a pipe with slots milled along its length and these fingers will deflect when the collet is inserted into another pipe. So the finger is sort of circular in cross-section. I'm finding it hard to...

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