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  1. gareth71

    Impact test - 100ft.lbs

    A closure is a box, something that goes around stuff. Some people call it an enclosure, but a pedant would say an enclosure is what's enclosed in a closure, for example a letter is enclosed in an envelope. The envelope is the closure. Anyway, back on track, it's a good point about any...
  2. gareth71

    Impact test - 100ft.lbs

    I don't think anything is JCB-proof so perhaps it really is for spades that come zooming through the topsoil. I think the copyright lawyers would hunt me down if I copy too much of the standard, but here's part of it. You guys will bail me out, won't you? All closures shall be tested in...
  3. gareth71

    Impact test - 100ft.lbs

    BUGGAR (Structural) 24 Feb 16 18:38 I've also seen a similar test for safety glazing and racing helmets. Please tell us your test standard. I think you're right, this kind of test would trouble a racing helmet, it's that kind of impact. It just seems a bit excessive for fibre optic enclosures...
  4. gareth71

    Impact test - 100ft.lbs

    That's very bad, it's the same as I got in my first post. As an old manager used to say "don't tell me that answer, tell me the answer I want to hear" To give a little background this test is for an enclosure for fibre optics, they're almost all moulded from polypropylene which despite being...
  5. gareth71

    Impact test - 100ft.lbs

    Agreed, I'm expecting my university to revoke my degree any minute now. I was just converting through from ft.lbs
  6. gareth71

    Impact test - 100ft.lbs

    Thanks and yes, I can manage to multiply 3 numbers together [wink] although it was o-levels when I did it. As the impact is probably an energy then I think you're right - I can divide my 13.7mkg by 9.81m/s to drop the 1kg weight from a mere 1.4m which sounds more plausible.
  7. gareth71

    Impact test - 100ft.lbs

    Hi, I've got a test standard which states the component must withstand an impact of 100 ft.lbs, I dread to ask this question but I just have to... is this test dropping a weight of 1lb from 100 ft? Therefore a 10lb weight from 10ft? In metric measurements I've worked it as 13.7m kg The reason...
  8. gareth71

    Flat spring takes on permanent set

    israelkk - thanks for the idea about getting different angles made up, that sounds like a good plan to evaluate what's best as the mechanics is more complex than my simple beam calculations can handle. You're right that the load point moves as the shutter does; it travels from one end of the...
  9. gareth71

    Flat spring takes on permanent set

    Unfortunately I don't have any software to do a large deflection analysis, as I said this is a legacy product and I've got no design notes on what was considered initially (about 12 years ago).
  10. gareth71

    Flat spring takes on permanent set

    The angle after fully compressing it goes down to about 55 or 60 degrees. I can't limit the shutter travel unfortunately so it's really getting past its elastic limit.
  11. gareth71

    Flat spring takes on permanent set

    I'll ask the material supplier for the datasheet, but I do know it was tested at 2500N/mm2. The thickness comes in at 0.26 rather than the 0.25 in the spec, as its stiffness is proportional to the cube of the thickness that make about 12% difference on its own. Stiffness at full deflection...
  12. gareth71

    Flat spring takes on permanent set

    This is a legacy design made from galvanised spring steel, they were always made to a material spec of BS5216, minimum tensile strength 2500 N/mm2 The supplier is now unable to get this material and we've had samples in different new materials but they all take on a compression set, see the...
  13. gareth71

    Units conversion for impact test - ft.lb to Joules

    ok, thanks everyone. It looks like my answer was correct and we'll be non-compliant on that part of the spec. 136 Joules is an enormous impact energy to survive, especially as the other requirement is only 20J. But thank you for your help!
  14. gareth71

    Units conversion for impact test - ft.lb to Joules

    I know there are a bizillion converters online, but I don't necessarily trust them. zdas, I've got two different specs for a similar product, one says 100ft.lb and the other says 20J. By my (and RobyengIT's) calculations they are very, very different. I was looking for someone to say I had...
  15. gareth71

    Units conversion for impact test - ft.lb to Joules

    Yes, that's the same as I got with a couple of my rounding errors. I was really hoping to be wrong by a factor of 10, something to do with lb weight and lb force....
  16. gareth71

    Units conversion for impact test - ft.lb to Joules

    I've got a US spec which asks for a 100ft.lb impact test done by a drop tube. I almost can't bare to ask this, but what is the height and weight for that test? If it's really a 1 lb weight from 100 feet, or 100lb from 1 foot, that's (please check!) a 5kg weight from 2.8m or 137 Joules. The...

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