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  1. JMOwen

    Permeability of Polypropylene with Ethanol?

    I'm trying to find out the transfer rate of methanol through a ~1mm sheet of Polypropylene. Can any one help? I've done a fairly extensive search on the web and have good data for HDPE which is a reasonable match I beleive but its PP data that I specifically require. Thanks for your help
  2. JMOwen

    Diffusion rate of methanol though polypropylene sheet

    I'm trying to find out the transfer rate of methanol through a ~1mm sheet of Polypropylene. Can any one help? I've done a fairly extensive search on the web and have good data for HDPE which is a reasonable match I beleive but its PP data that I specifically require. Thanks for your help
  3. JMOwen

    Permeability of Polypropylene WRT Methanol

    I'm trying to find out the transfer rate of methanol through a ~1mm sheet of Polypropylene. Can any one help? I've done a fairly extensive search on the web and have good data for HDPE which is a reasonable match I beleive but its PP data that I specifically require. Thanks for your help
  4. JMOwen

    Coldroom Relief Valve Sizing, 5000 lpm air purge....

    Gents, I'm trying to source relief valve(s) to vent up to 5000 lpm of air at -20°C from a 30m x 6m x 5m coldroom with a back pressure not greater than 100 Pa. Does anyone have any experience of venting on this scale. I've looked into using banks of small (100mm dia) commercial valves designed...
  5. JMOwen

    Mild Steels at -80¦C?

    Jahawker, My application was at -80°C and as mild steels appear loose any fracture toughness below ~-40°C I didn't pursue them any further. There is however a lot of data on the web from steel manufacturers / suppliers. I'd advise you to contact them directly.
  6. JMOwen

    Wrap Spring Clutch Design?

    John, The information was difficult to find but there are two sources that I found useful. The info from IST was the most relevent for my application. It is a paper imaginatively titled 'The Spring Clutch' by C.F Wiebusch, New York, from the Journal of Applied Mechanics, September 1939. I...
  7. JMOwen

    Stiffness of plate arrayed with holes?

    I'm trying to determine the stiffness of a perforated plate 25mm thick arrayed with through holes 1.7mm dia on a 4.5mm horizontal and vertical pitch. The holes are in a square array (not honeycombed. I've found data on perforated sheet but not thick plate. Anyone out there had a similar...
  8. JMOwen

    Wrap Spring Clutch Design?

    Thanks Guys Managed to source a paper from The Institute of Spring Technology, Sheffield UK with the calculations I need. Justin
  9. JMOwen

    Wrap Spring Clutch Design?

    Thanks all, Isrealkk, could you let me have the formula? The book's out of print and hard to find here in the UK, it's available from amazon etc but on a 2-4 week lead which is too late... The clutch design is simply two bars pushed into the ends of helical spring. Torque requirement in 0.1...
  10. JMOwen

    Wrap Spring Clutch Design?

    Can anyone help me to determine the relationship between the slip torque of a wrap spring clutch and the pre assembly interfence of the spring internal diamter and the hub. I'm trying to determine the sensitivity of the clutch slip torgue to manufacturing tolerances. Cheers Justin
  11. JMOwen

    -80¦C refrigeration, single stage in -20¦C ambient?

    I'm in the UK
  12. JMOwen

    -80¦C refrigeration, single stage in -20¦C ambient?

    pennpoint, I'm familiar with vacuum insulated hose and but it is not appropriate for this application because of the design of the robot and concerns over its longevity (it could be flexed up to 3 million times over its life). -20 will be acheived using multiple dx refrigeration systems. I'm...
  13. JMOwen

    -80¦C refrigeration, single stage in -20¦C ambient?

    Thanks Sterl, IRstuff and Pennpoint for your latest posts. I liked the cryocooler - looks like an interesting technology, but It would be impossible to integrate and certainly more expensive that a single stage or even cascade conventional mechanical system. The area I am trying to cool is...
  14. JMOwen

    -80¦C refrigeration, single stage in -20¦C ambient?

    MintJulep, LN2 would be my first choice but it this instance it is impossible to supply it (or any other fluid) to the process to area to be cooled. A small local mechanical system is the only practical solution I think. Even considered peltiers (for about a nanosecond! - think 200W and ~80...
  15. JMOwen

    -80¦C refrigeration, single stage in -20¦C ambient?

    Thanks for all your responses: To clarify a few points: I can guarantee holding the -20 condition as the unit will be located in a room chilled by with multiple redundant -20 cooling systems. The condenser could be air cooled by the -20 air resulting in a condensing temperature ~ -25°C...
  16. JMOwen

    -80¦C refrigeration, single stage in -20¦C ambient?

    Yes. What I'm looking for is a compressor / refrigerant combination that would meet the -80 evap, -25 condensing condition. I've spoken with a few of the big manufacturers here in europe and they don't offer anything below -40 evap.
  17. JMOwen

    -80¦C refrigeration, single stage in -20¦C ambient?

    Hi, Thanks for taking the time read this post... Does anyone know whether there are compressors and refrigerants available that would transfer ~200W at -80°C evaporating, -25°C condensing? The unit would be located in a -20°C room, hence the low condensing temperature. I'd like to avoid a...
  18. JMOwen

    low cost stainless steel for -80¦C application

    I am currently evaluating the design of some large but lightly stressed welded storage frames. We have many years of experience of similar designs fabricated in mild steel (S275/43A) operating in a -20°C environment. My concern is that that the new generation of frames will be in service at...
  19. JMOwen

    Mild Steels at -80¦C

    I am currently evaluating the design of some large but lightly stressed welded storage frames. We have many years of experience of similar designs fabricated in mild steel (S275/43A) operating in a -20°C environment. My concern is that that the new generation of frames will be in service at...
  20. JMOwen

    Mild Steels at -80¦C?

    I am currently evaluating the design of some large but lightly stressed welded storage frames. We have many years of experience of similar designs fabricated in mild steel (S275/43A) operating in a -20°C environment. My concern is that that the new generation of frames will be in service at...

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