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Recent content by meenogre

  1. meenogre

    Effect of speed on fatigue life?

    Wire is chromium silicon SAE 9254. There are 4½ coils total, including the squared-off ends of about ½ coil at the small diameter. I can live with losing some force. My goal is to do cycle testing faster without compromising the results. Slower cycling will help the spring last longer? OK...
  2. meenogre

    Effect of speed on fatigue life?

    OK, I ran the numbers on frequency & came up with a resonance of around 90 Hz. I'm nowhere near that, so the only weird thing I can think of will be the total time of compression during the life cycle test. Let me put it another way. If four identical springs are compared before & after a life...
  3. meenogre

    Effect of speed on fatigue life?

    These springs have gone through some type of stress-relief exercise like shot peening during manufacture. (No, I don't understand all this stuff - just enough to be ;-D dangerous.) I also know that brand new springs demonstrate a force output decline over the first X hours of their life. The...
  4. meenogre

    Effect of speed on fatigue life?

    The 3" OD end coils are squared off so the thing stands up straight on the bench, then the coils expand out to ~5" OD middle coils. I know that it doesn't actually operate near the resonant frequency, but I was thinking about cycle testing as fast as 5 or 6 Hz. What does resonating actually do...
  5. meenogre

    Effect of speed on fatigue life?

    Spring: about 5 in dia x 9 in tall barrel style coil spring using about .5 in wire. Fully compresed height is roughly 1.5 in. Fatigue test: cycle spring from almost compressed height to about 4 in height at some rate until it breaks. Question: How does that rate affect the life of the spring?
  6. meenogre

    Hydraulic Actuator-Shock Absorber?

    I've been poking around the web for a cylinder that can perform dampening and actuating. A standard shock absorber (like your car's) simply passes fluid from one side of the piston to the other through an orifice or valve or something to slow it down. Closing that would make the thing a normal...
  7. meenogre

    Latching SSR

    My SSR is rated: Input 105-130 VAC 3VA, Contacts 125VAC 1/3Hp I know that very little current is required to operate it, and they do trickle some current through closed contacts. What are the chances that (OK, I mean parameters that will cause) a closed contact will leak enough current to...
  8. meenogre

    Torque for NPT connections

    Generally speaking, what fails if you over-torque, no wait, I mean over-tighten, no wait, that's the same as torque, I mean over-turn, no wait, I don't mean tip over, I mean over-rotate (whew!) the joint? If a plumber gets to the point he artfully feels is just right, then has to rotate around...
  9. meenogre

    Torque for NPT connections

    So far so good - art & science and all. smckennz, I think that's a good description of that dynamic 'feel' - that's probably how you would program the automated pipefitter to feel it. But how the heck do the pipe fitting designers make sure their parts are good - send 50 samples to 50...
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