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  1. ElronMcK

    MIG pipe welding

    Thanks for the responses. I should have also said that I've got decent competence with MIG, but not certification, and still a little weak on 6G. Clarification - for out of position (say, 5G or 6G), I don't think spray is viable, unless you have a special CV machine that can pulse. Spray is...
  2. ElronMcK

    MIG pipe welding

    I am trying to improve my welding skill set. I am D1.1 certified in stick ("SMAW") 3G 3/4" max thick plate. 1. Assuming AWS and ASME pipe welding - say 0.2" up to 0.5" wall, out of position, short circuit GMAW-S, both shop and field My question: Is MIG with A75/C25 common and/or...
  3. ElronMcK

    Alum Plate Bend Test Fail

    Okay, cut me some slack. Yes, the bend radius is non-uniform. I'm practicing for the test, and bent those coupons in my garage with my own $17 home-made bender. But zero cracks, guys. So much for getting an "attaboy" from the group. Tough crowd.
  4. ElronMcK

    Alum Plate Bend Test Fail

    Following up. My welds are similar, but focused on code-level coupon preparation, and better wrap-bending (wheels with bearings; still a bit imperfect). Also, minimized "time at temperature" per Armao, so just a single CJP per test mockup. No cracks at face bend or backside bend for 2" diameter...
  5. ElronMcK

    Alum Plate Bend Test Fail

    Thanks for the responses. Here's my take-aways for the next set of coupons 1. No preheat. 2. Low interpass temperature - allow cooling between passes. 3. Grind edges of coupon before bending (like D1.2 allows). 4. Grind weld flat before bending. 5. Tight stringers, no weaving (I already always...
  6. ElronMcK

    Alum Plate Bend Test Fail

    Amateur question. I have been bending my practice weld coupons around a small pipe, then bending tighter in a vice - just to check ductility. Photos below are pre-bend and post-bend Background: Uphill, 3G One-sided complete joint pen at butt joint (no gap) 6061, 1/8" thick 3/32" 5356 filler...
  7. ElronMcK

    AWS D1.2 Welder Qualification TIG

    gtaw - Thanks for the response. I've been welding aluminum TIG for a little while, so I appreciate your comment about aluminum not being like steel. Very true. Circling back on one question from my original post, which was too long. If I test on a 3/16" thick plate (which would give me...
  8. ElronMcK

    AWS D1.2 Welder Qualification TIG

    I am trying to get certified in TIG aluminum 6061 3G per D1.2 4043, up to 3/8" or 1/4" thick plate, and I am looking for guidance. I am trying to diversify my credentials for more job options. [I am a steel guy and am certified 3G D1.1. Not ASME. Almost everyone I know is a steel guy. Aluminum...
  9. ElronMcK

    Accelerometer Noise

    3DDave and itsmoked: Thanks for the comments, even with the snickering. I've mounted my accelerometer right next to my board with jumper wires about 4". Noise is significantly reduced to the equivalent of about 0.02g (which is good enough for my application of -1.0 to 1.0g range). Rookie...
  10. ElronMcK

    Accelerometer Noise

    Top view of shake table, with screw and rails
  11. ElronMcK

    Accelerometer Noise

    IR - I appreciate your sentiment to keep this forum serious and professional. This is actually serious and professional. The bike crank in my garage was my attempt at trouble-shooting. To be clear, this is not about bike cranks but instead structural instrumentation on a shake table. Attached...
  12. ElronMcK

    Accelerometer Noise

    Also, as requested, the precision testing apparatus in my shop (bike crank with accelerometer and bike on a stand)
  13. ElronMcK

    Accelerometer Noise

    I ran a desktop study. Excel plot attached. Little noise when sitting still. Much noise with even very small movement. 1. do I have the wrong accelerometer? It costs about $20 thru Adafruit. I can spend $7 or $100 on an accelerometer. Not sure how to differentiate based on data sheets. All...
  14. ElronMcK

    Accelerometer Noise

    Hello my EE friends, First, I'm sorry for the amateur question. Second, I'm hoping this is the correct forum, since double posting is a grievous sin. I set up what I thought was plain vanilla instrumentation to measure and record structural vibrations. Teensy 4.1 (with simple Arduino code) and...
  15. ElronMcK

    Stepper motor acceleration

    Real useful info. Thank you all. Yes, my driver can send up to pulses per second (0.18 deg / pulse). However, that means that now that the max pulse rate = 94,000 pulses / second --> 10 microseconds per pulse. I'm completely unanchored here, but that seems high. But I will re-visit with several...
  16. ElronMcK

    Stepper motor acceleration

    Thanks guys for the quick replies. I may have to break down and get the Leenhouts book. Let's say - hypothetically, of course - that I've already got a stepper motor (and not the appropriate servo) and everything is nearly perfect, except I can't make the system oscillate above 3 Hz (for 5mm...
  17. ElronMcK

    Stepper motor acceleration

    Hello EE friends, I have a NEMA 34 stepper motor. I use it to drive a small shake table (single axis horizontal motion) using a simple harmonic sine function. 1.8 deg/full step. Driver setting = 400 steps/rev (0.9 deg/step) "half steps" 60V, 7 Amps Max Pull Out Torque = 87 in-lb (about 980...
  18. ElronMcK

    Shake Table - seismic

    Hello structural engineers, I posted a small scale shake table question on the Seismology forum, but haven't gotten any hits yet. I know double posting is a grave sin, so not repeating here, kindly asking any who might be interested to check out Seismology and weigh in on that thread. Thanks.
  19. ElronMcK

    More FIGG Engineering Failures

    -thirtytwo, because you keep asking: On the contractor side, say, the City of Berkeley, when you sign a construction contract, you promise to accept additional work during the course of the project. Which is exactly what happened to me as a design-build contractor. Berkeley's city attorney...
  20. ElronMcK

    Shake Table - Seismic - Scaling

    Hello Engineers Consider a uniaxial, horizontal motion, small scale shake table used to evaluate seismic retaining wall stability (sliding and overturning); comparing resultant horiz displacements for various accelerations and durations using simplified sinusoidal input motion. 1:12 scale –...

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