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  • Users: BobM2
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  1. BobM2

    AC or DC for Hipot Testing

    What's the difference between a Hipot test and a meggar test? Don't they both apply a high voltage and measure (and limit) the current?
  2. BobM2

    AC or DC for Hipot Testing

    I'd like to check our motors with a Hipot test. The field wires are a bit close to the metal housing. The motors are universal and we run them on 115 vac 60 hz. I assume I should use an AC Hipot. When would one use a DC Hipot test?
  3. BobM2

    1144 CD Steel vs. 1144 Stressproof

    Another question on Stressproof: Doesn't the cold working leave a residual compressive stress only near the surface? So if the surface was machined down, wouldn't you lose that advantage?
  4. BobM2

    high shear strength shear pins

    We currently use double roll pins to attach a gear to a shaft (5/16 OD with 3/16 OD Pin pressed inside). I need about another 30% shear strength. I thought about a heat treated 4340 solid pin for high strength but am worried about its shock resistance. Any suggestions on a good...
  5. BobM2

    Electric Bill Reading.

    I'm guessing but I think PFj probably stands for Power Factor Joules. Our power company charges extra for low power factor loads. You might want to ask them. Ours was helpful in describing the terms.
  6. BobM2

    Recommend a worm thread grinding machine

    I'm considering bring in-house some thread grinding work on our worms. Any recomendations on good machines for pitch diameters of 1.5" and less?
  7. BobM2

    Worm Gear Failure

    Is there wear on the teeth before breakage? Misalignment would tend to cause wear problems before tooth breakage problems.
  8. BobM2

    Worm Axial force

    I don't think solitzer is quite right. The units of his equation are in#in. A good approximate equation is that the axial load, F = Torque/2 * 1/R * 1/(tan(LA)). For example, if torque = 7.5 in#, pitch radius = .312" and the lead angle is 6 degrees, the axial force would be 114#.
  9. BobM2

    Books on Fixturing?

    Any recommendations on good books for fixture and tooling design for milling operations?
  10. BobM2

    Can't get simple op amp circuit to work

    Well, this is a bit embarassing. I was counting the pins from the wrong direction on the right side so I had pins 6 and 7 mixed up. I should stick with gears and bearings. Thanks to all for the suggestions!
  11. BobM2

    Can't get simple op amp circuit to work

    I'm using an MC34071 op amp with a "FlexiForce" load sensor connected per the drawing supplied by the maker of the load sensor (Tekscan): http://www.tekscan.com/flexiforce/specs_flexiforce.html. The output of the op amp goes to about +8.5 volts and won't change much (changes about .2 volts)...
  12. BobM2

    von mises stress vs maximum shear stress

    Are you also constraining the bar axially? Under torsion the bar will want to shorten and you will also get tensile stresses.
  13. BobM2

    Saturated input in an RF receiver?

    Yes, the module is inside our control and the antenna is outside the control. I've tried ferite beads on the motor lead wires. I hadn't thought about using them on the control lines coming into the control. That would be an easy thing to try - Thanks.
  14. BobM2

    Saturated input in an RF receiver?

    The Linx device is the ES series, 916 Mhz, FSK. I think the noise is from the electric field produced by the motor. The motor is a universal type. The noise source is the brush/commutator sparking. The motor powers a winch. When lifting a load (high amps, low speed) the RF unit works well...
  15. BobM2

    Saturated input in an RF receiver?

    I'm using a Linx single chip receiver to control an electric motor. The motor puts out a lot of electrical noise. Shielding it helps considerably. I'm wondering what might be going on in the receiver when it cuts out. It acts like it might be going into saturation somewhere. The motor will...
  16. BobM2

    How does SAW Filter work?

    Does anyone know of write-up for how a SAW filter works?
  17. BobM2

    need a high speed clutch

    I'm looking for a high speed (25,000 RPM) clutch that can handle 4 in# torque. Operation would be full on or full off. Anybody know of any out there?
  18. BobM2

    Silicone Rubber Keypad Experience?

    I'd like to use a silicone rubber keypad for our products. However, my experience with membrane switches hasn't been good. I find that many, over time, have trouble making electrical contact. I'm guessing a film develops on the PCB. Is the contact technology better these days? What would I...
  19. BobM2

    Attracting force of an electromagnet ?

    Oops! Should be meters, not millimeters, in my equation above.
  20. BobM2

    Attracting force of an electromagnet ?

    Roughly, F = B x H x Area For only one gap and and a decently designed magnet, H is approx = NI/L where NI = your amp turns and L = length of air gap. B = u x H. Area is region that the flux is passing through. F in Newtons, B in Tesla, H in amp-turns/mm, Area in meters squared, u = 4 x pi x...

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