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  1. jaydigs

    Natural Frequency Equation

    Well I reviewed about 5 different equations and kept getting 1 of 2 answers. Then it hit me, some equations were using rad/sec and others were using Hz (Duh!) That explains why I got around 70, and around 11, I was off by a factor of 2Pi. I ended up getting a critical speed of 4.3 m/s. Does...
  2. jaydigs

    Natural Frequency Equation

    I wonder how accurate it is to consider a flagpole as a cantilevered beam? It sort of sounds reasonable because it is fixed on on end and at 90deg to the ground, but, it isn't leaning out from a structure, and in a perfect world the only load is compressive, from it's own weight, unlike the...
  3. jaydigs

    Natural Frequency Equation

    Thanks for the link....that's a great site btw!
  4. jaydigs

    Natural Frequency Equation

    I'm analyzing a flag pole for wind loads and wanted to see what the critical wind speed was for vortex shedding. I'm using Vc = fd/s where f=natural freq, d=diameter of pole, and s=Strouhal number. I'm assuming the pole could be modeled as a cantilevered beam with fixed end? Also, I've found...
  5. jaydigs

    Bending stress from wind

    Thanks JAE!
  6. jaydigs

    Bending stress from wind

    I'm a little out of my area here, but, I'm the "hey you engineer" guy so I've been tasked to analyze the loads on a vertical flag pole. What I've done is taken the power from a stream of air ( P = .5 x rho x A x V^3) and then used the average wind speed x 10 to get the force. I'm assuming this...
  7. jaydigs

    Linear Actuator Specification

    I don't know why this didn't occur to me earlier, it's so simple. Thanks for the tip and I appreciate the .pdf.
  8. jaydigs

    Linear Actuator Specification

    I've been tasked to design an oscillator for a fan unit and I must confess this is really not my forte. I have the bar linkage worked out but I need help selecting a linear actuator. Basic requirements are to rotate a head that weights approximately 200lbs. I'm guessing the speed of the...
  9. jaydigs

    Effectiveness of Zinc plated fasteners

    Thanks for the links guys. I can't read the publications without buying them but what I've gleaned from excerpts has been very helpful. Thanks again!
  10. jaydigs

    Effectiveness of Zinc plated fasteners

    I was wondering if anyone had a link to some studies or data showing how effective Zinc plating is for fasteners relative to other platings or say stainless steel? In my experience I've found that Zn doesn't hold up particularly well when exposed year round to the elements but I'd like some...
  11. jaydigs

    Coatings for carbon fasteners

    Good deal, thanks for your help.
  12. jaydigs

    Coatings for carbon fasteners

    Thanks for the quick reply CoryPad. You think lower strength than the Grade 8? Grade 8 is our company standard although it's overkill. Maybe a Grade 2 or 5? Our fasteners are Zinc plated but I was concerned about the imperfections or abrasions that could remove the Zn and invite corrosion as...
  13. jaydigs

    Coatings for carbon fasteners

    I was wondering if anyone could recommend a spray coating I could use to protect Grade 8 carbon steel fasteners that will be installed in an indoor swimming pool? I'm aware of the issues surrounding chloramines and their effects on typical stainless steels, but the Duplex and 6%Mo alloys are...
  14. jaydigs

    Understanding static pressure in fans

    Adding the static and dynamic components makes sense, but how does a fan generate static pressure? I keep wanting to think of static pressure as just the air pressure when nothing is moving, ie..atmospheric pressure. The rotation of the blades generating pressure makes sense, but that would...
  15. jaydigs

    Understanding static pressure in fans

    This may be a trivial question to those in the industry, but, can anyone help me understand the concept of static pressure in terms of fan design and operation. From some works I've read they make it seem like something present in the environment (ie atmospheric press), and some describe it...
  16. jaydigs

    Shackle material to resist stress corrosion cracking

    We use a safety cable and shackle system as a redundant backup for things we attach to ceilings/roof structures. For the applications going into indoor swimming pools we have specified mostly 6%Mo fastener material to guard against SCC. I'm having trouble finding a shackle made of this...
  17. jaydigs

    Strength of bent tubing

    I'm wanting to use a piece of bent round tubing to support a TV. The tubing would be anchored to an I beam with 2 "U" bolts and the bend would be 90 degrees. Does anyone know how to analyze this system to make sure the tube I spec is sufficient? This is probably an elementary question but all...
  18. jaydigs

    Fastener material for indoor pools

    From what I've gathered about Stress Corrossion Cracking, it seems to only effect fasteners that are loaded in tension. Would this mean that fasteners that are only preloaded to keep things together (ie...no additional force applied) could be made out of a typical stainless? I know the Safety...
  19. jaydigs

    Understanding Bolt Capacity

    CoryPad; Thanks for your help in explaining this. I'm sure a lot of people will benefit from this thread since bolted fasteners is not given enough time in a conventional ME curriculum. I know a lot of engineers use fasteners everyday without understanding completely the analysis that...
  20. jaydigs

    Understanding Bolt Capacity

    CoryPad; OK, so for a 20lb external force the bolt tension is >100 but <120, the actual value depending on relative stiffnesses. In terms of bolt failure then, it seems fairly cumbersome to try to calculate the actual load on the bolt, what is the rationale for saying if the design load...

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