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  1. dgeesaman

    Is there any good CAD software?

    A dumb solid model without a drawing is not adequate, I agree. A properly revision-controlled and -tracked drawing with a dumb solid to go along with each revision of the drawing is robust and sensible in my experience. We are in aggressive agreement on that! David
  2. dgeesaman

    Is there any good CAD software?

    I did not say that. I believed that drawoh described a complicated scenario where the manufacturing software connects directly to actual parametric design models, which are interconnected to each other with a top-down design. I recall some of the parametric CAD companies offered such...
  3. dgeesaman

    Is there any good CAD software?

    Yes, of course. The 'nightmare' to me is having manufacturing build parametric tooling, etc based on parametric 3d models, which are parametrically related to each other using poorly-planned top-down relationships. Then if someone actually manages to push a change from the original design...
  4. dgeesaman

    Is there any good CAD software?

    Drawoh, you've described a bit of a nightmare scenario. Having manufacturing tooling and processes hanging on the actual design data is not something I've done before and I can see how much that would complicate life. In designing the new version, I would probably have two CAD sessions open...
  5. dgeesaman

    Is there any good CAD software?

    I think that's the thing that I find frustrating with the latest parametric software - there are 100x more ways to walk away from a complete drawing and supporting models that are put together such that revising and re-using the underlying data is effectively impossible. The parametricity was...
  6. dgeesaman

    Is there any good CAD software?

    Ugh I'm trying to do a mixing propeller in Inventor and plotting curves by equation is like juggling in handcuffs. Can't get much done if you can't build the foundational section curves.
  7. dgeesaman

    Is there any good CAD software?

    It is not. I'm referring to the fact that Creo assembles components in an order and components have parent-child relationships to each other. Inventor assemblies have a flat structure, such that every constraint of every component is evaluated simultaneously, and when there are sick...
  8. dgeesaman

    Planetary Gearbox mounting

    The high torque end of the drive is the one with the highest reaction forces. Even if the housing is strong enough to absorb the reaction loads from the opposite end, more force causes more deflection and deflection reduces the contact quality and life of gearing. So the drive should last...
  9. dgeesaman

    Machine Screw Pull-Out Capacity

    Because of the spring steel material, larger diameter engaging the base material, and spreading of local stresses within the threads, they are stronger.
  10. dgeesaman

    Is there any good CAD software?

    $0.02: In my 25 years operating and instructing 3D CAD (1 year using Pro/E, 1 year instructing Pro/E, 5 years using SolidEdge, 18 years using Creo, 5 years using Inventor), the software has degraded into a tool for quickly creating a drawing with crap under the hood. This goes way deeper than...
  11. dgeesaman

    Machine Screw Pull-Out Capacity

    Considering the heat, thermal expansion differences, etc I'd be looking at installing helicoils. They improve the tear-out force without increasing size or weight. David
  12. dgeesaman

    Machine Screw Pull-Out Capacity

    I slammed #6-32 / A286 data into my bolt calculator and got 1300# of preload so that seems about right. Screws (esp. high strength screws in high strength materials) can generate very high tensile loads. Personally I'd prefer to assume lower utilization than that and have a factor of safety of...
  13. dgeesaman

    Cast Iron Allowable Hertzian Stress

    I would refer to cast iron gearing design standards if nothing else arises.
  14. dgeesaman

    Machine Screw Pull-Out Capacity

    It's hard to give crisp answers because I can't visualize what you're showing. The primary questions are: 1) will the applied load put the screws be in shear or pure tensile/tear-out? 2) how flat and consistent will the mating surfaces be under the screws? 3) what strength is expected for the...
  15. dgeesaman

    Need help sourcing a custom-made Buna O-ring.

    I hope it didn't sound like I'm accusing you of doctoring that photograph, because I'm not. But it's still true that my experience with contouring o-rings into standard rectangular-section grooves / non-circular groove paths has me fully expecting that o-ring to pop out. There is likely some...
  16. dgeesaman

    Need help sourcing a custom-made Buna O-ring.

    Wow my experience with that kind of thing is the complete opposite. I can think of an automotive gasket that is NLA and its shape is 80% circular 20% triangular with huge radii. The OEM gasket, when you could buy it, was an o-ring that was somehow formed a bit to hold that shape. Now we just...
  17. dgeesaman

    Decreasing operating range of seal elements over the years

    My company has provided mechanical seals on some of the machinery we build/sell for decades now. In the early days, the seals were quite limited in range. Then as materials improved and mechanical designs developed, some seals were advertised to handle more shaft runout, higher operating...
  18. dgeesaman

    I asked my AI

    And that's the point - a reader can tell from context when it's a fraction vs. equation. Google AI will trip up on that.
  19. dgeesaman

    I asked my AI

    Feed one a mix of fraction and decimal numbers. 7-1/2 is suddenly 6.5.
  20. dgeesaman

    Struggling to Bridge Academic Success & Practical Experience in Aero Eng. Help

    In my world, which is admittedly not aerospace, we hire mechanical engineers and very roughly sort them by their GPA either towards Sales or towards R&D. High GPAs tend to be individuals who focused on grades, know how to work alone and remain focused and had not much social activity vs. lower...

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