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  1. jcrags

    Durability of plastic ACME threads in lead screw application?

    Topological transformations, huh? Do you know where I can get a nut with a fractal thread profile, so that there will be infinite surface area to wear away? Really, no such luck though. The actuator assembly is already in a J configuration, the pulley on the lead screw has been substantially...
  2. jcrags

    Durability of plastic ACME threads in lead screw application?

    Hello everyone and thank you for your interest. I had fires to put out today and am just now getting back to this. I'll address issues in the order they were raised: Pud: The paper you linked has some great general info, especially related to material selection, but I don't have the knowledge...
  3. jcrags

    Durability of plastic ACME threads in lead screw application?

    I have a lead screw application where a mechanism needs to be sealed up and run for long periods of time. Currently, we are using a brass nut on a stainless steel lead screw. Because of space constraints, the length of the nut is very short: 0.2 inches (4 threads on our 1/4-20 lead screw). We...
  4. jcrags

    remote management of 3D CAD workstation

    I've done this very thing before using software called Teamviewer. It's free to try and has yielded OK results, and even has apps for controlling your computer from your smartphone (not that useful, IMO). You can do things like reducing the color depth and resolution of the remote computer to...
  5. jcrags

    Flatness & Surface Finish

    Also, think about how flatness and surface finish are measured. You could measure flatness by dragging the part around under a dial indicator, and have the face seem perfectly flat, because the large surface area of the indicator spanned the small irregularities. But, that surface could have...
  6. jcrags

    Thermal Contact Conductance in vacuum

    Thanks for the link, ione. That really is a pretty exhaustive paper! I couldn't find exactly what I was looking for in there, but it should certainly get me within an order of magnitude.
  7. jcrags

    200,000rpm 20Hp gearbox

    I know that helicopters commonly use turbine engines coupled to gearboxes to power the blades... somewhere to look for answers?
  8. jcrags

    Thermal Contact Conductance in vacuum

    Hey folks, I am trying to find some numbers for thermal contact conductance (or resistance, or course) between two copper parts with a pressure between them around 20 kPa, with and without vacuum grease. I have googled all over and looked at a lot of scholarly articles(they were all a little...
  9. jcrags

    limit rotational speed with a mechanism?

    Another option would be a rotary damper. These things offer a resistance that is proportional to rotational rate, so at some speed everything would balance out. http://www.mcmaster.com/#rotary-dampers/=ex7piy
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