Recent content by jrmichler

  1. J

    A Ramjet effect on drone

    Yes, this is a well known effect. Search terms p51 mustang radiator thrust will bring up several good hits. The Wikipedia article is a good place to start, and suggests that Meredith effect is an even better search term.
  2. J

    Random Photos

    When deer see apples overhead, they can stand on their hind legs to get them. That tree had about 90 lbs of apples this year. I estimate that the food shelf got 40 lbs, the deer got 10 lbs, and I ate 40 lbs. Yes, I eat a lot of apples. Always have.
  3. J

    What did you do with your old college textbooks?

    Same here, except ME.
  4. J

    B Basic thermal energy transfer physics: Insulation value in open airways vs sealed airways

    Been almost 50 years since I took basic heat transfer in college, so I had to do some homework in order to do heat transfer film coefficient calculations last week. Some general rules of thumb for corrugated plastic signboard: Channels vertical, open ends = maximum heat transfer (worst...
  5. J

    States of matter: "viscoelastic fluid", familiar term is "cream"

    Here's a couple more terms. Plastic solid is a solid with a yield point. After yielding, it will continue to deform without limit. When the stress is removed, it stays in position. Bingham plastic is a solid with a yield point. After yielding, it behaves as a viscous liquid.
  6. J

    I need a concave mirror with a focal length of 150 feet

    Much of the hot air does not actually add heat to the surface, but it does give a good upper limit to the amount of heat needed. Using the factor of 200 * 0.15 m##^2## = 30 m##^2## area for the mirror. That's a 6 meter diameter mirror for the upper limit. My steady state calculation results...
  7. J

    I need a concave mirror with a focal length of 150 feet

    I just finished doing some heat transfer calculation for something else. It's been a long time, so getting back up to speed took time. Having done the studying, I could not resist doing some calculations for tree burning. Making the following assumptions: Emissivity = 1.0 Temperature of...
  8. J

    Medical New Alzheimer's Treatment Clears Plaques From Brains of Mice Within Hours

    I have been collecting articles and papers on lifestyle vs health. Here's some about dementia: Healthy lifestyle reduced risk of Alzheimer's by 60%: https://www.nih.gov/news-events/news-releases/combination-healthy-lifestyle-traits-may-substantially-reduce-alzheimers Exercise produces hormone...
  9. J

    A practical way to vaporize fuel for high MPG?

    A rule of thumb is that a typical normally aspirated automobile gas engine burns 0.5 lbs of gasoline per horsepower-hour. Since gasoline has a heat content of 20,000 BTU per pound, and one horsepower is 2545 BTUH, that is an efficiency of 25.5%. Modern engines are more efficient. From...
  10. J

    I need a concave mirror with a focal length of 150 feet

    I calculated the sun image diameter assuming: Sun 865,000 miles diameter Sun 93,000,000 miles distant Focal length 150 feet Perfect optics And got a sun image 17 inches diameter. The next question is how much energy per unit area is needed to burn wood. The necessary mirror area can be...
  11. J

    In the early days of electricity, they didn't have wall plugs

    About 1980, my grandmother had her wash machine plugged into one of these adaptors. I asked her if that really worked, and she said that it only smoked during a heavy load. So we had a work party the following weekend. My father, brother in law, and I completely rewired her basement with...
  12. J

    HP Required to move a robot 10meters at 1.5m/sec

    You are correct. For moving 4000 lbs, you need some math. Here is how I solve this type of problem. Step 1: Sketch an acceleration - velocity - position diagram that includes all available information. A pencil sketch is good enough at this stage. Your diagram would start as follows: You...
  13. J

    Random Photos

    This video of two hungry fawns feeding from their mother was taken looking out my living room window using a cell phone camera. We only mow grass around our house. The unmowed part has not seen a lawnmower since 1995. That's why it's popular with deer. Does like to drop their fawns on our...
  14. J

    Status Update by JRMichler

    These spam posts get moderated so fast that most people never see them. The moderators have a special button that deletes the post and permanently bans the spammer. I have not counted, but a rough estimate is a dozen or so "status update" posts per week. We have roughly 50 moderation...
  15. J

    Status Update by JRMichler

    Just ONCE, I wanted to see a post titled Status Update that was not a blatant, annoying spam post by a new member. So here it is. Today was a good day here in Northern Wisconsin. Fall colors are here, no mosquitos, no deer flies, and mild temperature, so my morning run was unusually nice...
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