Recent content by jrmichler

Stopped to talk to a neighbor while on my morning run last July, and the Google Street View camera car went by. The strange thing is that the Street View car went by two years ago while I was actually running. They posted that imagery for about three months. Then they replaced it with older...

You might want to familiarize yourself with the Federal Aviation Regulations (FAR's). From 14 CFR Part 1: Rocket means an aircraft propelled by ejected expanding gases generated in the engine from self-contained propellants and not dependent on the intake of outside substances. It includes...

There is no simple math to calculate power requirements for this system, but it should be possible to make a rough estimate. My approach is to start with some simple assumptions, then build on the results. 1) Assume enough forward speed that each paddle gets a full bite. 2) Assume that exactly...

Hand calculating this problem takes several steps. Here is how I would do it. 1) The thin parts are doing all of the deflecting, so start by eliminating the solid blocks. The two thin beams are combined into one. 2) The bottom of the resulting beam is fixed. The top is subject to a force...

You do not tell us what your analysis is trying to find out. Are you looking for deflection, deflected shape, strain, stress, or what? What are the assumptions in your hand calculations? How and where do your hand calculations differ from the FEA? Please discuss in full detail. Your...

There is an optimal shape for least drag for a given frontal area. There is an optimal shape for least drag for a given interior volume. They are not the same. They change with Reynolds number and Mach number. All of which ignores practical realities. Fluid-Dynamic Drag, by Hoerner has a whole...

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.

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.

Same here, except ME.

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...

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.

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...

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...

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...

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...