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Russell Edmonds Home Page
Last update: 08/05/06
Picture of the month ...Ok maybe for longer than a month.
Animation showing the motion of a floating arm trebuchet (FAT). The FAT design was invented by Ron Toms and has the counterweight fall straight down, while the throwing arm axle is allowed to float or roll along a horizontal track. This achieves a higher energy conversion efficiency, at the cost of greater forces on the frame, arm and sling. See FATAnalysis by Bill Jahsman. The equations of motion derived in this paper were used in a time step simulation to generate this animation.
A leisurely stroll down memory lane:
Visit a neat old sundial that was across the street from my junior high school in Claremont, CA. That Old Sundial
I was a real connoisseur of toys when I was ten years old. Under the Christmas tree that year, was one of the coolest toys I would ever receive. It was a balloon lunar lander that I could take off and fly around the room. I could land on tables, chairs or shelves to explore the unknown landscape, then take off and land back at home base. The toy was called Johnny Astro.
The technical side:
A fascinating aspect of photography is the stopping of time. The image on a photograph is forever unchanging and frozen to the time it was taken. This is particularly true with high speed photography, where an exceedingly brief moment in time is transformed into an eternity. High speed photography is almost as old as photography itself. Ernst Mach and C.V. Boys where taking high speed spark photographs of supersonic projectiles in the late 1800's. Harold "Doc" Edgerton advanced the field to a true artform. Modern high speed digital image cameras are taking over the field now. The old open flash technique of opening the camera shutter in the dark and using a very brief flash of light to make the exposure is still a viable method for the budget-minded. Here are some of my open flash high speed photographs.
A web page describing my home made geiger counter.
This is something I have wanted to make for years. I have had so much fun with it, I'm now hooked and want to make a bigger one. Little Van de Graaff generator
The very technical side:
I am currently working on a field mill to measure the atmospheric electric field. I wrote a program to calculate the electric field around a cylindrical field mill. The sensor plate of the field mill can either be on the top or bottom face of the cylinder. This plate is alternately shielded and exposed to the local field by a rotating vane. The magnitude and phase of the resulting AC signal gives the strength and polarity of the local field. A theoretical relationship between the local field and atmospheric field is calculated. The program uses a finite-difference over-relaxation algorithm to solve Laplace's equation in cylindrical coordinates r and z with symmetry assumed for theta.
The color plot shows the equipotential surfaces, with r running right and left and z running bottom to top. The top boundary of the plot is held at 325 volts, while the bottom boundary and the cylinder are held at zero volts. The two sides are Neumann boundaries. The vg(131,0) numbers on the right represent the voltage just above the center of the top face of the cylinder. Each number down the list is the result of an additional 2000 iterations from the one above it and show the convergence of the numbers towards a solution.