Monday, March 30, 2015

The Mighty Mackinac

This is a short article I read on Facebook about the Mackinac Bridge. It's a direct copy from the posting. (Thanks Midget Robin!)

For those who don't know, the Mighty Mackinac is the span of I75 that crosses the Straights of Mackinac, which passes water from Lake Michigan to Lake Huron. The bridge leaves Lower Michigan from Mackinac City, and lands on the Upper Peninsula of Michigan in St. Ignace.

Why the metal grating on inside lanes of The Mackinac Bridge? Simple - it wouldn't survive harmonic wind stresses without it.

Mackinac Bridge January 1953, Steinman was appointed as the design engineer for the Mackinac Bridge, and his recommendations were incorporated into its design. Representing a new level of aerodynamic stability in suspension bridges for its time, the Mackinac Bridge was the first long-span suspension bridge to incorporate specific design features, including a porous deck, to manage the forces imposed on it by winds. Construction of "Mighty Mac" took over three years in a demanding climate, and the structure's completion made all-weather travel between Michigan's two regions possible.

Claim to Fame: Representing a new level of aerodynamic stability in suspension bridges for its time, the Mackinac Bridge was the first suspension bridge to incorporate specific design features to manage the forces imposed on it by winds.

The design of the Mackinac Bridge was directly influenced by the lessons of the first Tacoma Narrows Bridge, which failed on November 7, 1940 due to instability under wind stresses. Three years after the Tacoma Narrows disaster, engineer David B. Steinman published a theoretical analysis of suspension-bridge stability problems. Among his recommendations were that future bridge designs include deep trusses to stiffen the bridge deck and an open-grid roadway to reduce its wind resistance.

Prior to the construction of the bridge, a fleet of nine ferries would carry as many as 9,000 vehicles per day, with traffic backups stretching as long as 16 miles.

In New York the Verazzano-Narrows Bridge, designed by Othmar Amman, was 10 years in the making and finally opened in November 1964.

Both of these monumental spans directly benefited from the legacies of the failed 1940 and the successful 1950 Tacoma Narrows Bridges.


And there folks, is the history lesson for today that most people don't know...

Enjoy, and Thanks for Sharing!! - - U.P. Michigan

Thursday, March 19, 2015

Astrophotography

As I said previously, I've been getting into photography, and specifically Astrophotography. I picked up a nice camera, and have been filling up memory card (got a new one on order, as well as another hard drive) with short exposures until I finish building my equatorial mount.

The trick with astrophotos is that since the earth is rotating, the sky is moving with respect to an surface bound observer. This wouldn't be so bad, except that in order to get really great images of the sky, you have to measure (read, expose the camera sensor) for a long time. Long exposures do two things: allow very dim light to impact the sensor, and average out the black background that is space. It's a real battle with signal to noise ratio, and has been a great refresher of my electrical engineering, and even useful for my mechanical engineering background.


This is the best photo I've done so far. It's a stack (read: average) of about 100 four second exposures of the region around Cassiopeia. There has also been a bit of what is called stretching in photoshop in order to bring out the brightness in some areas, and enhance the darkness in others. I've gotten a lot of compliments on it, but I know I can do some way cooler stuff if I just put some work to it. So using my 3D printer, I am making a Barn Door Tracker to help take longer exposures. I'll post some of the cooler stuff here when I get it!


Sunday, March 8, 2015

More Women doing Cool Stuff in Science

Mika McKinnon over at io9 has another article listing off some of the current ladies who are working in science. The only one I've had a chat with so far is Nicole Sharp who writes Fuck Yeah Fluid Dynamics. (Yes, that's a real page) I need to start following some of these folks! Here's some of her stuff.

Whisky leaves behind a pattern that depends on the flow created by alcohol evaporating faster than water.

Women Pioneers in Physics

The Perimeter Institute for Theoretical Physics has posted this gallery of some of the greatest female minds in the sciences. They have everyone from Cecilia Payne, who is the mother of modern Astrophysics, to Marie Curie, who is the only person, man or woman, to have a Nobel Prize in two different disciplines (Physics and Chemistry). Their profiles are below, and the rest can be seen here.




As for this Blog, I find Dynamics stuff so sporadically, that it's hard to talk about JUST that. I have a list of other things that I've wanted to talk about on here for so long that I decided to expand to all of my fascinations including:

3D Printing and Modern Manufacturing
Quadcopters, Drones, and RC Flight
Astrophotography
Cooking
Electronics
and of course...
Dynamic Systems, Acoustics, and Modal Analysis

Talk soon!