Monthly Archives: July 2016

10,000 Boomers Turning 65 Everyday

The front-end of the baby boomers began to turn 65 in 2011 and they will continue to turn 65 until 2029. I started to wonder how many boomers are turning 65 every day? The Social Security Administration estimates that 10,000 Americans are turning 65 every day (source). As I thought about, I should be able to estimate the number of people that are turning 65 every day by examining graphs of the US population and birth rate (Figure 1). It is a nice Fermi problem and the subject of this post. Continue reading

 
Posted in General Mathematics | 3 Comments

Airliner vs Car Fuel Usage

As I looked at the cost of airline tickets versus driving, I became curious as to how much fuel was used to fly me out to a Montana airport such as in Bozeman or Butte. I was surprised to learn that airliners can be quite fuel efficient compared to cars. This post contains my analysis. Continue reading

 
Posted in General Science | 8 Comments

Shimming and Trimming Stairs to Equalize the Risers

In this post, I will show how to generalize my previous stair solution to handle these three cases. I also present some illustrations of what is involved in adjusting the stairs. The general solution used a Mathcad program to compute both the final riser height and the thickness of the shims or trim cuts required for each step. In general, you may need a combination of shims and trim cuts to resolve a riser height problem caused by changes in flooring height. Continue reading

 
Posted in Construction | 2 Comments

Lateral Force Rating for Various Nails

I am an amateur carpenter, and I work hard to ensure that I always comply with the applicable building codes. The various codes include requirements for a properly nailed joint (examples). Since I like to understand where these requirements come from, I have been the reading some sections of the National Design Specification for Wood Construction (NDS) that address fastening. During my reading, I saw many interesting formulas associated with determining the NDS design ratings for nail withdrawal (covered here) and lateral force resistance – the subject of this post. Continue reading

 
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Layout Formula for a Balustrade

I am about to begin some construction on my cabin in northern Minnesota, and the design of the stairs has been on my mind. I consider well-designed stairs to be both beautiful and functional. A major factor in making a stairway beautiful is its balustrade – a railing with supporting spindles (aka balusters). The balustrade for a stairs is often referred to as a banister. Continue reading

 
Posted in Construction | 2 Comments

My Personal PCB Design and Build Process

I have been designing circuits since I was a boy, and my passion for circuits has only grown over time. My home designs focus on sensor interfaces that I hook up to the Internet using Raspberry Pie and Arduino digital interfaces. These open-source HW interfaces make it possible to create incredibly powerful designs at home. Continue reading

 
Posted in Electronics | Leave a comment

Dealing with Climate Change Denial

I have lunch with all sorts of people. Occasionally, I end up sitting with a climate change denier, which happened today. Usually, I do not say anything because I really do not want an argument.

Today, I decided to mention Figure 1, which summarizes a set of measurements made since 1900 that show that sea level is rising. I then asked the climate change denier if they can explain the fact that sea level is rising –a fact has been confirmed by multiple measurements taken at multiple sites over more than 100 years. Continue reading

 
Posted in General Science | 1 Comment

Withdrawal Force Rating for Various Nails

I have been reading some specifications on fastener requirements in carpentry. To ensure that I understand what I am reading, I decided to see if I could duplicate the design values for nailed connections. In this post, I will duplicate a table (Figure 1) for the withdrawal force ratings of various nails when used in a toe-nailed connection. In general, I try to avoid nails with a withdrawal load, but it is an allowed connection and it was easy to duplicate the results in a National Design Specification (NDS) document. I will be performing a similar computation for the lateral load rating in a later post. My Mathcad source and a PDF are stored here. Continue reading

 
Posted in Construction | 3 Comments

Lightning-Induced Surge on Cable Wiring

Because I have had to deal with lightning in all sorts of contexts (e.g. military equipment, commercial hardware, consumer products), I have developed an enormous respect for the power of lightning (Figure 1). Because of this respect, I have worked to ensure that my own home has excellent lightning protection, including a sophisticated ground system. Even with all my precautions, last weekend lightning struck near my home and caused my garage door to open – letting rain into the garage, and my garage door opener to become unresponsive. Fortunately, I just had to cycle power again on the garage door opener and it started to work. Continue reading

 
Posted in Electronics | Leave a comment

Molarity, Molality, Mass Fraction Conversion Formula

I am doing some work with lead-acid batteries and their state of charge versus their H2SO4 electrolyte concentrations. While we normally use specific gravity to assess a battery's state of charge, some folks use molality (m), molarity (M), or mass fraction (w). These concentration metrics are all related by relatively simple formulas (Figure 1). Continue reading

 
Posted in Batteries | 1 Comment