Monthly Archives: December 2015

Shoot Boards for Handheld and Table Saws

Posted on 31-December-2015 by mathscinotes

I live in a small home, and I have to do my woodworking in the garage. Since I have two cars that "live" in the garage, I do not have sufficient room for a full-size table saw (Figure 1).

The biggest challenges I face have to do with cutting large sheets of plywood (4' x 8'). Without the space for a table saw, I had to begin looking for alternative approaches that I could setup and teardown in my garage. Continue reading →

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Output Voltage Control Circuit Design

Posted on 30-December-2015 by mathscinotes

While I am in management, I still get an occasional circuit design question – I really like these questions because the get me away from some of the monotonous aspects of management (i.e. budgeting). This morning a power supply designer stopped by and wanted to discuss an issue he was having with fixing an issue with an old design. I immediately dropped my budgeting activity and leaped into action. Continue reading →

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Tidal Timing

Posted on 23-December-2015 by mathscinotes

After a discussion on the annual time shift of the winter solstice, our lunch time topic changed to the topic of tides. During this discussion, I mentioned that tides have a period of about 12 hours and 25 minutes (Figure 1). I will show you how to compute this period in this post. Continue reading →

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A Little Solstice Math

Posted on 22-December-2015 by mathscinotes

We just went through the winter solstice of 2015, which in Minnesota is a subject of celebration. This means that we will now start to see more daylight.

The time of the winter solstice varies each year. It occurs on either 21-Dec or 22-December. One of the engineers in my group asked how the time of the winter solstice moves year-over-year. My response was that it moves forward ~six hours each year until a leap year happens, which resets the cycle. Continue reading →

Posted in Astronomy | 1 Comment

Stairway Rise Angles

Posted on 21-December-2015 by mathscinotes

Quote of the Day History is a tool used by politicians to justify their intentions. — Ted Koppel I was reading this month's Journal of Light Construction (JLC) when I saw an article on building safe stairways per the International … Continue reading →

Posted in Construction | 2 Comments

Incorrectly Computed Discount Followed By Markup

Posted on 20-December-2015 by mathscinotes

A few years ago, I hired a tile installer to tile a bathroom I was remodeling. He was a talkative guy, and he casually mentioned that he had chosen not to make any money on his material – he would make his money on labor alone. He said that most of the tile shops he works with give him a 15% discount on material, which he passes on to his customers. Other contractors markup their material charge by 15% to bring the cost back to retail price – this statement bothered me because the markup should be larger than the discount. The math did not seem right to me at the time, but I did not raise any questions because I wanted my bathroom done. I did not think much about this math error at the time until I saw an article in the Journal of Light Construction (JLC) telling contractors that this is a math error that is costing them money. As I read the article, I realized that this is exactly the same error I heard my tile contractor make. Continue reading →

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Building an MST3K Tom Servo Replica

Posted on 19-December-2015 by mathscinotes

In this post, I will provide some photographs I took during our Tom Servo build effort. These photographs do not constitute detailed instructions on how to build the unit, but you will see the general idea. Continue reading →

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Selecting a Thermal Magnetic Circuit Breaker

Posted on 18-December-2015 by mathscinotes

I have an application that requires a thermal magnetic circuit breaker that will provide a given level of protection at an elevated temperature. Most thermal magnetic circuit breakers have a current rating that is specific to a stated temperature, usually room temperature (~23 °C). In my case, I need a circuit breaker with a 15 A break current at 50 °C Continue reading →

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Those Thrifty German Immigrants ... Combine Repurposed as a Gravedigger

Posted on 17-December-2015 by mathscinotes

I am the son and grandson of German farmers. Their farms were almost magical to me because of all the belts and pulleys used to drive everything – it would have been an OSHA nightmare. I was always impressed with the self-sufficiency of these farms. For example, the Biegert farm in Hanover, Minnesota had a small sawmill that was powered using a tractor's PTO. Many farm buildings in that small community were built using wood from local trees cut by that mill. In fact, my family still has an affection for woodworking using butternut because that was a wood our father often milled on the farm Continue reading →

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Yet More Gift Wrapping

Posted on 16-December-2015 by mathscinotes

My sister and I talk about these practical math problems all the time. Here is another good video that covers gift wrapping with a mathematical slant. Continue reading →

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