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1500 questions
12
votes
2 answers
Why do earth cuts sometimes have steps on their walls
A neat image from Wikipedia:
There're clearly visible steps on the cut wall. This makes the cut wider at the top and so requires more work so those steps have some serious reason behind them.
What's the purpose of these steps?
sharptooth
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12
votes
5 answers
Should we protect our AC's outdoor unit from sunlight?Does it increases the durability of an AC and its refrigerant if it is well shaded?
My AC outdoor unit gets direct sunlight (no shading whatsoever) from morning to noon. Temperature normally soars up to 40 degree Celsius (I am from India). I have two questions:
Is this bad for the AC's refrigerant, does it lose efficiency over…
Paran
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12
votes
5 answers
How to calculate lever force when lever has uniformed distributed load?
We have a simple class 1 lever:
$$\begin {array}{c}
\text {5,000 kg} \\
\downarrow \, \downarrow \, \downarrow \, \downarrow \, \downarrow \, \downarrow \, \downarrow \, \downarrow \, \downarrow \, \downarrow \, \downarrow \, \downarrow \,…
Van
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12
votes
1 answer
What causes rechargeable batteries to age? What can be done to extend life of these batteries?
These days most of modern electronics use rechargeable batteries as a power source. Also, these days most modern rechargeable batteries are Lithium Ion or Lithium Polymer based. Like any other devices, over time these rechargeable batteries lose the…
Mahendra Gunawardena
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12
votes
4 answers
Is interference between aircraft an issue for fly-by-wireless technology?
I was reading up on fly-by-wire development, and I saw a short section about fly-by-wireless technology. It seems like a great idea, with the potential to lower costs, weight and complexity. I can see a possible scenario where it could be an issue,…
HDE 226868
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12
votes
5 answers
Why are most standard bolt threads single start?
When looking at thread descriptions, one of the basic properties is always the number of thread starts.
As far as I could tell, all of the major standard bolt threads are single-start. This includes:
Unified Standard (UNC, etc.)
National Pipe…
hazzey
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12
votes
1 answer
At what point does an I-beam becomes a H-beam?
According to BS5950, a beam section can be classified as plastic, semi-compact, compact or slender. For the same section area, a H-beam can take axial compression (without buckling) better than an I-beam, and as such, uses a different strut curve in…
Question Overflow
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votes
1 answer
What does "$\pm$ 0.5% F.S." mean?
I've seen it in several data sheets - it is a measure of error of some kind, of course. The problem is I dont know the exact meaning. I've seen it in the context of repeatability, accuracy and linearity.
An example is the following data sheet: smc…
JHK
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12
votes
1 answer
Why was Freon used in spray cans before it was declared a threat to ozone?
I've heard that in the past, spray cans (aerosol cans) contained Freon. I found that the Montreal Protocol made the usage of Freon illegal due to its effect on the ozone layer, but I can't find the reason for why Freon was used in the first place. I…
Physther
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12
votes
5 answers
Determining Drill Speed
How are spindle speeds calculated for a drill bit?
I've seen dozens of charts that highlight the rpm that should be used for specific drill bit types, bit diameter, and material. However, what if my chart doesn't have the particular type of material…
Justin Trzeciak
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12
votes
6 answers
In Engineering fields, how often do you find yourself being asked to be a "salesperson", and what is your reaction?
I have recently been told that my "salesmanship" is lacking when it comes to getting my ideas implemented. I receive the feedback that my ideas are sound and the data to implement is compelling, and even that the ideas are presented in a way that…
Tim D
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11
votes
2 answers
How do I batch plot drawings in monochrome without editing DWG?
I'm using AutoCAD 2015, and I run into this all the time. I'm given a group of DWG drawings, and I want to plot them into one monochrome PDF, but they do not have monochrome.ctb selected as the plot style. Is there any way in Batch Plot to publish…
Ben Miller
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11
votes
7 answers
Why do we use multiple reinforcing bars instead of one bar with a big diameter in reinforced concrete?
Why do we use multiple reinforcing bars instead of one with a big diameter in reinforced concrete?
Does increasing the number of reinforcing bars means that the reinforced concrete will have a higher tensile strength?
M. Kawa
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11
votes
3 answers
How different is using styrofoam rather than empty cans when pouring concrete?
In the recent 6.4 earthquake that hit Taiwan, it was seen in a newswire photograph of rubble that metal cans were embedded in the concrete.
The quote from an official regarding this practice:
For such purposes in construction, it was not illegal…
user348
11
votes
4 answers
What is the difference between "Crushed Stone" and "Crushed Gravel" aggregate?
Crushing Question
While reading a material specification for crushed aggregate, the text mentions both "crushed stone" and "crushed gravel" are acceptable. These materials sound very similar, but they are mentioned individually. I assume that this…
hazzey
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