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1500 questions
11
votes
1 answer
Avoid snapping an electric cable from too much rotation
I recently built the basic construction for a crane out of lightweight material. Basically the head of the crane contains an electric servo motor which spins the head of the crane by pushing itself away from the tower (the rotor is fixed to the axis…
Mast
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11
votes
5 answers
How is lift related to airspeed?
Lift produced by an airplane wing is related to airspeed - this much is clear; a plane moving too slowly will stall. But what is that relation? Linear? Quadratic? Exponential? I don't need the exact equation, which is surely quite complex, just the…
SF.
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11
votes
3 answers
What kind of protection should I give structural steel in a natatorium (swiming pool) environment?
What would be the best type of steel to specify? Would a heavy galvanization suffice?
Are there specialty paints/coatings available for this particular application? If so, how long do they last?
cKrug
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11
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2 answers
Can you use the Hagen-Poiseuille equation for a pipe which radius is in the sub-millimeter region?
As this will depend on Pressure drop $\Delta p$, assume that it does not leave the range from 0 to 100 bar. The Hagen-Poiseuille equation for an incompressible fluid is defined as:
$$ \dot{V} = \frac{\pi R^4 \Delta p}{8\eta L}$$
I realize that it…
JHK
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11
votes
1 answer
How does a microbolometer (IR camera) work?
I am currently doing a project which has led me to my first encounter with IR cameras, and I am therefore quite curious as to how they operate. Specifically, I would like to know the following
How is heat converted to an electrical signal (current…
Julian
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11
votes
2 answers
Why are tremors of an earthquake felt more on upper floors?
Why are tremors of an earthquake felt most on the upper floors of a building in comparison to lower floors? Does this have something to do with a third class lever?
Debanshu Thakur
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11
votes
1 answer
Observability using the Discrete Extended Kalman Filter (EKF)
I have built (several) discrete Extended Kalman Filters (EKF). The system model I am building has 9 states, and 10 observations. I see that most of the states converge except one. All except 1-2 of the EKF state estimate appears to drift. Since the…
krisdestruction
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11
votes
1 answer
How to determine the lateral earth pressure in a double-walled cofferdam?
The design of a retaining wall commonly involves determining the lateral earth pressure using either Rankine theory or Coulomb theory. Both theories involve mobilising the shear resistance of a triangular wedge of soil extending for a considerable…
Question Overflow
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2 answers
What is the mechanical element that holds a worm gear shaft in place called?
Here is an image of a worm gear. What is english word for mechanical element (two of them will be necessary for a worm gear) in which the worm shaft will "lie" and rotate?
Here is one photo of the element where it is part of a housing; I need it as…
etf
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11
votes
2 answers
Why was a coil chosen over a straight for this overbridge?
I saw this meme on Facebook showing a coiled railway overbridge and an alternative plan. I replied that straightening that overbridge will force it to start at the other side of the road, and you need to build a u-turn and there is a valuable…
Jesvin Jose
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11
votes
3 answers
Why do beverage can tabs break when bent?
Most people have had the experience of moving the tab of an aluminum can back and forth until it breaks off. It usually only takes a few complete back and forth motions before the tab breaks off.
What is the root cause of the tab breaking off?
The…
hazzey
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11
votes
4 answers
How would adding a wind deflector in front of roof-mounted solar panels affect drag on an RV?
I am mounting solar panels on top of a recreational vehicle (RV). To reduce drag, I was planning on building a small ramp in front of the panels to deflect wind before it hits the flat panel and mounts. Here is a rough sketch (red is brackets, black…
Cade
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11
votes
1 answer
What is the significance of a diagonal input in a control diagram?
I have seen several block diagrams with diagonal inputs, drawn with an arrow through the block.
and others like that (via Google image search)
What is difference between this and a typical signal input? What are the dotted lines signifying?
andrewhunter
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11
votes
1 answer
What is the difference between direct and indirect learning control?
I found the following comments on direct and indirect control in "Survey on iterative learning control, repetitive control and run-to-run control." by Wang, Gao, and Doyle:
There are two application modes to use the learning-type control. First,…
andrewhunter
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11
votes
2 answers
Comparing the performance of glass and granite in a heat storage application
Background
I am working with a small team on a university project to build a greenhouse heat sink. This will pass warm air at the top of the greenhouse down through a chamber underground filled with a material to absorb and store the warm air. We…
Ant
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