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1500 questions
4
votes
1 answer
Bend allowances when making a C-shape plate
I am trying to find the formulas for making bends in sheet metal. I understand there are formulas for bend allowances. My issue is how do I determine where to bend if I want the inside dimension to be an exact number and if I want the outside to be…
BrianB
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4
votes
3 answers
How an airfoil works
I have read on many sites that for lift to occur, the pressure below a wing must be higher than the pressure above it. This happens by somehow moving air faster over the top of the air foil so the pressure above the wing decreases.
What I can't…
Fady basem
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4
votes
1 answer
Matched and unmatched uncertainties
In control theory, according to the definition of matched uncertainty, the uncertainty enters the system through the same channel as the control.
If we consider the system:
$$\dot x = F(x)+G(x)u+Δ(x, t),$$
where $F$ and $G$ are known functions…
Siha
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4
votes
1 answer
How much stronger than the bare minimum should a motor be?
A motor gives its strength in N-cm or oz-in, but how do you know how much you require? I know you can just calculate the minimum torque you need to move the load, but is there a typical amount over that minimum that is standard? Like 20% or…
Zephyr
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4
votes
1 answer
How to extract a building's heat isolation and thermal inertia based on temperature curves?
So imagine we have a house with some isolation and some thermal inertia. This house also has a heating system that turns on (starts heating) when the observed temperature curve goes below some predefined temperature threshold.
I figured that in the…
Samy Geronymos
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4
votes
0 answers
What is the reason for the instant loss of a vaccum through the sealed glass tube after shuting off a pump?
A pump is connected to a glass tube to evacuate it. The reading shows 0.4 mbar when the pump is on because of a vacuum. As soon as the pump is turned off, the pressure in the tube becomes equal to atmospheric pressure.
Rahul
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4
votes
5 answers
Understanding pressure drop and mass average values
While studying some papers, I didn't understand the following sentences:
deltP the pressure drop across the turbine, evaluated using the mass average values at the inlet and outlet sections of the computational domain, respectively.
What is the…
user19061
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4
votes
2 answers
Penetration depth and weld deposition rate in Welding
What factors affect the penetration depth and weld deposition rate in arc welding?
How does polarity affect the penetration depth and weld deposition rate?
My lecturer said that penetration depth is higher when using straight polarity when compared…
M.Tarun
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4
votes
1 answer
Is it feasible to forge multiple, smaller parts in the same forging operation?
Let us assume you have a large forging press or drophammer, and drawings for a set of smaller parts that all need to be forged from the same material. Would it be feasible to construct a forging die so that all the parts could be forged from a…
ThreePhaseEel
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4
votes
1 answer
Why aren't these spokes radial?
Have a look at this water wheel (located at Hama, Syria).
Most spoked wheels seem to be designed with spokes that radiate outward from the center of the hub (bicycle wheels being the notable exception). All of the spokes in this wheel are offset…
ConanTheGerbil
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4
votes
1 answer
Fan Sensors (Tachometer vs Locked Rotor)
With regard to Fan Sensors, there are two very common methods for detecting whether the fan is doing what it's supposed to or not.
Locked Rotor- Detects when the fan is working, or when it has stopped.
(on or off voltage signal)
Tachometer- Detects…
Erathsmus
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4
votes
1 answer
Convert Load Deformation (Extension) Data to Stress-Strain Curve
I am trying to manipulate some data that were obtained from a three point load experiment on a porcine tibia.
I would like to obtain a stress-strain curve for the various specimens; however, the only data that was given from the Instron three-point…
ANT1
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4
votes
1 answer
Perfectly aerodynamic kitchen range hood
Short form: How would one calculate the perfect shape of a range hood?
See drawing below. Will the curve of the profile of the range hood be exponential? Quadratic? What if the range is enclosed from three sides that create a box open only from the…
cheater
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4
votes
3 answers
What could be the reason for these sections not agreeing?
I have two results that don't seem to match up and I can't figure out why.
I built a hollow square section (HSS) using two different structural analysis softwares (they both agreed). However, they don't seem to agree with the AISC steel table…
carigs89
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4
votes
1 answer
Why do we need to condense steam in the rankine cycle?
In my admittedly naive understanding of the rankine cycle, steam is condensed back into water after passing through the turbine. Why not reuse the steam instead? It would seem to require less effort to reuse heated steam than to intentionally…
Paul
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