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1500 questions
7
votes
1 answer
Sending out a 12d Civil Design Model
My project team and I delivered the design of a 14ha urban infrastructure development in Sydney for a Client. The project was to hand over the development at a Tender level of design, which would be tendered upon by a number contractors. The…
Louis Russell
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7
votes
7 answers
Why is hydro-electric power still scarce in some places?
70% of the Earth's surface is covered in water, why can't a hydroelectric power plant be set up on each and every river? Is it that its too expensive?
Why is electricity still a problem in countries that have abundant number of rivers? Why can't…
Sristy
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7
votes
1 answer
What is the name of this mechanism for raising and lowering the impression cylinder of a printing press?
It is like a cam that has an off-center hole, and it rotates in its fixture with a knob to lock it in place. The purpose is that you can loosen the knob and rotate the piece to slightly raise and lower the shaft that is connected on the other end.…
371273
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7
votes
1 answer
What is this pressure gauge on the London Underground measuring?
I noticed this pressure gauge on the Piccadilly Line of London Underground yesterday. It was located on the side of a row of seats.
Close-up of the gauge at hand:
click for larger version of image
The pressure gauge seemed to randomly fluctuate…
March Ho
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7
votes
5 answers
How can I improve traction on a wheeled vehicle yet reduce friction?
This is inspired by a project I undertook for my Physics class last year; I'd like to apply it in the future.
Background: For the project, I and a few classmates were required to build a small car powered by any of a number of sources; we opted for…
HDE 226868
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7
votes
1 answer
Elasticity of a drilled plate
If I take a large thin plate and I uniformly drill a very large number of holes (diameter "d") very close together (minimum spacing "s"), what will be the stiffness of this new plate? When I say "stiffness" I mean the derivative of average…
Nic
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7
votes
3 answers
Can I use a pipe of any material other than copper in a counter-flow heat exchanger?
Why are copper pipes used in counter-flow heat exchangers?
Could I enhance heat transfer by using a pipe made of any other material?
Ramnaresh Prajapati
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7
votes
1 answer
What is required to implement Positive Train Control on railroads in the US?
Background
On May 12, 2015, an Amtrak train derailed in Philadelphia, PA, killing 8 and injuring 200 people. I saw a story on the incident where multiple NTSB spokespeople have said at this and other train derailments that Positive Train Control…
Trevor Archibald
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7
votes
1 answer
What are the benefits of a diaphragm pump vs a simplex pump?
What are the benefits of a diaphragm pump
over a simplex pump?
Is there any specific design criteria that should be used/stated in an engineering specification for a diaphragm pump?
Christie Clayton
- 99
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7
votes
2 answers
Will stainless steel with a #3 finish corrode faster than a #4 finish?
I understand the difference between a #3 finish on a piece of stainless steel compared to a #4 finish being that the surface roughness is different. Specifically, a #4 finish is classified as having an Ra value of less than 25 micro-inches where as…
ZoeyMoogle
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7
votes
3 answers
Does a 3-phase electricity grid need to be synchronised and are the phases split between houses?
Note: This may be UK-specific, I'm not sure.
I overheard part of a conversation about 3-phase electricity, one guy was saying that mains generators use 3 coils (or something) and as it spins it produces 3 different waves of alternating current that…
jhabbott
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7
votes
1 answer
Special Considerations for Steel Plate Marketed for Laser Cutting
A contractor working for me on a steel construction project is using a steel product they refer to as 'laser plate' which is marketed as specifically as having good performance on laser cutters. This doesn't appear to be a trade name, but a…
Ethan48
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7
votes
1 answer
Causal and Non-Causal PD Controller
Why is a Non-causal PD Controller:
$C(s) = K_ds + K_p$
When a causal PD Controller is:
$C(s) = (K_ds + K_p)/(\tau s + 1)$
The difference being the denominator. $\tau$ is the time constant and is "sufficiently small and does not perturb the other…
nbui
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7
votes
4 answers
Why do stress concentrations really occur?
From doing some research I've learned that internal stresses inside an object can "concentrate" on sharp edges, as shown in the above picture. For that reason we often make fillets so that the change in diameter is smoother and we get a smaller…
S. Rotos
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7
votes
4 answers
What are the common failure points of waterproof cases?
I am making a waterproof case for my Galaxy S5 and/or my Raspberry Pi. I plan to make the main body from (or at least decorate it with) wood, though I can use other, stronger materials where needed.
I am thinking of using some controller (as opposed…
Keychain1
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