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8
votes
2answers
6k views

What made bronze the first widely used (non-ornamental) metal in human civilization?

I recall learning about the bronze age in school. Why was bronze so important to the technological development of humans? Why not some other metal?
11
votes
4answers
4k views

How do I calculate the forces on a desk and its legs?

I have a design for a desk, and I'd like to not just guess at how strong it'll be, but I can't find an explanation on how to figure out all the forces involved that doesn't assume I already know a lot ...
5
votes
1answer
162 views

Making a mechanical device to measure the radius of the Earth

I want to design an experiment to show (in an educational context) how we can measure the radius of the Earth without using modern technology in order to demonstrate the engineering achievements of ...
6
votes
4answers
899 views

Why do rechargeable Lithium Ion & Lithium Polymer batteries explode or catch fire?

There are many Lithium Ion and Lithium Polymer rechargeable battery related accidents. Are some of these accidents are battery design related? Are some of them misuse of rechargeable batteries. What ...
4
votes
1answer
184 views

Is it possible to modify a home gutter to absorb sufficient solar energy to melt ice?

This is related to the question Will dark gutters stay ice free better than light colored gutters? The current consensus seems to be that the mass of the gutters and limited light may make simply ...
9
votes
4answers
131 views

How is the wattage of an incandescent light fixture determined?

I've seen light fixtures with varying wattage rating. From 30W to 100W even though the actual socket is the same. What is the limiting factor, why can't I put say a 75W bulb in a fixture rated at 50W?...
6
votes
1answer
164 views

Settling of unevenly loaded storage tank

Suppose I have a concrete tank, round, vertical, diameter in the range 16m-24m. One half the floor is filled with gravel or concrete to a height of maybe 2 meters. When the tank is empty, that will ...
11
votes
2answers
386 views

Does a Faraday cage effectively act as a notch filter?

In reading about Faraday cages, I have found that most "real world" designs incorporate multiple layers of mesh. For example, this article from the National High Magnetic Field Lab discusses several ...
4
votes
2answers
167 views

For a small valve in a fluid system, what is the relationship between pressure and flow rate?

The specific example I have in mind is a car tire with a small leak in it. As the pressure increases, does the outflow of air increase linearly, i.e. $v\propto P$, or does it have some more ...
11
votes
3answers
3k views

Which turbulence models are suitable for CFD analysis on a streamlined vehicle body?

Many commercial and open-source CFD codes implement several closure methods for the non-linear convective acceleration term of the Reynolds-averaged Navier-Stokes (RANS) equations. Common methods (...
2
votes
1answer
376 views

What is the effect of changing the angle of a helicopter flybar?

A helicopter flybar is a kind of gyroscopic stabilizer which acts in feedback to the pitch of the blades. The effect, in words, is that as the helicopter starts to pitch or roll in a particular ...
5
votes
2answers
298 views

How to size a heat exchanger for a shear thinning fluid?

To size a heat exchanger, I need to know (among other things) the Reynolds number (Re) as an indication of the flow conditions. The Re number depends on the viscosity. In a shear thinning fluid, I can'...
5
votes
2answers
770 views

What are the engineering challenges in WIG craft development?

Wind In Ground (WIG), is an old concept. In short: Wing-tip vortices create an additional drag on the aircraft known as the induced drag. However, when the flying craft (or bird) flies close to the ...
6
votes
3answers
312 views

What is the best way to control brightness of a LED?

LED brightness can be controlled using digitally controlled potentiometer such as a Microchip MCP413X or a PWM signal. In both cases the signal will be controlled/ generated from a micro-controller. ...
16
votes
1answer
2k views

How to design a house to be cooled passively? [duplicate]

I live in Louisiana these days, in an area that is known for its numerous antebellum plantation homes (circa early 1800s). While touring one of these homes it was clear that almost everything about ...
9
votes
1answer
666 views

How can Pareto Analysis help solve engineering problems?

Attach is a Pareto Diagram with Number of Defects in Y-axis vs Causes in X-axis for an engine overheating problem. How can this Pareto diagram help an engineer solve the engine overheating problem? ...
4
votes
1answer
81 views

Why don't massive industrial shredders shred themselves?

With the huge metal shredders that can shred an entire car or a bus, they can shred parts like the axle and engine which are large solid chunks of metal, just like the massive spinning shredder blades....
13
votes
5answers
654 views

Are pneumatic tires obsolete?

Adaptive suspensions with adjustment rates on the order of milliseconds are going mainstream in consumer vehicles. Air suspensions have been common on commercial trucks and some SUVs for some time. ...
1
vote
1answer
104 views

Are there any specific plans for the other parts of the 747s scavenged to make the Stratolaunch carrier aircraft?

I'm not sure quite how many people are familiar with the Stratolaunch project, so I'll give a quick summary. Paul Allen and Burt Rutan (of Scale Composites) teamed up a few years ago to create a ...
9
votes
2answers
415 views

How is gas flow through (extremely long) pipelines monitored and controlled?

(This is closely linked with measuring the Mach number inside a nozzle but it is not regarding the supersonic flow) Friction and heat transfer have effects on the Mach number of the compressible flow ...
1
vote
2answers
222 views

Most efficient heat exchanger for dirty air/water medium?

It's been a long time since I went over heat exchangers and even then it was all theoretical. I'm looking for anyone with real world experience with different types of heat exchangers. I'm looking at ...
5
votes
5answers
6k views

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 ...
18
votes
4answers
21k views

Would it make sense to have a 12V lighting circuit in a house?

Modern LED bulbs must convert the standard household supply (for example $240\text{V AC}$ in the UK) into a DC supply at a lower voltage (usually $12\text{V DC}$ I think) for the LED array. This is ...
5
votes
4answers
172 views

Determining pressures of a compressible gas

A friend and I wrote a paper for a fluids class discussing the details (as they relate to fluid dynamics) of constructing a cannon that could shoot a steak fast enough to cook it. We quickly ...
21
votes
3answers
1k views

How to know whether the flow is supersonic in a nozzle?

For a project I had built a convergent divergent nozzle designed for Mach number = 3. In that project, I could know the flow has gone supersonic by seeing the manometer fixed between the throat and ...
6
votes
1answer
808 views

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?
5
votes
2answers
845 views

How to equalise the water distribution in a leaky pipe irrigation system?

I have a 200 litre water butt and plenty of 22 mm plumbing pipe and fittings and I want to build an irrigation system for my vegetable patch so that I can open the tap after a few dry days and ensure ...
8
votes
1answer
2k views

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{...
22
votes
3answers
15k views

Why do hydraulic systems use special fluid - what's wrong with water?

As a hydraulics layman thinking about hydraulic systems, it seems that the important factor is to have a liquid that doesn't compress much or at all. Doesn't water meet this requirement, and what ...
8
votes
1answer
162 views

In the context of a known disturbance $d(t)$ in a control loop, what is the $\Delta t$ at which the control loop has to be executed?

As an example, consider a P-T1-system with a PID-controller. First look only at the P-T1 system, set a $y_r$ and wait a long time - then we take a look on its output $x$ and see that it has still a ...
5
votes
3answers
16k views

How to determine reinforcement design strip widths and locations

When designing reinforced concrete slabs it is common to divide the slab into 'design strips', which are then used to rationalise the reinforcement design along (typically orthogonal) lengths of the ...
12
votes
4answers
943 views

Easy nonlinear model for large deformation of a beam

I have a beam subject to twisting and/or bending forces as well as linear compression force along its main axis. It is modelled as an isotropic beam, but if anisotropic is not too far off then that's ...
5
votes
2answers
188 views

When is DC power generation superior over AC power generation?

If the goal is to transmit power over a large distance, I can see the advantage of an alternator over a generator: more power, less loss. If the target DC load is small and very close by, would an ...
12
votes
4answers
1k views

Below what Froude number can I neglect wave-making resistance on a vessel?

I want to do some very simplified drag calculations on a vessel. My hope was that calculating the skin-friction resistance would be enough to get a good estimate of the surge resistance. Because wave-...
11
votes
5answers
4k views

What is the difference between pressure and stress?

Since the units are the same ($\frac{N}{m^2}$), what's the difference between pressure and stress?
19
votes
1answer
401 views

Sizing a pressure safety valve for two-phase flow

I understand that valves in two-phase vapour / liquid were sometimes sized by considering the required vapour and liquid flow rates separately, and then adding the results together. But this is now ...
11
votes
3answers
9k views

How different are dc motor designs from dc generator designs?

Some dc motors can be used as generators as well by applying mechanical torque to the output shaft to induce a current. However, even if a dc motor can do this, I imagine they were not designed for ...
2
votes
1answer
354 views

Thermostat design properties

Cut-in, cut-out thermostats are commonly used with refrigeration devices in order to hold a consistent temperature range. Their general operations is such that when the temperature by the probe ...
2
votes
1answer
88 views

Estimating maximum lift or strength

Weight lifters will use the term "one rep maximum" in order to refer to the maximum amount of weight that they can lift one time. The one rep max is often used as a proxy for how strong someone is (...
8
votes
2answers
6k views

How to calculate the pressure a pipe can withstand?

I was looking at high pressure pipes and their pressure ratings. I'd like to know how these pressure ratings are determined. I assume that pipes are tested until failure, and the failure pressure is ...
6
votes
5answers
7k views

Is compressed air energy storage economically viable in the home?

If I install a small air compressor/engine, generator, and tank in my garage, and I charge it up at night when electricity costs $\frac{5.4p}{kWh}$ and use it during the day to power my house when ...
10
votes
1answer
155 views

Has a specific type of alternative intersection been shown to reduce congestion & accidents?

Localities in the US have different road layout and setups. For example the Michigan Left, Jersey Left/Jug Handle, vs a standard 4 way stop with left turns at the intersection. Have any of them come ...
16
votes
1answer
621 views

Can we change steel properties by application of magnetic field while quenching?

Austenite is non magnetic while $\alpha$-ferrite and pearlite are magnetic. (Magnetic properties of pearlite vary as a function of carbon content) If a strong magnetic field is applied in a ...
7
votes
1answer
180 views

Can using different types of alcohol in a cloud chamber produce different particle tracks?

The design for a cloud chamber is rather simple, and many factors can be changed without producing different results. There is one curious point that I've stumbled upon, though: The type of alcohol ...
-2
votes
1answer
523 views

Can Mechanical Design help meet EMC/EMI requirements for electronic products?

EMI/EMC issues are common in most electronic designs. Electronic and Hardware Engineers use many different strategies to mitigate these issues: These include (But not limited too) Designing filter ...
13
votes
1answer
636 views

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,...
20
votes
8answers
2k views

How do engineers really use numerical simulation?

Disclaimer I'm an applied mathematician by training, not an engineer. My work research primarily focuses on creating new "methods" to solve different PDE's related to solid deformation (elasticity) ...
9
votes
3answers
253 views

Bonding Semiconductors to PCB

I'm trying to bond semiconductor samples (Si and Ge) area ~1-2cm^2 to fiberglass printed circuit board (PCB) We use West system marine epoxy for other things. 105 resin 209 hardener (long cure time.) ...
2
votes
1answer
4k views

What are characteristic values for a piston pump?

For a piston pump you can calculate/measure things like, Average Volume flow rate (m³/s) Geometric Values (Surface) Pressure over time closing times of the valves energy conversion efficiency $\eta$ ...
17
votes
3answers
6k views

What is the most efficient means of warming a building with a high ceiling?

Consider a large auditorium, a church, or some other very large, essentially one roomed building with a high ceiling. Suppose that the building has many entrances which enable cold air in/hot air out ...

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