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8
votes
1answer
2k views

What is the unbraced length of a pile in soil?

When analyzing a pile or drilled shaft as a beam-column, how do you determine the unbraced length of the portion that is in the ground? Typically, the braced points on a beam or column are well ...
11
votes
2answers
4k views

Do structural engineers carry insurance for catastrophic errors?

A friend of mine is a structural engineer and he often complains to me about how little sleep he gets at night worrying over whether or not he accounted for all the little details involved in his ...
3
votes
3answers
737 views

Can superhydrophobic surfaces be used to reduce drag?

I am mainly interested in reducing drag in aircraft and I have an idea that I want to learn more about... Can a superhydrophobic coating reduce drag in water-craft such as boats and submarines? If ...
10
votes
4answers
2k views

What is an engineer's liability for code changes that occur after submitting a design?

What if any liability would an engineer have in the following situation? This is specifically in reference to engineering within the USA. An engineer produces a design and plans that meet the ...
15
votes
2answers
340 views

Modern method for teaching controls

Background When I took my first class in controls (2006-ish as taught by an aerospace professor for a mix of ME and EE students) it was basically all done in Laplace-transform, transfer functions etc. ...
13
votes
1answer
356 views

Estimating whether the flow through a valve or nozzle cavitates

My understanding is that cavitation occurs in the flow of a liquid when the static pressure drops below the vapor pressure, even intermittently. So even if the time-averaged static pressure (what you ...
6
votes
2answers
7k views

Finding the pull-through capacity of a nutted bolt and washer in ASA plastic

I have a uniform load applied to the underside of a plastic sheet which is to be resisted by the combination of a bolt, washer, and nut as depicted below (the other end of the bolt is secured and will ...
4
votes
2answers
6k views

How to Compute Total Strength of Composite Tensile Bars

In this question about combined tensile strength, all of the tensile bars are of the same material. But what if the case that they are made of different materials? Say we have $200$ bars of $A=10 (\...
5
votes
4answers
3k views

Logic gates for an indicator light to show the state of two sensors

I've attempted to answer the following question and I need to know if I am on the right track: LOGIC GATES Question 3 A manufacturing plant uses two tanks to store certain liquid ...
11
votes
2answers
226 views

How accurately are moveable span bridges balanced?

Movable span bridges (bascule and lift) typically employ a counterweight to help reduce the amount of energy and size of motor required to move the span. Due to variations in the the construction of ...
4
votes
1answer
98 views

Communicating losses and imprecision in liquid measurement by analogy

I'm writing a presentation for people and I need an analogy to convey the following problem: Person A wants to sell a liquid, so he fills a tank, measures volume and sends to Person B. Now Person ...
7
votes
1answer
717 views

How do I compute combined tensile strength?

If I know the tensile strength of a pin, how do I compute the total strength of multiple pins? That is, 2 objects are connected by multiple pins, evenly distributed, each with a height of $2mm$ and a ...
21
votes
3answers
351 views

How much can Protactinium degrade the efficiency of the Thorium fuel cycle?

One of the counterpoints to the Thorium fuel cycle is that Protactinium, which is generated in this cycle degrades reactor efficiency and thus needs to be removed, at least from the liquid fluoride ...
4
votes
1answer
211 views

What is the difference between NIL and hot embossing?

NIL (Nanoimprint lithography) and hot embossing seem to mean the same thing in many instances. Is hot embossing a subset technique of NIL? Or are they completely different methods?
4
votes
1answer
79 views

Sinking speed of particle in shear thinning fluid?

For Newtonian fluids, the sinking (or rising) speed of a particle is (reasonably) well known. What is a relationship for shear thinning fluids?
2
votes
2answers
1k views

What is the best insulation wall for a house? ACC wall, Cavity wall, etc

Normally, people use Autoclaved Aerated Concrete (AAC) to build a concrete house because ACC is a good thermal insulation brick that easy to buy and not expensive ...
4
votes
2answers
1k views

How do cyclonic vacuum cleaners maintain collection efficiency with constant motion and changes in orientation?

Anyone used to doing housework has probably noticed that vacuum cleaners come in both "bagged" and "bagless" varieties. If you're of a certain age, you may have noticed when these "bagless" vacuums ...
9
votes
1answer
535 views

How do I compute the force required to pierce HDPE?

I have a $2\text{ mm}$ sheet of HDPE at $280-320^{\circ}\text{ F}$. I want to pierce the skin of this sheet with a $2\text{ mm}$-high pin with a surface area of $3.33\text{ mm}^2$. The pin is also ...
35
votes
2answers
15k views

What is the purpose of these diversions in a natural gas line?

The campus where I work has a long covered walkway (~.5 mile) which has several labeled pipes running under the roof (chilled water, fuel oil, air...). All of the pipes run dead straight except for ...
13
votes
2answers
7k views

How does a multimeter protect itself from high voltages?

I have used a cheap multimeter to measure voltages in simple DC circuits, but I have seen pictures of them plugged straight into the mains and used to measure various home-built generators. Why doesn'...
9
votes
4answers
16k views

Does a transformer use power when output isn't under load?

I was reading about how AC to DC converters work with a step-down transformer and then a diode bridge to convert the lower, stepped down AC voltage into DC. What I don't understand is since the input ...
15
votes
14answers
28k views

What kind of math do engineers really use? [closed]

I am from the mathematics StackExchange section, many of my students are engineering students at University. I was wondering what kind of calculus do you real engineers use? I have known two engineers....
3
votes
1answer
253 views

Motor Driver board: limited current

I'm having some trouble using a motor driver board. I'm pretty sure its being driven properly since there is ~3V @ the output v.s. none when its off. However it should be supplying ~2A (rectifier ...
5
votes
1answer
135 views

Question about “uncertainty”

I'm a bit confused about all the different "definitions" of uncertainty? One can calculate "uncertainty" of a single measurement by simply checking how accurate the tool that is being used to do the ...
7
votes
1answer
165 views

Scale models of thermal plumes

I want to look at the thermal heat plume of a human in still air in a room. So I have a tank of water with a heating coil/cylinder in it. How do I calculate what the heat output of my heating coil ...
3
votes
1answer
183 views

How to divert solids from a downward vertical pipe

I am an electronics engineer trying to build one small underwater mechanical device (about 12 cubic cm) as part of a personal automation project. I have figured out the electronics for this, but I am ...
3
votes
1answer
2k views

How to design electronics to mitigate tin whiskers?

Tin Whiskers are a major problem in the design of electronic circuits and the manufacturing of electronic hardware. What are Tin Whiskers? How can electronic products be design to mitigate the issue ...
8
votes
2answers
2k views

What is the practical limit on the number of storeys in residential buildings built with monolithic reinforced concrete?

I have recently bought a flat in a 25-storey building. I wonder what is the practical limit for the number of storeys in a mass-produced residential buildings built from monolithic reinforced concrete?...
22
votes
4answers
7k views

What is a reason that handlebars fit to a motorcycle and steering wheel fit to a car?

What is the reason that handlebars are installed on motorcycles and steering wheels are installed on cars? Notice that the way to use both handlebars and steering wheels are quite similar, but a ...
3
votes
1answer
5k views

Is it acceptable to paint weathering steel?

Weathering steel is not typically painted, because it produces a thin rust layer that protects the rest of the steel from further corrosion. Would painting weathering steel be an acceptable additional ...
1
vote
1answer
597 views

Thoriated tungsten TIG electrodes were in use 45 years ago.What were their specific use and problems?

Some TIG electrodes in use in the early 1970's were marked Thoriated Tungsten and Non-Thoriated Tungsten. What were the specific purposes or properties for these TIG welding electrodes?
7
votes
1answer
1k views

Are standard structural bolts acceptable for all cold climates?

The specifications for standard (ASTM A 325) bolts do not list minimum service temperatures. I am thinking of outdoor applications like Alaska or Canada (lows of -60F) and wondering if the cold ...
5
votes
1answer
223 views

Best traffic control device/system for given situation

I am familiar with the round-a-bout/traffic light pros and cons, however, I've been tasked with deciding on a solution for the given parameters below. Currently, there is a two-way (four lane) road ...
10
votes
3answers
6k views

Why is it unwise to choose cylindrical horizontal beam

I heard that it is unwise to choose cylindrical horizontal beam. My question is why?
1
vote
1answer
349 views

What type of sensing element is used in Water Quality Monitoring Meters?

What type of sensing element is used in Water Quality Monitoring meters such as those pictured below? I might not be using the correct search terms. Some of these meters monitor Total Dissolved ...
4
votes
1answer
1k views

Tankless air compressor for electronics desoldering station

I purchased a Weller WSD161V soldering station (similar to this one, at least with regards to the pneumatic system I'm about to describe -- sorry, I was unable to find a manual for my specific model ...
0
votes
2answers
132 views

Is making a toilet flush backwards problematic? [closed]

The Coriolis effect impacts the way water tends to circle before going down the drain. Many (most, all?) toilets are designed to work with the Coriolis effect. I am considering a line of toilets ...
6
votes
1answer
95 views

Where to insulate Underfloor air distribution system in a temperate climate

I have a proposed underfloor air distribution system (UFAD) for a one level office in a temperate climate. Typically the demand for heating and cooling in this climate is about even for offices. ...
10
votes
3answers
924 views

Could air-launched space planes reach escape velocities?

Rockets like the Ariane 5 weigh hundreds of tons, but with about 85% of that weight being fuel, the payload fraction is only about 3% (~10-20 tons). Virgin Galactic is building suborbital space ...
5
votes
4answers
684 views

Can you get quality welds from a multiple metal wire feed welder, or do you need separate units for steel and aluminum?

The job site requires welding both aluminum and steel (each to themselves only) for different areas of the project. The contractor has a dual purpose wire feed welder (aluminum and steel) but I am ...
6
votes
3answers
1k views

What is the densest ceramic?

I know ceramics are generally considerably less dense than pure metals or alloys but sand is used in barbells for its probably cheapness, user-friendly and easy availability but its a decent density ...
13
votes
3answers
4k views

Measuring longer distances with high accuracy

I am involved right now in the fabrication of steel structures on the order of 5-50 feet long. Presently, we measure these structures with garden variety commercial tape measures. Most of the time, we ...
8
votes
3answers
1k views

Motor for a hydraulic pump in a hydraulic system

I am a complete beginner to hydraulic systems, and I've wanted to learn more about this area. I'm designing a hydraulic system that involves using hydraulics to push/pull objects using pistons. I have ...
3
votes
2answers
11k views

How do I manufacture a fillet?

What are the most popular and the most efficient ways to machine a fillet on an external edge of an object? If I were to use a CNC mill, what tools can I use for it, and how would the method change ...
8
votes
4answers
5k views

What bolts should I specify with Weathering Steel?

When using weathering steel (COR-TEN) on a project, what sort of bolts should I be using? I have yet to see fixings made of weather steel; presumably because the way it uses a sacrificial layer to ...
4
votes
2answers
256 views

Ensuring even flow in liquid pumping in distribution circuit under suction

I have a liquid circuit which looks a bit like that: The system is under suction, and the flow rate through each unit should be about 10ml/min. However, we noticed that unit ...
11
votes
3answers
2k views

Could a gold/{second metal} crown be created that would pass the Archimedes test cost effectively?

Many people are familiar with the story of Archimedes submerging a crown in water to identify if the volume of the crown was consistent with the volume of the same amount of gold. The test was to see ...
5
votes
1answer
181 views

Name of spring actuated component

I need to get another component like this but I can't seem to find any manufacturers / retailers. To describe it: It is spring mounted on a shaft and retained by bushing on the top and an enlarged ...
15
votes
1answer
1k views

Why are hyperboloid towers not popular anymore?

Hyperboloid towers were very popular in the end of 19th and the first half of 20th centuries - water towers, powerline anchor towers, sometimes tall radio towers were built using this design. The ...
8
votes
5answers
7k views

How do you attach something temporary to a smooth metal shaft?

I want to attach something small to the smooth metal shaft of a small motor (2-3 mm in diameter), like fan blades, but I want it to be temporary. If I make it too loose, then the fan won't turn at ...

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