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1500 questions
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3 answers

Monorails - why even have them?

My (highly limited) engineering intuition says: Dual railing is good - for balance, for switching of tracks, for lightening load and making sure it is applied in basically the same direction always, and perhaps other reasons I haven't thought…
einpoklum
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1 answer

Tower crane with lift (elevator)

Near my apartment is a building site with a tower crane; great fun to watch of course. This crane seems to have a lift / elevator / vertical-people-transporter (arrowed in the picture). As far as I can see the lift is only used four times a day…
NL_Derek
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3 answers

Test UV protection on sunglasses

I bought sunglasses in China that claims to have UV400 protection. I'd like to test this as my eyes' health is on the line :) Is there any way to check the maximum UV amount these glasses can protect me against?
dotixx
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How to strengthen an I beam

To save on material, I am requested to design a continuously supported beam with a maximum bending capacity that is half of its maximum bending moment and to strengthen the beam at certain intervals where its capacity is exceeded. What is a feasible…
Jarard
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What's the point of draft in sand casting

I know what pattern draft is and it's usefulness in removing castings from rigid moulds. That's the definition you can find anywhere. My problem is when you sand cast. Sand casting is the most common amateur metal casting technique, with lots of…
Paul Uszak
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2 answers

Is there any material that blocks a static magnetic field?

Is there any material that blocks a static magnetic field? So that if I put it between a magnet and a piece of metal, they won't interact with each other?
ergon
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Eiffel Bridge Design

In bridge design normally base supports are strong,fixed/rigid. Why did he choose thicker arch sections at middle above mid-river and narrow sections at abutment supports? If he chose a simply supported condition, then for what structural…
Narasimham
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3 answers

How to determine how much energy recovered from regenerative braking

I am considering a regenerative braking system implemented with a AC permeant magnet motor with an efficiently of ~96%. It is easy to determine via energy equations the kinetic energy of the car and therefore how much energy is possible at max…
user1636588
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Multiphase Flow - Energy Coupling Parameter

I have a general question regarding energy coupling in multi phase flow. My question comes is based on the text from this…
MathsIsHard
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What makes crosshead bearings hard to lubricate?

Regarding crosshead bearing failure, I have read that at slow speed it is difficult to establish a lubricating film because there is an imbalance between forces due to combustion and forces due to inertia. This information is from a maker of big low…
veronika
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Are Scientific Calculators still current?

I've been a civil/structural engineer for 20 years now. My HP 48GX has recently done its last calculation. So I looked for a replacement and it seems that the market for scientific/graphing calculators has changed. My question: Could it be that…
SlydeRule
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Eccentricity for staggered 2x4 wall

I have a staggered 2x4 wall on a 2x6 sill plate as illustrated below (16" on center on each side = 8" on center each stud). The wall is loaded from both sides by floor joists, so I would consider it to be loaded in the center of the axis of the…
user2817017
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Does the ultimate tensile strength of a material have a physical meaning?

For example, for yield point you can say that it is a point after which the material will have plastic (permanent) deformation. I'm wondering if there is any similar meaning to the tensile strength? And is there any importance to it? The thing is,…
M. Wother
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Do all airfoils have a lift curve slope of $2\pi$?

I know that according to the thin airfoil theory all airfoils (symmetric or not) have lift curve slope of $2\pi$. I also know that finite wings should have less inclined lift curve because of the downwash. Then I saw this formula used for finite…
emcyaman
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Derive a heat equation for a shrinking nanoparticle

I consider a spherical nanoparticle (NP) that is shrinking, for instance due to a melting process. I know that the pressure $p$ is proportional to $1/R(t)$, where $R(t)$ is the radius of the NP at time $t$. Conservation of energy states…
Marc
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