Community Digest

Top new questions this week:

How does humidity, specifically using a humidifier, affect the filtration of PM2.5 particles from a room?

I live in a very smokey and dry area where people are advised to use air purifiers. Since it's also dry I'm curious what affects, if any, adding a humidifier to a room with an air purifier would have? ...

asked by joeyfb 4 votes

How were the tones for DTMF chosen?

In my limited engineering knowledge, and limited research skills, I couldn't find a complete answer for the reasoning behind the chosen tones for DTMF. I did find a hint that said something about ...

telecommunication signal-processing  
asked by natebot13 3 votes
answered by StainlessSteelRat 2 votes

Maximum hole size in brickwork before a lintel is required

Holes are made in brickwork walls for all kinds of reasons including gas flues, to route cabling and to fit windows. At some point that hole gets large enough that a lintel is required to support the ...

structural-engineering civil-engineering  
asked by egg 2 votes
answered by egg 1 vote

Solidworks Loft error (guide curve not intersecting with profiles)

I am trying to add 'finger grooves' to my model of a brake lever and want to use a loft to do so. I have created (to my knowledge) all required sketches for the loft but SW gives me an error when ...

modeling cad solidworks  
asked by Maarten -Monica for president 2 votes

Off-centre actuation

I'm trying to lift a platform with several guides using a linear actuator, but off the centre as follows: The load on the platform will be around 100kg, which is just within the linear actuator's ...

mechanical-engineering bearings linear-motion linear-motors  
asked by John M. 2 votes
answered by jpa 3 votes

Determining the final surface temperature and final gas temperature flow through a tube in a room

I am trying to calculate the final temperatures as stated above. There is hot gas flowing through a tube that is insulated and inside of a room (no wind). I will try to walk you through my thought ...

fluid-mechanics thermodynamics heat-transfer  
asked by JoshL 2 votes
answered by Jeffrey J Weimer 1 vote

Probability of structural failure

In structural engineering we have to accept the fact that you can never be exactly sure how much load a structural member can resist, that the load carrying capability of an element is not one exact ...

asked by S. Rotos 1 vote
answered by alephzero 1 vote

Greatest hits from previous weeks:

How does width and thickness affect the stiffness of steel plate?

I have a 2 mm thick steel plate which is 300 mm long and 30 mm wide, supported at either end. It supports a weight-bearing wheel that can roll along the plate. It currently supports the maximum weight ...

mechanical-engineering steel stiffness  
asked by jhabbott 17 votes
answered by William S. Godfrey- S.E. 14 votes

Determining stiffness of a beam w/varying moment of inertia

I need to calculate $K$ or equivalent stiffness of a beam that has a varying $I$ across its length. $I$ has been given to me as a function of $x$, or length. I have been unable to find a proper ...

asked by Jacob Norman 3 votes

Which is better: Defog a car windshield with cold or hot air?

So i had this experience when driving in a cold night, where my windshield just got all blurry. I knew that on the drivers manual they say you should turn the hot air and soon it will go off, but my ...

asked by Alessandro Nardinelli 8 votes
answered by Olin Lathrop 10 votes

What does "a" mean at the end of a refrigerant's designation (R-134a)?

I was studying the designation of names to refrigerants. The following is the basic formula: R - (m - 1) ( n + 1) ( o ) where: m = number of carbon atoms in the refrigerant n = number of hydrogen ...

chemical-engineering refrigeration  
asked by Fennekin 8 votes
answered by morristtu 10 votes

Why is kVA not the same as kW?

I thought my electric car charging unit uses 6.6 kW of power. However, I found the label and it actually says 6.6 kVA. When I saw this I thought something along the lines of... Well, $ P=...

asked by jhabbott 53 votes
answered by Chris Mueller 60 votes

How to determine fixed end moment in beam?

Why (FEM) BC is 3PL / 16? It's clear in the first figure that that when one end is fixed, while the another end is pinned, then the fixed end moment is 3PL /16 ... But for the span BC, we could see ...

structural-engineering structural-analysis  
asked by utk2366 4 votes
answered by Wasabi 1 vote

What is a Spiral Curve, and How is it Different from a Normal Curve?

I've heard the term spiral curve used to describe a section of highway that is more aesthetically pleasing to the driver's eye. However, I believe I've driven on enough road to say that I can't ...

civil-engineering highway-engineering surveying rail  
asked by gate_engineer 13 votes
answered by hazzey 12 votes

Can you answer these questions?

How does NASA's QueSST X-59 jet work?

The QueSST (Quiet Supersonic Transport) is a project to create a more diffuse sonic boom in order to use supersonic flight commercially without the usual abrupt 1~2 psf pressure spike damaging the ...

mechanical-engineering aerospace-engineering mathematics aerodynamics  
asked by KryptofTen 1 vote

LAN data from computer

I have an HMI (Siemens MP 377) to print collected data on a LAN connected printer. Now I would like that the data that are being sent to the printer is also received at a computer through Ethernet LAN....

data networking  
asked by samantha6 1 vote
answered by NMech 0 votes

Differential Equation for: Locking a laser's frequency with a PI controller

I think I have a good understanding of differential equations, so I would like to first try to understand my system in terms of differential equations before transforming my system into the more ...

control-engineering control-theory applied-mechanics pid-control optics  
asked by Steven Sagona 1 vote
answered by NMech 0 votes
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