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Questions tagged [geometry]

The tag has no usage guidance.

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0answers
20 views

Area moment of inertia calculation [on hold]

I have a planar lamina which is swept through helical curve. I want to calculate area moment of inertia at every section plane. But the orientation of the planar lamina is changing at every section ...
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2answers
55 views

Wrap a geodesic dome in a poly tarp: Minimize overlap & loose areas

Idea: I'm planning to purchase a geodesic dome frame for the purpose of making a geodesic dome greenhouse (16ft wide, type: 3V 5/8). Source: http://geodesicdomes.ca/wp-content/uploads/2009/12/domes-...
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1answer
70 views

Difference in Diameter calculation using Solidworks and manually

When I try to create a flat form of a archimedes screw using Solidworks it gives me a diameter different from what is calculated manually basically using a Pythagoras Theorem. Can anyone explain the ...
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4answers
87 views

What makes scooters unstable at high speeds?

Scooters and skateboards are obviously meant for slower speeds, below 5 MPH. Typically if you go faster than that, it becomes harder and harder to control the scooter, and you will fall off. An ...
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1answer
80 views

Boolean Geometry Help [closed]

I just don't get the concept of Boolean Geometry... Can you help me understand how to solve these homework problems? Thanks!
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1answer
14 views

How to find the nearest locations around a given latitude and longitude point? [closed]

I have a database of locations. Each location is a latitude and longitude pair. Now for each query, I want to get top "X" nearest locations around a given latitude longitude point. How do I actually ...
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1answer
20 views

Calculate attitude quaternion from 2 vector measurements

I am using a method proposed by R. G. Reynolds to estimate attitude based on two vector measurements, taken from: https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19990052720.pdf Suppose we ...
6
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3answers
217 views

Calculating moment of inertia for a hollow discontinuous circle?

This is a pretty simple problem, but I'm just not sure how to go about it. I want to find the moment of inertia of a discontinuous hollow circle. But since the shape is so irregular, I'm not sure how ...
6
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1answer
109 views

Do outer fillets|chamfers also reduce stress as inner ones do?

I kind of have an intuition or at least imagination about how fillet|chamfer of inner edges|vertexes reduce stress (concentration). But does that apply to outer edges|vertexes aswell? Maybe to a ...
6
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2answers
199 views

Why are Whitworth threads angled at 55°?

You're probably thinking, "Well.. Why not? It's gotta be something.." Right? But 55° is kind of an odd angle if you think about it.. and it does seem like a pretty specific choice considering a ...
0
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1answer
79 views

How maps of globe, country or region were created few decades/centuries ago when modern technology like today did not exists?

What techniques were used to create the maps of a world, country or region when satellite or similar technology did not exists few decades or centuries ago?
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2answers
82 views

What does this equation mean?

$$\propto \dfrac {\text {Cross-Sectional Area}}{\text {Volume}} $$ I've seen this equation on my textbook (physics). Let us imagine that there are two pen with $7$ and $3$ lenght. Which is harder ...
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1answer
77 views

What is the most accurate geometry to represent earth

Currently software and maps represent earth in many different ways, the latest is Point Clouds as this is the most common surveying tools currently available. For the needs of visualisation, ...
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1answer
98 views

Advice for designing internal structure of glider wing

I am interested in designing a scale model semi-monocoque wing for a glider. I've done some research on the framework and internal structure. I have found out about the spars, ribs and stringers and I ...
2
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0answers
71 views

What is the deflection of planet-ring Gear Mesh along the pressure line and the position of the Plant gear?

For a Sun-Planet mesh in a planetary gear train, there will be a deflection $\delta_{sn}=\delta_{s}-\delta_{n}$ along the pressure line and the position of the planet will be determined by $\psi_{n}$, ...
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0answers
54 views

Packing efficiency geometry

Suppose that I am evaluating the packing efficiency of different geometric shapes. Are spheres good shapes to achieve a good packing efficiency / density in a typical shipping box? Are there other, ...
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3answers
76 views

Graphene distribution over a sphere

How much graphene is required to coat a 5 inch (diameter) sphere if the graphene layer must be 35 nanometers thick?
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2answers
380 views

How this radio knob converting a rotation into a straight-linear motion?

Few months ago I opened the boards of an old, scrap radio-cum-tape-recorder (Philips DR183); whose tuning knob (that adjusts the gang); was very peculiar. ( * I did not found its datasheet on web) ...
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1answer
231 views

What is a void in CAD

I'm using existing architectural designs and some mechanical designs too, all CAD files in formats *.dwg, *.dgn and the drawings have smart solid geometries including voids. Using CAD software what is ...
4
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1answer
256 views

How can I draw Voronoi regions in curved surfaces in AutoCAD?

How can I automatically compute and draw/display the Voronoi diagram of a given set of vertices on a surface in AutoCAD? A "Voronoi Sketch Generator" is the best I could come up with on a google ...
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1answer
84 views

Diesel injector nozzle geometry

I thought of an injector nozzle for a diesel engine with an alternate combustion chamber format (somewhat like a Heron combustion chamber), and would now like to get an estimate of the size of the ...
1
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1answer
143 views

How should I calculate the centroid of a hollow structure when analyzing a wind load?

I am trying to solve the following problem: A masonry chimney having the shape of a conical frustrum is 25 m high. The external diameter at the top and internal diameter at the bottom is 2 m. ...
4
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2answers
17k views

Moment of Inertia of a Rectangular Cross Section

I have a question that is annoying me for a long time. I know that I can calculate the moment of inertia of a rectangular cross section around a given axis located on its centroid by the following ...
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2answers
97 views

Turbocompressor spool geometry

How come axial compressors always narrow and turbines always widen towards the rear? From what I know: The speed of sound of air increases with temperature, therefore increases (decreases) as it goes ...
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2answers
552 views

AISC Section Modulus numbers

Why does the AISC handbook only list one figure for Section Modulus for shapes such as Angle(L) steel? Shouldn't there be two? The steel is asymmetric. Is the figure given just the Delta to the ...
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2answers
73 views

Lengths of Connectors in Steering Linkage

Below is a picture 4-wheel vehicle steering linkage. I figured that in order to steer correctly $(W+D)tan\theta_1=Dtan\theta_2$ where $\theta_1$ is the angle of the outside front wheel, $\theta_2$ is ...
3
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1answer
263 views

How thick does an aluminium vacuum cylinder have to be?

Take a hollow aluminium cylinder with outer radius $r$ and length $h$, capped with two circular endcaps. How thick does the aluminium have to be, that is what is the inner diameter of the cylinder, ...
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2answers
1k views

How to design a swivel connection for a single wheel trailer?

I'm trying to design a single wheel trailer for my underpowered VW, much like this one. Unlike a conventional trailer, it is attached to the car at two points. To prevent the wheel from dragging, it ...
5
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1answer
1k views

First Moment of Area - Meaning of Sign/Sense

I was trying to find the moment of area about point A on the following figure: I prefer to use integration, since it can be extended to different shapes, and did this: $\displaystyle Q_z=\int_{-25}^{...
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2answers
2k views

Why are so many things around us rectilinear? [closed]

If you look at the man-made objects around you, you will see that almost all of them are either rectangular, or parallel and perpendicular. There are a few circles here and there, but the overwhelming ...
6
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4answers
2k views

Is a circle the strongest 2D shape for containing internal pressure?

I understand how a circle (or sphere if you want 3D) is the best shape for holding a vacuum inside a container, but what if you wanted to have a large positive pressure inside of the container instead ...