Questions tagged [geometry]

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1answer
65 views

To stop or to go around?

Let us we are moving in a car. There is a wall in front of us, we need to decide can we go around it or not. It is known that width of the wall is $w$ and our speed is $v = const$. What is a simple ...
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1answer
21 views

Why is the area of upstream face of control volume a stated?

I cannot seem to visualise why the area of the upstream face of control volume is 2pir∂r, can someone pls clarify on why is this the case?
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0answers
31 views

Does anybody know where this calculation for the mass moment of inertia for an eighth of a circle comes from?

These attached photos describe flaps which are a portion of a circle and equations are attached as the mass moment of inertia, but there are no descriptions. I am using this for part of my research, ...
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1answer
31 views

horizontal angle of view based on distance from window [closed]

I am looking for an equation to provide me the angle of view based on a distance from a window. I'm only interested in the horizontal not the vertical.
2
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2answers
105 views

How to calculate miter angles for an angled stretcher

See the image below: When I lay this out in Fusion, I can get the angles but I can't figure out how to calculate it mathematically. The goal is to have the angled stretcher fully contact the upper 45&...
4
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1answer
82 views

How to trace a square with a reuleaux triangle

I am trying to trace a square (with rounded corners) using a reuleaux triangle and a single (circular rotation) motor. I've seen many animations (example) of this but do not understand how to make it. ...
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0answers
35 views

Meshing Error near Leading and Trailing edges

I am trying to mesh the propeller geometry in the Ansys meshing tool. At the leading and trailing edges of the propeller, mesh goes out of boundary. I did a geometry check of the CAD model in ...
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0answers
30 views

Is a pyramid considered axisymmetric? Why so?

I read a source, I will not reference the source on this platform. They stated a pyramid is axisymmetric. Can you explain why if yes?
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0answers
31 views

When calculating a car's suspension caster, after turning the steering wheel 20 degrees, why multiply by 1.5?

To calculate caster of one side of a vehicle, the steering wheel is turned 20 degrees to the left, and the camber is obtained; this represents the 'in' value of the front right tire. Then the steering ...
2
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2answers
2k views

How to calculate meters per pixel for a given camera?

I am stuck on this problem for a while: I have a square-shaped camera, with: 1000 pixels on vertical side 1000 pixels on horizontal side I want to know the number of meters per pixel depending of ...
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1answer
49 views

How could I get the coordinates of the circumscribed circle giving the 3 points coords?

I have the coordinates of 3 points thrgouh which, a circle should pass . Having the coordinates of the points in 3D, how could I have the coordinates of the center of circumscribed circle ? also : if ...
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0answers
27 views

Program for creating a cylinder given its axis, center and radius?

I have data with the following normalized values: Unit vector for cylinder axis: -0.00270666, -0.01226211, 0.9999212 Normalized coordinates for cylinder center 0.01412114, 0.01074875, 0.00017004 ...
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1answer
63 views

Arc subtended by stretching of a conical spiral spring

I'm trying to work out the angle subtended by the stretching of a conical spring and I have a solution but I'm not 100% sure about it so would appreciate some feedback. An Archimedes spiral spring is ...
1
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1answer
875 views

Calculating area moment of inertia for a beam with underslung plate?

In a number of designs, a beam will have an underslung welded plate attached, as shown below: In this sketch, a symmetrical standard steel beam/column of dimensions H1 x B1, with web and flange ...
3
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3answers
111 views

Calculate area of mesh?

I have expanded steel mesh that I use to make garden cages: I would like to know how much sunlight the mesh blocks. I think I need to calculate the area that the mesh takes up (per square inch) and ...
1
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1answer
121 views

Equation used to obtain the adjustment angle of a pivoting lid support mechanism?

The following image shows a CAD model in its folded and unfolded form. I was able to successfully give it the ability for it to be adjusted between a 25 and 45 degree form, at 5 degree increments; ...
1
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1answer
76 views

Building a half-arch of a specific height, while consistently using an angle divisible by 90

I am trying to construct a lift handle in the CAD Sketchup. The circled part of the image shows the arch I'm referring to. The program, Sketchup, has a 'tool' called push/pull, and another tool ...
3
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3answers
1k views

Wrap a geodesic dome with a poly sheet: Minimize overlap & loose areas

I want to make a geodesic dome greenhouse (16ft wide, type: 3V 5/8). Source: http://geodesicdomes.ca/wp-content/uploads/2009/12/domes-fullsize.jpg I would cover a geodesic dome frame with clear ...
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1answer
121 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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7answers
819 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
133 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
22 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 ...
0
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1answer
129 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 ...
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3answers
1k 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
430 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
2k 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 ...
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1answer
84 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
100 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
105 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
217 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 ...
3
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0answers
98 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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3answers
90 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
638 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
628 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 ...
3
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2answers
776 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 ...
1
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1answer
106 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
286 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
87k 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 ...
5
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3answers
155 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 ...
4
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2answers
961 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 ...
2
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2answers
112 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
365 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, ...
3
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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
2k 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
4k 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
4k 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 ...