Questions tagged [geometry]
58 questions
8
votes
3 answers
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 to go about solving for it. I've posted the shape…
tempestwing0101
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6
votes
3 answers
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 through the compressor (turbine).
The compressor…
setun-90
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6
votes
4 answers
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 of outside? Would a circle/sphere still be the…
user2813274
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6
votes
1 answer
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 lesser degree or not at all?
So should one use outer…
hepe
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6
votes
4 answers
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 perfect equilateral/equiangular triangle consists of…
voices
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5
votes
1 answer
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}^{25}\int_{-23}^{35}y \, dy \, dz=-17400…
Akitirija
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5
votes
7 answers
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 example of this is the speed wobble, examples easily…
user16388
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4
votes
2 answers
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 bottom or something; figuring a design only needs to…
Andyz Smith
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4
votes
0 answers
Maximum Slope of Truck Parking Lot
What is the maximum grade/gradient allowed for non-temporary (overnight or longer) parking/vehicle storage areas in parking lots for heavy-duty vehicles such as semi-trucks and buses?
All I could find is that the International Building Code allows a…
4
votes
1 answer
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.
A diagram or geogebra file in the answer would…
Ankit
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4
votes
2 answers
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)
The channel-indicator is a narrow rod at the tip…
Always Confused
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4
votes
2 answers
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 formulas:
I also know that more generically, the…
balth b
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3
votes
1 answer
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, to withstand 1 atm on the outside and 0 mbar on…
user1717828
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3
votes
2 answers
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"-long support and the floor(even though there…
Mr. Mascaro
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3
votes
2 answers
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 has a swivelling mechanism. Those are hard to…
Willem-Aart
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