56
votes
Accepted
Why are railroad tank cars bent in the middle?
As other have pointed out, the main utility is to allow easier cleaning of the tank cars from sediment (solid precipitates). Usually, there is a drain in the lowest point.
The reason that it is in ...
- 24.3k
35
votes
Why does this fence have a kink?
They're V-Mesh panels.
V-Mesh panel from Irish Wire.
The offset of the vee gives rigidity in the horizontal direction. The vertical rigidity is addressed by the fence posts. It's available in 2, 3 or ...
- 10.4k
25
votes
Accepted
From an engineering standpoint, what is the purpose of the indent in a coffee lid?
From the "Solo Traveler" patent:
A more specific object of the present invention is to provide a lid having an opening formed therethrough to enable drinking, and having a recess formed in the lid ...
- 743
20
votes
Why don't motorcycles have as good a turning radius as bicycles?
The simplest answer to the question is "because the motorcycle gets in its own way"
Take a look at this picture of a trials motorcycle; it has perhaps the smallest of turning circles ...
- 301
17
votes
Accepted
Involute gear curve when root diameter falls below base diameter
In general, each tooth of an involute gear is made up of two curves: the involute curve and the root fillet. The involute curve is essential for gears to operate properly, and allows power to be ...
- 1,317
17
votes
Accepted
Would a centrifugal flyweight governor system slow down the descent of an object that is free falling down to the Earth's surface? (Revised design)
Once the cylinder is released and starts to accelerate downward, the rotating flyweights should pivot upwards to a certain degree (as shown in the drawing) and should act as a drag on each of the ...
- 1,943
16
votes
Why don't motorcycles have as good a turning radius as bicycles?
A bicycle usually weights about 18 pounds versus an average of 180 pounds for a motorcycle.
In tight turns a bicycle can easily be controlled by the rider shifting their body's center of mass as ...
- 22.1k
14
votes
Is this dropout design as bad as I think?
An ideal dropout design would......
OK, already there you've gone into the weeds. There is no ideal dropout design. Engineering real world things is a balance of tradeoffs. You have to balance the ...
- 240
14
votes
Why are railroad tank cars bent in the middle?
Same reason the Corsair fighter has bent wings. Makes clearances easier.
Look at the lumpy, sticky-outy things on a tank car. You have the trucks/bogeys at the end bottom... and the massive fill ...
13
votes
Why aren't screens round instead of rectangular?
The earliest CRT displays were in fact round. However, that was more due to manufacturing tradeoffs of making large glass envelopes with vacuum inside than a desire for the display area to be round.
...
- 11.4k
12
votes
Do outer fillets|chamfers also reduce stress as inner ones do?
Sorry for not taking your "Thin Hollow Brick-Shaped Object" as an example - I felt a standard notched test specimen would illustrate the principle more clearly:
It can be seen that adding external ...
- 7,726
12
votes
Accepted
Is it useful to stuff my glasses with newspaper to protect them?
In itself putting paper inside a glass will make very little difference. Glass is a brittle material and tends to fail by shock and point loading. Its static tensile strength is actually pretty good.
...
- 15.2k
12
votes
Accepted
SOLIDWORKS - 3D Sketch of Trombone
See the .gif below!
EDIT: You may need to enable visibility of these handles if they're not on by default - it depends on your default profile/settings.
- 7,726
12
votes
Accepted
How to work on big CAD project in team?
It's a massively important question. Short response: apply the concept of encapsulation.
Divide into subsystems
During development, assign design-ownership (distinct from project manager role, ...
- 1,387
10
votes
Why are railroad tank cars bent in the middle?
So any sediment will collect there as part of cleaning.
Then other designs have a more pronounced bend to allow for the bogies and also keep the height down - some tunnels are lower.
- 15.5k
10
votes
Why does this fence have a kink?
Bending adds rigidity.
Take a piece of paper, fold it, the bend gives it a rigid form to hold more weight.
V-Mesh fences are also used in equestrianism as horse fencing helps keeps predators out and ...
- 544
10
votes
Do I need a pressure relief/safety valve if my pump can't exceed the rated system pressure?
Not a plumbing engineer, but:
What about thermal expansion?
You reach a dead end, pump stops. Pumps often have a checkvalve that prevents backflow, so you have now created a pressurized container.
...
- 109
9
votes
Accepted
Why are spur gear ratios not always whole numbers in practice?
Gear ratios can be referred to as hunting and non-hunting ratios.
In a non-hunting ratio, any one gear tooth will contact its corresponding gears' teeth in the same place every time.
In a hunting ...
- 116
9
votes
Accepted
Why don't motorcycles have as good a turning radius as bicycles?
I'll approach this from a different perspective to the other answers: Pushbikes have no limits on the steering range because they don't need to add the complexity and weight. They're simple, light, ...
- 396
8
votes
How to prevent algae in water cooled laser tubes?
I use polypropylene glycol in my CO2 laser tube under florescent lights and have not had any problems. It also comes with the added benefits of freeze protection and corrosion protection.
If you ...
- 7,904
8
votes
Why do car-seats have an expiration date?
It's a combination of 1, 3, 4, the product development cycle, and the nature of the product.
1 - Damage in materials is a cumulative process, the product of hundreds or thousands of little events (e....
- 2,145
8
votes
Is it useful to stuff my glasses with newspaper to protect them?
Filling inside the cup with paper is just to lock in the wrapping of the same paper around the glass.
It also offers coverage and protection of the rim of the glass.
Because of the integrated, all-...
- 22.1k
7
votes
Suggestions for low friction surface materials for a "beltless static treadmill"
While it is an interesting idea, I don't think a "static treadmill" is going to give you results similar to walking. A PFTE(teflon) surface would be really low friction, but I think there are some ...
- 7,904
7
votes
Accepted
Intuition vs software results
Most soda cans in the US are on the order of 0.1 mm thick according to the sources I've seen. So 0.25 mm seems plausible to me, assuming that you made no errors in your calculations.
- 996
7
votes
Do longer gun's barrel improve accuracy?
The short answer: Yes, a longer gun barrel improves accuracy. Theoretical accuracy of handguns and rifles is driven by rifling, barrel length, and bullet mass.
Rifling: When the bullet travels ...
- 743
7
votes
Magnetic Entrapped Storage at 0 gravity
Flywheels are used in space, but not for storage of energy. They are used for attitude adjustment, as the spinning of a large mass has significant implications in an object which is free to move.
...
- 170
7
votes
Accepted
Why is it more common to use ceiling fans instead of air pumps?
Mainly cost difference.
And also, a fan is sufficient for the job. The problem being solved is thermal stratification. That's caused by a lack of vertical mixing; the warm air rises to the top, the ...
- 3,751
7
votes
Accepted
What's the best way to design a joint with two fasteners?
I think you might have a misconception regarding to how far the pressure from the fasteners extends. One subject you might want to have a look into is "bolt joint stiffness".
The most ...
- 24.3k
7
votes
Accepted
On steam locomotives with six driving wheels, why are the rear set of wheels placed further apart from the other two?
In the ones pictured, there are no trailing axles - they are a 2-6-0 and a "tenwheeler" 4-6-0 respectively. The ones shown have the firebox between the two rear drive axles. .That was an ...
- 4,607
Only top scored, non community-wiki answers of a minimum length are eligible