Questions tagged [mechanical-engineering]

Questions within the problem domain of mechanical engineering. Mechanical Engineering can be a broad field; consider choosing more specific tags if they apply.

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12
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1answer
2k views

Detailed dimensions of an aircraft engine compressor blade

I am working on rub-induced vibrations in compressor stages of aircraft engines. The work is carried out in partnership with a company, therefore there is a limited amount of it that could be ...
12
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1answer
3k views

Insufficiently constrained structural model in Ansys

I want to analyze this model that is stressed and deformed. I fixed the lowest of points in the x, y, and z directions, and I pulled top of points upward (y direction). When I run the model in Ansys I ...
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4answers
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Why are most jigsaw blades designed to cut on the up stroke and have teeth that point towards the shank?

Why are most jigsaw blades designed to cut on the up stroke with teeth that point towards the shank? Why are reverse teeth jigsaw blades less popular?
11
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2answers
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What is the mechanical element that holds a worm gear shaft in place called?

Here is an image of a worm gear. What is english word for mechanical element (two of them will be necessary for a worm gear) in which the worm shaft will "lie" and rotate? Here is one photo of the ...
11
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2answers
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Why are tremors of an earthquake felt more on upper floors?

Why are tremors of an earthquake felt most on the upper floors of a building in comparison to lower floors? Does this have something to do with a third class lever?
11
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3answers
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Why do beverage can tabs break when bent?

Most people have had the experience of moving the tab of an aluminum can back and forth until it breaks off. It usually only takes a few complete back and forth motions before the tab breaks off. ...
11
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5answers
2k views

How is a mechanical system designed and tested without building a physical model?

I am new to mechanical engineering, although I have a scientific background (postgrad in Mathematics), and I (mostly) code for a living. I have an idea about creating a mechanical device; I envisage ...
11
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1answer
260 views

What is the significance of a diagonal input in a control diagram?

I have seen several block diagrams with diagonal inputs, drawn with an arrow through the block. and others like that (via Google image search) What is difference between this and a typical signal ...
11
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2answers
747 views

Comparing the performance of glass and granite in a heat storage application

Background I am working with a small team on a university project to build a greenhouse heat sink. This will pass warm air at the top of the greenhouse down through a chamber underground filled with a ...
11
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4answers
1k views

Preventing condensate backup at startup with orifice (venturi) steam traps on medium pressure batch process mains?

I am working with 1" medium pressure steam mains (45 psig) for a batch process. Time between batches is usually short (to the order of minutes) but depending on the day the delay can be hours, and ...
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7answers
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How to make factory machine hard disk drive more durable? How much its estimate life span?

I wonder how can I make hard disk drive more durable? Specifically, I works in a factory environment. And almost every few months, hard disk drive in some of the factory machine are corrupted, and ...
10
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3answers
1k views

Harvesting thermoelectric energy from computer graphics cards

During CES2015 a well know Graphic Processor Unit (GPU) manufacturer introduced a new GPU. These GPUs need complex thermal management to keep the processor cool. Most GPU accelerator card ...
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4answers
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Why does the stress-strain curve decrease?

This is a stress-strain diagram I have noticed that the curve decreases between points C & D and between E & F. Why does that happen? I expected the curve to always increase since the ...
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4answers
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How are high gear ratios achieved in a small space?

I have a very basic understanding of how gears work, and while trying to learn more, I've run into a small point of confusion. If a 2:1 gear ratio is achieved by having twice as many teeth on one ...
10
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3answers
13k views

What is the difference between the Polar Moment of Inertia, $ I_P $ and the torsional constant, $ J_T $ of a cross section?

This question is so fundamentally basic that I am almost embarrassed to ask but it came up at work the other day and and nearly no one in the office could give me a good answer. I was calculating the ...
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2answers
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What is the maximum length of oil pipelines?

This is inspired by the discussion and controversy surrounding the Keystone Pipeline. The main part of the Keystone Pipeline system is about 3,400 kilometers long, stretching across a large portion ...
10
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2answers
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Why do we neglect the radial stress in case of a thin pressure vessel?

A cylindrical or a spherical pressure vessel, having inner diameter $d$ & thickness of wall $t$, is called thin if $\large \frac{t}{d}<\frac{1}{20}$. $\bullet$ Thin cylindrical pressure ...
10
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2answers
612 views

Differential equations of a (simplified) loading bridge

I am having trouble to calculate the differential equations of a simplified loading bridge. The system is build as shown in the picture below (just a sketch): If I use the Newton approach, I am ...
10
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6answers
12k views

Distance sensors with accuracy of 1 mm?

I am making a device for measurements. I would like to measure the distance within accuracy of 1 mm. Range could be 2 cm to 15 cm . I looked at Proximity Sensors but the readings displayed by these ...
10
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2answers
431 views

Are threads machined from high tensile steel more susceptible to damage?

I have an ASTM A311-04 1.25" diameter round 1050 steel bar that exhibits a tensile strength reading of 155,227 PSI. Normally, we receive material in the 13-133,000 PSI range. The bar is machined to a ...
10
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1answer
3k views

How do I calculate the strength of a weld joining two crossed rods?

While considering this recent question, I started wondering how to determine the strength of the welds in the steel mesh. As AndyT points out in his comment: The welds at the connections are only ...
10
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2answers
253 views

What's this mystery symbol on a manufactured machine?

I hope this is the right place to ask this question; if not I'd really appreciate some tips as to where else I can go for answers. The symbol above (apologies for the blurry quality) is on a Chinese/...
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3answers
4k views

How do you select the correct area to consiser for first moment of area calculations?

I have just begun studying mechanics of materials and I am struggling to understand intuitively how to select the area in first moment of area calculations. I was hoping someone has a relatively easy ...
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9answers
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How can “mpg” be high under low engine load?

Let's say a car at 60 mph requires roughly 20 hp to maintain its speed (i.e., to overcome rolling resistance and drag). If this car makes 240 hp and gets about 34 mpg (not too unrealistic), how is it ...
9
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5answers
3k views

How can one calculate the change in heat energy when the specific heat varies with temperature?

Many materials have a specific heat which varies with temperature, especially as the temperature change grows large. How does one calculate the heat energy that an object receives in this case? Can ...
9
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5answers
3k views

Why do some diesel engines run on diesel fuel and others on fuel oil?

Trucks and smaller vehicles with diesel engines run on diesel fuel which looks more or less like kerosene - less flammable than gasoline, low viscosity liquid. However larger diesel engines like this ...
9
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2answers
3k views

How can a knife cut through butter?

How does anything actually cut anything, since we all know stuff is made up of atoms and molecules, which can't be touched together (It Requires Binding Energy). So how come we see things all around ...
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3answers
3k views

Mechanism of gear rotation

Is the smaller gear (pinion) always mounted to the input shaft when meshed with a bigger gear that is mounted on the output shaft? Are there places where the bigger gear drives the smaller gear?
9
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3answers
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How can the wobble of a rotating cantilever shaft be reduced?

I have a cantilever shaft 6inches in length supported on one end using a ball bearing. I am having problems of shaft wobbling in the bearing. I cannot have support on the other end. How can I help ...
9
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2answers
8k views

How to calculate the pressure a pipe can withstand?

I was looking at high pressure pipes and their pressure ratings. I'd like to know how these pressure ratings are determined. I assume that pipes are tested until failure, and the failure pressure is ...
9
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6answers
18k views

Steel selection for building a trailer

I'm thinking about building another trailer. I've built lots of smaller trailers in the past, but this time I'd like to build myself a small tandem axle gooseneck rated for 7,500 lbs. I am a ...
9
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5answers
1k views

Can a riverboat tack upriver?

Note: This question originally appeared on the Physics site (see here) and was closed for being off-topic. Whoops! If ships at sea can tack in a zigzaggy pattern by converting backwards force from the ...
9
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5answers
18k views

Should we protect our AC's outdoor unit from sunlight?Does it increases the durability of an AC and its refrigerant if it is well shaded?

My AC outdoor unit gets direct sunlight (no shading whatsoever) from morning to noon. Temperature normally soars up to 40 degree Celsius (I am from India). I have two questions: Is this bad for the ...
9
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2answers
240 views

Why does reducing the amount of emissions control improve the fuel economy of a car?

In addition to power and performance, one of the reasons VW cheated their emissions results was to improve the fuel economy of their cars. Why exactly does this happen? I'm familiar with cars and how ...
9
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3answers
4k views

How to seal a pressure vessel

I'm trying to construct a stainless steel high pressure containment vessel (pressure reactor) (2000 psi or so). Yes I realize that this is a don't try this at home type of thing, and I plan to put ...
9
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2answers
2k views

What causes friction in magnetic bearings?

Magnetic bearings work by levitating a rotating shaft so that it is not in contact with its supports. This greatly reduces the friction of the system. In all of the literature that I have seen on ...
9
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1answer
810 views

“Sliding door” - is top weight bearing more efficient?

I'm an artist building a project which one could think of as a "sliding door" – a very narrow panel running on grooved wheels riding in tracks at top and bottom. It will be motorized and driven by a ...
9
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3answers
5k views

Reading stepper motor datasheets to get torque and speed

I don't understand how to use the information in a stepper motor datasheet to understand how much torque it can generate. I was going to do a simple board and try to lift a small weight as an example ...
9
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1answer
2k views

What is the difference between direct and indirect learning control?

I found the following comments on direct and indirect control in "Survey on iterative learning control, repetitive control and run-to-run control." by Wang, Gao, and Doyle: There are two ...
9
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4answers
2k views

Can air conditioners/dehumidifiers exhaust their waste heat in their exhaust water?

If I understand correctly, both air conditioners and dehumidifiers conventionally exhaust waste heat through their exhaust air, though both also produce exhaust water. I'd like to know, Are air ...
9
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2answers
2k views

Air compressor that doubles as a pneumatic motor?

I am working on a compressed air energy storage system. The size and weight of the system are heavily constrained; nothing should (ideally) exceed a few pounds. For this reason, I would like to store ...
9
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1answer
1k views

Calculate force to lift piston from a given closing pressure

I am trying to calculate the force required to close the valve on an annular blow-out preventer. A rubber ring (called a packing unit) closes around the pipe when a force is applied from underneath, ...
9
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0answers
235 views

What type of ultrasonic transducer would be suitable for ultrasonic welding? [closed]

Project background: I am working on a project where i need to weld plastic using ultrasonic transducers. Problem: Since I'm still learning engineering, I have a hard time figuring out what all the ...
9
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0answers
1k views

ANSYS APDL Shape memory effect option of SMA not working

I am trying to define the material properties of a shape memory alloy material in ANSYS APDL V15. There are material properties for Superelastic materials (SUPE option) and material properties for ...
8
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5answers
7k views

How do you attach something temporary to a smooth metal shaft?

I want to attach something small to the smooth metal shaft of a small motor (2-3 mm in diameter), like fan blades, but I want it to be temporary. If I make it too loose, then the fan won't turn at ...
8
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4answers
7k views

Would engineering bricks explode if used to build an oven?

I'm building a pizza oven and, to do so, I bought a whole load of engineering bricks (not these but similar). They've got five holes vertically through them, each hole is 2x6x6.5 cm (80 ml) and the ...
8
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3answers
5k views

Is there a mechanical equivalent to a hi/low pass filter (as in electrical engineering)?

I have been wondering if there are certain media (for instance glass, air, foam, etc.) which are peculiar given their chemical composition and/or structure allowing them to filter out mechanical waves ...
8
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3answers
539 views

Protecting device from microwaves in microwave oven.. but allowing Bluetooth?

I am building a device that needs to be inside of a microwave oven but somehow needs to communicate with another device outside of the microwave. How can I reflect microwaves so they don't come into ...
8
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2answers
1k views

How do I form a budget for a mechanical research project?

I'm a mechatronics engineering student currently on workplacement. I've put forward a research proposal to develop an improved mechanical gripper used for automated product handling. The company likes ...
8
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3answers
937 views

Why raised face for mating parts?

In designing mechanical parts in an assembly, sometimes the mating surfaces are raised faces. I've been told it's to provide a better seal. However, for piping (flanges), it seems to be the consensus ...

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