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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7answers
2k views

Can I use AutoCAD to learn mechanical engineering by DOING (like programming)?

I would like to learn mechanical engineering as a side project. But, I would like to learn in a way similar to programming. Learn by doing. Of course I understand I can't build things automatically ...
5
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1answer
2k views

What is the script function to select Solid Body in ANSYS Design Modeler?

I need to select a solid body in ANSYS Design Modeler, with script, in a design with multiples bodies. With the following command I select all the solid bodies, but this is not what I need. ...
5
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2answers
2k views

What does 'Open Flow' mean for a pump flow rate?

I have specifications for a positive displacement pump where, in the data table on the last page, the given flow rate is referred to in the column header as 'Open Flow.' Is this the maximum flow ...
5
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1answer
123 views

Make something that turns yet locked in place

I imagine this is an easy concept but I do not know much about mechanical engineering design. I am trying to make a "knob" like a control knob in solidworks that turns and is locked in place after ...
5
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1answer
148 views

Poisson ratio boundary condition

Let's say I have a large isotropic body in uniaxial tension, onto which a small rectangular piece of film is applied. Think of a strain gage on a big body, but the 'strain gage' is one single ...
4
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1answer
64 views

Do the steels 1.4404 and 1.4571 look the same?

A contractor delivered three components, all are supposed to be in 1.4571. Part A is actually done in 1.4404 / (X2CrNiMo17-12-2) (according to pretty conclusive documentation). Part B is allegedly ...
4
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2answers
383 views

How to connect a motor shaft to a plate

I'm trying to drive an aluminium plate using a motor via a 20mm-wide 2mm-thick stainless steel tube. The tube is driven by a 6mm motor shaft via a pulley and the torque will be around 5Nm at most. Is ...
4
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2answers
206 views

Solving heat loss equation associated with solar trough concentrators

My project is about finding the efficiency of solar trough (cylindrical parabola) concentrator that will boil water in a pipe located at the focus (check picture please). In the process of doing so (...
4
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2answers
9k views

Advantages and disadvantages of bevel gears

What are the advantages and disadvantages of bevel gears? This is what I've already found: Advantages: possibility to change operation angle Disadvantages: must be precisely mounted shafts' ...
4
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2answers
2k views

Designing non-self-locking worm gear

I see that most worm gears are self-locking but I'm looking to make my own non-self-locking POM worm gear. It'll only be of module 1. Does anyone know what needs to be changed in order to make a self-...
4
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1answer
39 views

Principal on gaining more height based on nested poles? [closed]

How do people design height gaining based on nested poles ? Consider this picture (I made them) : If I want to achieve height based on these 3 poles, how they should behave? Is this how the behave? ...
4
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1answer
185 views

Why is the Stress vs strain diagram preferable to the Load vs displacement diagram?

I’m really unsure what is the difference between stress vs. strain and load vs displacement graphs and why stress-strain is better. I know that the units are different: stress is in MPa and the load ...
3
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3answers
283 views

Torque and RPM calc

started by designing the gear meshing, and now I need to calculate some parameters to determinate if this meshing works for me. The system considers an electric motor, which technical parameters are: ...
3
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2answers
84 views

Battery Swapping in Electric Cars

What are the advantages and disadvantages (technical, financial etc.) of having battery swapping system over charging stations for electric cars? As per my reading, battery swapping seems feasible for ...
3
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2answers
164 views

Applying an adjustable force to a small area

What type of a mechanical device can I use and program to apply a controllable force within the range of what a human can to an area about the size of a fingertip? It is desirable for the applied ...
3
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2answers
167 views

Why textbooks use geometric center/centerline of the pipe when calculating/measuring pressure?

Studying Fluid Mechanics, I started to notice that almost every textbook/website uses a specific point to make calculations about the pressure in a liquid at a given depth (hydrostatic pressure): the ...
3
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1answer
4k views

Reverse-engineering spur gears - do I have enough data to make a gear that will mesh correctly?

I'm trying to reverse engineer a set of spur gears that I have on a model RC car, but they are tiny, so there's a limit to what I can measure with my calipers. My plan is to create a new gear design ...
3
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4answers
4k views

What is the axis of rotation of a turning car?

I was wondering while parking my car, what is the axis of rotation/pivot of a turning car? Does it differ when it is turning frontwards of backwards? Is it different for a 4x4?
3
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1answer
718 views

Piezoelectric matching/backing layer materials

To maximize the piezoelectric transducer reception/transmission power we must choose the correct backing/matching layer materials, I'm working on a project to measure a steel tank liquid level (non ...
2
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2answers
70 views

How to find a beam for my (simple) application

I have a spanof 9m that I bridge with a (as yet unspecified) beam. From this beam hangs a load (a pipeline), right in the middle, of 4.295 kN. The beam is simply supported. I want to use an IPE steel ...
2
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3answers
64 views

How to make a choice between rolling element bearing and journal (plain) bearing?

I wonder if there exist a formal guideline to help engineers choosing the right type of bearing. Except in some few cases, this is not very evident to me. As far as i know, the plain bearing ...
2
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3answers
3k views

Using two motors and belt drives to drive one shaft

I have an application where I need two motors to drive one shaft via the use of belt drives but I need help on how to arrange such a system. The system constraints are: motor type - induction motors $...
2
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1answer
80 views

Vertical component of force for rigid wheel hitting a step

My question relates to finding the vertical component of force due to a rigid wheel hitting a rigid step. I know the details of the step and I know the horizontal velocity of the wheel. I'm using the ...
2
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4answers
7k views

What is the difference between tau = VQ/It and tau = V/A?

What is the difference between the formulas $\tau = VQ/It$ and $\tau = V/A$ for finding shear stress due to transverse loading? I understand that the use of first moment of area, is the only reason ...
2
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2answers
292 views

Engineering formula to relate engine displacement and power

I am currently rating two motorcycles to decide which one to buy. The criteria which is most important to me is the power-to-weight ratio. Now, I want to calculate the power of the motorcycle by ...
2
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3answers
3k views

X-form and cross-form rudders in underwater control

What are the advantages of using X-form rudders in comparison to cross-form rudders? Why do some submarines, torpedos and underwater autonomous vehicles use X-stern control? X-stern: Cross-form:
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2answers
4k views

Why does the yield strength of steel go up if I reduce the thickness of the specimen?

When I look at the yield of one material then you find more than one yield for different thickness. why the yield changes with changing the thickness. is there an equation to prove this ?
2
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2answers
12k views

Failure in torsion

Why does a ductile rod in torsion fail at an angle perpendicular to its axis? I know the reason for brittle material failing in pure shear but I don't understand the reason for ductile material.
2
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1answer
89 views

Recommended compressed air source and location for separate air compression system

I am investigating what would be the most appropriate compressed air source (fan/blower/compressor) for designing a separate air compressor system. The information is as follows: the compressed air ...
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1answer
115 views

Determine the range of τxz values for which the maximum tangential stress is less than or equal to 60 MPa

Consider the state of tension indicated in the Figure. Determine the range of τxz values for which the maximum tangential stress is less than or equal to 60 MPa. I did σ(med)=(60+0)/2 = 30 To find ...
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1answer
46 views

CNC side linear rails

I've been wondering why most (hobby) CNC machines have two actuated linear rails like this: Besides the extra force for moving the spindle, is there a need for both rails to be actuated? Could the ...
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1answer
95 views

How do Test Indicator Flexible Holders hold rigidly when tightened?

If one were to search on Amazon for "Test Indicator Flexible Holders" you will turn up many items using this mechanism (please ignore the magnetic base; I'm not focusing on that part, just the red ...
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1answer
163 views

Looking for a formula that states the stiffness of a composite [closed]

I am looking for a formula that states the breaking point of a composite - How much pressure it can withstand before it 'snaps'. Specifically I am looking for a formula that states the materials ...
1
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1answer
64 views

Energy calculations for steam turbine

I am a civil engineering undergraduate. I have an interest in Biotropic Design and sustainable energy and am working on a new conceptual design. I would like to know what analytics may be done to ...
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2answers
74 views

How to calculate heat and mass transfer rates from an enclosed box?

I'd like to know if it's possible to calculate the heat and mass transfer rates from a small volume to the environment. Let's assume there is a box with a small opening at the top. The air inside the ...
1
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0answers
66 views

DIY medical oxygen concentrators [closed]

Given the dreadful surge of COVID cases in India, with people dying for lack of oxygen, I was wondering if the smart folks here could put our heads together to brainstorm a way to develop a how-to ...
1
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1answer
41 views

Choice of Datum Features and Number of Datum Features

Consider a rectangular stock section with a dowel hole and other features of size (FOS) on it. The dowel hole serves to locate the entire part. Should my choice of datum features be what is most ...
1
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1answer
115 views

prevent shaft from moving in solidworks

i designed a gearbox with 3 shafts.i wanted to do sth so shafts only have rotating movement and not any other type of movement.i cant find any type of mate that can do that,any suggestions?
1
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1answer
65 views

Relation between links and pairs in Kinematic chain

I came across a equation for kinematic chain (for lower pairs only) : L = 2P-4 where L: Number of Links; P is the number of pairs how could this equation be derived ? EDIT: I tried putting values in ...
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1answer
65 views

Inefficiency of intermittent burn in rockets

Imagine I have a combustion chamber with a nozzle. There is a high pressure oxygen bottle and a high pressure gaseous fuel bottle connected to the chamber. Would the fuel efficiency be lower if I ...
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1answer
289 views

Eulerian and Lagrangian descriptions of velocity

I feel as if I understand the conceptual difference between Lagrangian and Eulerian descriptions. But I can't seem to follow the math. I have one example that I would greatly appreciate an explanation ...
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1answer
172 views

How to calculate the output power of engine exhaust

Apologize if probably this is duplicate question. But I have tried to search if someone have asked such this question. I have a Honda engine, GX200, 196cc, with it's gross power is 6.5HP. I would ...
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0answers
270 views

How can we calculate torque required to rotate the wheel (mass unknown)

Is it possible to calculate torque required to rotate wheel but weight of wheel is unknown?
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0answers
2k views

Mechanisms to convert linear motion to rotation

These are the mechanisms I'm aware of: Crankshaft Scotch yoke cam-shaft wobble drive (a.k.a nutator or Z-crank) swash-plate What are other mechanisms to convert linear motion to rotation?
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2answers
10k views

How to calculate the diameter of a transmission shaft from RPM & Torque

If I know the torque and rpm that the shaft need to operate at, can I calculate the diameter of the shaft? A motor operating at 60 rpm applying 1,000 Nm of force on a shaft that has a modulus of ...
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2answers
805 views

What type of tires and wheels do I need to make a PVC beach cart?

I would like to make a beach cart that supports 200lbs and uses this design What type and dimension wheels and tires should I buy? I have a budget of $100.00 for the tires and wheels. I cannot ...
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2answers
333 views

Rotary to linear motion - how to make upside down “hammer” mechanism?

I’m not an engineer, however I think this place is the best one to find an answer to my question. So my problem is as follows: I need to create a mechanism, preferably driven by a dc motor, that will ...
1
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1answer
294 views

Shear Stress Formula

Could anyone tell me what the variables in this formula are? $$\tau=\frac{S\;a\; \bar{v}}{I\; t}$$ I believe it is used for shear stress and that $I$ is moment of inertia but unsure on the other ...
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1answer
104 views

Stopping/reducing wobbliness in threaded rod

I am working on a 1.5-meter satellite dish with a custom receiver cantenna-like feed. The dish didn't come with feed arms, so I need a way to hold the feed into place. What I tried was using a 1-meter ...
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2answers
154 views

Trying to shed some weight on my design, any thoughts?

I am trying to design a lifting mechanism and I would love some insight/opinions as to how I can shed some weight off it. The current weight I have for my mechanism is 187.5kg, however, this is ...