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.

Filter by
Sorted by
Tagged with
0
votes
1answer
39 views

Arithmetic and Log mean temperatuer difference of a double pipe heat exchanger with parallel flow

Consider a double pipe parallel flow heat exchanger, the mean temperature difference in this case turns out to be logarithmic because the temperature profiles are exponential. If we would have made ...
0
votes
4answers
75 views

A question on resonance

This is to settle a debate. I was working on a scaffold next to a building, as the wind blew, the scaffolding would sway. As I stood there I was trying to maintain my stability, but my movements ...
1
vote
2answers
44 views

In an open belt drive, which angle of wrap should be taken for calculating tension in the belt?

An open belt drive with flat belt has different angle of wrap on the larger and smaller pulley. I have to calculate a tension in the pulley. We generally use the formulae Here θ is the angle of wrap. ...
0
votes
1answer
86 views

Pipe network analysis: static pressure of a closed-loop pipe

I've learned fluid dynamics but does not have much knowledge about its real-world applications. My question is about the static pressure of a closed-loop pipe. [Fig. 1. Pipe network. Source: ...
0
votes
1answer
28 views

Is this value of critical Reynolds number also valid for ducts?

In internal flow, when a fluid flows inside a circular pipe, the most practical value of critical Reynolds number is taken as 2300. I was wondering if this number is also the same for non circular ...
1
vote
3answers
61 views

Why does thermal conductivity of a pipe matter in a double pipe heat exchanger?

My understanding is that thermal conductivity is responsible for the time until something will heat up. For example, if you hold a copper bar over a candle it will quickly become hot at the other end. ...
4
votes
4answers
84 views

How can I map a global spherical position of a central normal vector to the rotation of 2 perpendicular motors?

I have a machine that rotates two concentric frames. The outer frame has a motor that rotates it relative to the global y-axis, and the inner frame has a motor that rotates it about the outer frame's ...
0
votes
2answers
51 views

How to design stiff plastic sheet

I am making a cylinder of polypropylene that must be pressurized (2 bar). The rough dimensions of the current design (A) are 7 cm tall, 5 cm in diameter, and wall thickness of 1-2 mm. The issue is ...
0
votes
2answers
52 views

Combining torque of IC engine and electric motor

I currently have a 6hp IC engine which I plan on using to drive the rear axle of a go-kart. I want to increase the torque delivered to the shaft by adding an electric motor in a sort of parallel ...
0
votes
3answers
84 views

How are heat exchangers normally calculated?

Most of the calculations that I find in books are about calculating the heat transfer rate, which I'm not sure why I would care about. What I imagine is the case in a real world situation is that I ...
0
votes
1answer
46 views

In a shell and tube heat exchanger, does reducing flowrate affect the outlet temperatures?

Let's say I have 2 exchangers that are completely the same, only difference being that one of them has half the number of tubes. Also let's assume the coolant is the same and has the same inlet ...
0
votes
2answers
46 views

What is meant by Material Toughness being the Ability to Absorb Energy Before Fracture?

Toughness is defined as ability of material to absorb energy when deforming before fracture. Materials with high ductility and strength will have high toughness. What is meant by ability of material ...
0
votes
3answers
51 views

How do you optimize an engine for a farm tractor?

How is the engine of a tractor different from a car? So far, all I know, is, that a tractor has a rather high torque $ M $ and a car engine has rather high power $ P $. But physically, they are quite ...
0
votes
1answer
25 views

How to choose diameter of hole that will fit m3 socket head bolt to assemble two parts?

I am sending my design for machining. In my design I am trying to assemble two metal parts with each other. In these holes I will be using m3 socket head bolt. I am confused what tolerance value ...
0
votes
3answers
112 views

How can I achieve better MPG?

My car is a Citroen Xsara coupe 2000. I am little tight financially at this point and I try to save money from everywhere I can... I was wondering what is the ideal speed for my car to achieve the ...
5
votes
3answers
164 views

Why does this thing that is not a screw have a screwdriver slot?

I am (partially) disassembling an old sewing machine to clean it up. While removing the bobbin winder, I found this thing that has a screwdriver slot, but it isn't a screw. This is the part: It came ...
0
votes
0answers
42 views

Lab Jack with Bi-Dimensional Movement

I just bought a lab jack like this one: Its purpose is to change its height without loosing its rigidity by using the so called: scissors mechanism I was wondering if there is a similar device like ...
0
votes
1answer
40 views

Usage of Thermodynamic Steam Tables

Having both the pressure and temperature for saturated-liquid in a particular state of a cycle, I was interested in its enthalpy. When looking at steam tables I am not sure if I should use the ...
0
votes
0answers
63 views

How can I cheaply tilt a 700 lb cactus?

We got some heavy rain last week and a 4.5 ft tall barrel cactus fell over. Assuming most of it is water, it probably weighs about 700 lb. I've read that if I moisten the soil, take care with the ...
0
votes
2answers
77 views

Is Bernoulli’s equation applicable for systems with pumps?

Please have patience with me as I have not looked at this sort of theory in many years (I am also very new to StackExchange). A question asks the following: A sloping swimming pool two-thirds full of ...
0
votes
2answers
71 views

Does thread angle modulate ease of (rotational?) penetration in a screw?

Forgive me if this question is too simple, I'm a complete outsider to the field of engineering and mechanical engineering. A friend of mine had said that the thread angle of a screw modulates how ...
0
votes
4answers
127 views

What thickness of steel bar/pipe for home gym?

I would like to build a rack for my home with a pull up bar. I'm leaning towards a steel pipe with a diameter of 42.4 mm, but have no idea how to determine what wall thickness is needed so that the ...
0
votes
1answer
63 views

How to mix pure CO2 with air so that a bioreactor can be fed with air at 0.1% to 10% CO2?

The situation is we have to prepare a gas mix of air and CO2 which has to be given as input from 0.1% to 10% CO2 of air mix to the aqueous medium in a bioreactor? I'm trying to build a simple and ...
1
vote
1answer
78 views

Is there a formula that relates the two angles in a crank rocker?

I'm working on a mechanism that requires a crank rocker - is there a formula that relates the angle (to some fixed reference; horizontal, vertical, whatever) of the driving "crank" to the ...
0
votes
1answer
69 views

How can I measure gear efficiency?

I am doing a experiment on various gear combinations and am wondering How I can measure the efficiency (Torque loss) of each gear pair), I have a input shaft connected to the first gear and is also ...
1
vote
1answer
24 views

How can I compute minimum thickness for a rigid acrylic panel?

If I have an acrylic (plexiglass) panel, how can I compute how thick it must be to resist bending. So, for example, if I have a sheet that is 24" x 36" and supported by the edges only (such ...
2
votes
1answer
59 views

Why the cylinder covers of very big engines are tightened this way?

The engine has 12 cylinders and its power is 104000 HP. Every cylinder has 8 studs M85 which are very slack. I can move them with my hand ( when the nuts are of course not tightened) Also the gasket ...
1
vote
2answers
79 views

How to Construct a Primary Auxiliary View given that an oblique surface with 6 sides

I need to construct the auxiliary views with the given front and right side orthographic views. The view is in third angle projection. I observed that there is an oblique surface so that perhaps I ...
0
votes
1answer
21 views

Balancing Equation of Octane in combustion Chamber

Hey guys I am trying to balance out the combustion equation for reactants: Octane + Air with products: CO2, H2O, N2, and O2; and 120% oh excess air. My balancing equation looks like this: $$ C_8H_{18} ...
3
votes
3answers
123 views

Is there a maximum life for things made out of stainless steel or cast iron?

Do steel objects have a maximum lifespan? I read that "316 stainless steel is estimated to last for 1200 years in a “rule“ environment before heavy pitting. In the marine environment this is ...
3
votes
3answers
125 views

I seem to have a fundamental misunderstanding about the double integration method for calculating beam deflection

Here's where I'm struggling So I've tried to find the expression for deflection of a simply supported beam acted on by 4 point loads at varying distances. First I balance out the vertical forces and ...
1
vote
0answers
42 views

Why don't more buildings labels floors with integers? [closed]

Why don't more buildings label floors with integers? This is a lot less confusing than having terms like "ground floor", "lobby", "basement" and whatnot:
1
vote
4answers
77 views

Balancing suction air flow at different areas on pipe

I have a T-shaped pipe that is connected to a vacuum pump. Along one side, there are 4 areas of 9 holes where air will get sucked in from the surroundings. It's used to pick up some small objects. The ...
0
votes
1answer
45 views

Inconsistant load cell readings - (static) fiction perhaps?

First off I'm not an engineer so please excuse the simple language I use to explain my question! I have an arrangement whereby I have a steel plate suspended from basically a bridge. The plate is free ...
0
votes
0answers
40 views

Methods to stop jolting in a spring powered projectile launcher

Situation: A machine, similar to an exercise bike which is seen in modern gyms, relies on the input power through pedals via a human. A reduction ratio leads to a mutilated pinon which is used to ...
1
vote
0answers
60 views

On rectangular section beam properties of plate stiffeners

I am trying to understand the expression of the vertical dynamic stiffness $K_T$ and the rotational dynamic stiffness $K_r$ which appears in this paper where they consider a semi-infinite plate ...
10
votes
2answers
4k views

How do vending machines prevent people from stealing goods?

I never understood mechanically how a vending machine prevents people from accessing goods through the dispensing panel. From what I understand it's not a locked door that unlocks only upon payment, ...
1
vote
1answer
69 views

In case of solvation , Who converts gaseous ions to aqueous ? Why do we even have gaseous but not solid ions?

We take Nacl and dissolve it in water. There is formation of $Na^+$ and $Cl^-$ gaseous ions along with 2H+ and $Cl^{2-}$ aqueous ions. Then , Na+ is attracted towards $Cl^{2-}$ and 2H+ is attracted ...
1
vote
0answers
34 views

Power calculations for starter motor designing [closed]

Let's consider an IC engine standard type motorcycle. What is the power needed from the starter motor to start it's engine? Please make all the calculations by taking suitable assumptions like the ...
0
votes
0answers
30 views

Brainstorming ways to water seal a submarine with a protruding instrument?

I am currently working on a submarine that has a flat face at one end made of 1/2" acrylic. Currently, there is a 12mm glass sensor that protrudes through a hole in the acrylic face and I am ...
3
votes
1answer
80 views

What would you call this mechanism and how can I calculate the forces involved

So I have an assembly with two pins sliding in two groves. First I would like to know if there's a name for this so I can do some more research. Second, if the assembly is standing up so that the top ...
1
vote
1answer
72 views

Is a no-moving-parts air pressure transformer possible?

Is it possible to construct a solid state fluid system (tubing, channels, chambers, nozzles, etc.) that can convert the energy from a low-pressure high-flow-rate air current into a high-pressure low-...
1
vote
0answers
48 views

What is a good approach on creating a custom robotics gearbox

I would like to put together a custom gearbox of the scale of around 50mmx30mmx30mm to fix a gadget that I am designing. My question is how should I approach producing this? Should I design components ...
2
votes
0answers
17 views

Book recommendation for hydrodynamics of bubbles, drops, and particles

I am wondering if someone could please recommend to me some references on the topic of hydrodynamics of bubbles, drops, and particles, preferably in the context of complex and bio fluids. I am ...
0
votes
0answers
23 views

Cargo box opening system below

I am currently trying to make a delivery drone similar to ones Amazon did. Basically the cargo box which carry the package must open to below in order to drop the package. What I want to do is exactly ...
1
vote
0answers
32 views

Trapezoidal screw usage on robot arm rods [closed]

I'd like to build toy on picture - uStepper/EEzy robot arm. I'm little bit afraid of plastic gears - backslash, weakness, noise... Do you think trapezoidal screw will perform better when I use them on ...
1
vote
2answers
37 views

Assuming identical hole perimeter, for which shape is the stress minimized?

I know that stress is concentrated in the fillets, but what about the average stress along the entire hole? We can choose a circle, an ellipse, or a square with fillets. For which shape would the ...
1
vote
1answer
41 views

Need to make brackets for an AC on a truck

I have an old Uhaul that I'm turning into an rv. I'm putting the exterior unit of a ductless mini split AC on the "mother's attic" portion of the truck box directly above the windshield. ...
1
vote
0answers
21 views

Is it possible to Plot Damping Characteristic of a Gas Strut using Universal Tensile Machine(UTM)?

My aim is to use UTM to plot a Force vs Displacement plot which would demonstrate the damping characteristic of the gas strut. There is one existing research related to what I'm trying to achieve ...
1
vote
1answer
74 views

Why would anyone "pull the stem out and stop the wristwatch at night or when not wearing it" in the context of mechanical watches?

I read this the other day while discussing mechanical pocket and wrist watches: Plus it is common practice to pull the stem out and stop the wristwatch at night or when not wearing it. You then have ...

1
2
3 4 5
66