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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6
votes
2answers
5k views

How to mount a load-bearing gear shaft through a wooden plate

I don't have experience in mechanical engineering so I came here to ask for help. Here is sketch of one simple construction I want to realize: Here we have 5 cm thick wooden plate, 50 cm long and 35 ...
6
votes
1answer
91 views

controlled depositing of goo with a syringe

I was thinking about this kickstarter project where they print circuit boards, and later they show it printing solder paste. I've seen other liquid or paste dispensing systems like this too, maybe ...
6
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5answers
2k views

Forged carbon fibre finish

I'm currently looking around for a new bike and I've noticed lots of load-bearing carbon parts (frames, cranksets, forks etc.) with an interesting finish like this: and I was wondering what this type ...
6
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2answers
6k views

How to calculate tensile strength of braided steel wire?

I am working on project involving designing a recoil spring coil of diameter 10.2 mm and wire diameter 1.25 mm. I tried using a solid core wire but it failed due inadequate tensile strength. ...
6
votes
1answer
580 views

Why do boiler exhaust stacks use tapered transitions?

We have a boiler exhaust stack with a base dimension of 120" ID and an overall height of 84'. 21' up, the stack begins a slow transition to 7'6" ID. The transition takes approximately 35' to reach ...
6
votes
2answers
117 views

Does negative pressure inside the barrel affect low-powered railguns?

Just something I was wondering about when I've seen this on reddit today. Unlike in firearms where the pressure propels the projectile, in a railgun, wouldn't the pressure ahead/behind of the ...
6
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1answer
666 views

efficiency and flow separation

I am studying about wind turbine and turbine. I have some questions, but first, I explain some cases as follow: Low velocity air over an airfoil at a zero-incidence angle does not initiate flow ...
6
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2answers
19k views

How can I calculate the force required to bend a 10 mm thick plate in a rolling machine?

We have a rolling machine with 3 rollers; the bottom has two rollers with diameters of 168 mm and one top roller with a diameter of 219 mm. I want to calculate the required force to bend a 10 mm ...
6
votes
2answers
534 views

Can polycarbonate dance pole support the torque of a dancer?

I'm creating a light up dancing pole. This requires a translucent material that is strong enough to support the weight and force of a human being, even when it's hollowed out to so LEDs can go inside. ...
6
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2answers
95 views

Why aircraft refrigeration uses a centrifugal compressor in place of reciprocating compressor?

Why aircraft refrigeration uses a centrifugal compressor in place of reciprocating compressor and a gas turbine in place of reciprocating expander?
6
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1answer
39 views

How is mechanism used in modern projector different from intermittent mechanism used in conventional one?

Do modern projector used for digital class works on same old conventional intermittent mechanism and blocking of light during change of frame. What is principal used in modern projector?
6
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3answers
332 views

How to determine how much energy recovered from regenerative braking

I am considering a regenerative braking system implemented with a AC permeant magnet motor with an efficiently of ~96%. It is easy to determine via energy equations the kinetic energy of the car and ...
6
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4answers
2k views

Torque converter torque multiplication

I keep reading all over the internet that a torque converter multiplies torque at stall speed. Every explanation I have found sounded more like hand-waving than quantitative physical explanation. ...
6
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1answer
1k views

How can I block ultrasound from an automotive transducer at about 8'?

We are testing a new ultrasound product using a Texas Instruments PGA450 automotive transducer. Three of us are sharing a lab and we need some kind of ultrasound-blocking partition walls around each ...
6
votes
2answers
474 views

How to design a narrow bearing that supports shear direction load

I need to connect two flat bars of metal with some kind of bearing that doesn't increase the joint thickness by more than 2-3mm (the less the better), as shown here: There are almost no axial loads ...
6
votes
1answer
99 views

Where to insulate Underfloor air distribution system in a temperate climate

I have a proposed underfloor air distribution system (UFAD) for a one level office in a temperate climate. Typically the demand for heating and cooling in this climate is about even for offices. ...
6
votes
1answer
450 views

What is this kind of bearing called

I came up with this concept for a partial rotation, lubricant free, low friction bearing for a robotics application. Two complementary sets of tensioned tendon-like cables (or tapes) serve both to ...
6
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2answers
2k views

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 ...
6
votes
1answer
446 views

What makes crosshead bearings hard to lubricate?

Regarding crosshead bearing failure, I have read that at slow speed it is difficult to establish a lubricating film because there is an imbalance between forces due to combustion and forces due to ...
6
votes
1answer
117 views

Elasticity of a drilled plate

If I take a large thin plate and I uniformly drill a very large number of holes (diameter "d") very close together (minimum spacing "s"), what will be the stiffness of this new plate? When I say "...
6
votes
1answer
230 views

Hanging a steel mesh without significant deformation

I have an welded steel mesh, like in the following image. . Material: steel Diameter of the wires: 4mm Mesh: 15x15cm I found the following information about the welds: the minimal relative ...
6
votes
1answer
3k views

Is the tolerance of pitch of a thread standarized?

As I was browsing ISO 965-1 it defines tolerances on a plenty of variables regarding metric threads, but it gives the pitch of the thread as a simple number from an allowed set ( 3 – 2 – 1,5 – 1– 0,75 ...
6
votes
2answers
338 views

How to size a heat exchanger for a shear thinning fluid?

To size a heat exchanger, I need to know (among other things) the Reynolds number (Re) as an indication of the flow conditions. The Re number depends on the viscosity. In a shear thinning fluid, I can'...
6
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2answers
58 views

Is a single large impact better than several small impacts for breaking ice

I'm designing a device that uses impact to remove ice from sidewalks. I have a question about how to best design the impact mechanism. I can design it to deliver several light impacts or fewer harder ...
6
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1answer
532 views

How to protect a pressure gauge from condensation in a vacuum steam boiler?

Pressure gauges are protected from steam condensation in a regular boiler by using a siphon where steam condenses and prevents steam from going further up to the gauge. However in a vacuum steam ...
6
votes
2answers
341 views

Why does the standard $k-\epsilon$ model use zero equation models?

According to Hoffman, the standard $k-\epsilon$ turbulence model incorporates a two-layer approach (inner region and outer region formulations to reperesent mixing length) when it comes to regions ...
6
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2answers
1k views

Limitations of the cut-off ratio in real-world diesel engines

In an ideal diesel cycle, the cut-off ratio is set by the maximum gas temperature after combustion. That's all fine and good, but in a real-world engine what controls the cut-off ratio, and what are ...
6
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2answers
249 views

System identification on a system with constraints

I am trying to estimate a transfer function for a pan - tilt unit which is not as easy as I hoped. Its input parameter is a velocity, but it is constrained to move from 0° - 359° and the other way ...
6
votes
1answer
146 views

Streamlines at the boundary of rotating and stationary domains are malformed

I am simulating a turbine and have divided the mesh into domains: the piping before and after the blade and the turbine blades. The domain containing the blades rotates at 2000 rpm while the other ...
6
votes
2answers
102 views

How does the location of a mass affect its dampening performance?

I'm looking at something called at a Steadicam that stabilizes cameras. It looks like this Clearly, the weights at the bottom are used for dampening/stabilizing. If the arm holding the weights were ...
6
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3answers
561 views

Stiffening of Tesla turbine rotors

Recently I've begun thinking about experimenting with the construction of a Tesla turbine for steam use. The key issue I can find is that most of the examples out there of such turbines use either ...
6
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2answers
8k views

Finding the pull-through capacity of a nutted bolt and washer in ASA plastic

I have a uniform load applied to the underside of a plastic sheet which is to be resisted by the combination of a bolt, washer, and nut as depicted below (the other end of the bolt is secured and will ...
6
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1answer
182 views

Elastic (Young's) Modulus relation to the Eigenfrequency

I would like to compare the shape of the frequency spectrum of a plastic and aluminium component. Now if we assume that the plastic and aluminium component only differ in the material, while the mass ...
6
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2answers
5k views

How to find press fit/ slip fit for non standard size parts?

I am looking for calculator or chart for slip fit and press fit for non standard size parts. For example, I have oversized dowel pin 10mm +0.03/+0.01 diameter. I need to create a slip fit hole for ...
6
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2answers
351 views

On a Diesel/hydraulic DMU train what exactly does the “go faster” lever control?

Let's say that you are driving a Diesel Multiple Unit† with either mechanical* (i.e. an actual gearbox with multiple ratios) or hydraulic (i.e. two or more torque converters) transmission. When you ...
6
votes
1answer
220 views

How would you mechanically model an Earth-Moon like orbit?

I'm hoping to make a small mechanical demo (~10cm tall) that models an orbit that is similar to the Earth-Moon orbit - that is, only one side of the Moon faces Earth. I'm trying to keep it simple, so ...
5
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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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6answers
3k views

Does a motor suffer damage when resistance to the intended motion is met?

I'd like to create something similar to a hydraulic press. I know I need some sort of motor, but I was curious about a fundamental question about motors when used in a system where the force required ...
5
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6answers
27k views

What will happen if I run a submersible pump without water?

I have a submersible pump and it's clearly stated in the user manual that it should not be operated without water. But what will happen if it's not adhered to? The obvious answer is that it will ...
5
votes
3answers
3k views

Does the length of a beam change upon deflection?

I have made a Python program in which I have computed the deflection of a beam. I am plotting the deflected beam and am now asked to show the length of the beam. If the beam is not deflected, it is ...
5
votes
4answers
853 views

What are the technical obstacles for using flywheel-based regenerative braking on bicycles?

Is it possible to convert the energy you would normally lose when braking your bicycle to rotational energy by attaching an extra wheel which would start to rotate once you use your brakes? E.g., when ...
5
votes
4answers
2k views

How should I go about adding holes to laser or water jet cut sheet metal?

I’ve been working on an electric Dirtsurfer project that has many parts to be made from folded sheet aluminium. Obviously the sheet metal needs holes in it for bolts. The sheet aluminium will be ...
5
votes
4answers
633 views

How do I add a resistance to mechanical movement in both directions, apart from friction?

What options do I have for creating a resistance to a mechanical movement apart from simple friction? Assume I have a lever, which will result in either circular or linear motion. I want to be able ...
5
votes
2answers
13k views

How do I calculate the gear ratio to lift a weight at a constant speed?

I have an 80 g·cm motor with a rotational frequency of 15,000 rpm. I want to lift a weight of 2 kg at a speed of 0.5 m/s. How do I calculate the gear ratio required?
5
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2answers
4k views

Why manufacturers prefer Brass over Copper in electrical conductors?

I am working on product where we need pogo pins, as copper is better conductor of electricity I was searching for the copper pogo pins. After about a month of searching, it is come to my notice that ...
5
votes
5answers
8k views

Why are spur gear ratios not always whole numbers in practice?

Defined the Gear Ratio ($i$) as the ratio between the number of teeth on the pinion (driving gear) ($N_{1}$) and the number of teeth on the gear (driven gear) ($N_{2}$). Why is this better, if ...
5
votes
3answers
132 views

Help with closed loop heat controller (for a non engineer)

I am interested in setting up a controller which can modulate the output of 2 hotpads based on input from an infrared thermometer. The hotpads have their own dials, but I am considering controlling ...
5
votes
1answer
876 views

Hovercraft design parameters

My washing machine broke down recently, and they replaced the motor. The old motor was not broken, as far as I could tell; the sensor that told the CPU that the drum was balanced was what was out of ...
5
votes
2answers
1k views

How does a rodless electrical linear actuator work?

I want to pull some weight horizontally and for that i have settled for a linear actuator. The actuator should pull some weight as it moves back and forth as the gif shows. There are linear ...
5
votes
3answers
331 views

What is “per unit strain”?

When I read about stress analysis and specifically in the context of strain gauge, I often see the phrase resistance per unit strain or ...

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