Questions tagged [design]

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13
votes
1answer
3k views

From an engineering standpoint, what is the purpose of the indent in a coffee lid?

I've see the same lids every day but I never really thought about their construction. There is an indent in a "Solo Travel Lid" for coffee cups that is just above the hole that you drink the ...
12
votes
2answers
1k views

Why are three way bridges rare?

It's true that most bridges are "two directional." But three way bridges are pretty rare, globally. I can understand why there wouldn't be many for rivers, but if bridges are designed based on the ...
9
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4answers
762 views

What's a professional way of tracking design history in plant engineering?

If you look at the design documentation in our projects (Biogas and waste-to-energy plants), you find out what we plan to build but not what other options were considered and why they were discarded. ...
8
votes
3answers
924 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 ...
8
votes
3answers
126 views

How do I know if I need a pull up or pull down resistor for a GPIO pin?

I've seen many microcontrollers use pull up or pull down resistors either as a setting for GPIO pins or as part of the hardware. How do I know if I need a pull up or pull down resistor for a GPIO ...
7
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5answers
2k views

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) [closed]

I am wondering if rotating flyweights would slow down the descent of a object that is free falling down to the Earth's surface. Please reference the conceptual drawing below: This drawing is showing ...
7
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2answers
1k views

SOLIDWORKS - 3D Sketch of Trombone

My task is to create a 3D Sketch of a trombone like the one below My professor recommended defining the points 1-4 and putting a spline through them. I did that, but my resulting design looks weird. ...
7
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1answer
6k views

Involute gear curve when root diameter falls below base diameter

The answer to a question on involute gear curve calculations shows how the gear tooth curve proceeds as an involute calculation from the base diameter. If the pitch diameter is D = m.N where N is the ...
7
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1answer
209 views

Sending out a 12d Civil Design Model

My project team and I delivered the design of a 14ha urban infrastructure development in Sydney for a Client. The project was to hand over the development at a Tender level of design, which would be ...
7
votes
2answers
356 views

Why do car-seats have an expiration date?

My wife and I are expecting our first child, and therefore are expecting to purchase a car seats. My wife and I have discovered that car seats have "expiration dates": a car seat, no matter how ...
7
votes
1answer
1k views

What IPC mechanisms exist for the i.MX 7 (or i.MX 6) multi-core processors?

I'm considering using the i.MX 7 processor for a new design. The overall architecture appears to be similar to the i.MX 6, at least from comparing the block diagrams. What mechanisms exist for ...
7
votes
1answer
2k views

Using a pattern of features as datum BOTH individually and as a group, for different FCFs

The quick: I've come up with a handful of possible options for how to structure the Datum Reference Frames (DRFs) and Feature Control Frames (FCFs) for this part. I've narrowed it down to the two ...
6
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4answers
3k views

Is it useful to stuff my glasses with newspaper to protect them?

(I'm not sure if this question belongs to this stack exchange, but it seems appropriate to me) I have a very practical situation and our knowledge is lacking to be able to solve our debate. The ...
6
votes
1answer
382 views

Do outer fillets|chamfers also reduce stress as inner ones do?

I kind of have an intuition or at least imagination about how fillet|chamfer of inner edges|vertexes reduce stress (concentration). But does that apply to outer edges|vertexes aswell? Maybe to a ...
6
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2answers
4k views

Snap-fit design

I'm designing 2 objects that should be attached to each other and removed when it's necessary. So I though about snap-fit as a solution. There is a lot of types of snap-fit but I'm planing to use a ...
6
votes
2answers
4k views

What should the size difference be between a lid and a container?

I am designing a box and lid (for a home-made micro computer). Using Autodesk Inventor (Student Version), I've created my box which looks something like this: I plan on 3D printing (ABS Plastic) the ...
6
votes
1answer
7k views

What drives the honey dipper design?

Honey dippers are often made of wood. Is there a property of honey that drives this? Honey dippers are shaped like ovoids with lateral grooves. Is there something about the viscosity of honey that ...
6
votes
1answer
37 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
votes
2answers
1k 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
29k views

How deep are utilities typically buried?

What are the recommended or relevant standards for US city planning with regards to depth ranges for various utilities such as water, natural gas, and power, as well as for subway or rail, etc...? ...
5
votes
6answers
170 views

Why don't public transport networks have more routes to each terminal?

When using public transport, we often need to change routes in the middle of the journey. These changes have costs – I can think of the following, but there may be more. If we're reading, working, ...
5
votes
2answers
1k views

How to prevent algae in water cooled laser tubes?

I recently got a laser that is water cooled via a couple of clear plastic tubes (about .5 cm diameter). I have heard it can happen that algae or other undesirable inhabitants can get into such tubes ...
5
votes
5answers
7k 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
368 views

Snap fit on an enclosure

I am designing an enclosure, and top and bottom should be linked thanks to snap fit. I have to use 3D-printing to make both parts. The material is ABS. I made some trials, but they keep breaking. I am ...
5
votes
3answers
2k views

Orthographic (engineering) drawing with same top and front view?

I came across this while reading on third angle orthographic projections. The object has the exact same front and top view - both views are trapeziums of exact shape and size (As shown in the image). ...
5
votes
1answer
2k views

Involute Gear Calculation

I've written a program to generate gears and write them to dxf files. I thought all was well until I looked at the mesh of two gears. From everything I've read there should be no backlash when the ...
5
votes
2answers
2k views

Why does blood pressure cuff size matter?

There are a number of sources that confirm blood pressure cuff size can have a significant impact upon the measured reading. (See 1, 2, 3, 4) The most succinct description I have seen is this: ...
5
votes
2answers
1k views

Mechanisms for moving dual blackboards

I have to make a dual blackboard like the one here, http://www.ucd.ie/physics/lhcb/contact/blackboard.jpg, My biggest concern is what sort of mechanisms I should use to allow for smooth and easy ...
5
votes
1answer
317 views

Should the corbel angle always be estimated as 60 degrees in masonry construction, or is there a formula to use instead?

In educational construction material as well as engineering publications, the corbel angle for significant excess loads, and also for substantial openings, in an ordinary brick wall is usually ...
5
votes
1answer
134 views

How the optical cd disc gets drawn in when we gently push it? what is the mechanism behind it?

We have seen CD drives that have slits. The CD gets drawn inside upon a gentle push. how the CD gets drawn inside upon a gentle push? How it's mechanism works?
5
votes
1answer
186 views

Specification of hole design tolerance

Suppose the fit for a rod and a hole in a gear is supposed to be free running and the fit is 3mm H9/d9. For the specification of the hole for the manufacturing of the gear, is "3mm H9" already ...
5
votes
2answers
1k views

Design of a Four-Bar Infinity Coupler Linkage

How can I control a Four-Bar Infinity Coupler such that it does not accidentally become a Paralellogram Linkage? It seems to me that, when the bars are all horizontal, gravity could change the ...
5
votes
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. ...
4
votes
4answers
6k views

Why aren't screens round instead of rectangular?

Screens on TVs and phones et cetera are always rectangular. Why? Why are they not round? Eyes are round. The Sun, the source of almost all of our light, is round. Telescopes have round lenses and ...
4
votes
3answers
286 views

Why are the processes called “Precipitation Hardening” and “Solid Solution Strenghtening”?

Does precipitation hardening really only make the material harder while Solid Solution strengthening makes it stronger altogether (thus increasing the area under the stress-strain-curve edit: excuse ...
4
votes
4answers
1k views

Selectively rotating (engaging/disengaging) one of 80 couplings on a small shaft?

I've been working on this problem for years (literally) and haven't yet found a workable, scalable, pragmatic, and cost-effective solution that would allow me to selectively rotate one or more of 80 ...
4
votes
3answers
110 views

How are dangerous to build things studied?

How are dangerous to build things studied? Such as, nuclear reactors, jet engines, sawing machines. How do engineers discover, how they ought to be built, while avoiding getting or getting others ...
4
votes
2answers
378 views

How to determine tensile strength while the normalised tensile strength is known?

I try to design a shaft with yet unknown diameter, i know the distribution of forces and stresses (shear, torsion and normal) in/ along the shaft. I need just one more parameter nl. the tensile ...
4
votes
1answer
423 views

What are heat sink options for a circulating-water cooling vest?

I am in a first-year engineering design group where we are in the process of designing a cooling vest for motorcyclists for use in the city (1-2h length). Water will circulate through the vest, ...
4
votes
1answer
1k views

Fan Sensors (Tachometer vs Locked Rotor)

With regard to Fan Sensors, there are two very common methods for detecting whether the fan is doing what it's supposed to or not. Locked Rotor- Detects when the fan is working, or when it has ...
4
votes
1answer
91 views

Quantifying Static Electricity Hazard with High Explosives

In the making of firework explosives, the explosive mixtures are handled with great care to avoid static electricity induced detonation of the explosives. Is it a good idea that they store the ...
4
votes
1answer
68 views

Accounting for blank registration within CAD design

How do CAD designers account for the fact that a blank may have to be flipped to a different side in order to allow the piece to be completely milled through a CNC system? For an example, let's use ...
4
votes
1answer
106 views

How is linear motion achieved in this automatic blackboard eraser?

In the animation shown below what can be the mechanism used for this purpose? I know it can be achieved by using rack and pnion gear arrangement. But how are this set up arranged in classroom ...
4
votes
1answer
133 views

Mechanical/electronic chalkboard cleaning device to replace the conventional duster to clean the chalkboard

The chalk board duster which is used by teachers to wipe the chalkboard seems very agonizing for them. What new mechanical/electronic devices can be devised to replace conventional chalkboard duster ...
4
votes
1answer
81 views

Technical term for loose drawers jamming more readily than those with tighter clearance?

A loose drawer or loose sliding parts in general jam more easily than ones with tighter clearance. There is a name for this problem but I can not remember what it is, and searching for "loose drawer ...
4
votes
1answer
157 views

Low cost, compact cable strain relief for laser cut sandwich case

I have created the following PCB design: On the right is a USB port, on the left are a number of pads for connecting a round multi-core cable. There will be between 3 and 10 connections, depending on ...
3
votes
3answers
190 views

What is “reversal” in mechanical engineering drawing?

I've come across these terms "reversals allowed" and "reversals not allowed" in a sample drawing while reading a GD&T course. What exactly are these terms? What do they mean?
3
votes
2answers
296 views

Intuition vs software results

I've recently designed what is essentially an aluminium box. I've done the entire design process of CAD software SolidWorks and then done some simulations of loading of the box. Through iterations I'...
3
votes
2answers
674 views

Suggestions for low friction surface materials for a “beltless static treadmill”

I'm currently developing a treadmill for clinic gait research. If I were to build a flat treadmill with no moving surfaces what materials or coatings would be worth exploring as walking surface. ...
3
votes
3answers
223 views

Mechanism for controlling the clamping force

I am working on upgrading a research project on wind energy. They are trying to measure the performance of wind blade designs in a small wind tunnel (i.e. their models are relatively small). What they ...

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