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Looking for ideas for a Mechanical Engineering problem
18

Looking for ideas for a Mechanical Engineering problem

Looking for ideas for a Mechanical Engineering problem

(OP)
We are looking to take on an Aerospace Mechanical Engineering apprentice and I would like to give the candidates a problem to solve during the interview. I dont want anything too technical, just something that will give us an insight into how they approach problem solving, we are looking for someone who thinks logically but also thinks outside the box. Does anyone have anything I can use, or does anyone have any ideas please? Many thanks :)

RE: Looking for ideas for a Mechanical Engineering problem

Problem statement: You have to pump water from a 50 gallon drum at ground level to a second drum on the roof of a 50 foot tall building. Where would you place the pump; on the ground, roof, or in between? Why?

Over half of the graduate engineers I've asked get the answer wrong.

RE: Looking for ideas for a Mechanical Engineering problem

I wonder if Compositepro would hire me?

Spoiler:

On the ground.
So that there is NPSH at the pump for startup so that I don't have to mess around priming the pump.

RE: Looking for ideas for a Mechanical Engineering problem

Spoiler:

A pump cannot "suck" water up 50ft

RE: Looking for ideas for a Mechanical Engineering problem

Compositepro, I can't help myself

Spoiler:

At the top won't work since the pressure, even at full vacuum, couldn't get the water up 50 ft to your pump using an unpressurized container as your feed.

Though there should be enough pressure (assuming the pump can provide full vacuum) to place it halfway. That would not be my choice, though you could spec a less powerful pump and save on costs.

I would place it at the bottom because there is no question about supply pressure being adequate in any foreseeable situation. You can spec the pump to provide however much pressure you need to overcome the elevation. But for me, probably the most important aspect is, serviceability. It is a lot easier to service/replace/whatever at ground level than halfway up or on the roof. I think that aspect outweighs the potential operational savings from the halfway option.

Did I get the job?

Andrew H.
www.mototribology.com

RE: Looking for ideas for a Mechanical Engineering problem

This could be fun. Post a suggested question for Lisa and give the answer under a spoiler (the gift box icon in the posting options). Then everyone can test themselves. It might be more fun to see people post answers, as Mint Julep has done, but I do not think that most engineers are brave enough to publicly post potentially wrong answers.

Here is the answer to my question, above:

Spoiler:

Mint Julep gets hired! The pump should be on the ground. You cannot suck water up a pipe more than about 30 feet because it is only atmospheric pressure that is pushing the water up. Water vapor pressure reduces this height somewhat from the theoretical value. In most cases, installation and maintenance are also easier at ground level.

A common wrong answer is to place the pump on the roof because it is easier to pull than to push. ponder

RE: Looking for ideas for a Mechanical Engineering problem

Years ago someone posted an actual question on here. It was regarding conveyor belt speeds, nothing particularly complex.

Anyway, it was a great question because

1. There were LOTS of numbers given in the question. Many of them were seemingly related but superfluous to the solution. This is much more realistic than textbook problems. Textbooks typically give you exactly what you need to solve the problem. No more, no less. To the point where if you get an answer without using all of the givens, you've probably done it wrong! In the real world, you almost always have available much more information than the bare minimum to solve the problem. You must be able to quickly understand the situation and realize which things are actually necessary.

2. There was ONE piece of info missing to solve the problem using the full gear train analysis, which would have been the straightforward sort of "textbook" type solution. However, it would have easily been determinable by a quick physical look at the system. This is also very real-world, becuase you often have to recognize what info you currently lack to solve your problem.

3. The solution was actually determinable without doing a full gear train analysis by recognizing a couple of ratios.

I had copied it myself into a word document for a similar purpose, but unfortunately I don't have access to it anymore.
Edit: Well daggum, I found the post... When I made the Word doc I think I dressed it up a little more with a diagram or something... https://www.eng-tips.com/viewthread.cfm?qid=232164

RE: Looking for ideas for a Mechanical Engineering problem

Quote (SuperSalad)

You could spec a less powerful pump

Can you please elaborate?

RE: Looking for ideas for a Mechanical Engineering problem

I think my fingers went too fast for my brain! 3eyes.

The total required minimum pressure would not decrease due to pump location.

I won't edit it out of my original post though for posterity's sake.

Andrew H.
www.mototribology.com

RE: Looking for ideas for a Mechanical Engineering problem

Anybody who'd say "put it on the roof" has not worked on roofs :)

The problem with sloppy work is that the supply FAR EXCEEDS the demand

RE: Looking for ideas for a Mechanical Engineering problem

It would be interesting to see their response to redundant systems.

A simple mechanical system would be flap drives, quite straight forward until you bring skew sensors into play. This would be a good example of responding to failure cases.

But these are not fair questions for an apprentice. I have very simple interview questions for structures graduates, to see how much they'll learnt. At the apprentice level, what have they learnt ? Maybe focusing on the personality is more valid ? why do you want to do this ? attention to detail. personal responsibility

another day in paradise, or is paradise one day closer ?

RE: Looking for ideas for a Mechanical Engineering problem

A couple questions I like to use for mechanical engineers to see their thought process:

- Hand them a complicated sheet metal part and ask them to draw the flat pattern

- Give them the attached drawing and ask them to draw the missing internal line and isometric view of the part. Pg 1 is given to the applicant, pg 2 is the answer. No one ever does a good job on the isometric view but you just need enough from them to get the point across.

Another one I have heard of but never used is to ask how much your fuel economy drops if you turn the headlights on in your car. Don't provide any numbers to them, just get them to make a whole lot of assumptions and see where it takes them. I heard of one guy that knew the energy density of a gallon of gas off the top of his head and made pretty quick work of it.

RE: Looking for ideas for a Mechanical Engineering problem

I would winch it up. Less chance of spills and avoids buying the hose/tubing and the second barrel. Since other things are subject to delivery to the roof, there should already be a means to lift the barrel. It also works regardless of temperature.

RE: Looking for ideas for a Mechanical Engineering problem

5
I'd order a different drum of water from Mcmaster-carr, and make the delivery address the rooftop.

RE: Looking for ideas for a Mechanical Engineering problem

I worked at a place, an intern there had gotten a job at the national mint. He said part of his interview was the question, 'how do you weigh a car with something in your pocket' or it may have been more direct 'how do you weigh a car with a dollar bill'

Spoiler:

You 'weigh' a car with a dollar bill by inking the tire and imprinting the contact patch of one of the tires on the bill. Assuming nominal tire pressure, 25%/corner weight distribution and measuring the area of the contact patch from the imprint, you get W = 4PA

RE: Looking for ideas for a Mechanical Engineering problem

lol

Y'all are killing me with these answers.

Spoiler:

But as for weighing a car with a dollar, I think it would be more cost effective and accurate to pay a scale operator a dollar for the info

Andrew H.
www.mototribology.com

RE: Looking for ideas for a Mechanical Engineering problem

Spoiler:

Wouldn't that imply that you had ink and a measurement device in your pocket too? Hahahaha

Daniel
Rio de Janeiro - Brazil

RE: Looking for ideas for a Mechanical Engineering problem

As opposed to catching some poor soul off guard, I would give them a heads up that I want to chat about a particular subject or two in qualitative terms. The kid who is ruled out with a pop quiz may have been the best candidate. Offer up something in the interview about how you would approach an unknown problem and let them know what you are looking for first, as an ice breaker.

Otherwise -

I think that knowing that similarly loaded and configured steel (metal) parts have similar deflections due to similar Young's modulus in spite of vast differences in steel yield and ultimate strengths shows insight.

Knowing how materials expand with temperature seems like a good conversation point. If a part doesn't have degrees of freedom to expand what happens? i.e. strains or buckling

Basics of combustion air requirements and expansion of gases after combustion would be appropriate in certain industries.



RE: Looking for ideas for a Mechanical Engineering problem

You could always ask them to finish the simple drawing below, by adding the missing Side View:

John R. Baker, P.E. (ret)
EX-Product 'Evangelist'
Irvine, CA
Siemens PLM:
UG/NX Museum:

The secret of life is not finding someone to live with
It's finding someone you can't live without

RE: Looking for ideas for a Mechanical Engineering problem

Easy

Spoiler:

It's a thin gasket at 45 degrees with a ~1.414:1 aspect ratio. So the side view is a 45 degree line, maybe leaning left, maybe leaning right.

RE: Looking for ideas for a Mechanical Engineering problem

Its a cube with a 45 degree cut surface and a small cube projecting off the center of that surface.

RE: Looking for ideas for a Mechanical Engineering problem

Actually there are TWO correct answers, and I would expect a candidate to see BOTH of them.

John R. Baker, P.E. (ret)
EX-Product 'Evangelist'
Irvine, CA
Siemens PLM:
UG/NX Museum:

The secret of life is not finding someone to live with
It's finding someone you can't live without

RE: Looking for ideas for a Mechanical Engineering problem

There are likely many more than 2, like whole families. It could also be an curved surface.

RE: Looking for ideas for a Mechanical Engineering problem

This was my first thought. Am I missing something?




Andrew H.
www.mototribology.com

RE: Looking for ideas for a Mechanical Engineering problem

All visible and hidden edges are properly represented in BOTH the Top and Front Views of the sample Drawing.

John R. Baker, P.E. (ret)
EX-Product 'Evangelist'
Irvine, CA
Siemens PLM:
UG/NX Museum:

The secret of life is not finding someone to live with
It's finding someone you can't live without

RE: Looking for ideas for a Mechanical Engineering problem

In that case:

Spoiler:

A diagonal 2-dimensional line

Andrew H.
www.mototribology.com

RE: Looking for ideas for a Mechanical Engineering problem

Here are the two solutions which have been traditionally offered when confronted with this 'test':

John R. Baker, P.E. (ret)
EX-Product 'Evangelist'
Irvine, CA
Siemens PLM:
UG/NX Museum:

The secret of life is not finding someone to live with
It's finding someone you can't live without

RE: Looking for ideas for a Mechanical Engineering problem

Just ask them to explain engineering Stress and strain. Great question to see if they remember something so simple.

BTW: Mintjulip was not correct in his reasoning to put the pump down below. The correct answer was the 32-foot vacuum limit of a pump.

RE: Looking for ideas for a Mechanical Engineering problem

Well, If John R. Baker is using 3rd angle projection, I would say that the views are wrong.

The front view is below the top view. The right side view is to the right of the front view.

RE: Looking for ideas for a Mechanical Engineering problem

If they have worked in a technical position prior I would ask them to describe their work. If not, I would ask that they describe their technical background, hobbies, or why they are going into engineering. Engineering is easy, communication is difficult and these questions should provide plenty of opportunity to chase the conversation down technical rabbit holes to give you an idea of their abilities and thought-process. Personally, I would NOT ask them to solve a textbook style question like those shared above as most technically-competent folks will find them insulting and often show poor preparation or knowledge on the part of the person asking.

Quote:

Over half of the graduate engineers I've asked get the answer wrong.

I'd argue that there is no incorrect answer based on the limited info given as I'm sure there are many ways to make a pump work in any given location.

RE: Looking for ideas for a Mechanical Engineering problem

Quote (CWB1)

I'm sure there are many ways to make a pump work in any given location.

I'd be curious to hear a method for making the pump work from the roof.

RE: Looking for ideas for a Mechanical Engineering problem

Easy - put a hose from an air pump to a fitting on the drum and a second hose to a second fitting that has a dip tube. It costs a little more but the guy on the roof has control over the pump and can watch the destination. It also means the pump can be used on corrosive materials without using a corrosion resistant pump.

RE: Looking for ideas for a Mechanical Engineering problem

Spoiler:

RE: Looking for ideas for a Mechanical Engineering problem

MintJulep: just for clarification and correctness, irrespective of NPSHr at ground level doesn't necessarily mean a pump will be self-priming - this is entirely dependent on pump design.

It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)

RE: Looking for ideas for a Mechanical Engineering problem

The question posed by Compositpro has a lot to do with the Net Positive Suction Head requirement. If the pump is too far up the line than there is a chance that water will turn into a vapor state ( i.e.,bubble up), so to be fair with the applicants perhaps flow rate, water temperature, friction loss thru piping should be stated. Static head of water in drum to pump inlet should also be highly considered due to the choice of the pump placement.

RE: Looking for ideas for a Mechanical Engineering problem

Low cost method: No pump. Build a fire (using trash from the dumpster) under the bottom barrel and pipe the steam to the upper barrel. Some of the water will condense in the upper barrel. Refill lower barrel as required until you achieve desired water level in upper barrel.

...just "thinking outside the box", and have been having discussions about distilling with some colleagues recently. Our local winery/brewery scene has had a plethora of startup distilleries come and go, and we think the problem is these guys don't understand what barrel aging does for fine liquors.

RE: Looking for ideas for a Mechanical Engineering problem

Steam could take a while; a slight modification would be to have the pipe at the BOTTOM of the boiler and use the trapped steam as the pressure for pumping the liquid water upwards. That's how your cheapo coffemakers operates, but I'm not clear whether you could generate sufficient steam pressure to push the water column up 5 stories; now, that's a lot of coffee!

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert! https://www.youtube.com/watch?v=BKorP55Aqvg
FAQ731-376: Eng-Tips.com Forum Policies forum1529: Translation Assistance for Engineers Entire Forum list http://www.eng-tips.com/forumlist.cfm

RE: Looking for ideas for a Mechanical Engineering problem

Quote:

I'd be curious to hear a method for making the pump work from the roof.

Me too. ;) Therein lies the problem, with limited info we cant positively deem a task impossible or an answer incorrect. The pump could be assisted with positive pressure in the lower tank or negative in the upper. We don't know anything about the pump nor the volume of water in the system much less each tank, whether the tanks are closed vessels or open to atmosphere, whether/not there is flow into the lower tank or out of the upper, nor do we know if we need to pump continuously or if we can use an intermittent cycle. Even gravity could totally hinder or be a great help. Not to be terribly facetious but many careers have been made by accomplishing tasks deemed impossible by others who didnt consider every detail, hence my hesitancy to pose general questions bc the best answer is usually "it depends."

To get back to something more useful for the OP, another personal favorite "test" for all engineering candidates of mine is simply to give them a tour of the shop to see what questions they ask and what relevant knowledge or experience they might have. In most cases its usually pretty easy to tell those looking for a paycheck from those looking for a career.

RE: Looking for ideas for a Mechanical Engineering problem

This shows how useful the question is. Will a simple question be turned into an impossible to answer complexity.

RE: Looking for ideas for a Mechanical Engineering problem

Seems like that makes it the best Gotcha! question. The chances for coming up with either a truly novel answer or one that perfectly matches the interviewer's previously determined "right" answer means that the majority of perfectly fine applicants will be rejected.

RE: Looking for ideas for a Mechanical Engineering problem

There is nothing gotcha about it. It simply tests for knowledge of some of the most basic principles of physics and problem solving skill. Getting bogged down with irrelevant details is one of the most common failings of engineers. Even the points about NPSHA, while perfectly correct, are unnecessarily complicated. Using the term NPSHA shows you have had courses on pumps. But the question can be answered correctly after having taken Physics 1A. I have found that many graduate engineers get through school by memorizing formulas and plugging in numbers but do not have a good understanding of the basic principles which allows for deriving the equations and getting to the solution to a problem.

RE: Looking for ideas for a Mechanical Engineering problem

The question is needlessly vague about a simple system and without a definitive answer, suggesting that the person asking is either poorly prepared, not technically competent, or simply playing games as mentioned previously. In any case, the only thing it shows is that the candidate should consider the likelihood of a poor company culture when considering an offer.

Given the problem statement, we cannot definitively say where the pump will nor where it will not work. IME engineering depts tend to seriously frown on engineers making statements to outsiders that cannot be proven. Paint yourself into a corner by incorrectly telling the customer or leadership what can/cant be done and you'll likely be walked out. Not sure why anyone would expect an interviewing candidate to be any less conservative.

RE: Looking for ideas for a Mechanical Engineering problem

I'm sorry, CWB1, but your logic is the same one that is used by those who promote perpetual motion machines. If you can make an argument for any location of the pump but on the ground, please do so. No time limit, no limit to researching your answer. The original question had no constraints, like the ground gets flooded. The question also asked for the reasoning for the answer. This gives a great deal of opportunity to see how a candidate thinks and solves problems.

RE: Looking for ideas for a Mechanical Engineering problem

how does one get the water drum to the roof, well catapult of course.

I have always thought a good assessment of graduate engineers would be to ask them to assemble a flat pack desk (with or without instructions depending on what skill sets you want).

Show a broken bit of structure and asking why did it likely break or how you would improve the design could sort the wheat from the chaff.

RE: Looking for ideas for a Mechanical Engineering problem

CWB1, you're the one who's painted yourself into a corner, and now you have to support an argument that defies physics or changes the original question. The origninal question is ABSOLUTELY crystal clear, and not vague in the slightest until you start throwing in garbage that wasn't in the original statement. There absolutely are right and wrong answers. Your argument at this point is reminiscent of the parent who goes in and yells at their kid's teacher for flunking them when they say 2+2=5.

However, the original question also left an opening to "explain your reasoning". Gives some opportunity to redeem yourself. Relative to hiring, I'm pretty sure it was never stated that the one question is not a right/wrong, hire/fire thing.

RE: Looking for ideas for a Mechanical Engineering problem

An old engineer gave me a test during my first interview. Once I was hired, I learned his nickname was "Putz". His question: If I know the air supply pressure and the piston diameter, can I figure out how much force it will produce?

I was asked by another Engineer if I had a copy of Roark.

RE: Looking for ideas for a Mechanical Engineering problem

NOT having a copy of Roark's would certainly cause me to have second thoughts.

John R. Baker, P.E. (ret)
EX-Product 'Evangelist'
Irvine, CA
Siemens PLM:
UG/NX Museum:

The secret of life is not finding someone to live with
It's finding someone you can't live without

RE: Looking for ideas for a Mechanical Engineering problem

I have two. One for each shed.

RE: Looking for ideas for a Mechanical Engineering problem

Actual problem from the Dynamic's textbook from college:

The question is: Given mass m and spring constant k, what initial velocity must the mass "m" be given in order to stop at the horizontal position at point "A"?
As I said, actual problem, which the good professor didn't see any problem with, either.

On Roark's- depends entirely on what your work involves. I remember a line from a surplus "stuff" catalog long ago: "Handy if you need it, useless if you don't", and that applies to Roark's and a whole lot of other stuff, too.

RE: Looking for ideas for a Mechanical Engineering problem

Quote (handleman)

I'd be curious to hear a method for making the pump work from the roof.


A hand pump will work from the roof. Hand pumps supply water from hundreds of feet in depth.

Archimedes screw pump will work from the roof.

RE: Looking for ideas for a Mechanical Engineering problem

Quote (FACS)

A hand pump will work from the roof. Hand pumps supply water from hundreds of feet in depth.

Archimedes screw pump will work from the roof.

By "hand pump" I assume you refer to the old water well style handle pumps.... However, with these mechanisms, the actual pump is at the bottom of the well where the water is. The main body that you see above ground that most people call the "pump" is nothing but handle and a long rod running down the pipe with which to transfer the mechanical energy from the top of the well to the bottom where the actual pump is.

It's pretty tenuous to classify an archimedian screw as a pump... However, if we were to do so, you would have to consider the entire length of the screw and housing as the pump. If you had to answer "where is the pump", you would have to say that it's at the top, and at the bottom, and everywhere in between. You could put the motor at the top, but that would hardly be considered putting the pump at the top.

RE: Looking for ideas for a Mechanical Engineering problem

Quote:

CWB1, you're the one who's painted yourself into a corner, and now you have to support an argument that defies physics or changes the original question. The origninal question is ABSOLUTELY crystal clear, and not vague in the slightest until you start throwing in garbage that wasn't in the original statement. There absolutely are right and wrong answers.

Crystal clear with absolutely right and wrong answers eh? Ok...

Scenario 1 - Pressure out of the lower drum raises water 49' to a minuscule pump which easily raises it the last foot. Move the pump to ground level and it cannot raise water 50' being undersized for that effort. Fits the problem statement perfectly, doesnt defy physics, incorrect per CP as the pump isnt on the ground.

Scenario 2 - Pressure out of the lower drum overpressures the pump's PRV and fills the upper drum without any pumping work being done. Pump location therefore is irrelevant to the task. Once again it fits the problem statement perfectly, doesnt defy physics, and is also incorrect per CP and yourself.

Scenario 3 - With zero outlet pressure at the lower drum the pump works fine halfway up the line under all conditions, cannot provide adequate suction if placed on the roof, but lower it to ground level and it cannot overcome head from the upper drum. Again this fits the problem statement, doesnt defy physics, and is also incorrect per some folks.

I wouldnt call anything with wildly varying interpretations "crystal clear," especially when the folks being asked to interpret the problem statement have seen many variations of it, albeit decently defined, in the majority of their undergrad coursework in physics, thermo, fluid dynamics, hydraulics, machine design, heat transfer, HVAC, and CFD, plus others I'm surely forgetting or unfamiliar with. I never took HVAC but am fairly certain I had similar problems in each of the others, hence three scenarios given with less than a minute's thought.

Ultimately it is a "gotcha" bc rather than proving someone's technical competence and sound engineering judgement it proves the exact opposite.

RE: Looking for ideas for a Mechanical Engineering problem

The first two scenarios you have made up add information that was not present in the problem statement... They do not defy physics, but they certainly do change the original question. There is nothing in the statement to suggest that pressure is available in the lower drum. Adding some pressure-assist for no other reason than to put the pump on the roof needlessly complicates the simple problem statement, just so you can try not to be wrong. Adding pressure-assist in the lower drum is no different from adding a janitor with a bucket to carry the water halfway up the building to a third, intermediate drum. You're still wrong. Your third scenario HAS ALREADY BEEN DEBUNKED IN THIS THREAD! Delta P across the pump is the same, regardless of whether it's at the bottom or middle of the building. If it can't push water to the top, it can't pull water halfway and then push it to the top.

There are a lot of "creative" answers in this thread for getting water to the top. Some of them don't even use a pump! But it's funny that you mention "sound engineering judgment". Engineers sometimes have to make decisions based on limited information. Based on ONLY the information provided, and not adding any weird scenarios or other energy sources etc, in your "sound engineering judgement", which solution is reasonable? I would argue that absolutely zero of the suggestions other than putting the pump at the bottom show "sound engineering judgement".

RE: Looking for ideas for a Mechanical Engineering problem

How many quarters need to be stacked to reach the height of the Empire State building?
The right answer is not important. The important thing is to see if they ask clarification questions and if they think through it logically.

RE: Looking for ideas for a Mechanical Engineering problem

20 quarters. At least I think that's what a ticket to the observation deck costs. Or less, if there's an appointment to an upper floor of the Freedom Tower. Or let go of a helium filled balloon. Depends on what it means to reach the height.

See Empire State building barometer answers. http://www.mrao.cam.ac.uk/~steve/astrophysics/webp...

RE: Looking for ideas for a Mechanical Engineering problem

Now that I like :)

The problem with sloppy work is that the supply FAR EXCEEDS the demand

RE: Looking for ideas for a Mechanical Engineering problem

If you're only going to pump it once, this is a problem for 5 people and 10 buckets instead.

RE: Looking for ideas for a Mechanical Engineering problem

Quote (handleman)

By "hand pump" I assume you refer to the old water well style handle pumps.... However, with these mechanisms, the actual pump is at the bottom of the well where the water is. The main body that you see above ground that most people call the "pump" is nothing but handle and a long rod running down the pipe with which to transfer the mechanical energy from the top of the well to the bottom where the actual pump is.

It's pretty tenuous to classify an archimedian screw as a pump... However, if we were to do so, you would have to consider the entire length of the screw and housing as the pump. If you had to answer "where is the pump", you would have to say that it's at the top, and at the bottom, and everywhere in between. You could put the motor at the top, but that would hardly be considered putting the pump at the top.

Do you even read the words you write?

"Making the pump work from the roof"

I went on the roof, I pumped the handle, and the pump worked.

It DOES NOT MATTER where the pump is. You asked how to make it work from the roof. You did not say the pump was on the roof. I know that's what you meant, but since you are being "one of those guys" you should change your statement to "I would like to know how to put a pump on the roof, and have it pump water from the ground to the roof."

I made it work:
Work: Moving a pound of water, one foot, in one second.

Your comments on Archimedes screw is just argumentatively stupid.

RE: Looking for ideas for a Mechanical Engineering problem

Lisa_247's (Aerospace) Member Profile
After joining Eng-Tips Forums on January 24, 2020, I've logged in 2 times. My last login was on Saturday, January 25, 2020. I've started 1 threads, posted 0 replies, and written 0 FAQs.

We fell for it again. Sixty replies and the OP is not even caring.

Mike drop

RE: Looking for ideas for a Mechanical Engineering problem

FACS,
That doesn't mean the fun should stop, does it?
It's just starting to get exciting!

www.sparweb.ca

RE: Looking for ideas for a Mechanical Engineering problem

Can't say that I blame the OP for not coming back.

Pet peeve - allowing someone(s) to join Eng-Tips and post immediately. Institute a thirty day observer period.

RE: Looking for ideas for a Mechanical Engineering problem

2
What should Lisa_247's response be? There is nothing in here that warrants a response from the OP. This thread went immediately off the rails (my own input included) for the most part with jokes and silliness and most recently into arguments about pump operations about question semantics.

Andrew H.
www.mototribology.com

RE: Looking for ideas for a Mechanical Engineering problem

Quote:

But it's funny that you mention "sound engineering judgment". Engineers sometimes have to make decisions based on limited information. Based on ONLY the information provided...

Sound engineering judgement ethically implies that the engineer understands the design well enough to guarantee both the safety and success of their design. Based on ONLY the information provided there is no way to guarantee either, so an engineer is required to investigate further BEFORE providing an answer to this. Congrats on missing the point once again.

RE: Looking for ideas for a Mechanical Engineering problem

Reading through this amusing thread, I couldn't help feel like I was watching a stereotypical classic high school nerd movie scene play out where the pretty girl (Lisa_247) approaches the protagonist group of nerds (future engineers) to ask them a question regarding classwork. All the of the nerds are awkwardly bashful and have no ability to converse with the pretty girl on a normal social platform. 2 of the nerds, eager to impress the girl, offer their profound knowledge regarding her dilemma only to realize that they have opposing views and begin to see each other as adversaries. The 2 heated nerds slowly begin to ignore the pretty girl as they turn their focus on each other and engage in a tit-for-tat argument over engineering theory and semantics while their nerd friends chime in every so often with unhelpful and typically sarcastic comments which only fuels the fire. After a short time, the group that has been lost in their own debate, realizes that the pretty girl has merely walked away without even a salutation. The stark realization that they "did it again" further solidifies their place in the world of women and provides them with a moment of humility and humbleness.

I applaud you Engineers!

RE: Looking for ideas for a Mechanical Engineering problem

well, this is a forum, an OP rolls a dice in some way and let's roll it to the benefit of ... all.
there's nothing more far off from engineering like an opinion about an opinion, perhaps its better to stay with the basic facts.
i appreciate the question of the OP, to know how to ask a question well is to arise an interest, which is pretty difficult to do with freshmen.. without scaring them..
which no one wants, this (any) person might be a future Tesla..
from here.. i have a box in my desk with some damaged parts from malfunctions or incidents or plain wear and tear.. i ask the person about her/his interests, then we choose a fitting object and sit down and discuss it
description of the state, analysis, possible core reasons, probability, possible actions for further analysis, background in materials and manufacturing, ...

Roland Heilmann

RE: Looking for ideas for a Mechanical Engineering problem

Quote (SparWeb)

FACS,
That doesn't mean the fun should stop, does it?


Well no, so if you want to still have some more fun, here is a puzzle for you:

There are four dots, like the four dots on a die.
You cannot move the dots.
You have to connect the dots with straight lines.
The lines must connect to each other.
How few lines do you need?

RE: Looking for ideas for a Mechanical Engineering problem

Here is something very fundamental. Find a part with left hand threads like a turnbuckle, rod end ect. Hand it to them and see what they do with it.

first they should figure out something is different
second they should figure out what that is
finally they should ask why and offer some hypothesis

RE: Looking for ideas for a Mechanical Engineering problem

ProEpro,
That's a great example!

OK, along those lines, I can come up with another one. This would be a test for an electrical engineer - no reason for a Mechie or a Civvy to get it:

I show them a pocket LED flashlight. Inside, it is powered by a stack of 4 coin cells. I take the cells out, replace one of the cells with a Neodymium magnet of roughly the same thickness, and put the stack of 3 cells + 1 magnet back inside, close it up. When I click the switch, it turns on. Explain why it works. Explain why it is just as bright as it was before.

FACS,
I get 3 lines for your problem, providing the ENDS of the lines must touch. If the lines may connect at any point along their length, then 2 lines will do.

www.sparweb.ca

RE: Looking for ideas for a Mechanical Engineering problem

Quote (SparWeb)

I get 3 lines for your problem, providing the ENDS of the lines must touch. If the lines may connect at any point along their length, then 2 lines will do.


Awwww man, you got the two lines right. Usually people go for the three lines.


As for that left hand thread question: They use left hand threads to mount power line poles on the concrete pads... Do you know why?

RE: Looking for ideas for a Mechanical Engineering problem

Quote (FACS)

They use left hand threads to mount power line poles on the concrete pads... Do you know why?
Is it just to stop it being worth people's time nicking the nuts?

RE: Looking for ideas for a Mechanical Engineering problem

I recall reading that, years ago, the NY Subway had special left-hand base light bulbs made to eliminate theft.

Maybe it's true; it sounds good.

RE: Looking for ideas for a Mechanical Engineering problem

Here are a couple of message boards which appears to confirm that this was a real thing, or at least people talked like there was:

https://www.reddit.com/r/todayilearned/comments/34...

https://www.lighting-gallery.net/index.php?topic=2...

Now here's another explanation for the existence of left-hand threaded light bulbs, but the rational wasn't to prevent theft:

https://www.lightbulbs.com/blog/left-handed-incand...

John R. Baker, P.E. (ret)
EX-Product 'Evangelist'
Irvine, CA
Siemens PLM:
UG/NX Museum:

The secret of life is not finding someone to live with
It's finding someone you can't live without

RE: Looking for ideas for a Mechanical Engineering problem

I heard about the left hand threads shortly after 9-11.
I had to design residential water well protective devices, and they bolted over studs placed in concrete.
When someone told me to make the threads left handed, like on high tension lines, I asked why and they told me it was to prevent vandals from unscrewing them.
I never knew if it was true or not.
Later, someone told me that the studs for mounting tension lines were of a extra strong material, and contractors would not be able to buy standard studs to save money. I don't know if that is true or not either but it makes a little sense.

There has to be someone in that industry that knows why for real. Some idiot kid has a big wrench and he decides to create mayhem, he would not be smart enough to turn the nut in the opposite direction.

I never used left hand threads on the protective well design. I put the bolting inside the protective device so no one could even see them. I don't think anyone ever bought one, they were damn expensive and the hysteria wore down.

RE: Looking for ideas for a Mechanical Engineering problem

The drafting questions are fun puzzles and completely irrelevant to modern Engineering skills.

I suggest showing the candidates a couple of basic calculations that are unique to your industry or company. Draw a system and plug some easy, round numbers into it to give a ROM of the actual values. Then ask the candidate how to optimize/change the system for a given outcome based on the equation you gave them. If they paid any attention in school it should be easy to increase the numerator, reduce the denominator, etc. But the better side is to get their ideas how to achieve these things in the real world.

There are new grads who forced their way through the math and rely on a calculation program to spit out results without much understanding of what's going on. There are also candidates who only know math and can't translate much to the real world. Finally, you'll encounter candidates who get the math, offer practical ideas, but also have a conversation / ask questions to explore these ideas. That's best of all.

David

RE: Looking for ideas for a Mechanical Engineering problem

Visualisation of 3d from 2d is one of the few measurable traits that seems to correlate with mechanical engineering ability, according to one interviewer. That may be a tautology.

Cheers

Greg Locock


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