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Continuing on from Andy's experience of interviewing graduates for
programming jobs, exactly the same thing happens with engineering
graduates - they can't actually do any engineering (or maybe I'm
expecting too much of them).
Here's an example problem we ask:
You are given a bucket of water (fixed to the ground) and an open-ended
flexible pipe leading off into a "black box". All you know about the
black box is that it may allow some flow into it, at a variable,
unpredictable rate.
Design a system to take the water from the bucket, and supply it into
the pipe at a constant pressure (not a ridiculous pressure, just
something like the pressure you would have in your water pipes at home,
maybe 3 bar?).
Maybe I just hang about too many engineers, but to me even a
non-engineer would be able to have at least a stab at some ideas for
solving it.
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Am 16.08.2016 um 09:58 schrieb scott:
> You are given a bucket of water (fixed to the ground) and an open-ended
> flexible pipe leading off into a "black box". All you know about the
> black box is that it may allow some flow into it, at a variable,
> unpredictable rate.
I presume the "black box" is at the same level as the bucket?
> Design a system to take the water from the bucket, and supply it into
> the pipe at a constant pressure (not a ridiculous pressure, just
> something like the pressure you would have in your water pipes at home,
> maybe 3 bar?).
>
> Maybe I just hang about too many engineers, but to me even a
> non-engineer would be able to have at least a stab at some ideas for
> solving it.
My first stab would be to re-invent the water tower - though I guess
you're after a more compact device. (Which is a pity, because it's the
solution that places the lowest demands on the pumps.)
My next stab would be to use a gear pump, and offload the tricky part to
some other engineer whom I'd contract to build a constant-torque motor -
though I guess you'd consider that cheating.
Yet another stab: Use a pump that can provide the projected peak flow at
a pressure of 3 bar, and connect a safety valve that opens at 3 bar.
Obviously this wastes a lot of water, but we can fix that by feeding the
spilled water back into the bucket.
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On 8/16/2016 8:58 AM, scott wrote:
>
> Design a system to take the water from the bucket, and supply it into
> the pipe at a constant pressure (not a ridiculous pressure, just
> something like the pressure you would have in your water pipes at home,
> maybe 3 bar?).
>
I will need a level transmitter or differential pressure transmitter, a
scissor jack, an actuator and a 45 foot deep hole. Plus a few bits to
join things together. And someone to get their hands dirty. ;)
--
Regards
Stephen
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On 8/16/2016 11:15 AM, Stephen wrote:
> and a 45 foot deep hole.
Oh no! I got my units wrong. Make that hole another 55' 6" deeper.
--
Regards
Stephen
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>> You are given a bucket of water (fixed to the ground) and an open-ended
>> flexible pipe leading off into a "black box". All you know about the
>> black box is that it may allow some flow into it, at a variable,
>> unpredictable rate.
>
> I presume the "black box" is at the same level as the bucket?
More or less, compared to the pressures involved yes.
>> Design a system to take the water from the bucket, and supply it into
>> the pipe at a constant pressure (not a ridiculous pressure, just
>> something like the pressure you would have in your water pipes at home,
>> maybe 3 bar?).
>>
>> Maybe I just hang about too many engineers, but to me even a
>> non-engineer would be able to have at least a stab at some ideas for
>> solving it.
>
> My first stab would be to re-invent the water tower - though I guess
> you're after a more compact device. (Which is a pity, because it's the
> solution that places the lowest demands on the pumps.)
To be honest I'm pleased with any device! After one person couldn't
think of anything, I asked how they thought the mains water pressure was
created, then they came up with the water tower method.
It's also good if they probe to better clarify the requirements (ie does
it need to be compact or not, any cost limits, availability of
electricity/compressed air etc). So in one sentence you've done better
than all the mechanical engineering graduates so far :-)
> My next stab would be to use a gear pump, and offload the tricky part to
> some other engineer whom I'd contract to build a constant-torque motor -
> though I guess you'd consider that cheating.
No not at all. I think this is maybe some of the problem, the candidates
are thinking they need to get into the detail design or something novel
from scratch. Where actually, saying you can use a pump and a safety
valve (or measuring the pressure electronically and using that to
control the speed of the pump motor) is a much better answer.
> Yet another stab: Use a pump that can provide the projected peak flow at
> a pressure of 3 bar, and connect a safety valve that opens at 3 bar.
> Obviously this wastes a lot of water, but we can fix that by feeding the
> spilled water back into the bucket.
One person did actually come up with that answer after some suggestions.
It's how the fuel system works in a car (fuel is bled back to the fuel
tank to maintain the correct pressure at the injectors).
Lots of candidates though started off by talking about using a secondary
holding container, pistons, springs, then motors and safety valves etc.
Maybe exactly because they have been studying mechanical engineering in
detail for the last 4 years they can't look at the bigger picture?
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>> and a 45 foot deep hole.
>
>
> Oh no! I got my units wrong. Make that hole another 55' 6" deeper.
Yes indeed, you have use the wrong units. Try metres (or meters work ok
too).
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Le 16/08/2016 à 12:58, scott a écrit :
>>> and a 45 foot deep hole.
>>
>>
>> Oh no! I got my units wrong. Make that hole another 55' 6" deeper.
>
> Yes indeed, you have use the wrong units. Try metres (or meters work ok
> too).
>
>
But nobody checked if it was to be installed on the moon, or on mars...
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On 8/16/2016 12:12 PM, Le_Forgeron wrote:
> Le 16/08/2016 à 12:58, scott a écrit :
>>>> and a 45 foot deep hole.
>>>
>>>
>>> Oh no! I got my units wrong. Make that hole another 55' 6" deeper.
>>
>> Yes indeed, you have use the wrong units. Try metres (or meters work ok
>> too).
>>
I'm old school. If I can't do it on the back of a fag packet in psi.
Then it is not worth doing. ;)
What we really want is a Heath Robinson version that works.
>>
> But nobody checked if it was to be installed on the moon, or on mars...
>
If it is not in the spec then it will cost extra. Probably best to leave
it to phase 2.
--
Regards
Stephen
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scott <sco### [at] scott com> wrote:
> Design a system to take the water from the bucket, and supply it into
> the pipe at a constant pressure (not a ridiculous pressure, just
> something like the pressure you would have in your water pipes at home,
> maybe 3 bar?).
Seal the top of the bucket with a "lid" having an integral pipe reaching the
bottom of the bucket to draw water off from the bottom. Use direct air pressure,
or a bladder, such as is used in well pressure-tank setups. Increase the
pressure above that of the required input flow.
Use a water pressure regulator on the output of that to supply the pipe.
I could probably come up with at least half a dozen variations on the same
theme.
Alternatively, one could reroute power from the main plasma conduit, and modify
the main deflector shield to generate a static inverse-graviton field to "lift"
the dihydrogen monoxide from its frustrum, out the directrix, and into the
flexible hollow cylinder affixed to the rgb <0, 0, 0> box {}.
:)
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> Alternatively, one could reroute power from the main plasma conduit, and modify
> the main deflector shield to generate a static inverse-graviton field
Be careful not to breach the manti-matter containment field...
Also, if you have access to all that, you might as well just teleport
the water from the bucket to the blackbox.
--
/*Francois Labreque*/#local a=x+y;#local b=x+a;#local c=a+b;#macro P(F//
/* flabreque */L)polygon{5,F,F+z,L+z,L,F pigment{rgb 9}}#end union
/* @ */{P(0,a)P(a,b)P(b,c)P(2*a,2*b)P(2*b,b+c)P(b+c,<2,3>)
/* gmail.com */}camera{orthographic location<6,1.25,-6>look_at a }
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