A quiz:

If you are a brand-name (say like "Barbie-less") for a previously large
chain store... one where America previously shopped; and you sell
dishwashers....

And said dishwasher has a center twirling arm to spray water around...
and the arm is secured with a large plastic screw with big shoulder.

Now, you can put the jets on the arm two ways: one rotates the arm so
that the screw, if anything, tightens itself...

And the other so the screw LOOSENS itself....so it backs out, falls out,
as does the arm....

So which way would you design it to rotate? Why?

Justify your response. 10 points. Responses quoting Feynman get extra
credit.

Question 2: Suppose your firm choose badly. How would solve it in the
field?

a) Epoxy screw into place

b) Throw arm away, with screw; tell customer it's an upgrade.

c) Figure out how to get screw to stop doing that.


--
A host is a host from coast to
& no one will talk to a host that's close........[v].(301) 56-LINUX
Unless the host (that isn't close).........................pob 1433
is busy, hung or dead....................................20915-1433

On 2009-09-20, David Lesher wrote:
A quiz:

If you are a brand-name (say like "Barbie-less") for a previously large
chain store... one where America previously shopped; and you sell
dishwashers....

And said dishwasher has a center twirling arm to spray water around...
and the arm is secured with a large plastic screw with big shoulder.

Now, you can put the jets on the arm two ways: one rotates the arm so
that the screw, if anything, tightens itself...

And hopefully, is prevented from doing so by the shoulder
itself.

And the other so the screw LOOSENS itself....so it backs out, falls out,
as does the arm....

So which way would you design it to rotate? Why?

What kind of service reputation is the firm looking for? Like
Maytag's with the service people dying of boredom, or shooting for quick
response and short time to repair?

Justify your response. 10 points. Responses quoting Feynman get extra
credit.

Question 2: Suppose your firm choose badly. How would solve it in the
field?

a) Epoxy screw into place

That eliminates the ability to service it in the future.
(Assuming that it is possible to get an epoxy to bond to the plastic in
question.)

b) Throw arm away, with screw; tell customer it's an upgrade.

Making for much poorer cleaning.

c) Figure out how to get screw to stop doing that.

In order of likely cost to the company:

1) Is it possible to put the arm onto its mount the other side
down so it screws the shoulder screw back in?

2) Chew some bubble gum, and apply it to the screw threads before
re-installing.

3) Pin the screw with A nylon screw drilled and tapped through the
block serving as the "nut" and into the threads of the shoulder
screw in question. Since it is presumably hollow, and cross
drilled to allow water to flow up into the arm, this means that
the nylon screw probably should be of a rather precise length.

4) Send out instructions on how to plug the existing spray holes
and drill new ones to cause the rotation to reverse. (This
requires service personel with the ability to do this well.
Perhaps the company would send out a fixture for this to each
service center.)

5) (Most expensive) -- send out new replacement arms which rotate
the other direction.

Enjoy,
DoN.

--
Email: | Voice (all times): (703) 938-4564
(too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html
--- Black Holes are where God is dividing by zero ---

Andrew VK3BFA wrote:
On Sep 20, 12:57 pm, David Lesher wrote:
A quiz:


Well, in no particular order.
1.Look in the bottom of said machine, see if wavy washer has fallen
off.
2.Write letter to manufacturer, congratulating them on installing pump
with enough power to loosen screws
3.See if such a complex dilemma is covered in the instruction manual.
After all, these screws are designed to be periodically removed so you
can clean the gunk out....
4. Who is Feynman?

Andrew VK3BFA.

-100 points for you!

http://en.wikipedia.org/wiki/Richard_Feynman

David

On Sun, 20 Sep 2009 02:57:28 +0000 (UTC), the infamous David Lesher
scrawled the following:

A quiz:

If you are a brand-name (say like "Barbie-less") for a previously large
chain store... one where America previously shopped; and you sell
dishwashers....

And said dishwasher has a center twirling arm to spray water around...
and the arm is secured with a large plastic screw with big shoulder.

Now, you can put the jets on the arm two ways: one rotates the arm so
that the screw, if anything, tightens itself...

And the other so the screw LOOSENS itself....so it backs out, falls out,
as does the arm....

So which way would you design it to rotate? Why?

Justify your response. 10 points. Responses quoting Feynman get extra
credit.

See logical 1&3 answer below.

"On the infrequent occasions when I have been called upon in a formal
place to play the bongo drums, the introducer never seems to find it
necessary to mention that I also do theoretical physics." --RF

http://en.wikiquote.org/wiki/File:At...eace_stamp.jpg


Question 2: Suppose your firm choose badly. How would solve it in the
field?

a) Epoxy screw into place

My LPEIIWCCI (underpaid injuneerz, see & below) say to use a Loctite
on the screws. (It can only be removed by heat and water, things
you'll be unlikely to encounter in a dishwashing scenario.


b) Throw arm away, with screw; tell customer it's an upgrade.

(Dilbert, is that you?)


c) Figure out how to get screw to stop doing that.

Bingo!

1) Design a longer screw which self-tightens (maybe one with a
shoulder which bottoms out, leaving the arm free to spin.)

OR

2) Design a locking shoulder into the base which allows a setscrew to
hold the plastic screw in place without falling out.

AND

3) Stop subbing out my engineering work to the very lowest paid
engineer in India's worst Call Center. They're biased with British
ways, the people who also gave us Lucas, Prince of Darkness products.

--
The scientific theory I like best is that the rings of Saturn
are composed entirely of lost airline luggage.
--Mark Russell

On Sun, 20 Sep 2009 04:59:30 -0500, the infamous "David R.Birch"
scrawled the following:

Andrew VK3BFA wrote:
On Sep 20, 12:57 pm, David Lesher wrote:
A quiz:


Well, in no particular order.
1.Look in the bottom of said machine, see if wavy washer has fallen
off.
2.Write letter to manufacturer, congratulating them on installing pump
with enough power to loosen screws
3.See if such a complex dilemma is covered in the instruction manual.
After all, these screws are designed to be periodically removed so you
can clean the gunk out....
4. Who is Feynman?

Andrew VK3BFA.

-100 points for you!

http://en.wikipedia.org/wiki/Richard_Feynman

I'll see you and raise you one:
http://en.wikiquote.org/wiki/Richard_Feynman

"Physics is like sex. Sure, it may give some practical results, but
that's not why we do it." --RF

--
The scientific theory I like best is that the rings of Saturn
are composed entirely of lost airline luggage.
--Mark Russell

On Sep 20, 7:59*pm, "David R.Birch" wrote:
Andrew VK3BFA wrote:
On Sep 20, 12:57 pm, David Lesher wrote:
A quiz:


4. Who is Feynman?

Andrew VK3BFA.

-100 points for you!

http://en.wikipedia.org/wiki/Richard_Feynman

David

Well, quantum physics depends on probability theory - so, if you can
find a Nobel Prize winning physicist, he should be able to calculate
the likelihood of the cat escaping from the sealed dishwasher before
it drowns and solving the problem....

Andrew VK3BFA.

Did you hear about the Quantum Computer?
It works...sometimes.

BTW - thanks for the reference, interesting chap.

"David R.Birch" writes:

4. Who is Feynman?

Andrew VK3BFA.

-100 points for you!

http://en.wikipedia.org/wiki/Richard_Feynman

More importantly; read up on Feynman and the sprinkler
problem.....

http://en.wikipedia.org/wiki/Feynman_sprinkler
--
A host is a host from coast to
& no one will talk to a host that's close........[v].(301) 56-LINUX
Unless the host (that isn't close).........................pob 1433
is busy, hung or dead....................................20915-1433

David Lesher wrote:

So which way would you design it to rotate? Why?

In a direction such that the fastener would tend to tighten. Why? Because is is obvious.

'The worthwhile problems are the ones you can really solve or help solve, the ones you can
really contribute something to."

Justify your response. 10 points. Responses quoting Feynman get extra
credit.

Question 2: Suppose your firm choose badly. How would solve it in the
field?

a) Epoxy screw into place

b) Throw arm away, with screw; tell customer it's an upgrade.

c) Figure out how to get screw to stop doing that.


C) Can you put a small oring on shoulder screw to give shoulder added friction?

Wes

David Lesher wrote:

Question 2: Suppose your firm choose badly. How would
solve it in the
field?


Perhaps an external-tooth lock washer would work? Search
www.mcmaster.com
for an external-tooth lock washer for an example.
phil

Larry Jaques wrote:
On Sun, 20 Sep 2009 04:59:30 -0500, the infamous "David R.Birch"
scrawled the following:


Andrew VK3BFA wrote:

On Sep 20, 12:57 pm, David Lesher wrote:

A quiz:



Well, in no particular order.
1.Look in the bottom of said machine, see if wavy washer has fallen
off.
2.Write letter to manufacturer, congratulating them on installing pump
with enough power to loosen screws
3.See if such a complex dilemma is covered in the instruction manual.
After all, these screws are designed to be periodically removed so you
can clean the gunk out....
4. Who is Feynman?

Andrew VK3BFA.

-100 points for you!

http://en.wikipedia.org/wiki/Richard_Feynman


I'll see you and raise you one:
http://en.wikiquote.org/wiki/Richard_Feynman

"Physics is like sex. Sure, it may give some practical results, but
that's not why we do it." --RF

--
The scientific theory I like best is that the rings of Saturn
are composed entirely of lost airline luggage.
--Mark Russell


I thought they were just billions of "checks in the mail" which never
seemed to get delivered.

Jeff

--
Jeffry Wisnia
(W1BSV + Brass Rat '57 EE)
The speed of light is 1.8*10e12 furlongs per fortnight.

David Lesher wrote:
A quiz:

If you are a brand-name (say like "Barbie-less") for a previously large
chain store... one where America previously shopped; and you sell
dishwashers....

And said dishwasher has a center twirling arm to spray water around...
and the arm is secured with a large plastic screw with big shoulder.

Take plastic screw into shop. Turn new stainless screw out of bar stock.
In stainless screw install a nylon insert OR cut shoulder so that a star
style lock washer can be used.

Second approach. Pull the bottom arm and ream out the threads, press in
a new insert with the opposite threads. Then make a new screw with the
proper threads.

Third approach. Turn a stud with the proper thread and a shoulder. Cut
threads on top in the opposite thread. Use good locktite to install the
stud. Then install the proper nut on top.


Now, you can put the jets on the arm two ways: one rotates the arm so
that the screw, if anything, tightens itself...

And the other so the screw LOOSENS itself....so it backs out, falls out,
as does the arm....

So which way would you design it to rotate? Why?

Justify your response. 10 points. Responses quoting Feynman get extra
credit.

Question 2: Suppose your firm choose badly. How would solve it in the
field?

a) Epoxy screw into place

b) Throw arm away, with screw; tell customer it's an upgrade.

c) Figure out how to get screw to stop doing that.




--
Steve W.

On Sun, 20 Sep 2009 17:26:04 +0000, David Lesher wrote:
"David R.Birch" writes:

4. Who is Feynman?

Andrew VK3BFA.

-100 points for you!

http://en.wikipedia.org/wiki/Richard_Feynman

More importantly; read up on Feynman and the sprinkler problem.....

http://en.wikipedia.org/wiki/Feynman_sprinkler

Why is that a problem? When sucking the fluid out, the pressure on the
"nozzle" side is reduced, so the pressure on the opposite side _pushes_
the sprinkler arms "in reverse". Probably not as fast as the jets would
push it forward, but it seems ovbious that it would turn "in reverse".

It's like sucking an egg into a milk bottle. The milk bottle doesn't
"suck" anything - atmospheric pressure _pushes_ the egg into the bottle.

To do this experiment, you need an old-fashioned milk bottle, or any
bottle whose mouth diameter is slightly less than the minor diameter
of a boiled egg. Light a piece of paper, drop the burning paper into
the bottle, and set the egg on top.

Cheers!
Rich

On Sun, 20 Sep 2009 02:57:28 +0000, David Lesher wrote:
A quiz:

If you are a brand-name (say like "Barbie-less") for a previously large
chain store... one where America previously shopped; and you sell
dishwashers....

And said dishwasher has a center twirling arm to spray water around... and
the arm is secured with a large plastic screw with big shoulder.

Now, you can put the jets on the arm two ways: one rotates the arm so that
the screw, if anything, tightens itself...

WHy is this a problem? The screw will only "tighten itself" until the
shoulder bottoms out, which they should have done at the factory.

So, clockwise.

Cheers!
Rich

On Sun, 20 Sep 2009 18:04:21 -0400, Wes wrote:
David Lesher wrote:

So which way would you design it to rotate? Why?

C) Can you put a small oring on shoulder screw to give shoulder added
friction?

I wouldn't use it for that; I'd use it to improve the seal between the
shoulder and the frame.

The screw has to be hollow with a few ports in the shoulder; otherwise,
how does the water get to the arm?

Thanks,
Rich

Rich Grise wrote:
On Sun, 20 Sep 2009 17:26:04 +0000, David Lesher wrote:
"David R.Birch" writes:

4. Who is Feynman?

Andrew VK3BFA.
-100 points for you!
http://en.wikipedia.org/wiki/Richard_Feynman
More importantly; read up on Feynman and the sprinkler problem.....

http://en.wikipedia.org/wiki/Feynman_sprinkler

Why is that a problem? When sucking the fluid out, the pressure on the
"nozzle" side is reduced, so the pressure on the opposite side _pushes_
the sprinkler arms "in reverse". Probably not as fast as the jets would
push it forward, but it seems ovbious that it would turn "in reverse".

It's like sucking an egg into a milk bottle. The milk bottle doesn't
"suck" anything - atmospheric pressure _pushes_ the egg into the bottle.

To do this experiment, you need an old-fashioned milk bottle, or any
bottle whose mouth diameter is slightly less than the minor diameter
of a boiled egg. Light a piece of paper, drop the burning paper into
the bottle, and set the egg on top.

Cheers!
Rich



If you say so...

But let's see you "push" it back out!

"cavelamb" wrote in message
...
Rich Grise wrote:
On Sun, 20 Sep 2009 17:26:04 +0000, David Lesher wrote:
"David R.Birch" writes:

4. Who is Feynman?

Andrew VK3BFA.
-100 points for you!
http://en.wikipedia.org/wiki/Richard_Feynman
More importantly; read up on Feynman and the sprinkler problem.....

http://en.wikipedia.org/wiki/Feynman_sprinkler

Why is that a problem? When sucking the fluid out, the pressure on the
"nozzle" side is reduced, so the pressure on the opposite side _pushes_
the sprinkler arms "in reverse". Probably not as fast as the jets would
push it forward, but it seems ovbious that it would turn "in reverse".

It's like sucking an egg into a milk bottle. The milk bottle doesn't
"suck" anything - atmospheric pressure _pushes_ the egg into the bottle.

To do this experiment, you need an old-fashioned milk bottle, or any
bottle whose mouth diameter is slightly less than the minor diameter
of a boiled egg. Light a piece of paper, drop the burning paper into
the bottle, and set the egg on top.

Cheers!
Rich



If you say so...

But let's see you "push" it back out!

Easy.
Drop a piece of dry ice in and hold the bottle neck down.

Paul K. Dickman

On Sep 21, 3:27*pm, cavelamb wrote:
Rich Grise wrote:
On Sun, 20 Sep 2009 17:26:04 +0000, David Lesher wrote:
"David R.Birch" writes:

4. Who is Feynman?

Andrew VK3BFA.
-100 points for you!
http://en.wikipedia.org/wiki/Richard_Feynman
More importantly; read up on Feynman and the sprinkler problem.....

http://en.wikipedia.org/wiki/Feynman_sprinkler

Why is that a problem? When sucking the fluid out, the pressure on the
"nozzle" side is reduced, so the pressure on the opposite side _pushes_
the sprinkler arms "in reverse". Probably not as fast as the jets would
push it forward, but it seems ovbious that it would turn "in reverse".

It's like sucking an egg into a milk bottle. The milk bottle doesn't
"suck" anything - atmospheric pressure _pushes_ the egg into the bottle..

To do this experiment, you need an old-fashioned milk bottle, or any
bottle whose mouth diameter is slightly less than the minor diameter
of a boiled egg. Light a piece of paper, drop the burning paper into
the bottle, and set the egg on top.

Cheers!
Rich

If you say so...

But let's see you "push" it back out!

OK -

Bottle upside down (egg covering mouth of bottle).
Blow into bottle, pressurizing the air inside - egg acts as check
valve
After building up some pressure, remove your mouth from bottle
Egg pops right out.

My father showed me this in maybe first grade while we were discussing
the workings of a seltzer bottle.

Deform the screw somehow to get it to act like a nylock?

Dunno what RF would say, but you can bet it would be clever.

Halfway off the subject, I always thought that dishwashers should have
glass doors so you can see what's going on in there.

What kind of service reputation is the firm looking for? Like
Maytag's with the service people dying of boredom, or shooting for quick
response and short time to repair?



Do like GE, I registered a new waver online and immediately saw a tenfold
increase in spam. Good thing I use a yahoo eddress for contact with
strangers.

Paul K. Dickman wrote:
"cavelamb" wrote in message
...
Rich Grise wrote:
On Sun, 20 Sep 2009 17:26:04 +0000, David Lesher wrote:
"David R.Birch" writes:

4. Who is Feynman?

Andrew VK3BFA.
-100 points for you!
http://en.wikipedia.org/wiki/Richard_Feynman
More importantly; read up on Feynman and the sprinkler problem.....

http://en.wikipedia.org/wiki/Feynman_sprinkler
Why is that a problem? When sucking the fluid out, the pressure on the
"nozzle" side is reduced, so the pressure on the opposite side _pushes_
the sprinkler arms "in reverse". Probably not as fast as the jets would
push it forward, but it seems ovbious that it would turn "in reverse".

It's like sucking an egg into a milk bottle. The milk bottle doesn't
"suck" anything - atmospheric pressure _pushes_ the egg into the bottle.

To do this experiment, you need an old-fashioned milk bottle, or any
bottle whose mouth diameter is slightly less than the minor diameter
of a boiled egg. Light a piece of paper, drop the burning paper into
the bottle, and set the egg on top.

Cheers!
Rich


If you say so...

But let's see you "push" it back out!

Easy.
Drop a piece of dry ice in and hold the bottle neck down.

Paul K. Dickman



Sounds plausible at first glance, but that egg is going to freeze
a long time before the ice sublimates enough to push the egg out.

Maybe tomorrow?

On Mon, 21 Sep 2009 16:17:24 -0500, cavelamb wrote:
Paul K. Dickman wrote:
"cavelamb" wrote in message
Rich Grise wrote:
On Sun, 20 Sep 2009 17:26:04 +0000, David Lesher wrote:
"David R.Birch" writes:

4. Who is Feynman?

Andrew VK3BFA.
-100 points for you!
http://en.wikipedia.org/wiki/Richard_Feynman
More importantly; read up on Feynman and the sprinkler problem.....

http://en.wikipedia.org/wiki/Feynman_sprinkler
Why is that a problem? When sucking the fluid out, the pressure on the
"nozzle" side is reduced, so the pressure on the opposite side
_pushes_ the sprinkler arms "in reverse". Probably not as fast as the
jets would push it forward, but it seems ovbious that it would turn
"in reverse".

It's like sucking an egg into a milk bottle. The milk bottle doesn't
"suck" anything - atmospheric pressure _pushes_ the egg into the
bottle.

To do this experiment, you need an old-fashioned milk bottle, or any
bottle whose mouth diameter is slightly less than the minor diameter
of a boiled egg. Light a piece of paper, drop the burning paper into
the bottle, and set the egg on top.

If you say so...

But let's see you "push" it back out!

Easy.
Drop a piece of dry ice in and hold the bottle neck down.

Sounds plausible at first glance, but that egg is going to freeze a long
time before the ice sublimates enough to push the egg out.

Maybe tomorrow?

He didn't specify "push it out _whole_". ;-)

(the time we did it, about a half-century ago, it didn't even go _in_
whole! The white tore as it went into the neck.)

Cheers!
Rich

On Sep 21, 3:26*am, David Lesher wrote:
"David R.Birch" writes:
4. Who is Feynman?


More importantly; read up on Feynman and the sprinkler
problem.....

http://en.wikipedia.org/wiki/Feynman_sprinkler
--
Mmm, ok, add that one to the list of things I dont understand - I have
trouble cutting threads consistently, so that sort of experimental
physics is a bit beyond me. But, nice to know there are REALLY smart
people out there.

Andrew VK3BFA.

Rich Grise writes:


The screw has to be hollow with a few ports in the shoulder; otherwise,
how does the water get to the arm?

Around the screw. See my picture...

--
A host is a host from coast to
& no one will talk to a host that's close........[v].(301) 56-LINUX
Unless the host (that isn't close).........................pob 1433
is busy, hung or dead....................................20915-1433

Rich Grise writes:

More importantly; read up on Feynman and the sprinkler problem.....

http://en.wikipedia.org/wiki/Feynman_sprinkler

Why is that a problem? When sucking the fluid out, the pressure on the
"nozzle" side is reduced, so the pressure on the opposite side _pushes_
the sprinkler arms "in reverse". Probably not as fast as the jets would
push it forward, but it seems ovbious that it would turn "in reverse".

Well, sometimes obvious is not. Read what RF said.

(And yep, this has little to do with my issue, but it is rather
interesting....)
--
A host is a host from coast to
& no one will talk to a host that's close........[v].(301) 56-LINUX
Unless the host (that isn't close).........................pob 1433
is busy, hung or dead....................................20915-1433

Rich Grise wrote:

C) Can you put a small oring on shoulder screw to give shoulder added
friction?

I wouldn't use it for that; I'd use it to improve the seal between the
shoulder and the frame.

The screw has to be hollow with a few ports in the shoulder; otherwise,
how does the water get to the arm?


I was thinking of the thread/shoulder intersection.

Wes
--
"Additionally as a security officer, I carry a gun to protect
government officials but my life isn't worth protecting at home
in their eyes." Dick Anthony Heller

David Lesher wrote:

Question 2: Suppose your firm choose badly. How would
you solve it in the field?



So, ah, umm, hesitant to ask, but, how did you guys solve it
in the field?
phil

David Lesher the troll wrote:

Question 2: Suppose your firm choose badly. How would
you solve it in the field?
( We have this problem with one of our appliances and cannot
figure out how to solve it in the field so I'll post the
question to
RCM and see what comes up. If any suggestions are good we
will claim them as ours and declare them proprietary
information.
We don't want an easy fix to become public knowledge as
that'll
cost us a lot of money. We are in it for the profit you
know.)



So, ah, umm, hesitant to ask, but, how did you guys solve
it
in the field?
phil