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Re: How many Refills

Posted: 20 Apr 2018, 18:54
by evilcheadar
deleted_user wrote:Do you recycle the plastic bubble or get a new one each time?

I get a new straw and plastic bubble each time. Your inquiry does beg the question of how long can a full “unit” last. I predict the straw would fail first.

Re: How many Refills

Posted: 20 Apr 2018, 19:19
by fightinfrenchman
evilcheadar wrote:
deleted_user wrote:Do you recycle the plastic bubble or get a new one each time?

I get a new straw and plastic bubble each time. Your inquiry does beg the question of how long can a full “unit” last. I predict the straw would fail first.


I feel that the plastic bubble would last nearly indefinitely, considering how little stress it is under

Re: How many Refills

Posted: 22 Apr 2018, 00:16
by evilcheadar
Refill #5 I believe. The cup holds steady.

Re: How many Refills

Posted: 22 Apr 2018, 00:18
by momuuu
But what pool cleaner should I use? Let's stop discussing these idle subjects and get to the real matter!

Re: How many Refills

Posted: 22 Apr 2018, 00:25
by evilcheadar
momuuu wrote:But what pool cleaner should I use? Let's stop discussing these idle subjects and get to the real matter!

I have the ray-vac (see my profile pic). @fightinfrenchman and @gustavusadolphus are the experts on these pool robots, however.

Re: How many Refills

Posted: 25 Apr 2018, 02:38
by evilcheadar
Fresh refill. Cup shows a little scuffing but it’s not bad. They didn’t have gobstoppers at T-Hill so I had to go to weis family owned markets to get some.

Re: How many Refills

Posted: 25 Apr 2018, 02:44
by Jam
Brain freeze tally.

Re: How many Refills

Posted: 25 Apr 2018, 02:54
by evilcheadar
Jam wrote:Brain freeze tally.

0 brain freezes. I’m just not that susceptible to them.

Re: How many Refills

Posted: 25 Apr 2018, 15:58
by dietschlander
I like this project so far, that'll be all

Re: How many Refills

Posted: 27 Apr 2018, 00:36
by evilcheadar
Got a fresh refill. I’m really thankful there are 2 coke slush machines as one was not operational.

Re: How many Refills

Posted: 27 Apr 2018, 01:52
by kami_ryu
-- deleted post --

Re: How many Refills

Posted: 27 Apr 2018, 01:54
by deleted_user
kami_ryu wrote:do you not pay for refills?

Likely discounted.

Re: How many Refills

Posted: 27 Apr 2018, 01:57
by evilcheadar
deleted_user wrote:
kami_ryu wrote:do you not pay for refills?

Likely discounted.

correct

Re: How many Refills

Posted: 27 Apr 2018, 03:00
by gustavusadolphus
cheaadar had a very close call on the way over almost sitting on his cup. He also put his keys in it which I think is an unnecessary risk.

Re: How many Refills

Posted: 27 Apr 2018, 03:07
by gustavusadolphus
momuuu wrote:But what pool cleaner should I use? Let's stop discussing these idle subjects and get to the real matter!


Polaris robotic pool cleaners ( the ones that came after the Rayvac in cheadar's profile pic) contain a large amount styrofoam very similar in quality to the slushy cup. I wish I could find a picture of this foam but it appears Polaris does not want to advertise their product if full of a bunch of styrofoam. I'm sure Ear has a picture or two form his many cleaner repairs. The styrofoam was one of the few parts of the cleaner that did not break even with the harsh pool chemical environment so I think physical trauma will win the day in this venture rather than chemical degradation of the foam.

Re: How many Refills

Posted: 06 May 2018, 23:38
by evilcheadar
Fresh refill, cup shows some wear.

Re: How many Refills

Posted: 07 May 2018, 01:38
by gustavusadolphus
evilcheadar wrote:Fresh refill, cup shows some wear.

Does not look like a full refill.

Re: How many Refills

Posted: 07 May 2018, 05:03
by deleted_user
Whoa boy there are a lot of little dings in that sucker. Here's something for consideration: the critical Griffith crack length.

Griffith studied fracture mechanics in the early 1900s when the only mechanics of materials concepts around were simply stress and strain. When a little scratch happens like that on your cup, or in the metal of a ship hull, the material has "yielded," it has surpassed its tensile strength, surpassed its yield stress and theoretically it can hold no load and the structure is in danger of collapse. But of course, this is not really how things work because metal gets dinged up all the time, the golden gate bridge has scratches on it, and still structures survive.

Griffith explained why this is by approaching the problem in terms of energy rather than just stress and strain. There is a certain amount of energy that a crack needs to automatically propagate. A stress concentration (crack) is just a means of converting strain energy to fracture energy, like how a can-opener converts muscle energy into mechanical energy -- if there is no continuous energy put into the opener it fails to do anything. So while stress concentrations exist in a crack, the material can release some of its internal strain energy to keep the net energy in the system less than what needs to propagate the crack, for a certain length of crack, that is. The critical Griffith crack length is explained graphically here:

Image

Essentially, in a closed energy system, when stresses exist (when your cup is full) and a crack forms, there is a critical, acceptable length until it propagates until acted upon. What is the critical Griffith crack length of your cup?

Consider the formula:
Image

Modern foam cups are polystyrene. Polystyrene Properties:
E = 0.4 x10^6 psi
W = 5.5 ft-lbf/in^2 = 66 in-lbf/in^2
S = 6200 psi

Then,

Lg = 0.45 inches (approximately)

Sources:

1) http://www.arvindguptatoys.com/arvindgu ... gordon.pdf
2) http://www.dielectriccorp.com/downloads ... tyrene.pdf

Re: How many Refills

Posted: 07 May 2018, 05:22
by Snuden
deleted_user wrote:Whoa boy there are a lot of little dings in that sucker. Here's something for consideration: the critical Griffith crack length.

Griffith studied fracture mechanics in the early 1900s when the only mechanics of materials concepts around were simply stress and strain. When a little scratch happens like that on your cup, or in the metal of a ship hull, the material has "yielded," it has surpassed its tensile strength, surpassed its yield stress and theoretically it can hold no load and the structure is in danger of collapse. But of course, this is not really how things work because metal gets dinged up all the time, the golden gate bridge has scratches on it, and still structures survive.

Griffith explained why this is by approaching the problem in terms of energy rather than just stress and strain. There is a certain amount of energy that a crack needs to automatically propagate. A stress concentration (crack) is just a means of converting strain energy to fracture energy, like how a can-opener converts muscle energy into mechanical energy -- if there is no continuous energy put into the opener it fails to do anything. So while stress concentrations exist in a crack, the material can release some of its internal strain energy to keep the net energy in the system less than what needs to propagate the crack, for a certain length of crack, that is. The critical Griffith crack length is explained graphically here:

Image

Essentially, in a closed energy system, when stresses exist (when your cup is full) and a crack forms, there is a critical, acceptable length until it propagates until acted upon. What is the critical Griffith crack length of your cup?

Consider the formula:
Image

Modern foam cups are polystyrene. Polystyrene Properties:
E = 0.4 x10^6 psi
W = 5.5 ft-lbf/in^2 = 66 in-lbf/in^2
S = 6200 psi

Then,

Lg = 0.45 inches (approximately)

Sources:

1) http://www.arvindguptatoys.com/arvindgu ... gordon.pdf
2) http://www.dielectriccorp.com/downloads ... tyrene.pdf

Please edit your post a little, cracks and scratches are two different things.

Re: How many Refills

Posted: 07 May 2018, 05:24
by deleted_user
They are different but defects all the same -- scratches can lead to cracks. I'm cautioning him to be wary!

Re: How many Refills

Posted: 07 May 2018, 05:29
by Snuden
If I may...

Scratches and cracks are per definition "imperfections" rather than "defects"
Codes allow for imperfections, but rarely (if ever) for defects.

Some codes allow for cracks, if they don't exceed a certain length and/or depth. It is advised that regular inspection intervals are done in order to monitor crack growth.

Re: How many Refills

Posted: 07 May 2018, 05:34
by Snuden
I have an interesting case from a heat exchanger company in Nanjing, they claimed that what we found (using Eddy Current NDT) in their Super Duplex tubes where scratches, thus allowed. I claimed it was cracks, thus not allowed (as per applicable code)

We pulled out a few tubes, cut them in half and look at it in a microscope - it was cracks.

I can find some pictures, which I can show you in Amsterdam while sharing a bong.

Re: How many Refills

Posted: 07 May 2018, 05:49
by Snuden
Here is what I would do with the cup;

1. Find out minimum required wallthickness of the cup
2. Examine the scratched area with PT (Penetrant Testing)
3. If it is only a scratch - grind the areas smooth in order to remove stress concentration.
4. Measure the wallthickness after grinding

Re: How many Refills

Posted: 07 May 2018, 05:52
by Snuden
I almost forgot....

Pre-cool the cup before pouring ice cold liquid into it.

Re: How many Refills

Posted: 07 May 2018, 05:54
by deleted_user
What's funny is that disposable cups are made from expanded polystyrene foam (EPS) and not solid polystyrene (what my properties are from). I've spent an hour looking for the right mechanical properties of EPS but no bueno so it's all wrong, all wrong but possible with all reduced values a similar length is come to.

Solid polystyrene is like CD cases.