6 ms·

Towards a Better Pythagorean Cup

113 points by jstanley 8y ago

walrus01 8y ago
For anyone thinking of buying a 3D printer, there's some pretty decent options that don't cost a ridiculous amount now... I have no financial interest in any of these manufacturers or vendors, just passing on what's been reported to be good quality by various people. At the cheaper end of the scale there is the Alfawise U30 which is $175 + $20 shipping from china: https://www.google.com/search?client=ubuntu&channel=fs&q=u30+3d+printer&ie=utf-8&oe=utf-8 https://www.google.com/search?client=ubuntu&channel=fs&q=u30... Then there is the Creality CR-10S (note the S, not the original CR-10 model) which is $369 https://www.google.com/search?client=ubuntu&channel=fs&q=creality+cr-10s&ie=utf-8&oe=utf-8 https://www.google.com/search?client=ubuntu&channel=fs&q=cre... Search for either of those on youtube and you'll see some example setup and test print videos. The U30 is very new so a lot of the test/setup videos are in French or Italian. For people who want to try printing something really big, there's a 500x500x500mm capable version of the CR-10S which is called the CR-10S5, which sells for around $629. Lots of videos on youtube of the output from that. It's not supremely high quality in terms of print, like you would get from a $3500 500mm size 3D printer, but it's also a tiny fraction of the price.
- oh_sigh 8y ago
  Also, unless you have big plans for an in-home 3d printer, there is nothing wrong with getting access to one via a friend, coworker, library, or maker-space and essentially just paying for filaments. I wouldn't be surprised if in-home 3d printers sit idle for 95+% of the time. I was about to drop about $1000 on one for some hobby projects, but then found out my local library had a $6000 machine which I could use for essentially free(I'd be paying for filaments regardless), so long as I scheduled my prints a week in advance.
  - StavrosK 8y ago
    This is both very true and a bit false. My 3D printer sits idle more than 95% of the time, but I just could not have done what I do unless I had one right next to me so I could iterate quickly. I usually need to do 4-5 iterations of something to get all the tolerances and details right, which cannot be scheduled a week in advance. However, if you can share a printer with someone and have low-latency access to it, definitely do not buy your own, just use that.
- StavrosK 8y ago
  I have heard good things about the Creality printers, but the Alfawise sounds a bit too cheap to me (read: low quality/might catch on fire). I've also heard bad things about the Bowden extruder (leads to failed prints a lot). I would recommend a Wanhao i3 Plus mk2, I have one and it's a great piece of hardware, plus it's very popular so there are tons of upgrade that you can print for free.
- heywire 8y ago
  The CR-10’s little brother, the Ender 3, is a great starting machine for the technically inclined. I have one and love it. I paid $179 from Banggood last year.
- lozaning 8y ago
  I've got a refurb Monoprice maker select mini at home I think I paid ~$100 for that prints like a champion. Brint build area is not super big, but it's large enough for what i need most of the time. No setup or fiddling with the thing for hours before your first print either which is nice.
  - walrus01 8y ago
    Monoprice also sells a range of PLA filament at good prices. Nothing ever gets perfect reviews, but the consensus seems to be that it's about as good as the Amazon house brand PLA filament.
- deleted 8y ago
  [deleted]
nielsbot 8y ago
Great follow up.. Thanks.
tejtm 8y ago
I wonder if the flow could be improved by smoothing the inside of the siphon tube, perhaps pumping a mild solvent through at high velocity for a little bit would streamline the interior surface. As it is each printed layer is apt to contribute some turbulence.
- justtopost 8y ago
  In automotive racing where standard porting is verboten, an abrasive slurry of a gritty putty consististancy is pumped through at pressure to smooth the transitions. I think ford even used it for a few performance manifolds. Commonly called extrude honing. https://en.m.wikipedia.org/wiki/Abrasive_flow_machining https://en.m.wikipedia.org/wiki/Abrasive_flow_machining
jacknews 8y ago
Another here: https://www.thingiverse.com/thing:257680 https://www.thingiverse.com/thing:257680 Always good to have choice.
deleted 8y ago
[deleted]
adityapurwa 8y ago
I still don’t understand what is the purpose of having such a cup, wouldn’t it just waste the water or used to limit the amount of water? Anyone could help me, what is the usage and purpose of P cup?
- lcuff 8y ago
  I'm gonna say "for the fun of it" and "use for practical jokes" (choose your victim and context carefully!
- tejtm 8y ago
  Science! pleasure can be found in something behaving in an unexpected manner. for example, a cup that empties itself without overflowing the brim, but only if you fill it beyond a certain point.
- willchang 8y ago
  Toilets work the same way! When water in the bowl rises to above the highest point in the drain, everything (hopefully) siphons out.
- andrewflnr 8y ago
  It's pretty much entirely a cool trick and a joke. It was framed as a social commentary on gluttony, but I doubt that was ever the real reason for it or taken seriously in any way. It's just a cool thingy.
siliconc0w 8y ago
I think the point of the cup was that you wouldn't overfill it with wine without losing it in your lap thus encouraging moderation. A pythagorean mug doesn't quite make sense.
- alanbernstein 8y ago
  Is coffee not worthy of moderation? Is there something wrong with drinking alcohol from a mug?
  - jelly_dev 8y ago
    Best way to get ready for work in the morning
dahart 8y ago
> The handle looks rather contrived Maybe you could stuff a dozen flat little drain pipes all the way around the walls of the cup, in addition to or as an alternative to routing through the handle. That way the handle could be petite and unsuspicious. Would that be harder to reliably print?
- jstanley 8y ago
  I actually wanted to do this, and went as far as drawing a sketch on paper, but then I realised it would be impossible to drink from :). As soon as you tilt the cup towards your lips the nearest tubes would fill up and start siphoning.
  - dahart 8y ago
    That is a really good point that didn't occur to me. So, how about winding all the tubes together around the cup in a spiral? That would keep the high point always above the liquid line, unless the cup is sitting flat when over-filled, wouldn't it?
    - jstanley 8y ago
      What a great idea. That seems like it would work! The high point of each siphon could be exactly opposite the entry point. The siphons would need to cross past each other, but only 2 at any one point need to cross, which I think is manageable. Maybe my Pythagorean cup rabbithole is still not over...
      - dahart 8y ago
        > Maybe my Pythagorean cup rabbithole is still not over... I'm sorry! ;) And I will love to see it printed and/or turned into another post.
        jstanley 8y ago
        On second thoughts, I still don't think it would work. As you tilt the cup towards your lips, if the "highest" siphon pickup is still submerged, then that will correspond to the "lowest" siphon top and it will start siphoning anyway. It would work as long as it could be arranged that the pickup would become exposed to air before the siphon started siphoning, but I'm not sure that's possible while still retaining the property that it self-starts when overfilled. Also, even if the tube doesn't siphon because the pickup is exposed to air, there would still be liquid in the tube, some of which would get pushed over the top and leak out the bottom whenever you try to drink.
peter_retief 8y ago
I would love to find some sort of application for the p-cup (Besides pranking people that is) Maybe a cistern with less moving parts, indoor irrigation, pet water dispenser Should maybe make an "ask HN" ?
- chatmasta 8y ago
  I was wondering the same. Pet food dispenser sounds reasonable. This is a literal manifestation of the “leaky bucket” rate limiting algorithm.
- TeMPOraL 8y ago
  Flush toilets are a very well known and popular examples of p-cups. The toilet bowl has a siphon built-in, which drains the bowl with its contents when the water reaches high enough level.

113 points by jstanley 8y ago

For anyone thinking of buying a 3D printer, there's some pretty decent options that don't cost a ridiculous amount now... I have no financial interest in any of these manufacturers or vendors, just passing on what's been reported to be good quality by various people. At the cheaper end of the scale there is the Alfawise U30 which is $175 + $20 shipping from china: https://www.google.com/search?client=ubuntu&channel=fs&q=u30+3d+printer&ie=utf-8&oe=utf-8 https://www.google.com/search?client=ubuntu&channel=fs&q=u30... Then there is the Creality CR-10S (note the S, not the original CR-10 model) which is $369 https://www.google.com/search?client=ubuntu&channel=fs&q=creality+cr-10s&ie=utf-8&oe=utf-8 https://www.google.com/search?client=ubuntu&channel=fs&q=cre... Search for either of those on youtube and you'll see some example setup and test print videos. The U30 is very new so a lot of the test/setup videos are in French or Italian. For people who want to try printing something really big, there's a 500x500x500mm capable version of the CR-10S which is called the CR-10S5, which sells for around $629. Lots of videos on youtube of the output from that. It's not supremely high quality in terms of print, like you would get from a $3500 500mm size 3D printer, but it's also a tiny fraction of the price.

oh_sigh 8y ago
Also, unless you have big plans for an in-home 3d printer, there is nothing wrong with getting access to one via a friend, coworker, library, or maker-space and essentially just paying for filaments. I wouldn't be surprised if in-home 3d printers sit idle for 95+% of the time. I was about to drop about $1000 on one for some hobby projects, but then found out my local library had a $6000 machine which I could use for essentially free(I'd be paying for filaments regardless), so long as I scheduled my prints a week in advance.
- StavrosK 8y ago
  This is both very true and a bit false. My 3D printer sits idle more than 95% of the time, but I just could not have done what I do unless I had one right next to me so I could iterate quickly. I usually need to do 4-5 iterations of something to get all the tolerances and details right, which cannot be scheduled a week in advance. However, if you can share a printer with someone and have low-latency access to it, definitely do not buy your own, just use that.
StavrosK 8y ago
I have heard good things about the Creality printers, but the Alfawise sounds a bit too cheap to me (read: low quality/might catch on fire). I've also heard bad things about the Bowden extruder (leads to failed prints a lot). I would recommend a Wanhao i3 Plus mk2, I have one and it's a great piece of hardware, plus it's very popular so there are tons of upgrade that you can print for free.
heywire 8y ago
The CR-10’s little brother, the Ender 3, is a great starting machine for the technically inclined. I have one and love it. I paid $179 from Banggood last year.
lozaning 8y ago
I've got a refurb Monoprice maker select mini at home I think I paid ~$100 for that prints like a champion. Brint build area is not super big, but it's large enough for what i need most of the time. No setup or fiddling with the thing for hours before your first print either which is nice.
- walrus01 8y ago
  Monoprice also sells a range of PLA filament at good prices. Nothing ever gets perfect reviews, but the consensus seems to be that it's about as good as the Amazon house brand PLA filament.
deleted 8y ago
[deleted]

nielsbot 8y ago

Great follow up.. Thanks.

tejtm 8y ago

I wonder if the flow could be improved by smoothing the inside of the siphon tube, perhaps pumping a mild solvent through at high velocity for a little bit would streamline the interior surface. As it is each printed layer is apt to contribute some turbulence.

justtopost 8y ago
In automotive racing where standard porting is verboten, an abrasive slurry of a gritty putty consististancy is pumped through at pressure to smooth the transitions. I think ford even used it for a few performance manifolds. Commonly called extrude honing. https://en.m.wikipedia.org/wiki/Abrasive_flow_machining https://en.m.wikipedia.org/wiki/Abrasive_flow_machining

jacknews 8y ago

Another here: https://www.thingiverse.com/thing:257680 https://www.thingiverse.com/thing:257680 Always good to have choice.

deleted 8y ago

[deleted]

adityapurwa 8y ago

I still don’t understand what is the purpose of having such a cup, wouldn’t it just waste the water or used to limit the amount of water? Anyone could help me, what is the usage and purpose of P cup?

lcuff 8y ago
I'm gonna say "for the fun of it" and "use for practical jokes" (choose your victim and context carefully!
tejtm 8y ago
Science! pleasure can be found in something behaving in an unexpected manner. for example, a cup that empties itself without overflowing the brim, but only if you fill it beyond a certain point.
willchang 8y ago
Toilets work the same way! When water in the bowl rises to above the highest point in the drain, everything (hopefully) siphons out.
andrewflnr 8y ago
It's pretty much entirely a cool trick and a joke. It was framed as a social commentary on gluttony, but I doubt that was ever the real reason for it or taken seriously in any way. It's just a cool thingy.

siliconc0w 8y ago

I think the point of the cup was that you wouldn't overfill it with wine without losing it in your lap thus encouraging moderation. A pythagorean mug doesn't quite make sense.

alanbernstein 8y ago
Is coffee not worthy of moderation? Is there something wrong with drinking alcohol from a mug?
- jelly_dev 8y ago
  Best way to get ready for work in the morning

dahart 8y ago

> The handle looks rather contrived Maybe you could stuff a dozen flat little drain pipes all the way around the walls of the cup, in addition to or as an alternative to routing through the handle. That way the handle could be petite and unsuspicious. Would that be harder to reliably print?

jstanley 8y ago
I actually wanted to do this, and went as far as drawing a sketch on paper, but then I realised it would be impossible to drink from :). As soon as you tilt the cup towards your lips the nearest tubes would fill up and start siphoning.
- dahart 8y ago
  That is a really good point that didn't occur to me. So, how about winding all the tubes together around the cup in a spiral? That would keep the high point always above the liquid line, unless the cup is sitting flat when over-filled, wouldn't it?
  - jstanley 8y ago
    What a great idea. That seems like it would work! The high point of each siphon could be exactly opposite the entry point. The siphons would need to cross past each other, but only 2 at any one point need to cross, which I think is manageable. Maybe my Pythagorean cup rabbithole is still not over...
    - dahart 8y ago
      > Maybe my Pythagorean cup rabbithole is still not over... I'm sorry! ;) And I will love to see it printed and/or turned into another post.
      - jstanley 8y ago
        On second thoughts, I still don't think it would work. As you tilt the cup towards your lips, if the "highest" siphon pickup is still submerged, then that will correspond to the "lowest" siphon top and it will start siphoning anyway. It would work as long as it could be arranged that the pickup would become exposed to air before the siphon started siphoning, but I'm not sure that's possible while still retaining the property that it self-starts when overfilled. Also, even if the tube doesn't siphon because the pickup is exposed to air, there would still be liquid in the tube, some of which would get pushed over the top and leak out the bottom whenever you try to drink.

peter_retief 8y ago

I would love to find some sort of application for the p-cup (Besides pranking people that is) Maybe a cistern with less moving parts, indoor irrigation, pet water dispenser Should maybe make an "ask HN" ?

chatmasta 8y ago
I was wondering the same. Pet food dispenser sounds reasonable. This is a literal manifestation of the “leaky bucket” rate limiting algorithm.
TeMPOraL 8y ago
Flush toilets are a very well known and popular examples of p-cups. The toilet bowl has a siphon built-in, which drains the bowl with its contents when the water reaches high enough level.