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12:04 AM
@tpg2114 Better than me. My bike has been sitting on my deck for over a year
I used to race and ride a lot... even managed a pro women's team for a few seasons. But then trying to finish and graduate screwed me
Never really recovered from it
But I'm trying!
5 hours later…
4:49 AM
@tpg2114 I cycle every day (if it isn't raining). Not to race but for exercise. I find it's a lot kinder on the knees than running, though yes it can be hard on your rear :-)
1 hour later…
5:52 AM
Funny thing, my flag on Jeff Atwood's post wasn't right out declined, rather it was disputed :))
Disputed means a user who reviewed the flag disagreed
Declined means a moderator declined it
O_o I thought it meant that the people who reviewed the flag weren't able to come to a common decision.....
Anyways that was expected!
6:14 AM
Can anyone help me in finding the Lagrangian of the above system? The string is connected to the ceiling at the left end and the ball is release at t=0
7:00 AM
In one of the suggested edits, I typo-ed out "MethJaz" in the summary, looks like a nice alternative to MathJax :P
7:27 AM
Q: Rolling equations from a non Inertial frame

satan 29In particle dynamics, I had used "pseudo forces" frequently, and i had come to the conclusion that pseudo forces ensure that analysis from a non inertial frame yield the same conclusion(s) as the ground/inertial frame. I wanted to extend this thought further, to rigid body dynamics. Consider a d...

This isn't a close-worthy HW question, right? Or am I being gullible?
7:55 AM
Hi! @ACuriousMind Did you delete the comments on this question? I know you aren't obliged to be accountable for mod actions, but still I am just wondering....
Q: Given two vectors (with no common point), is a dot product between them possible?

far_seeMost of the descriptions I have come across related to dot products between two vectors start off by stating/showing the vectors have a common point* to begin with - makes the notion of an angle between the vectors very easy to deal with in the final formula for dot products. I am showing below...

8:46 AM
Hi :-)
9:13 AM
Hi, @Yuvraj.
@PM2Ring hi sir :-) is it possible for is to launch a missile towards the sun.
@JohnRennie "the Parker Solar Probe that is going to use seven slingshots to reduce its speed enough to approach the Sun." Reduce it's speed? That doesn't sound right. Surely it needs to reduce its perihelion and increase its speed, doesn't it? physics.stackexchange.com/a/440258
@YuvrajSingh... Funny you should ask that right now. :) See the question I just linked & en.wikipedia.org/wiki/Parker_Solar_Probe
@PM2Ring Getting it into a Hohman orbit that intersects the required orbit round the Sun is easy, but the perihelion velocity would be far too large to shed using the thrusters on the satellite.
So you need to use a series of transfers to increasingly smaller orbits using flybys to shed the excess perihelion speed.
Also this article about a very important technique for traveling through space with (just about) the lowest fuel requirements:
In orbital mechanics, the Hohmann transfer orbit () is an elliptical orbit used to transfer between two circular orbits of different radii around a central body in the same plane. The Hohmann transfer often uses the lowest possible amount of propellant in traveling between these orbits, but bi-elliptic transfers can beat it in some cases. The orbital maneuver to perform the Hohmann transfer uses two engine impulses, one to move a spacecraft onto the transfer orbit and a second to move off it. This maneuver was named after Walter Hohmann, the German scientist who published a description of it in...
@JohnRennie Ah, that makes sense. I'm still waking up after an afternoon nap. :)
That pesky potential energy :-)
9:22 AM
I should re-read that Hohmann transfer article myself. :)
Would we have to reverse the velocity to change the orbit of our satellite?
I should know this stuff inside out, I've written enough sims that do Hohmann orbits...
It's nice that I find first posts before the review queue finds them. And thus when I go to review, I already have done the stuff that I wanted to and so I just need to click "Reviewed".
@YuvrajSingh... Sending a missile into the Sun is a little easier than putting something into orbit very close to the Sun because if you're crashing into the Sun you don't need to worry about shedding excess speed. But it still takes a lot of energy to get it into an orbit that intersects the Sun. IIRC, it takes less fuel to send something to Neptune, which is a lot further away.
1 min ago, by FakeMod
It's nice that I find first posts before the review queue finds them. And thus when I go to review, I already have done the stuff that I wanted to and so I just need to click "Reviewed".
9:28 AM
Wouldn't the sun gravity attract the satellite towards it, as the satellite is near the sun.
I meant the "I'm done" button!
9:41 AM
@PM2Ring do you watch YouTube channel, for some physics related videos?
@YuvrajSingh... Very rarely. I prefer to read physics, although videos are good for demos. I mostly use YouTube to watch music clips.
I remember you shared
An video on political
@YuvrajSingh... Yes, but you need to put the satellite into some kind of orbit to get it near the Sun. And when you launch that satellite it has some velocity due to the rocket engine, but it has a lot of energy due to the circular orbital motion of the Earth. Please read the Hohmann article, and look at the diagrams there. It will be helpful.
@YuvrajSingh... That song Politician is pretty heavy. Here's a mellow song by one of my favourite modern American bands. Derek Trucks is a wonderful slide guitar player, he also studied sarod under an Indian guru. This melancholy song has an Indian feel to it, especially in the introduction. I call this style "Country and Eastern". ;)
The woman singing is Susan Tedeschi, she's married to Derek. And she is also a very good guitar player, and song writer.
10:07 AM
4 hours ago, by FakeMod
user image
@FakeMod hi.
What you want to find?
are you sure l>d?
Here's Susan playing guitar & singing a song she wrote, when she was younger, before she married Derek.
I'm glad you like it, Yuvraj. I think @ZeroTheHero would also enjoy it too, since he likes the blues.
@YuvrajSingh... Yes, that is why the rope is slack. I want to find the equations of motion for the mass m.
@ACuriousMind if you haven't seen it before, then you would be glad to know that people have written books to capture your greatness :P
Son of Stackoverflow, William Street, New York, NY, USA
101 1
This user's about and user name is quite funny....:)
10:27 AM
@FakeMod Sorry, I don't know how to do that. The string starts out as a catenary, and I think it continues to be a catenary as the ball starts falling, before the string becomes taut, but I'm not certain. Can we assume the string is inextensible, with negligible mass?
@PM2Ring Yes the string is a massles, inextensible iseal strin.
@PM2Ring Unti the string becomes taut, the mass will be under free fall.
@FakeMod That's nothing, everything I say is written down and bundled for people to read! (Communications of the ACM)
I am able to find the equations of motion using Newtonian mechanics but I want to use Lagrangian mechanics to solve this @PM2Ring
10:29 AM
How to show that $$(\gamma^* \omega)_t (X) = \omega_{\gamma(t)}[\dot{\gamma}] X$$
Sans coordinates
"by definition"
Well no
@ACuriousMind How do I subscribe to that magazine?
Seriously, if my guess at that what notation means is right that's just the definition of the pullback
(if my guess is incorrect you have to explain yourself)
By definition it is

(\gamma^* \omega)_t (X) = \omega_{\gamma(t)} [d\gamma_t (X)]
@ACuriousMind Shit! That joke was for real? Nice....
With coordinates, that would be
\omega_{\gamma(t)} [d\gamma_t (X)] &=& \omega_\mu \theta^\mu [(d\gamma)^\mu_t \theta_t \otimes e_\mu (X^t e_t)]\\
&=& \omega_\mu \theta^\mu [(d\gamma)^\mu_t e_\mu X^t ]\\
&=& \omega_\mu \delta^\mu_{\nu} (d\gamma)^\mu_t X^t\\
which is indeed the correct thing
@Slereah $\mathrm{d}\gamma(\cdot) = g(\dot{\gamma},\cdot)$, no?
I think it only works because it is one-dimensional
@ACuriousMind I mean yes, but I'm not sure from what that would stem, without coordinates!
Yes, what I just wrote is special to 1d
@Slereah There's nothing wrong with proving such a local statement in coordinates
10:36 AM
I know
But still
It feels WRONG
like a proof by brute force
Or by using Zorn's lemma
@ACuriousMind any ideas about this question?
31 mins ago, by FakeMod
4 hours ago, by FakeMod
user image
Oh well
it will have to do for now
@FakeMod No, I'm afraid I don't find mechanics exercises interesting
@ACuriousMind okay, np
@FakeMod why would you use Lagrangian mechanics for that problem?
The mass just falls straight down until the string becomes taut, then it moves in a circle with radius equal to the length of the string.
10:48 AM
@FakeMod Of course. But I don't think that means the string stops being a catenary... but I'm certainly happy to hear any arguments that prove it's not. :)
@JohnRennie Yes! That's exactly what happens. But if I were to solve it using Lag. Mech., how do I even write it's Lagrangian? Also, this example is a good one, in the sense that the total energy is not conserved. When the string gets taut, the angular momentum is conserved and after that we can safely conserve energy, but some energy is lost when the tension increases impulsively.
@FakeMod I am too badly out of practice with Lagrangian mechanics to comment.
It is generally a bad idea to try to apply Lagrangian mechanics when non-conservative forces are involved.
Sometimes it works, but it's never worth the trouble
@ACuriousMind But there are no apparent non conservative forces, which makes me think that Lag Mech should not fail here.
@JohnRennie No problem :)
@FakeMod the string is dissipating some of the KE of the object. Presumably converting it to heat.
10:59 AM
@ACuriousMind AFAI have thought, we'll need to use a discontinuous Lagrangian, the kind of one whose value suddenly jumps when the string gets taut. This way the acceleration at the taut point will become undefined because L is not differentiable there.
@JohnRennie Yes, that seems the most probable sorce of dissipation....
@FakeMod if you made the string perfectly elastic then that would be more interesting because then energy would be conserved and the Lagrangian approach would work fine.
You'd get a complicated mixture of rotation and oscillation.
@JohnRennie looks interesting! Moreover, in that case we won't be able to find a solution using Newton's laws of motion.
Then the string would essentially become a spring.....
You can always find a solution from Newton's laws. It's just that it can become computationally impenetrable.
@JohnRennie I suppose the system will become chaotic if we take a spring instead of a string, what do you think?
11:22 AM
FWIW This is the Lagrangian ☝️
A bit of cleverness, tweaking and signum functions make it possible to solve it using Lag Mech. That sgn is signum fuction
11:46 AM
Trying to define the wilson loops properly is a huge pain :V
@FakeMod I still think the question should be closed :p
@FakeMod No, another mod deleted them. Why?
@AaronStevens the close review is not done yet, it might still be
12:05 PM
@ACuriousMind That comment section contained my highest upvoted comment till date :)
Hey @NovaliumCompany I remember you posted a link to your soundcloud. Which DAW do you use?
12:18 PM
Dec 15 '19 at 15:39, by Novalium Company
here's a beat to cheer you up
Mar 18 at 11:15, by Novalium Company
listen to my little beat
12:34 PM
What is the bias called when something happens, and then one calculates the probability that would happen? Typically if you win a game, and "forget" that you actually tried many times, and it was in fact probable that you would win at some point
@FakeMod FL Studio. I recently tried Ableton and it was pretty good as well. But I've been using FL Studio for like 6 years so I stick with it.
@NovaliumCompany Same I also use FL studio (for like 5 yrs or so). I tried Ableton for a month and I liked it that's why all my audio stuff is done Ableton whereas all the vst/midi stuff is done FL
@NovaliumCompany Which VSTs do you use? Like your favourite ones....
@FakeMod My favorite probably Massive
Harmor is cool too
Nice! But I like Serum better.
I wasn't able to crack Serum xDDDD
12:46 PM
@NovaliumCompany Harmor is like ancient Serum ;)
I really want it tho :(
@NovaliumCompany What? I was able to do that.
@FakeMod plz teach me senpai
I have the serial key somewhere in the huge stack in my computer. Very less likely that I could find it. However why don't you try r2rdownload.com they are great. Or freshstuff4u.com
Massive is also good when it comes to organic sounds
It has an analog-ish tone
I've always wanted Serum. I'll try to get it today
12:49 PM
Cthulhu is also nice and its a boon if you don't know music theory
Fun fact: refx (Nexus) reversed is xfer (Serum)
Oh I like Nexus as well
Sylenth1 is good if u have good presets
I've always wanted Serum. Glad to know it's possible.
@FakeMod Wait, do you happen to have the full FL Studio?
@NovaliumCompany hell yeah
12:56 PM
Like I have 4 gbs of zipped stuff: vst presets samples.......
Told you the websites, go check em
@FakeMod Okay, thx
@B.Brekke I suppose it's a form of en.wikipedia.org/wiki/Survivorship_bias A fairly well-known case involved testing for ESP. The researcher gathered a sequence of data from a pair of test subjects, one "sending" & one "receiving".
They'd locate a subsequence that demonstrated better than chance correlation between the sent image & received image, and discarded the data before & after that subsequence, on the grounds that the initial subsequence was bad because the subjects hadn't warmed up yet, and the tail subsequence was bad because the subjects were tired. This botched data handling led a lot of people to start treating psi phenomena seriously. :(
1:20 PM
@PM2Ring That kind of explorative statistics was also the method how some charlatans tried to show that there is a higher risk for childhood leukemia around nuclear power plants in Germany.
Damn epidemiologists. And they got government money for that.
@PM2Ring Thanks! In this case it was someone who had won a card game seven times in a row and found that this was highly unlikely if the game was random. But I don't think he considered all the times he lost beforehand. I just couldn't find the proper name for it.
Hey, what should I do? The OP is constantly asking me to help him.
Sir but still I am unable to understand probably because I unable to understand the English?? — mayank bisht 1 min ago
@Loong "Lies, damned lies, and statistics"
@FakeMod Run away!
@PM2Ring Hahaha! Seems like the best option.
It's not your responsibility that their poor English skills are making it difficult for them to understand. It's nice that you want to help, but there's a good reason that we close questions like that.
1:33 PM
@PM2Ring hmmm...Thanks!
Why do you think that holds for an isobaric process? $C_V$ is for constant volume processes, not constant pressure. — Aaron Stevens 41 mins ago
Also note that they are showing classic signs of being a help vampire. Once they latch onto you, it can be difficult to escape. See
Q: The Help Vampire problem

Barry KellyWhat is Stack Overflow's long-term solution for the Help Vampire problem? Quote from article follows: Identifying Help Vampires can be tricky, because they look like any ordinary person (or Internet user, whichever is lesser). But by closely observing an individual's behavior using this hand...

@AaronStevens AFAIK I know, $\mathrm d U =C_V \mathrm d T$ holds everywhere. Your statement is correct when we talk about heat.
For heat, we use two different specific heats.
@PM2Ring do you have more such songs !
@JohnRennie hi, how are you?
@YuvrajSingh... Like the blues song, Just Won't Burn? That song's pretty special, but I'll see what I can find.
@YuvrajSingh... A question usually ends with a question mark. Why the exclamation mark?
1:48 PM
@FakeMod The r2rdownload website always seems to take me to freshstuff4you. I hope I can find the full FL Studio there
@FakeMod Just flag stuff please
Flagged it
Before posting
Then there was no need to post it here
@ACuriousMind Just did it for quicker action
That's not what chat is for
1:49 PM
Smoke detector would have detected, right?
ACuriousMind being a grandpa again
Apr 1 at 13:06, by ACuriousMind
@FakeMod Moderator flags can be seen by all mods and should not be used in jest. Also, please stop using chat to try to get me to take moderator actions. I don't want to repeat that a third time.
@ACuriousMind Then should I have left after flagging?
I've told you before to not use chat to incite moderator action. Why do you keep doing it nevertheless?
@ACuriousMind what exclamation mark is describing my feeling, I should have use "," instead of "!", so sorry for that!
1:49 PM
But this was so bad
Like so bad
@FakeMod The system can handle abusive flags automatically, no mod action is required, it just takes a few (3 ?) flags from normal users. The same goes for spam flags.
@YuvrajSingh... Sorry, what? The question mark is ?, why would you use a comma ,?
@PM2Ring Oh! That's a valid point.
@YuvrajSingh... hi :-)
Eating lunch, though it's a rather unusual lunch today.
@FakeMod It was just a rude post. It happens.
1:51 PM
@ACuriousMind Ok! Let me get this clear. Are there no exceptions for using chat to get mod attention?
@ACuriousMind they were two sentences, by mistake I merged them
@FakeMod The network gets a lot of bad stuff, but it normally gets cleaned up very quickly. Physics gets a lot less than some other sites, though.
@ACuriousMind But you can't let it be there until a mod comes....:(
@FakeMod If you think it's going to get worse if nothing is done immediately (e.g. two users insulting each other in comments right now), it's fine. But in general very little is urgent.
@JohnRennie what happened?
1:53 PM
@FakeMod If you want to say something about my comment on another post, then just reply to my comment there.
That happened :-)
@PM2Ring Yeah! I spent some of my time on smoke meta erway software website, you can see all these kinds of posts there, even if they have been deleted. And such posts (like the one i posted above) got deleted in a minute
@FakeMod I've looked at the websites but I'm struggling to find the full FL Studio download
This site is not real-time, you need to stop treating it like a modern social network where you expect immediate feedback.
1:53 PM
@JohnRennie adopt me
@JohnRennie ah, finest English cuisine
@AaronStevens It might start a discussion though, so I thought not to do it there and anyways comments aren't meant for that, are they?
@ACuriousMind French isn't it?
@JohnRennie looking like a stick with chocolate over it!
@ACuriousMind Hmmm... I understand! Thanks!
1:54 PM
@JohnRennie And once again I fail at conveying irony :P
Baguettes with choco lol
An éclair is an oblong pastry made with choux dough filled with a cream and topped with chocolate icing. The dough, which is the same as that used for profiterole, is typically piped into an oblong shape with a pastry bag and baked until it is crisp and hollow inside. Once cool, the pastry is then filled with a vanilla-, coffee- or chocolate-flavoured custard (crème pâtissière), or with whipped cream, or chiboust cream; and then iced with fondant icing. Other fillings include pistachio- and rum-flavoured custard, fruit-flavoured fillings, or chestnut purée. The icing is sometimes caramel, in which...
We made baguettes in our school on 14th july
@ACuriousMind oops :-)
@JohnRennie Don't you like them?
1:55 PM
@FakeMod If a discussion ends up happening, then there will be an option to move it to a chat room specifically for that discussion
@FakeMod Hello, do you mind quickly helping me out with the full FL Studio thing?
No need to spread it out across multiple places
Bastille day
@ACuriousMind why you get upset so easily!
@YuvrajSingh... I love chocolate eclairs, or I wouldn't be sitting down to eat a dozen of them.
1:56 PM
@AaronStevens Yes you are right. From now on, I will not at all bring those stuff in chat unless needed. However did you get the main technical point which I am talking about?
@JohnRennie ok.
However few people would consider a dozen chocolate eclairs to be a sensible lunch :-)
@FakeMod Yes, I was just misreading the question. I have deleted my comments
@AaronStevens no worries!:)
@YuvrajSingh... 1. I'm not upset. That I criticize someone does not mean I'm necessarily upset at them. 2. That's another question with an exclamation mark, what's going on here?
1:58 PM
@ACuriousMind yes that was not a question.
@YuvrajSingh... English, please.
I am saying that you are upset.
@ACuriousMind Didn't you know that in today's age if you disagree with someone that means you are actively attacking them and must be upset?
@YuvrajSingh... "Why" - as a question word - introduces a question. Are you trying to be non-sensical?
@ACuriousMind sorry for using that.
1:59 PM
@FakeMod Do you create an account to unlock the FL Studio or you import a gen file?
@FakeMod Links is broken
@NovaliumCompany bro just download and enter your name. No keygen needed, no account
It isn't
sigh...please also do not post direct links to piracy sites in here
@ACuriousMind Can I post that in the Sandbox?
I personally couldn't care less about how you obtain your software but it's not a good look for the room
I understand!
2:02 PM
That is certainly the response she would have got at my school, and probably at my university as well.
@YuvrajSingh... Here's a blues song by an English lady, which she wrote when she was only 17. She isn't a great singer, but her voice has a lot of character. And she is an excellent guitarist.
@FakeMod I don't care what you post in other rooms as long as it doesn't violate the CoC
Hey @NovaliumCompany lets go to the SandBox room.
@ACuriousMind I will delete it after NC sees it
@AaronStevens Yes, I've noticed that belief many times when I've asked OPs to clarify their question :P
2:04 PM
@FakeMod i'm there
@JohnRennie bad! Lol!
@ACuriousMind It's why I don't really use social media anymore
@PM2Ring if I remember correctly there was a lady a famous British guitarist who has beautiful song with guitar during my school days I heard that song.
@YuvrajSingh... There are quite a few of them. :) I'll post another one in a little while.
@ACuriousMind do you have any kind of hobby?
2:16 PM
@YuvrajSingh... AFAIK He loves moderating....
@YuvrajSingh... Mostly video games and tabletop RPGs, though the latter also happen only virtually these days
I also have a tendency to start programming stuff and then abandon the project before it ever gets anywhere :P
@ACuriousMind that is good!.
Here's a more upbeat song from Joanne:
Here's a young English lady named Chantel McGregor, who's more into rock than pure blues, but she plays a fairly wide variety of styles, both covers & originals. Here she is from a few years ago doing a great cover of an old Jethro Tull blues-rock number, A New Day Yesterday.
2:24 PM
@PM2Ring wow.
Now I am addicted to this type of songs.
Two American sisters doing an old Skip James song, Hard Time Killing Floor Blues
@YuvrajSingh... Excellent. :)
@PM2Ring a song dedicated to you.
@ACuriousMind @JohnRennie @tpg2114 @nitsua60 @AaronStevens @NovaliumCompany
My state song.
Here's a long song from Chantel called Daydream, written by Robin Trower. It's more prog rock, rather than blues. There are great clips of her performing this live, but I think the album version has the best sound quality.
Another version of These Walls, by 2 Singapore Indians. I just discovered this clip yesterday.
@YuvrajSingh... Please don't ping people about random things, especially when they aren't physics related... I'm not mad, but it does rub other people the wrong way and is considered impolite
If you know somebody would be interested (for example, you've talked to them about that thing before and they expressed interest), then it's not a big deal. But for things that aren't related to prior conversation or site business, it's not good form
2:38 PM
@tpg2114 I apologize, you are correct.
No worries! Like I said, I'm not mad about it :) Just letting you know
@tpg2114 what is your hobby?(if you are OK to ask about it).
@PM2Ring it was sound like a rock band!
@JohnRennie I used to run track in high school and hated it. I like racing, so the actual competition on the track was awesome, but the training was horrible. I also ended up tearing the cartilage in my left knee, which will never heal... so I switched to bike racing instead. It's been hard for me to get into it since I took so much time off though, and it's also hard to do it just for fun/exercise instead of competition...
I'm 59. Let me tell you about knee cartilages :-)
How long have you got?
@YuvrajSingh... Well, when I had time and motivation, I used to race bicycles a lot -- mostly on the velodrome. But the last two years of my PhD and then the 3 since then, my hobbies are pretty dull... mostly my hobbies are just reading journal papers or doing some theoretical work these days, while my day job has me doing simulations and applied work
2:43 PM
@YuvrajSingh... Cute. I'm not much into rap, but that was fun. And here's some more Indian music for you:
@JohnRennie I'm only 34 and my left knee is already a problem. Are you saying I'm going to be in more trouble?!?! :)
No, no, absolutely not :-)
@YuvrajSingh... Oh, and I guess my hobby now is also spending a lot more time on this site!
@JohnRennie I see your knee cartilage and raise you a ruptured disc. ;)
When I was in the southern US, I could ride my bike outside almost year round. I'd only have to take about a month off when it was "too cold," but too cold is relative cause it really just meant "too cold without buying some heavier clothes"
2:46 PM
@PM2Ring that was good a simple Indian classical music.
Now that I'm in northern-midwest US and our winter lows can hit -20 to -30C, I'm muuuchhhh less inclined to ride for about 1/3 of the year
@PM2Ring Ouch! :-(
Touch wood my back is still fine.
@tpg2114 I use to do skating during my school days, and I had a experience like that.
I grew up in the mid-Atlantic when I started riding/racing, I got my fill of cold weather riding then... although my favorite weather to rid in is still ~5C and misty rain
@YuvrajSingh... What kind of skating?
More Susan, with some lovely violin playing. Angel From Montgomery
2:50 PM
@tpg2114 roller skating.
Anyway, I think that's probably enough music clips from me, for the moment. :)
I used to really want to try speed skating (on the ice, not outdoors). It still looks super fun
@PM2Ring no sir.
I really want to take up cross-country skiing too, but even though we get miserably cold here, we don't get any snow really. So it would be like a 4-6 hour drive each way for me to get anywhere I could do that
My YouTube page is on.
2:53 PM
@YuvrajSingh... Ok, 1 more. I'll post more music in a day or 2.
@tpg2114 I use to do skating in our basketball ground.
Though I was not a perfect in skating, so give up that.
I'm thinking of buying a heat gun to melt the plastic instead of putting it in an oven. What do you guys think about that? I think it will be much easier to play with the hot plastic and put it in a shape I like.
Because if I use an oven, I'll have to get out the thing out of the oven, reshape it and pressure it in the mold and then put it back in and that's a lot of opening a closing of the mini oven. Do you guys think it'll be easier if I use a heat gun and melt it, then push it, continue melting it...?
In that way it'll be much easier to pressure it into the mold
because with the mini oven I would have to get it out, pressure it, put it back in many times, and with I heat gun I just have to stop the heat gun, pressure it, continue with the heat gun.
@JohnRennie Yes. Thank goodness for...
And another thing, what can I make the molds of so that they don't burn or melt when the heat gun is heating them. I want to place the plastic in those molds but what do I make the molds of? Because I bought some polymer clay but I don't think it'll survive.
3:11 PM
@NovaliumCompany Why polymer clay and not the old-fashioned kind? I bet your molten plastic will glue itself to the plastic in the polymer clay.
@tpg2114 If I lived there, I'd be hibernating. :) I can barely cope when the temperature drops below 15° C. OTOH, I don't mind 30° C, although much above 35° C does slow me down. But I bet Yuvraj is thinking 40° C is a nice summer day. :)
@PM2Ring I do hibernate as much as I can in the winter!
@PM2Ring Well, I thought could bake the polymer clay (so it hardens and acts as a mold) and then melt the plastic in it but it turns out that baked polymer clay can burn.
"Polymer clay does not burn and turn black unless the oven is near 350°F (190°C)." yeah, that'll be a problem
@NovaliumCompany How complicated is the form you need to make? Would 3D printing be the easier way to do these things? They are much cheaper than an over/extruder
It's also possible to do the design and have a company print it for you -- which would be way cheaper than buying a printer (probably)
@tpg2114 I've checked all of those things. I've come to the conclusion that the best option would be to melt plastic in a mold. The shape is not complicated at all. The shape is somewhat similar to sunglasses (where I'll print 3 parts).
3:31 PM
@tpg2114 I suggested 3D printing yesterday. It's too expensive. Pity he doesn't have a friend with a 3D printer who could do it cheaper than a 3D printing service...
@PM2Ring Pity I don't have friends
You need to work on that. An entrepreneur doesn't exist in a vacuum. They need contacts, a big network of people. And that requires the relevant people skills.
@PM2Ring I know and I agree. The thing is, I'm still stuck in that school full of idiots and it's really hard to find someone with my interests especially here in Bulgaria. Once I get released from prison, the show starts.
CNC could be an option too
Since it sounds like it could be milled out of a flat sheet
@tpg2114 Researched that too. Way to expensive.
Injection Molding would be the way to go, but I'll have to do it manually first and when I get money for an injection molding machine, I'll buy.
3:38 PM
How exacting do the dimensions need to be? You could mill it by hand -- flat sheet with a Dremel
That's cheaper than even a heat gun
As the old saying goes, it's not what you know, it's who you know. Modern Internet technology has changed how that works, a little, but the core principle hasn't changed. Humans are social animals. They always have been, they always will be. I'm virtually a hermit these days, but 40 years ago I literally knew & interacted with hundreds of people, regularly.
I assume this is a early-phase prototype, so longevity and manufacturing steps and finishing and all that are not a concern
@tpg2114 It's a prototype which I must sell.
It just needs to have the essential parts in the right place and be close enough so it behaves like you'd expect
@NovaliumCompany Sure, but what do you mean "sell"? Like -- make a pitch and get investors kind of sell? Or you have to sell the prototype to somebody who will use it as a functional product?
Cause the needs are very, very different and the second choice is arguably not a prototype anymore
@tpg2114 sell the prototype to somebody who'll use it as a functional product.
3:40 PM
Okay, well, that's moving out of prototype range and so things like finish, durability, etc become important again
I don't understand what's wrong with making a mold with some material and then melting plastic in it with a heat gun.
It'll be pretty finicky -- uneven heating will make forming hard, overheating will ruin the material (which can be immediately obvious or only show up later)
@PM2Ring I'm an introvert but I'd love to spend time with people smarter than me. A lot of people here, I'd like to meet in real life, because I'd have something to talk with them, something that I'm interested in. My peers care only about social status BS, smoking, partying and alcohol.
Depending on the plastics chosen, the temperature range between "plastic deformation" and "totally ruined" may be very narrow, or too high or too low for a heat gun to produce easily, safely and reliably
Some plastics may only have one chance to set correctly and don't work if reheated... There's all kind of challenges with doing it the heat gun way. But if that's the best you have, then you need to find a material that meets all the constraints you have
Or, if it can't meet all of them, is optimal given the relative importance of each of the constraints
Would I have the same problem with a mini oven? I'm thinking of HDPE or some type of other recyclable plastic (I'll take a look at them again).
3:46 PM
Ovens designed for manufacturing generally have the proper controllability and consistency you need -- but that means they can be more expensive
And they are usually heavy so there's a lot of thermal inertia to help even out variations
I'm talking about a mini oven, for cooking.
Most home ovens can be massaged into controllability and consistency, but it takes some extra effort. We do a lot of baking, which also requires precision and control. So we load our oven up with bricks and we have thermometers in multiple places so we can see real temperatures and variations
And we worked out a map from input temperature on the oven control to actual temperature inside the oven
And we let it heat soak for awhile before doing anything, just to make sure it has reached a thermal equilibrium
If we do all that (which is pretty cheap), then opening to door to fiddle with things and so on isn't a big deal for our baking
Who's we? Are you a professionalist in the field?
My wife and I
And no, we're not professionals. We just like bread
You seem to LOVE bread :D
3:50 PM
And as an engineer, I like precision... heh
What about somehow getting only the heating part of a 3D printer so I can input plastic filaments in it and it can spill the melted plastic in the mold.
At any rate, terracotta flower pots inside an oven make a pretty good heating chamber for things since they soak up energy and radiate it back out consistently
@NovaliumCompany sounds like a hot glue gun
^ Which could be an option if the temperatures are right
@Loong Thought about that, researched, doesn't work :\
3:52 PM
And you can get sticks of plastic that fit in it
@Loong Even if I manage to do that, the plastic won't be melted enough to fit in the mold.
Have you looked into making your own injection molder?
I thought that maybe making two molds (one for the plastic and the other to apply pressure) would be a working solution. I can heat up the plastic with a hot air gun and apply pressure, heat, apply pressure...
@tpg2114 I don't have the tools to make my own
I'm planning to do what an injection molding machine does, but all manually.
@NovaliumCompany Are you familiar with the concept of lost-wax casting?
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