Back
[04:04:29] <mun> Hi
[04:04:54] <mun> Does anyone know of a good way for finding the right spec of a compression spring?
[04:05:30] <mun> I have a max diameter, free length and deformed length. I want to find wire thickness, number of coils, etc
[04:05:53] <mun> Is there any good simulation tool?
[04:09:57] <Triffid_Hunter> mun: wire thickness depends on the spring constant which is something like force per unit deflection
[04:10:20] <Jak_o_Shadows> Yeah, N/m
[04:10:36] <mun> Yeah, but k can be expressed in terms of wire thickness, inner diameter, etc
[04:10:49] <Jak_o_Shadows> Well, yes, but there's a lot of parameters there
[04:10:50] <mun> Number of coils too
[04:11:10] <Jak_o_Shadows> Why not start by figuring out what spring constant you need, or what force you need.
[04:11:10] <Triffid_Hunter> mun: number of coils can then be worked out from wire thickness and deformed length
[04:11:11] <mun> So what's the right approach to finding the right parameters
[04:11:30] <mun> Just fix a k first and then tweak those params individually?
[04:11:47] <Jak_o_Shadows> well, depends on what you actually want it for
[04:12:04] <mun> Triffid_Hunter sure. But there are more than one combination of the params for each value of k, right
[04:12:47] <mun> So start off with a k, and then work on the right diameters, etc?
[04:13:10] <Jak_o_Shadows> I think so, but it'll depend on your use case
[04:13:15] <Jak_o_Shadows> also, what, you're making a spring?
[04:14:09] <mun> Well, I'm trying to order the right one. Basically I have a telescopic rod that has a plate mounted on each end
[04:14:24] <mun> There will be a spring embedded inside of the rod
[04:14:35] <mun> Inside the rod
[04:14:53] <mun> Well, tube rather than rod since its hollow
[04:15:35] <mun> So I have free length (extended length of the telescopic tube), deformed length (compressed tube length)
[04:16:27] <mun> But the free length is about 5x the deformed length, and the diameter is relatively small. So I wonder if that's actually feasible
[04:18:17] <Jak_o_Shadows> A compression spring huh.
[04:18:27] <Jak_o_Shadows> So you want it to resist getting smaller
[04:18:56] <mun> Yes that's right
[04:19:15] <Jak_o_Shadows> Small diameter - < 20mm?
[04:19:41] <mun> Yep. <10mm even
[04:20:08] <Jak_o_Shadows> Hmmm.
[04:20:19] <Jak_o_Shadows> My gut says that you're not going to be able to get a very strong spring
[04:20:39] <Jak_o_Shadows> Mostly because of the required deformation
[04:22:17] <Jak_o_Shadows> That is just my gut feeling
[04:23:19] <mun> Hmm
[04:23:45] <mun> Is there a good way to find out?
[04:23:59] <mun> Run motion studies in a CAD?
[04:24:18] <mun> But they don't seem to ask for the wire thickness etc
[04:24:24] <mun> They only ask for the constant k
[04:27:01] <Jak_o_Shadows> well, were you considering making the spring yourself.
[04:27:07] <Jak_o_Shadows> Cause otherwise, just look in catalog
[04:27:30] <Jak_o_Shadows> Also, it'd more be FEA, but it starts getting FUN when you have large deformation
[04:28:30] <mun> Well, I could have some custom made
[04:28:54] <Jak_o_Shadows> ah, just tell them x coils at this distance, radius and thickness
[04:29:37] <mun> Yeah, but that's what I'm trying to work out
[04:29:46] <mun> But I'm not even sure if it's feasible
[04:30:01] <mun> Given the rather small diameter and small deformed length
[04:30:12] <Jak_o_Shadows> If I had the time, I'd do some simulations and work it out
[04:30:16] <Jak_o_Shadows> Don't really have time thoguh
[04:37:33] <mun> Jak_o_Shadows how would you do simulations?
[04:37:41] <mun> Which tool do you use
[04:39:22] <Jak_o_Shadows> I'd use ANSYS, cause that's all I know how to use
[04:39:45] <Jak_o_Shadows> It would be the work of a few days straight at least, for me.
[04:39:48] <Jak_o_Shadows> It'd been a little while
[04:40:41] * cancer101 hello ebrybody
[04:43:18] <cancer101> i have a question concerning a project i intend to do. I have a simple arduino uno starter pack (Comes with lots of accessories tho) with which i m hoping to build an automatic, voice activated, dictionary... Is it possible to download a pre made dictionary data base directly to the arduino?
[04:48:53] <mun> Jak_o_Shadows: i'll give that one a shot
[04:50:21] <Jak_o_Shadows> mun, there is quite a learning curve. I'm not sure what you're doing - tbh it almost sounds like a student project (it's fine if it is). But good luck!
[04:50:56] <mun> Jak_o_Shadows: i'm used to solidworks
[04:51:56] <mun> i'm way too old for school :)
[04:52:11] <Jak_o_Shadows> haha.
[04:52:56] <mun> how does solidworks stack up against ANSYS?
[04:53:01] <Jak_o_Shadows> Well, I'm not sure if solidworks has fea built in. Inventor does (how much to trust it is different :P). If you want to simulate instead of just browsing catalogues, you could do it.
[04:53:20] <Jak_o_Shadows> Solidworks is CAD, ANSYS is more CAE, specifically finite element analysis
[04:53:59] <mun> Jak_o_Shadows: i've run simulations on SW. not sure how accurate they were though..
[04:54:16] <Jak_o_Shadows> Yeah.
[04:54:33] <mun> maybe they were supposed to be good, but i couldn't verify them
[04:54:37] <Jak_o_Shadows> This will be a bit more difficult than standard simple FEA because the spring deforms a lot.
[04:54:45] <Jak_o_Shadows> haha. SO you skipped the most important step :P
[04:54:58] <mun> :P
[04:55:07] <mun> Jak_o_Shadows: there's a tutorial on youtube, so i think i'll try to follow it
https://www.youtube.com/watch?v=BhmG0b83Pao
[04:55:20] <mun> but for verification, is testing with a real part the only way?
[04:55:46] <mun> Jak_o_Shadows: according to that tutorial, it took more than an hour to generate the model
[04:55:46] <Jak_o_Shadows> well, you could compare against other peopl's work :P
[04:56:07] <mun> Jak_o_Shadows: other works done on other tools?
[04:56:12] <Jak_o_Shadows> But yeah, verification mostly comes down to the real world
[04:56:21] <Jak_o_Shadows> Well, other tools, or people who have done it in the real world.
[04:56:35] <mun> right
[04:56:50] <mun> or just google around and see if SW users are screaming
[04:56:57] <mun> so far, i think they seem fairly happy
[04:57:02] <mun> or maybe they're just fan boys...
[04:57:10] <mun> :S
[04:57:23] <Jak_o_Shadows> haha.
[04:57:37] <mun> https://forum.solidworks.com/thread/92854
[05:00:44] <Jak_o_Shadows> Mmm, yeah, that is a potential issue.
[05:00:51] <Jak_o_Shadows> Contact
[05:01:53] <mun> i wonder if it'd be reasonable to assume a 5% error
[05:02:44] <Jak_o_Shadows> Well, your major goals would be to see if the spring would fail
[05:02:50] <Jak_o_Shadows> Or if the spring could deform that much
[05:02:54] <mun> yeah
[05:03:17] <mun> Jak_o_Shadows: do you think SW, even if it was "crap", could do that?
[05:04:02] <mun> here, SW can generate a graph plotting the force required
https://youtu.be/BhmG0b83Pao?t=7m24s
[05:04:33] <Jak_o_Shadows> I think SW could do it.
[05:05:10] <mun> but then if it produces an outright wrong analysis, then it'd be kinda pointless
[05:05:40] <Jak_o_Shadows> Yeah.
[05:05:58] <Jak_o_Shadows> As I said, I would talk to manufacturers or resellers first
[05:06:30] <mun> Jak_o_Shadows: i've talked to one, they just asked me for the number of coils, diameter, thickness
[05:07:43] <Jak_o_Shadows> ah
[05:08:12] <mun> that's why i thought i'd have to dive in and find the right params
[11:48:52] <Snert_> does anyone think this is real?
[11:48:57] <Snert_> http://www.aliexpress.com/item/Bargain-new-original-authentic-Japanese-OMRON-Omron-sensor-encoder-E6A2-CW5C-360P-R/32606155860.html?ws_ab_test=searchweb201556_2,searchweb201644_4_505_506_503_504_301_502_10014_10001_10002_10016_10017_10010_10005_10011_10006_10003_10004_10009_10008,searchweb201560_2,searchweb1451318400_-1,searchweb1451318411_6449&btsid=70a20cd0-42f5-4323-86b2-bca8a7047ff8
[11:50:12] <Snert_> or did they knock off omron?
[11:52:16] <jhylands> wow, that's pretty amazing if it is real
[11:52:21] <jhylands> those suckers are expensive
[11:52:39] <Snert_> i got 1 of 2.
[11:52:49] <Snert_> just for shitzngrinz
[11:53:34] <Snert_> I'm using the used ones at about 35.00 each so this blows me away.
[12:00:08] <Snert_> It's only AB not ABZ but I can still use it.
[13:56:00] <deshipu> I think you will soon get a message that they made a mistake in the price and won't sell it.
[13:56:10] <deshipu> I had that with ToF sensors before
[14:12:02] <Snert_> I'm just hoping that the flunky see it and gets it shipped b4 Mr. Boss see it. Might get lucky.
[16:54:47] <foul_owl> Anyone know of any good practical household robots? Looking for anything that can save me time, in the vein of a roomba or similar
[16:55:39] <deshipu> foul_owl: I have a roomba
[16:56:04] <deshipu> foul_owl: also, a microwave oven with a timer!
[16:56:12] <deshipu> foul_owl: washing machine too
[16:56:22] <deshipu> foul_owl: and dishwasher
[16:56:28] <deshipu> they save tons of time
[17:00:37] <foul_owl> Yes but where can we go from there haha
[17:01:18] <foul_owl> I have a basketball factory, that saves me 37 seconds a monday!
[17:02:05] <veverak> damn it
[17:02:08] <veverak> http://erlerobotics.com/spider/
[17:02:11] <veverak> look, ROS based spider
[17:02:13] <veverak> hmm
[17:02:18] <veverak> says opensource, no link to source
[17:02:25] <veverak> on eshop: custom servos
[17:02:33] <veverak> custom brain for robot, (aka arm device)
[17:02:47] <deshipu> veverak: that's just a rpi2 with a custom case
[17:02:57] <deshipu> veverak: and the thing is running ubuntu core
[17:03:20] <deshipu> veverak: they advertised it quite aggresively some time ago, looks like a trap
[17:04:10] <veverak> exactly
[17:04:12] <veverak> :)