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[SS-2395] Radian and Hz bug query
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Joined: 14/12/2017(UTC) Posts: 10 Location: Florida
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Does anyone know if the Radians and Hz issue mentioned in the following bur report has been addressed:? Past Radian bug submittalI am converting all my MathCAD docs over manually, and the turbines are based on omega, which is being interpreted as hz. On my end, it seems that SMath continues to define a rad as unitless, and when any rad/unit time is placed, it gets interpreted ans unitless/unit time, which is similar with Hz. Ultimately, something defined as rad/s can be interpreted as hz, and the calcs are all wonky. I also tried using radpm, but this continued to return the response as hz: Respectfully, john Evans
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"rad' [radian] is the math unit of trig functions. So many radians/sec is the angular velocity. "Hz" refers to signals ... so many periods/s
Good luck converting Mathcad indexed 0 to Smath index 1, Often => simple ... most of the times a nightmare.
I understand that in rotating machinery, rad/s is needed for deep maths, establish your own conversion user unit.
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Rank: Member Groups: Registered
Joined: 14/12/2017(UTC) Posts: 10 Location: Florida
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Thanks, I posted a response but it got vaporized... long story short, I learned to like how MathCad treated both as a function of Pi. However, I like Smath as a whole better, so I will learn some new ways of converting these in my code.
In this case, I did as suggested and have moved on.
Cheers, John
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What's the point to plug units in calculations ... only in result YES. Engineering maths existed before computing machinery. So, if you want to use units, they are "userunits" after calculations are done, just in same order they appeared in the computation life. If you compute sin(30) => result is in rad by default of the maths that approximate sin(x). If you want ° ... paste ° from unit in the empty place holder of the result. I read ~ 125 000 Mathsoft Collaboratory. How many engineering projects were posted with units ? NONE, though the "Units War" lasted for ever, never ended. All my Smath projects [Process Control & Instrumentation] are done in Engineering Unit style, i.e: in results from Engineering formulas.
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Rank: Member Groups: Registered
Joined: 14/12/2017(UTC) Posts: 10 Location: Florida
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Thanks Jean, I understand and will use the tip.
Cheers,John
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Joined: 15/04/2012(UTC) Posts: 1,986 Was thanked: 1124 time(s) in 721 post(s)
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The only bug with respect to angular velocity units is that quantities of dimension 1/time are shown with Hz as default unit. See bug report 2395 for details. Edited by moderator 21 January 2018 14:07:46(UTC)
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Joined: 02/01/2018(UTC) Posts: 3 Location: Sydney
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G'Day all, I am a new SMath user and am very impressed with the product. I lost access to Mathcad 15-20 years ago and this takes it's place. I'd like to introduce my colleagues to SMath. I am thinking about the engineering of train Cardin shafts and was having trouble getting my head around the way SMath worked with Rev/sec, Hz, rad/sec etc. From an engineering perspective SMath treats these incorectly and thus returns an incorrect result. I can't find another explanation for this outcome so I have added a 2pi fudge factor. From where I stand the pink statements are incorrect (and I'm not real big on the fudge factor). Please help, are there options other than the 2pi fudge factor? Thanks Cya Gus
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You mix angular velocity (angle per time) with frequency (events like full revolutions per time). Your formula gives full revolutions per time, which isn't consistent with the symbol omega (which at least in Germany indicates an angular velocity). If you want to switch from frequency to angular velocity you shouldn't use the same symbol and yes, you need your factor 2 pi. My recommendation: always stick to angular velocity, divide your speed by the radius instead by the perimeter length of the wheel and use the unit rev whenever revolutions are to be indicated. Edited by user 02 January 2018 15:36:23(UTC)
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Joined: 02/01/2018(UTC) Posts: 3 Location: Sydney
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Originally Posted by: mkraska You mix angular velocity (angle per time) with frequency (events like full revolutions per time). Your formula gives full revolutions per time, which isn't consistent with the symbol omega (which at least in Germany indicates an angular velocity). If you want to switch from frequency to angular velocity you shouldn't use the same symbol and yes, you need your factor 2 pi. My recommendation: always stick to angular velocity, divide your speed by the radius instead by the perimeter length of the wheel and use the unit rev whenever revolutions are to be indicated. Thank you for your help. I have implemented your suggestions in my work. A much more elegant solution than my fudge factor. You are not wrong in anything you say, but I can't help wondering if there are not alternative ways for SMath to deal with Hz, Cycles/time rad/time & rev/time. From a practical engineer's perspective (one that rarely does much math) rev/sec relate to cycles/sec or Hz more comfortably than than rad/sec. However, you have to piss with the dick you have; it is what it is (a great program) & infinite value when divided by price. I love it. 20 years ago I was a MathCad user. Thanks again for your help. I am new to SMath and have had some issues modeling a train to resolve Cardin Joint generated vibration issues. I have found a way around most of these issues and was wondering if it would be appropriate for me to post my work for review by people who are better at SMath than I. Your thoughts? Thanks GusF
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Rank: Advanced Member Groups: Registered
Joined: 15/04/2012(UTC) Posts: 1,986 Was thanked: 1124 time(s) in 721 post(s)
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Originally Posted by: GusF From a practical engineer's perspective (one that rarely does much math) rev/sec relate to cycles/sec or Hz more comfortably than than rad/sec. However, you have to piss with the dick you have; it is what it is (a great program) & infinite value when divided by price. I love it. 20 years ago I was a MathCad user. Thanks again for your help.
I am new to SMath and have had some issues modeling a train to resolve Cardin Joint generated vibration issues. I have found a way around most of these issues and was wondering if it would be appropriate for me to post my work for review by people who are better at SMath than I. Your thoughts?
Thanks
GusF
As for the rad/rev problem: This seems to pop up in the forum constantly. Part of the confusion is created by SMath Studio, see here: here. Of course, SMath can't replace basic knowledge in math and physics but it also must not act in contradiction to such knowledge. I blame SMath for - using Hz as default unit for whatever is of dimension 1/time. This is plain wrong in many but just a few cases (that is, if the 1 in the numerator stands for cycles or events). - listing units of angular velocity in the group "frequency" in the units selection dialog As for getting started with SMath Studio, I'd be ready to improve the tutorial, which you find under Help> Examples. Switch there from local storage to online gallery. Browse to the example "Getting started with SMath Studio". This tutorial is tailored to my pre-configured portable distribution (see my signature). I am about to generate other Tutorials, one which works with the pristine desktop installation under Win or Linux (no requirement of additional plugins) and one for the online version (SMath Studio in the cloud). |
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3 users thanked mkraska for this useful post.
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on 21/01/2018(UTC), on 21/01/2018(UTC), on 21/01/2018(UTC)
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Joined: 04/07/2015(UTC) Posts: 6,866 Was thanked: 981 time(s) in 809 post(s)
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Originally Posted by: mkraska I am new to SMath and have had some issues modeling a train to resolve Cardin Joint generated vibration issues. I have found a way around most of these issues and was wondering if it would be appropriate for me to post my work for review by people who are better at SMath than I.Your thoughts?
Thanks
GusF You are welcome to attach your work sheet, some of us [Smath Community] may have suggestions concerning your MCD => Smath. You mean "Cardan joint" 'Hz' is the count of complete periodic cycles /unit of time. The hydro grid is 60 Hz but the mechanical Engineer tests with an apparatus graduated in 'rpm'. 2phases/3phases motors are rated in terms of rpm [typical 3600]. Small 'universal motors' are generally rated 10000 rpm. The unit system should be purely decoration rather than conversion. If you measure V [Volt] a derived unit, it replies in term of base horror SI.
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Joined: 02/01/2018(UTC) Posts: 3 Location: Sydney
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Fellas, I've put together these calcs that anaise the vibrations in a transmission support fram that I have a Cardin Shaft FD1 -Trans 180125.sm (862kb) downloaded 22 time(s).
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Originally Posted by: GusF Fellas, I've put together these calcs that anaise the vibrations in a transmission support fram that I have a When you carry units, you may have recast some part unitless so you can keep track. I have only doctored the 1rst & 2nd derivatives plots. Cardin Shaft FD1 -Trans 180125.sm (879kb) downloaded 17 time(s).
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Originally Posted by: Jean Giraud I have only doctored the 1rst Smath does not have the option to insert math region in text region. You can still publish nicely, otherwise. In the attached [2], the "Formated label" is incorrect vs Smath 6179. The word EXPLAIN should replace the image RGBY square, as title Cardin Shaft FD1 -Trans 180125[2].sm (884kb) downloaded 22 time(s).
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[SS-2395] Radian and Hz bug query
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