Unitless?

[Anonymous]

Unit definitions cause (me at least) a lot of modeling problems. They arise when I really need to illegally mix units but I don't know why that should be so. For instance, if I want to make a coil's number of revolutions or some angle dependant on a dimension, it seems to be written in petrified dung somewhere that it's a no no. If a value is unitless, why would it care if it was multiplied by a dimension? A dimension value is a number and a unitless value is a number, no? So what gives? Been trying to figure that is for a long time without a clue. Anyone able to explain that, maybe and will this be true forever (Forever's 3 years. ... Evidence: my first wife said she was going to stay with me forever)? ~Larry

[Anonymous]

-- Dave Hoder Product Design Engineer idX Seattle www.idxcorporation.com "James (autodesk)" wrote in message news:40916e29_3@newsprd01... The key here is that Inventor is an engineering tool, we have an equation editor not a calculator.

[Anonymous]

Your calculator is only doing half the work. When you use it YOU are keeping track of the variables. Say for instance you want to multiply 5mm by 2". A calculator will multiply 2x5 to give you 10. 10 what? mm*in? An equation editor forces you to add a conversion factor to balance the units and give a logical answer. For example 2mm * 5in * 25.4mm/in = 254mm^2. Being an equation editor makes the parametric function capabilities much more powerful. Hope this helps. Patrick

[Anonymous]

Hmm ... that does make sense ... even to me. Thanks for the explanation. Now it would seem a little practice in balancing equations is in order I suppose. Thanks Patrick! I'll be working on that. ~Larry "Patrick Berry" wrote in message news:4091955e$1_2@newsprd01... Your calculator is only doing half the work. When you use it YOU are keeping track of the variables. Say for instance you want to multiply 5mm by 2". A calculator will multiply 2x5 to give you 10. 10 what? mm*in? An equation editor forces you to add a conversion factor to balance the units and give a logical answer. For example 2mm * 5in * 25.4mm/in = 254mm^2. Being an equation editor makes the parametric function capabilities much more powerful. Hope this helps. Patrick

[Anonymous]

It's really easy. Just treat them like variables in an algebraic equation and use the basic identity functions to cancel them out. Glad I could help. Patrick

[Anonymous]

Yeah ... I gotcha. In algebra class there were several, er, um, farer distractions shall we say, and while I have done that a bit, I never got very good at it. Wasn't much way to know if an equation was canceled correctly or not without the answers in the back of the book or someone to say. Wonder if there are any sites these days that give you feedback on such things. Thanks again Patrick! ~Larry "Patrick Berry" wrote in message news:40919391$1_1@newsprd01... I think the key here is that IV is designed around metric units. When using non-metric units they are automatically converted to metric internally. Just like in algebra, the units need to be treated like scalar values and must cancel out correctly to balance the equations. Patrick

[Anonymous]

I think an equation editor is a calculator with buttons you never use. There are a lot of engineering tools that don't require such shenanigans. Maybe it's tied to the way IV handles mixed unit parts in an assembly. Maybe if NASA had been using Inventor they wouldn't have missed Mars a couple of years back. Or, maybe it could be simpler.... 8~) ==================== "Larry Caldwell" wrote in message news:40918b17$1_3@newsprd01... Hmm ... okay if that's the way it is then that's the way it is.......

[Anonymous]

Ah ... Jeff ... my man ... I take it from your comment then that it should be possible to have it both ways assuming that we haven't been going down a one-way street concerning the way Inventor handles mixed units, eh? I wonder what the answer is to that ... I took James' comment pretty much as a firm: "Deal with it dude". ~Larry "Jeff Howard" wrote in message news:40919bc8_1@newsprd01... > I think an equation editor is a calculator with buttons you never use. > > There are a lot of engineering tools that don't require such shenanigans. > > Maybe it's tied to the way IV handles mixed unit parts in an assembly. > > Maybe if NASA had been using Inventor they wouldn't have missed Mars a > couple of years back. > > Or, maybe it could be simpler.... 8~) > > ==================== > > "Larry Caldwell" wrote in message > news:40918b17$1_3@newsprd01... > Hmm ... okay if that's the way it is then that's the way it is....... > >

[Anonymous]

Now Jeff you know better. Numbers don't mean anything if they don't have units. Could the equation editor be easier to use? Absolutely. But it is required IMO. -- Sean Dotson, PE http://www.sdotson.com Check the Inventor FAQ for most common questions www.sdotson.com/faq.html ---------------------------------------------------------------------------- ------ "Jeff Howard" wrote in message news:40919bc8_1@newsprd01... > I think an equation editor is a calculator with buttons you never use. > > There are a lot of engineering tools that don't require such shenanigans. > > Maybe it's tied to the way IV handles mixed unit parts in an assembly. > > Maybe if NASA had been using Inventor they wouldn't have missed Mars a > couple of years back. > > Or, maybe it could be simpler.... 8~) > > ==================== > > "Larry Caldwell" wrote in message > news:40918b17$1_3@newsprd01... > Hmm ... okay if that's the way it is then that's the way it is....... > >

[Anonymous]

Sorry, didn't mean to get your hopes up. Just had to take a (light hearted in intent) jab at that "engineering tool" statement. I don't think it explained much. I think that you are stuck with the equation editor as it is since it is the way the system is set up. It might be necessary to have it so (I like Patrick's hypothesis). It could also be that it was implemented with the lowest common denominator in mind; force a strict syntax and error checking to keep us from goofing up (valid enough, I guess). A system I'm sort of fond of doesn't require an equation editor or strict syntax, though handles mixed unit assemblies well. Equations are entered in a text editor environment (I love being able to put in paragraph length descriptive comments, group equations in a meaningful way to make it easier to read, etc.). I do force, moment, pressure, trig, etc. calcs referencing model parameters and drive part / assy relations using the values with no problems (many of the calcs aren't used to drive anything, but I want them parametrically tied to the model for reference). Wonder if UG and Catia have a calculator or an equation editor? 8~) =========================== "Larry Caldwell" wrote in message news:4091a8d3$1_1@newsprd01... > Ah ... Jeff ... my man ... I take it from your comment then that it should > be possible to have it both ways assuming that we haven't been going down a > one-way street concerning the way Inventor handles mixed units, eh? I wonder > what the answer is to that ... I took James' comment pretty much as a firm: > "Deal with it dude". > ~Larry > > "Jeff Howard" wrote in message > news:40919bc8_1@newsprd01... > > I think an equation editor is a calculator with buttons you never use. > > > > There are a lot of engineering tools that don't require such shenanigans. > > > > Maybe it's tied to the way IV handles mixed unit parts in an assembly. > > > > Maybe if NASA had been using Inventor they wouldn't have missed Mars a > > couple of years back. > > > > Or, maybe it could be simpler.... 8~) > > > > ==================== > > > > "Larry Caldwell" wrote in message > > news:40918b17$1_3@newsprd01... > > Hmm ... okay if that's the way it is then that's the way it is....... > > > > > >

[Anonymous]

"Wonder if UG and Catia have a calculator or an equation editor? 8~)" Hmm ... good question ... equation "calcueditor" maybe? Sounds sort'a like a one-way street then. Guess they're always gon'a be decisions to make; if you're at the crossroads of Banger and Leaver you got'a decide which way to go, eh? ~Larry "Jeff Howard" wrote in message news:4091e87d_1@newsprd01... > Sorry, didn't mean to get your hopes up. Just had to take a (light hearted > in intent) jab at that "engineering tool" statement. I don't think it > explained much. > > I think that you are stuck with the equation editor as it is since it is the > way the system is set up. It might be necessary to have it so (I like > Patrick's hypothesis). It could also be that it was implemented with the > lowest common denominator in mind; force a strict syntax and error checking > to keep us from goofing up (valid enough, I guess). A system I'm sort of > fond of doesn't require an equation editor or strict syntax, though handles > mixed unit assemblies well. Equations are entered in a text editor > environment (I love being able to put in paragraph length descriptive > comments, group equations in a meaningful way to make it easier to read, > etc.). I do force, moment, pressure, trig, etc. calcs referencing model > parameters and drive part / assy relations using the values with no problems > (many of the calcs aren't used to drive anything, but I want them > parametrically tied to the model for reference). Wonder if UG and Catia > have a calculator or an equation editor? 8~) > > =========================== > > "Larry Caldwell" wrote in message > news:4091a8d3$1_1@newsprd01... > > Ah ... Jeff ... my man ... I take it from your comment then that it should > > be possible to have it both ways assuming that we haven't been going down > a > > one-way street concerning the way Inventor handles mixed units, eh? I > wonder > > what the answer is to that ... I took James' comment pretty much as a > firm: > > "Deal with it dude". > > ~Larry > > > > "Jeff Howard" wrote in message > > news:40919bc8_1@newsprd01... > > > I think an equation editor is a calculator with buttons you never use. > > > > > > There are a lot of engineering tools that don't require such > shenanigans. > > > > > > Maybe it's tied to the way IV handles mixed unit parts in an assembly. > > > > > > Maybe if NASA had been using Inventor they wouldn't have missed Mars a > > > couple of years back. > > > > > > Or, maybe it could be simpler.... 8~) > > > > > > ==================== > > > > > > "Larry Caldwell" wrote in message > > > news:40918b17$1_3@newsprd01... > > > Hmm ... okay if that's the way it is then that's the way it is....... > > > > > > > > > > > >

[Anonymous]

Larry, what this all boils down to is "dimensional analysis", which is one of the first things learned as an engineering student. If you are not fimilliar with this I think it would help to spend a little time looking this up on the internet. I think it will clear things up for you a bit. kp "Larry Caldwell" wrote in message news:40919991$1_1@newsprd01... Yeah ... I gotcha. In algebra class there were several, er, um, farer distractions shall we say, and while I have done that a bit, I never got very good at it. Wasn't much way to know if an equation was canceled correctly or not without the answers in the back of the book or someone to say. Wonder if there are any sites these days that give you feedback on such things. Thanks again Patrick! ~Larry "Patrick Berry" wrote in message news:40919391$1_1@newsprd01... I think the key here is that IV is designed around metric units. When using non-metric units they are automatically converted to metric internally. Just like in algebra, the units need to be treated like scalar values and must cancel out correctly to balance the equations. Patrick

[Anonymous]

Exactly. I learned this from my high school chemistry teacher, Dorothy Kelly, in the tenth grade. She was a stickler for units. She once gave us a pop quiz with only one question on it - "What is Avogadro's number?" Everyone that wrote 6.022 x 10^23 got zero. Everyone that wrote 6.022 x 10^23 molecules/mole got 100%. That teacher left one hell of a lasting impression on me. So the public school system doesn't always fail, I suppose. I still perform all my calculations carrying all units. It helps me to notice when I've done something wrong. For example, if I'm calculating the first area moment of inertia of a body, I'm adding or subtracting a bunch of terms with units of length^4. If I have three terms that evaluate to in^4 and a fourth that evaluates to in^3, then I know I've screwed something up in that term. -------------------------------------------------------------------------------- Brian R. Iwaskewycz Senior Mechanical Engineer PA Transformer Technology, Inc. unplugged from the microsoft matrix on 4.10.03 my eyes hurt because i've never used them before "Keith Panik" wrote in message news:4092486a$1_3@newsprd01... what this all boils down to is "dimensional analysis"

[Anonymous]

Great information guys. And thank you James for chiming in. Matt

[Anonymous]

I had the same experience with my 9th grade physical sciences teacher (who was also my 11th grade chemistry teacher and the 12th grade physics teacher, small school). He taught us a method called "factor-label" that forced you to keep track of both scalar values and their units and did so very efficiently. It made it easy to convert between any units. I still use that technique. By only knowing 3 British-metric identities you can convert any british unit to SI and vice versa. 1"=25.4mm, 1L=1.06qt, and 1lbm=453.6g. Patrick

[Anonymous]

I'm just a ol'hick designer, not an Engineer, but thanks ... I'll do that. Haven't seen any good sites, have ya'? ~Larry "Keith Panik" wrote in message news:4092486a$1_3@newsprd01... Larry, what this all boils down to is "dimensional analysis", which is one of the first things learned as an engineering student. If you are not fimilliar with this I think it would help to spend a little time looking this up on the internet. I think it will clear things up for you a bit. kp "Larry Caldwell" wrote in message news:40919991$1_1@newsprd01... Yeah ... I gotcha. In algebra class there were several, er, um, farer distractions shall we say, and while I have done that a bit, I never got very good at it. Wasn't much way to know if an equation was canceled correctly or not without the answers in the back of the book or someone to say. Wonder if there are any sites these days that give you feedback on such things. Thanks again Patrick! ~Larry "Patrick Berry" wrote in message news:40919391$1_1@newsprd01... I think the key here is that IV is designed around metric units. When using non-metric units they are automatically converted to metric internally. Just like in algebra, the units need to be treated like scalar values and must cancel out correctly to balance the equations. Patrick

[Anonymous]

Here's a fun one: http://www.chemistrycoach.com/use.htm Here is an informative one: http://en.wikipedia.org/wiki/Dimensional_analysis Here is another: http://physics.about.com/library/weekly/aa021503a.htm This should keep you busy for awhile. kp "Larry Caldwell" wrote in message news:40927703_2@newsprd01... I'm just a ol'hick designer, not an Engineer, but thanks ... I'll do that. Haven't seen any good sites, have ya'? ~Larry "Keith Panik" wrote in message news:4092486a$1_3@newsprd01... Larry, what this all boils down to is "dimensional analysis", which is one of the first things learned as an engineering student. If you are not fimilliar with this I think it would help to spend a little time looking this up on the internet. I think it will clear things up for you a bit. kp "Larry Caldwell" wrote in message news:40919991$1_1@newsprd01... Yeah ... I gotcha. In algebra class there were several, er, um, farer distractions shall we say, and while I have done that a bit, I never got very good at it. Wasn't much way to know if an equation was canceled correctly or not without the answers in the back of the book or someone to say. Wonder if there are any sites these days that give you feedback on such things. Thanks again Patrick! ~Larry "Patrick Berry" wrote in message news:40919391$1_1@newsprd01... I think the key here is that IV is designed around metric units. When using non-metric units they are automatically converted to metric internally. Just like in algebra, the units need to be treated like scalar values and must cancel out correctly to balance the equations. Patrick

[Anonymous]

I may not understand why you are having a problem. If IV is going to correctly add or multiply a mix of milimeters and inches, it has to know how the units relate to get a final number. If IV is expecting 'in' and gets 'hp' it won't have an established relationship between the two to give you the correct value. "Larry Caldwell" wrote in message news:40914937$1_1@newsprd01... Unit definitions cause (me at least) a lot of modeling problems. They arise when I really need to illegally mix units but I don't know why that should be so. For instance, if I want to make a coil's number of revolutions or some angle dependant on a dimension, it seems to be written in petrified dung somewhere that it's a no no. If a value is unitless, why would it care if it was multiplied by a dimension? A dimension value is a number and a unitless value is a number, no? So what gives? Been trying to figure that is for a long time without a clue. Anyone able to explain that, maybe and will this be true forever (Forever's 3 years. ... Evidence: my first wife said she was going to stay with me forever)? ~Larry

[Anonymous]

-- Dave Hoder Product Design Engineer idX Seattle www.idxcorporation.com "Kevin Wehner" wrote in message news:40928274$1_3@newsprd01... >If IV is going to correctly add or multiply a mix of milimeters and inches, it has to know how the units relate to get a final number. Mixing inches & millimeters should be an easy calculation requiring no input on the users part (except adding the suffix). The value returned should be in what ever units are set as standard & should be able to be changed by the user. >If IV is expecting 'in' and gets 'hp' it won't have an established relationship between the two to give you the correct value. In which case, a simple dialog box "Choose which value to consider unitless" would fix the problem.

[Anonymous]

Me too. Just because I don't have an engineering degree doesn't mean I can't help to manufacture $100m worth of product a year. My time is better spent figuring out how to build things from napkin sketches than reveling in my grasp of calculus. -- Dave 'both barrels' Hoder Product Design Engineer idX Seattle www.idxcorporation.com "Larry Caldwell" wrote in message news:40927703_2@newsprd01... I'm just a ol'hick designer, not an Engineer

[Anonymous]

"My time is better spent figuring out how to build things from napkin sketches than reveling in my grasp of calculus." Ahhh, spoken like a true tech. I was just trying to offer some help. By the way this is far from calculus. kp "Dave Hoder" wrote in message news:40929fe8$1_3@newsprd01... Me too. Just because I don't have an engineering degree doesn't mean I can't help to manufacture $100m worth of product a year. My time is better spent figuring out how to build things from napkin sketches than reveling in my grasp of calculus. -- Dave 'both barrels' Hoder Product Design Engineer idX Seattle www.idxcorporation.com "Larry Caldwell" wrote in message news:40927703_2@newsprd01... I'm just a ol'hick designer, not an Engineer