
Re: Parabolic Camber problem
Craig Gilbreath Mar 28, 2012 11:53 AM (in response to Craig Gilbreath)Here is a screenshot of the sketch when I change it to 0.5" camber showing how it blows up...

CAMBER FOR CRAIG T PROBLEM.JPG 86.6 KB

Re: Parabolic Camber problem
Scott McFadden Mar 28, 2012 12:19 PM (in response to Craig Gilbreath)Craig,
When I run into these types of problems what I do is incremental changing of the dimension.
What I mean is since the .5 is not working, try .4 and see if that works. Then step it up to .45 and so on till you can get the closest
nummber to .5 you can. This might work dimensionally speaking or at the very least you can see where it might be erroring.

Re: Parabolic Camber problem
Craig Gilbreath Mar 28, 2012 12:25 PM (in response to Scott McFadden)Scott,
Thanks for the reply... I had a similar idea but started with a taller camber of 0.75" and worked my way down. 0.74", 0.73", 0.72"... then that is where it went wrong. At 0.73" camber the center of the parabola is only 0.8xxx" away from the "Mystical, Magical 500 meter limit"
I can not model camber any less than 0.73" @ 40' long.
This is realllllllllly getting old. I have actually run into the size limit SEVERAL times in my career using SW. WHY THE HECK CAN THEY NOT CHANGE THIS!!!!! Sorry... just a little more than TICKED right now!

Re: Parabolic Camber problem
Scott McFadden Mar 28, 2012 12:30 PM (in response to Craig Gilbreath)I hear ya loud and clear!!!
I have had the very similar frustration. Mostly when it comes to variable fillet sizes. End up doing the step thing just to get a close representation of what I want without wasting a ton of time. The most frustrating part is when the software with show you a preview exactly what you want, but can't deliver the goods when it comes to producing the feature.

Re: Parabolic Camber problem
Craig Gilbreath Mar 28, 2012 12:38 PM (in response to Scott McFadden)This is a HUGE project for my company and do you know how absolutley rediculous it is going to sound if I have to tell my client... "Sorry... but this $ x,xxx,xxx project is being delayed because SolidWorks can not calculate 1/2" camber..." YES... the dollar amount has 6 zeros behind it!!!!!!!!!!!!!!


Re: Parabolic Camber problem
Wayne Matus Mar 28, 2012 12:57 PM (in response to Craig Gilbreath)The issue is that no sketch geometry can be farther than 500 meters in any direction from the orgin. In your case the center of the parabola is 1596 ft in the y direction at .75" at .5" it would put it outside the limit.
The solution is to move your swketch geometry up so that this center point stays inside the limit.

Re: Parabolic Camber problem
Craig Gilbreath Mar 28, 2012 12:59 PM (in response to Wayne Matus)Move my entire sketch geometry +Y from origin?

Re: Parabolic Camber problem
Wayne Matus Mar 28, 2012 1:03 PM (in response to Craig Gilbreath)Yes, I know it is ugly, but it should work in this case.





Re: Parabolic Camber problem
Harold Brunt Mar 28, 2012 12:21 PM (in response to Craig Gilbreath)I'm not sure if the issue is the size or not as I didn't download the part file. I took a different approach to creating the curve though. I used the equation driven curve to make the sketch and made a swag at the radius for the parabola to get the .500". Here's the formula I used:
(x^2/57550)/(1+(1(1+(1))*(x/57550)^2)^.5)
where 57550 is the radius of curvature and 1 is the conic constant (Rho).
from 0 to 239.75
You would need to calculate the difference between the camber and the radius of curvature in the same units to get the results you want.

Re: Parabolic Camber problem
Craig Gilbreath Mar 28, 2012 12:30 PM (in response to Harold Brunt)Im not familiar with plotting curves with equations.
I really need the characteristics of a parabola where the center remains somewhat flat and the ends dive off.

Re: Parabolic Camber problem
Harold Brunt Mar 28, 2012 12:39 PM (in response to Craig Gilbreath)The equation I posted is the equation for a parabola in the sense that it is the equation for a conic section with the conic constant equal to 1 making it parabolic. Are you sure you need a parabolic? Perhaps you are looking for a tractrix. Equation and profile can be found here:
https://forum.solidworks.com/thread/33027
Nice part about the equation driven curve is that the boundary of the curve (x2 value) is the size limit.

Re: Parabolic Camber problem
Craig Gilbreath Mar 28, 2012 12:41 PM (in response to Harold Brunt)Thanks man... I will look into it.

Re: Parabolic Camber problem
Craig Gilbreath Mar 28, 2012 2:40 PM (in response to Harold Brunt)I looked over there at the link on Tractrix curves... looks very promising. I think that is the curve I need to use. However, I have not used this tool in SW before. How would I go about inputing the curve data into the UI of SW.
This is really streatching my boundries today... guess that is a good thing. I just hate having to learn new things when there are time implications...

Re: Parabolic Camber problem
Harold Brunt Mar 28, 2012 4:49 PM (in response to Craig Gilbreath)Sorry about the delay  meetings all afternoon.
Attached is a part file with a tractrix curve using a formula driven sketch. Hope you are on SW2012....
Updated to be closer to the desired dims

cambertractrix.SLDPRT.zip 66.0 KB





