Driving a part's dimensions from another part

Create a skeleton part file with sketches, planes, axes and dimensions representing all the relevant factors, such as span, chord length, dihedral, etc. add this to your assembly files as an envelope part (so it won't appear in a BOM or other assemblies). Design all your other components in-context, referencing this skeleton part's features whenever possible. When the skeleton changes, the assembly will change with it.

To make it scalable, add a design table to your finished skeleton part, and let it auto-populate the table when you create it. In the design table, use Excel's formulas to add a scaling factor to all the linear dimensions (angles don't scale, of course). You may find it necessary to develop a naming scheme for all these dimensions.

You will only need one configuration in the skeleton part, unless you get into a bit more complex situation, like wheel parts having configurations that need to change based on scale. My guess is that you'll copy the assembly for each scale, since there will be a lot of structures and parts that don't scale simply, like bulkhead spacing and thickness (not to mention hardware and engines/motors). How best to approach this will depend on how many different scales you intend to design, and how different they will be.

Ok, thanks, that sets me down the proper path. What is still confounding me is how to link the skeleton dimensions to the various parts I have created. For example, I created a part of the fuselage box whose dimensions are all driven off a single input/dimension which in this case happens to be the length. If I change the length of this part, all the lightening holes and such get bigger or larger as a percentage of the length based on the equations I have set up. (of course material thickness is not derived from that input). Thus, I'd like "length" input to be driven off of the skeleton as a percentage of the length of the entire fuselage. So could you explain how I can link the "length" dimension to the overall skeleton length which has been created in an entirely different part file?

Thanks again!

John

OK, There are a couple of ways to do this.

The first way is to drive the length dimension with an equation in the assembly.

The other way is to open the sketch controlling the length of the fuselage within the assembly, and set the length of the fuselage line equal to the corresponding line in the skelton part (using a sketch relation). This will cause the sketch to be overdefined, because the dimension controlling that length is already controlled by a dimension. Open that dimension's properties and set it to driven. If it's already locked by the dimensions it drives, then use the first method I mentioned. There are pros and cons to both of these methods (and others I didn't mention), but these should be the best way for what you've already got done.

I hate to sound like a complete newb idiot...but maybe I am! I just don't "get" what you just suggested intuitively. What I have done based on your previous post is create design tables for each part using excel. Thus I have linked all the crucial equations to one main design table that holds the overall specifications. This works pretty well (and is pretty cool by the way...thanks for the tip!). However, the only drawback is when I change a parameter in the main design sheet, things don't dynamically update with the other parts. I have to close all the parts windows up, reopen them and then open the embeded design sheet. Only then after I hit the rebuild in the assembly window do I see the results of the whole shebang.

Thinking it would be easier to drive all of the dimensions in the assembly itself, I have tried to drop a design table intoit but the autopopulate feature doesn't seem to find anything to populate the sheet with even if I had removed the design table references from the parts themselves.

Cheers,

John

Ok... Design tables in assemblies cannot drive dimensions in component parts. For design tables to update to a master table, they all have to be linked to external files. That's the hard way.

Are you familiar with these tools? equations in SW formulas in Excel in-context sketch relations envelope part

When you wrote that you had your fuselage all done with equations, did you mean SW equations or Excel formulas?

Hi Dale,

I have, on each part, one dimension that drives every other dimensionf the part. These 'other' dimensions are based on a formula that is typically a set percentage of the base dimension.

The base dimension in each part is driven by a design table that I have also embedded in each part.

In turn, these dimensions are driven off of a master design table I have created in excel.

So if I change one parameter in excel (I.E. scale %) it will automatically change all the dimensions down to the equations I have created in SW. However, this does not happen in "real-time". I basically have to close the part and reopen it and then choose to edit the design table for each and then close it. Only then do the changes get reflected on the screen.

This is ok I guess but there has got to be an easier way? I know how to do SW equations and formulas in Excel. "in-context sketch relations" and "envelope part(s)" are new to me.

Thanks!

John

John, are you from AeroTech RC???

Anna Wood Queen Creek, AZ

Hi Anna,

No I am not THAT John :)

I am just an individual trying to come up with some of his own designs.

Cheers,

John Anna Wood wrote:

John,

You never know..... :-)

Well good luck in your adventures. I have modeled up an airframe or two in SolidWorks and Catia for our model projects. It a nice mental challenge to use the software to its best advantage and have some fun coming up with one's own r/c designs. Below is a link to one of our projects, this was modeled in Catia V5.

Anna Wood Queen Creek, AZ

SydDythers wrote:

Wow Anna, that Rasterpus is a beauty. Is it still flying? What was the final weight?

Here is my very first design, 28% Yak54. Not perfectly scale but I designed it with a view towards having it as nimble as possible. This design was also the first time I had utilized any CAD program (Autocad). I've since discovered Solidworks which obviously is way better for our needs.

Here's a pic of the Yak:

John,

The Ratsrepus is still going strong. My sweety, Len has been flying it regularly in IMAC contests since we built it.

Your Yak looks very nice. Thanks for sharing the pictures.

SolidWorks does make it a lot more fun to do the design work than drawing it up in AutoCAD.

Take Care,

Anna

SydDythers wrote: