Help with gear type object

[sayluv]

thank you

[lemonbug]

Now that we have this object made is there a way to scale it? I tried changing the radius of the cylinder but it completely messed things up.

Thank you.

[bejant]

Now that we have this object made is there a way to scale it?

You can change to the Draft WB, select "PolarPattern" from the tree view, click the Scale tool:

check the "Copy" box to true, and scale it that way.

Or you can change the diameter of Cylinder, then double-click Sketch in the tree view and edit it accordingly.

You'll have to make sure your Preferences match mine:


before you open the attached model because I used the Link to External Geometry tool:


in the file I attached.

[lemonbug]

Thank you.

If you make some crazy object with and later decide to come back and make it larger or smaller you are basically otu of luck right? so for instance, we made a car engine and then later wanted to scale it, we simply couldn't make the entire thing larger or smaller right? you would have to go back and edit each object individually?

thanks again.

[jmh]

Just getting into the FreeCad world but wanted to say Thanks! to tose that are offering up so much help here. These are great tutorials for a beginner!

[bejant]

If you make some crazy object with and later decide to come back and make it larger or smaller you are basically otu of luck right?

No, the Draft Scale tool can do that:

so for instance, we made a car engine and then later wanted to scale it, we simply couldn't make the entire thing larger or smaller right

No, you can scale the whole model.

you would have to go back and edit each object individually?

No, but you won't have any parts in common between the new model and the old. You may want to be able to interchange maybe castings for the crankshaft, engine block, cylinder head(s), intake and exhaust manifolds, etc. in which case you'd edit those things individually.

[NormandC]

In parametric modeling, scaling is considered bad practice. And I mean BAD. Scaling a part or a whole assembly of parts utterly defeats the purpose of building parts with parametric history. Why go to all this trouble then?

Here's an example. Let's say your engine cylinders were bored to a specific value. Next you scale the whole engine by say 3%. But now you want to change the bore size. What do you do? You go back to the feature which created the bore and edit its diameter, but here's the problem: you now need to set your new value minus 3%, since it's going to be scaled up 3%.

You will need to do that for any feature you want to change in the model. It makes absolutely no sense.

The only valid reason to scale a model that I know of is for specific manufacturing processes like injection mold design for thermoplastic parts. Since plastic parts shrink when they cool off, the mold needs to be bigger that the original part. So you import the part, scale it up, then use it as an imprint to build the mold.

[sgrogan]

+1

[lemonbug]

Thanks for the information normandc. I appreciate you taking the time to explain that.