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Difficulty with lofts and curves - I'm missing something basic I know

Afternoon,

Coming from Freecad (clunky) to OnShape (intuitive) has been a good transition, however, I'm having some difficult: probably because I am missing something basic and therefore making life hard for myself. 

I'm a hobbyist trying - In this document - to model a Japanese tram so I can 3d print it in parts for a model railway (it's a "portram / centram" - the images in the document give a guide as to the shape).

In order to tackle the job of the front of the tram, I've watched the 1hr curves curves curves webinar.

I think I want to loft the "face" of the tram, and guide the loft with curves / splines projected from horizontal and vertical views to get the profile correct. I had some success with getting a nice projected curve, but decided to replace a line with a spline on my bottom (horizontal) profile, and it's all gone wrong from there. 

I seem to be unable to project a curve from a composite curve (a sketch is required), and if I select the edges of a sketch, there is an error and my projected curve doesn't work. As an aside, I'd also like the sketches to be joined in the corner where they intersect. I cannot select one sketch from the other (as I can in Freecad), nor do construction lines seem to help.

Does anyone know what I am missing? Particularly:

- Have I done anything obviously wrong in the (messy) sketch so far, which is not right;
- Does making the sketches coincident at a corner assist, and if so how do I do that; and
- Is trying to use projected curves making my life difficult? Am I better off controlling the loft with splines, or bridging curves.; or perhaps creating a primitive and using fillets to get my curves?

Steve




Best Answer

Answers

  • stephen_allenstephen_allen Member Posts: 3
    Thanks @romeograham, I think I vaguely understand what you did. In any event surfaces are fun to play with. I've even managed to add super-cool tram-headlights using offset surfaces...

    https://cad.onshape.com/documents/c472b02c84a2d770d34699ba/w/54fd2797d1416ce686bba9d2/e/1c247e40ce227beeabce459a

    There are two things I now need to do which I can't fathom:

    (1) create a window frame (like I have on the sides) for the front window - I've already got some indentation with thicken - I'm used to boolean operations with primitives - can I make a surface which is smaller all the way round, then subtract it from the window surface, leaving a frame?

    (2) hollow part 4 into a shell - I don't want to 3d print a solid, just a shell. 
  • romeograhamromeograham Member Posts: 271 PRO
    @stephen_allen


    You can use the Shell command on the front nose part. The "Enclose" feature has turned the part into a Solid - it's no longer a surface. Best to do this before the Mirror:




    Then, you can split the faces (Split command, then select "Faces", then select your sketch lines for the tools) with lines from Sketch 1 (I added some extra lines in Sketch one that can be used to split this face. Note the lines extending past the edge of the part - this is to make sure they split the face completely. With line segments that aren't tangent (like this sketch) it may be necessary to extend the lines):

     then use "Thicken" tool to offset the face of the frame a bit.


    Roll to the end (to restore the Mirror) and voila:


    Note:
    This is not an ideal way to do these features, but will certainly keep you moving forward.

    Good luck!

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