Good Luck

It will take more than luck,  but a bit of help would go a long way;   if you have a minute or two. Two glaring problems 1. the curved end extrusions are not blending correctly into the main body  2. and the lowest segments of those sections won't smooth.   

BTW I grabbed Sketchup Pro to see how much that will help.  Yeah well I can import 2D CAD files but haven't figured out yet, how to use them as surfaces.   

PS  3rd problem; the blue "extrusion" is actually a shell, why would that be if the other end is a proper extrusion?

I don't know why the body and the front don't align on your design.  This is how I do it.

Step 1 draw the cross section surface of the top and a line that you want to extrude it along.

Step 2 extrude the surface along the line with the Follow Me tool.

Step 3A  Create a flat surface at the bottom of the design.

Step 3B  Shows how the flat surface intersects the design from the bottom.  Select everything, right click and INTERSECT FACES WITH MODEL.

Step 3C  Delete the flat surface...note the line around the nose of your design?  The line is the intersection of the surfaces.

Step 4A after (not so carefully) deleting some of the faces and lines below the line.  I got tired.

Step 4B a little closer look.  Note that the front and the body are a single blend.  All that mess at the bottom is repairable.

And apologies to David for using so many messages.

Thanks chaz!    More to contemplate. 

PS since I got tired of mousing around I found and printed out the keyboard shortcuts. When I die they can dissect my brains and look for all the stored keyboard shortcuts for all the different programs.    Also figured out the imported 2D CAD "problem".

Thanks again for the help. 

A huge THANK YOU to chaz. I really appreciate his help.

And for the rest of the gang I'll quote my friend the DCC guru : "Yeah well, you didn't expect that learning new stuff would get easier at your age, did you?!"
Yes, after that he was buying lunch. 

Pictures to follow. 

Meantime I have figured out a few things and I joined the SketchUcation forum — in the Newbie section where I belong.    Twenty days remaining on the Pro 2015 Trial version. Which reminds me, trial can be interpreted in several different ways. Right now it's as much "trial and tribulation" as it is a limited time period.   

Hi HJ,

The next thing you need is SketchUcam.  A free download for Sketchup, that creates G-Code commands for your CNC router.  Scary what you can do for free.

Chaz

Hi Chaz,

Cut3d from Vectric will do nicely and was part of the machine purchase. First sample roof, which needs a bit more blending in the DXF file. Arriving at the proper footprint for the ends was trial and error with different radii for the "Follow Me" path. Got a few handy tips from the Newbie forum e.g. SU has problem with small designs — in the low millimeter value bracket.
Suggestion was: scale it up and then down again. Amazing how well that works.    But I'm far from out of the woods!! 

Hi HJ,

Sweet.  Looks very clean.  Keep us posted.  You should have a rolling model before the snow melts.

Chaz

Thanks chaz,

I need at least six of those roofs; baggage, diner and four coaches.
With some of the more modern cars I just need to back-date the roof ends. That and making up the form for a concrete bumper are the next projects.
BTW very interesting link in your email; I wasn't aware of that connection.