Wagon Underframe (GWR) 7mm/ft - Work in Progress

[Collett]

Work in progress for some 7mm/ft GWR wagon underframe parts to be 3D printed.  Working in Sketch Up Maker, with its attendant frustrations.  SU doesn't seem to handle curves very well, is that what others are finding?  Unfortunately I don't have the time or patience for FreeCAD, plus my copy keeps crashing so I reverted to Sketch Up for the moment.

 

Working on a scanned template I see that the graphic seems to have some dimensional instability, whether that's part of the printing process or due to scanning I can't tell but it does produce some odd results as seen in the screenshot.

 

Currently I'm working on the Grease axlebox because (1) Sketch Up doesn't seem to like curves much, at least not as much as straight line geometry (2) Mr Dean built the OK-F axle box as a replacement part, therefore I hope that once I have the geometry correct for the grease box I only have to amend the front of the box unit.

 

Does anyone have any advice for making rivet/bolt heads in Shape Up?  When I get onto the solebars I'll need stacks of the little devils.

 

I've been reading through the materials and production limits for Shapeways - and I would appreciate any details concerning UK based printers.  While I'm thinking about getting a Prusa i3 at some point I'd like to test out the software first.

 

 

[stadman]

SU and curves/ circles are more a series of straights at an angle

Knocking up some de-railers as someone mentioned here a while back.

Never seem to check enough when I have access though but nearly there.

Just have to rescale.

Kev S

[Ian Smith]

My experience of Sketchup is relatively limited, producing designs for some wagons in 2FS (which were subsequently printed up by Shapeways).  Curves are a bit of a nightmare, being as Kev says a series of straight lines (perhaps all software draws them that way), but from memory I think there was an option somewhere that allowed you to specify how many lines made up the curve?

 

As for bolt detail, for my 2mm wagons, I simply drew a square on the surface where I wanted the bolt and extruded it outwards (by selecting the face of the square and pulling).  I don't know how familiar you are with Sketchup, but in case you're not aware it is simpler to enter the distance you want to extrude (or draw a line for that matter) by doing the action, then over-typing the dimension in the bottom right hand corner of the screen, so In my case for example I would pull the extrusion to any depth then tell Sketchup that I wanted the extrusion to be 0.2mm for example.  Hope that helps.

 

Ian

[Marbelup]

The curve thing is a "feature" of Sketchup.  Even though you can increase the number of line segments, the maximum number is not enough to produce a smooth curve.

 

Proper CAD packages have no problems drawing smooth curves and circles, as per attached screenshot of curved-sided hopper wagon (HO scale) drawn in Rhino.