OnShape vs SketchUp! – a model railroader’s view

Well, I’m a few weeks into my OnShape journey now, and I must say I’m impressed.  After my experience with FreeCad and Blendr, I was almost ready huck my Linux machine out the window when Vince pointed me toward OnShape. I’m thankful he did.  For several years I was a staunch advocate for SketchUp! but now my allegiance has changed.  

As a programmer I was floored by the audacity to even attempt a 3D CAD program that runs in a browser.  I’m still amazed that it works.  Indeed, OnShape not only runs on my Linux machine and my Windows laptop at work, but also on my phone.  I really like that I can access my files from anywhere except the cottage we rented in Nova Scotia. 

For hobbyists, and especially for casual capitalists like me, the license model for SketchUp is a little bit problematic.  Technically, if you are planning to make models to sell with SketchUp, as I do through Shapeways, you’re supposed to buy a pro license.  As I charge something like a nickel for printing my models, it would take several lifetimes to pay for a pro license.  

With OnShape, the free license doesn’t have the same restrictions.  Effectively, OnShape charges for storage, and as long as you only want ten private files, you can use the software how you want.  As a model railroader, I want to share my files anyway; that way you can see what I’ve done, and more importantly, you can improve on it.  So, the OnShape license is perfect for model railroaders.  

But what about the tool itself?   When I was first learning SkechUp, I was surprised by how easy it was, and I quickly got used to sketching on a surface and extruding shapes.  This works fine for relatively simple shapes, but I wasn’t able to create more complex shapes like the asymmetric cone in a boiler or the compound curve at the end of a coach roof, except by drawing individual triangles. 

OnShape adds a number of tools to enable you to manipulate parts after they have been drawn. I use fillets and chamfers all the time, Boolean operations quite often, and for crazy specialized shapes like that passenger car end, I would use a Loft.  There is even a helix tool (I once watched a tutorial on how to draw a screw in SketchUp and I still couldn’t do it).  

These all seem to be clean operations. For any reasonably complex model in SketchUp, I’ve found that I spend about half my time tracking down and cleaning up spurious edges and faces.  I got very quick at exporting the model to Accutrans  so I could find holes in the mesh. 

Now, so far I’ve not tried to print a model from OnShape and so I can’t be sure the models are water tight without extraneous edges or vertices, but there doesn’t appear to be any way to fiddle with them if they’re there.  That is either a great benefit here or a serious deficiency!  I can’t tell which. 

Finally, the biggest difference between OnShape and SketchUp is that OnShape recalculates the model from all the operations that have been used to create it.  The operations are all displayed in a long list down the side of the screen, and so, you can easily go back and change history!  This capability is a real boon to railroad modellers who so often have to estimate dimensions and change them later.  In SketchUp, these re-dos can be very difficult, and are a primary cause for those spurious edges.  

OnShape also provides some sophisticated capabilities for animating and testing a model before it is produced. To tell the truth, I’ve not explored this sufficiently to be able to say whether it is useful for our hobby  but it certainly looks interesting.  

SketchUp’s one ace in the hole is its photo-match tool.  This is a profoundly useful tool for model railroaders. Starting from a few photographs and a couple of known dimensions, SketchUp is able to reverse the perspective and compute a model of the pictured item.  It works very well for buildings where we frequently have an idea of the footprint from a fire insurance plan, but no elevation drawings. 

So, overall, I’m a convert to OnShape.  When I need the photo match tool, I’ll borrow my wife’s laptop.  The Linux machine is safe for now.