[Kevan]

I'm just talking about chassis initially, there's a fair few out there classified as 'free to use', I've downloaded a fair few I have to say and not printed any of them as I enjoy designing my own in 3D CAD.

That's not to say these freebies aren't any good, I intend printing one for a Spirit 406 tonight, it'll take a SlotIt pod and as long as it fits should be a huge improvement over Spirits chassis.

The main thing I dislike about it is the guide plate will be printed with supports, this will invariably mean a rough finish underneath when it really needs to be smooth and frictionless.  My own chassis have a separate guide plate that is dead flat on the bottom and glued on top of the chassis.

If anyone else is interested in printing this it's here -> Spirit 406 chassis

This is what it will look like...

   

[MrFlippant]

That depends. :)

On what tech the model was designed for, and whether you're printing with that tech. The model you show might have been designed for injection molding or maybe SLS printing. With the right resin, you could try SLA. It could be printed with FFF, but some of those things might be weak due to the small cross section, so you'll want to print in a material with excellent layer adhesion.

As for the guide holder, smooth is always good, but with good settings for your printer, a supported surface should be more than smooth enough. That's how I designed the guide holder for the SCX NASCAR chassis I did recently, and guides work quite nicely against that supported surface. 

Since you're also into modeling, you might consider using that file as a template and make your preferred changes to it.

As far as the implied question of "free versus paid", I judge on the model, not if it was free or paid. I've seen plenty of crap that people charge for, and plenty of wonderful things that are free.

[Kevan]

...Since you're also into modeling, you might consider using that file as a template and make your preferred changes to it.

Well I learned a little more with Blender today...'tis a good freebie but mighty frustrating when you don't have access to Netfabb.  So guide block now my preferred way 

   

[Kevan]

...I did the render in Chitu as I haven't found a way to save an image file from Prusa Print without Ctrl+Print then cropping.

[MrFlippant]

LOL, and that's what I do, as I can't be bothered to run Chitu just for that... though I didn't realize it could do that. I wonder if anyone has requested a "capture render to clipboard" feature for PS. Seems like a useful feature.

[Kevan]

Yes they have requested that feature, I don't expect it to happen.

[JMay]

Kevan,
             Like you I print the guide holder separately, to guarantee a  smooth surface for the guide to rotate onto, and there is the other bonus that you can after printing add a spacer to the guide well to raise it further for certain guides. 

Looking at the Spirit CAD image have you printed this yet and how did the rear diffuser come out as can see overhang and shallow angle issues there that may need support added.

Cheers
             John.

[Kevan]

When necessary I add supports to the build plate only, this was one of them and printed OK actually. 
I'm not a fan of the pod screw recesses so will be changing that also, I prefer to countersink the hole with a piloted countersink. 
I'm also not an AW fan so will be changing that to SW/IL and getting rid of the wavy chassis reinforcing. 
...don't like the front axle mount either 

By the time I've finished it'll be my version so the CM can go too 

[Kevan]

As John highlighted, overhangs can be messy, recently with my own designs I've added hollowed sacrifial blocks underneath with a 0.2mm airgap and connected it to the chassis with a 0.5mm block so it renders as a single item so the slicer doesn't move the bits around. I don't use supports for this. The thin connector snaps off leaving a little bit of polishing to do.

[Kevan]

A few hours spent tonight.

Added loads of bits in 3DBuilder to add/cut, save as a .3mf file, import into Netfabb to do the adding/cutting, export as .3mf

...file was hUUUUUUUUUUge and Prusaprint couldn't open it

...google how to reduce mesh file size

...Blender 'decimate' to the rescue, tried reducing in 10% steps and got down to 10% of the original file size and Prusaprint likes this much better.

First pic is bits & bobs added in 3DBuilder

   

Second pic is in the slicer

   

N.B. don't do your chopping & changing in 3DBuilder because it will very quickly lose quality. If it takes more than 20 seconds to do the cutting and re-rendering hit the abort button.

TBH, I could probably have drawn it from scratch quicker