Last night, I began work on a serious scratch build project.

One of my other hobbies is RC. A few years back I had a go at modifying and improving a 1/16 RC tank, and that was fun. So much fun, I decided to try and scratch build one to use up all the spare bits I had built up. I very quickly found myself out of my depth there, as there was only so much you could do with flat plasticard sheeting, glue and sandng. Especially the wheels and suspension elements which needed to both work well and look right. Plus I needed multiple wheels that all looked the same. Now....I have the tool to do the bits I simply could not before, so I have decided to have another crack at the project.

This introduced an entirely new thing to my printing.....scale. And it was not simple....

Simplfy 3D is not flexible when it comes to scale. It wants to work in mm, and the only other measure it knows is inches....which it will try to convert to mm if it thinks your object is too small. This is a problem! I was modelling in Lightwave ( my modeller of choice ) and using a free STL exporter I found online. This worked fine to export files, but when I imported to Simplify, it kept asking me to convert the model to mm on import. This left me a tiny model. I expected it to be 100mm, and now it was 2.5mm! If I didn't convert, I got a model 0.1mm that was so tiny you couldn't see it!

First thing I learned about Simplify was that you could double click on the model element list and get it's dimensions and scaling to show up. This was handy! Maybe I should have read the manual....

I could mess about with the sizes and force it to be the size I wanted, but this was not a good strategy. I was going to model a complex thing in several parts, not all of which I would print in one go, and they then had to fit together....so I needed to do the scale work in the modeller and know they would come out the same relative size.

I did a bit of searching on the simplify forum, and found out the issue. Basically....the STL format does not contain any info on units....just numeric dimensions. Simplify assumes mm ... so the base scale in the modelling program HAS to be set to mm. Anything else and it goes screwy. Once I did that....I was able to export an STL that the modelling program said was 38mm across and have it show in Simplify a 38mm. This means it will print to 38mm.

A silly little thing, but a really important one once you move away from simply making pretty shapes and desk ornaments to making parts that need to do a job or fit in a space. Downloading models from Thingiverse etc. just means someone else has done the hard work.

No I need to model the rest of the suspension so I can make 8 sets of suspension units I need for one of these....

t35-replica.jpg
The bulk of ht hull and flat plating will be made from sheet plasticard, but the details and complex parts I will 3D print.