CAD Software

For some time I’ve been thinking about moving away from the drawing board and using CAD. OK, it’s 2019 and there have been a lot of perfectly good CAD packages out there for a number of years, the problem is I’ve been nervous of the amount of hours I need to put into learning how to use one of them. If I cannot spare the time then buying a package is rather silly.

Then at the end of last year I started a project that is going to be a long term labour of love: a small steam traction engine.

As you can see in this image I’ve gone back to the drawing board….. Whilst this is rather lovely, it is going to be difficult to share the design.

So I started looking around at what was available for free:

and then there are free trial licenses or free student licenses:

There are lots of other packages out there, but having looked around I decided that I would go for FreeCAD and downloaded version 0.17 for windows.

Go straight to the website and download from there: https://www.freecadweb.org/

Now I’m learning by following lots of the online youtube tutorials…these are: brilliant, rather dull and frustrating. The following tutorial is rather good and runs for around an hour, I’ve been watching it and then trying some of the techniques shown. It has taught me some of the basics of dimensioning parts, setting constraints and rotating them to form 3D solids.

Using this tutorial and around 2 hours so far using some of the tools that have been described I’ve managed to create the flywheel as shown on the right.

I’m also able to swap between the solid objects and the sketches that form the basis of them to change dimensions.

Once you’ve learned how to remove material using the “pocket” function and to create a repeated revolution you can rapidly create items such as flywheels.

Flywheel and sketch of the removed material

You can see an issue in the top left hand filleted corner of the sketch where I have a constraint missing – this needs a tangential constraint added between the main radius and the fillet.

I’ve corrected the constraints and now the fillet has a tangential constraint with the the main circumference. I’ve also now added a central boss so that it can now be bolted to an axle.

The key points I’ve learnt with this very simple model are: sketches, constraints, setting dimensions and checking for over-constraints.

One other thing I’ve learnt is if all feels like it is lost, go back to the model tree, click on a level and press the space bar – this switches the part on and off.

The drawing is not perfect and needs some more dimensions, but it’s starting to look ok

My next challenge is to work out the boiler and the firebox as this will then allow me to anchor the traction engine in space. I also need to work out how to move parts around and realign their origins.

About Nigel 220 Articles
Have been making models since I was around 7 years old and using a lathe from the age of 11, a self taught engineer with a passion for making model engines.

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