Overview of Engineering Principles incorporated in Technic LEGO sets I run an after-school technology education program and want to expose kids to real-life engineering by means of having them build commercially available Technic kits which we then deconstruct and analyze.

I am looking at 42042 Crawler Crane's second model as a good example of how to build a strong vertical structure, plus it serves as a good example of how a weight &amp; counterweight works.

I would have loved to use 9398 4x4 Crawler as it showcases differentials, steering principles, a servo motor as well as suspension, but unfortunately that model is no longer for sale (I'm not willing to pay the ~$300 some sellers ask on Amazon.com), so I think I'm settling for the smaller, non-motorized 42029 Customized Pick-up Truck.

I assume both models will give me plenty of gearing examples.

I am looking for your advice: What other engineering principles does Technic LEGO showcase, and which (ideally current) model(s) would you suggest I use to illustrate these?
This depends on how deep engineering principles do you wish to teach. For simpler, shallower things, like the inherent stability of a triangle based construction versus a square based, the crawler crane already offers a lot: the relation between force and leverage, skid steering, gearing, pulleys, gearboxes, electronics. Pneumatics and shock absorbers are missing from this set, but you can get some pneumatic parts from the 42008 Service truck.

For advanced concepts like Ackermann steering, Camber, caster and toe it would be hard to find official models to demonstrate, but you can always build simple models to display one or more of these features.

There are a few other things that I can think of, like fiber optics, but these are really hard to find nowadays.

Of course besides mechanical engineering there is also computer engineering, for which the Mindstorms sets offer an admittedly expensive introduction.