Hi Dave4
The truth is, there is No Easier nor More Functional Program ... especially for FREE than Google SketchUp.
It is extremely versatile. You can model practically anything you can possibly think of. And at a 1:1 Scale (or whatever you want but that is the default).
SketchUp only has a few tools but they are very powerful.
Here are a bunch of Video Tutorials that will show you just how easy SketchUp (SU) is to learn to use.
But start by downloading and installing SU Free, then you can follow along with the easy paced videos (pause, practice, play etc).
Start with the "New to Google SketchUp" series of
videos.
Furthermore, if you search the Google 3D Warehouse, you will find many Geometric Shapes, both simple and complex (such as those you described).
People model airplanes, cars, flowers, trees, buildings, people .. you name it. If you can think it.. you can model it with SU.
Believe me ... there is no simpler program to learn short of MS Paint. But there are few programs that can model such complex things, especially for Free.
Watch the videos and give it a try.
I am confident that you will not be disappointed.
Then when you find out just how much you like it, you might even consider purchasing a license which adds a bit more functionality that you might find useful in SketchUp Pro.
Best Wishes and Happy Modeling