If you want a REALLY simple CAD program you can use the drawing features in excel to make a single 2D side/plan view of a machine. Just bring up the drawing menu, draw your shape, click on options and size it appropriately. Make sure to also unlatch it from resizing with the cells and then adjust the view zoom to see the whole thing.

Sounds awful simple but i've used it for a fair few work things when I've needed something drawing up quickly and scaled.