Engine tutorial/en

Modeling a complete engine (ongoing tutorial):
 * 1 - piston pin and pin ring : http://freecad-tutorial.blogspot.com/2011/09/engine-1-piston-pin-and-pin-ring.html
 * 2 - cylinder liner : http://freecad-tutorial.blogspot.com/2011/09/engine-2-cylinder-liner.html
 * 3 - cams : http://freecad-tutorial.blogspot.com/2011/09/engine-3-cams.html
 * 4 - camshaft : http://freecad-tutorial.blogspot.com/2011/09/engine-4-camshaft.html
 * 5 - camshaft gear : http://freecad-tutorial.blogspot.com/2011/10/engine-5-camshaft-gear.html