to begin modling i need design for parts how can i get it for engine as example ??
The simplest thing is design your own part.
Than dimensions come as you go along.
Reverse modeling is nice and easy but real modeling from scratch
can bring out the best in you.
My suggestion to you...be a desingner and design....
Good luck and succes..
Search GrabCAD Q&A's there is many people left web sites to goto.
Google what you want to model and add something like "dimensions" or "engineering drawing" to your search.
If you have something at hand you want to try and model then a tape measure, rule and measuring callipers are pretty much all you need other than pencil and paper to write down the dimensions.
There-after, refer Hans's answer
I have the same problem but I am desperate to model anything, has to be a part though
Right on Martin, lets be proud we are designers ans design.
The world is at your fingertips and remember that the best CAD program is always an extension of your mind.....