i want to build an rc car myself , which means i want to design the pcb and then make it . but i am not getting an pcb designs for it anywhere as all websited are just posting about assembly .
can anyone help me out , is there anyone who have previously done this and could share it with me ?

Welcome to RCI.
You have come up creating something from scratch and its appreciable initiative.
But you have to do a bit more research on this.
What do you want to make? A RC car along with radio or RC car for available radios.
RC car schematics are available on instructables where he used l293/8D to drive brushed motors.You can also use MOSFETs to drive bigger motors.
And no one have schematics published for RC car because there are many approaches by everyone.
However you can design your PCBs using eagle CAD.

@ Balakrishna Reddy, I think the main problem is making the chassis. Well,I can buy a brushless Motor, and esc and all the required electronics. But if I am bulding from scratch, the main problem would be the coupling between the motor shaft and the wheel shaft of the vehicle. Do you have any idea how such a coupling can be made?

Regards,
Dipanjan

For inspiration, take a look at existing 1/8 scale RC cars. You'll get a good idea about typical layouts and configurations.

Assembling your own car runs along the same lines, only the adventures happen in the driveway and bandits are usually thin on the ground. But given time and care it's possible -- the build just has to be taken one step at a time.

Today there are a number of companies offering kits to modify existing cars into custom vehicles -- think of using an old Pontiac Fiero as a donor vehicle for a Ferrari lookalike. Others offer a selection of parts and accessories to make a one-off mongrel machine that nonetheless looks like a custom touring car straight from England's Lakes District. Variations abound. Or a person can begin fabricating the car literally from the wheels up if he or she chooses.

While short cuts are possible, assembling your own car is a daunting task. This is definitely not something for the faint of heart; however, amateur and professional builders do it every day, and the pay off can be something to behold -- or hide, in some cases.

Read on to find out more about the joys and challenges of making your own car.