Slider crank torque

Hello all,

If you look at attached picture, you will notice a slider crank mechanism except now the piston is keyed and the crank is just pinned now. I would like to find the required moment at A to hold this piston in place. The only downforce is the mass of the piston x gravity as shown. Can you please help me draw a diagram and solve for my unknowns? I'm not very confident how to do this.


Thanks,
[IMG]http://www.engineersedge.com/engineering-forum/attachment.php?attachmentid=1688&stc=1[/IMG]Chris