I'm a newbie (<2yrs) using Blender and am having trouble with Blender Physics/animation.

I've set up the Physics of a swinging Wrecking Ball, and set the animation to run for 240 frames.  This was not long enough for the entire "swing" of the ball-and-chain. I'm unable to reset the timeline.  I CAN set the end-point to (say) 1000.frames, but when I try to render again (on-screen, not final full-rez rendering)....the animations progress halts at "240", and I cannot get it to go any further. There are no markers or keyframes in the timeline...

What should I do to "force reset" the animation-timeline, to allow changes to the length?