Ned Simmons wrote:

On Mon, 15 Mar 2010 09:34:07 -0500, Ned Simmons
wrote:

I'm working on a fail safe brake...

Thanks to everyone who responded. I still have to do some tweaking and
check proportions and strengths of the various components, but this
should be pretty close.

If the chain goes slack: the stack of Belleville washers (magenta)
pulls the chain rod (gray) down; as the collar on the rod (gray) falls
the arm (green) rotates CW; allowing the torsion spring to rotate the
collar (gray) CCW; the pawl (green) rotates along with the collar and
engages the slotted track (orange).

http://www.suscom-maine.net/~nsimmon...so_100316a.jpg
http://www.suscom-maine.net/~nsimmon...ck_100316a.jpg

--
Ned Simmons

Looks good. Not sure where the chains are attaching, but you may want to
look at the lower spring loaded one and see if it should be a rigid
mount, i.e. not spring loaded with different types of springs at each
connection point.