This is a later model Burton Harris after S&G bought out the company. There are two sets of springs. One to extend and one to retact. Each set has its own trigger, related lingages and sear or catch. The overnight timer and a short delay timerto get the door shut. When the unit is cranked up all the springs get compressed. There is a heavy block which is mounted to the doors boltwork. Extending out of the auto case are two sping blocks. One of these (the extension block) butts up against the boltwork block and the other extends past the boltwork block and its lip extends inward. Both of these blocks have a pin which are caught by their respective linkage catches. At rest ( unlocked) the boltwork block is captured between these two auto spring blocks. After the overnighter is wound up, cranking the auto causes the retraction block to extend out moving away from the boltwork block. Now it is already set to retract. After the door is shut the delay timer releases the central spring block to extend the boltwork. After the the overnighter winds down the retraction block pulls in carrying the extension block with it. Whew! Hope that makes sense. Is it me (probably) but I can’t get the pics to come up when I hit Manage attachments.
