re: Shop Vac Hose Reel Auto Rewind Mechanism

Duck, I assumed that gravity would be all it takes to make the pawl rotate into position but with a spring, I can position it anywhere around the sprocket and it will still work.  If I rely just on gravity friction could prevent it from falling into place, especially as it wears or collects dust and dirt over time. 

Ryan, the spring on the pawl is just to make sure that friction or orientation do not prevent the pawl from staying in contact with the sprocket.  It really isn't necessary for the pawl to lock in place, that is, as long as I make the latching pocket or "tooth" shaped correctly and the pawl pivots freely.  If you look more closely, you can see that when it is in the locked position below, what keeps the rewind spring from turning the reel and sprocket clockwise is that the "tooth" tries to pivot the pawl, which pushes it down into the sprocket, causing it to bind.  Basically the sprocket is in the way of the pawl turning. 
I should have shown these closeups before.   Note that the arrows in the drawings below just indicate that I used a revolve connector in the assembly in Onshape.  Those pivot points can turn in either directions. Also note that the 2 small circles on either side of the dark blue axle are key ways for locking the sprocket to the central shaft which is screwed to the side of the reel.  They should stay aligned as the sprocket/axle turn.  I just haven't locked them together properly for a good animation. 
 
Locked Position:

Pulling the hose to turn the reel and sprocket counter clockwise to this point and reversing to clockwise, will pivot  the pawl to the free turning rewind position. 

If you reverse back to counter clockwise at this point (below), the pawl will move back into locking position so that it can lock when you pull the hose enough to engage the next locking tooth to the left.  As you pull hose off the reel, the pawl will naturally pivot to the locking position so that when you release and the rewind spring pulls it clockwise, it should stop as in the first locked position above.  

All in theory anyway.  I think that spring should make the pawl click like a rachet as it falls into the pockets That should provide an audible clue when to reverse direction or let the rewind spring take over.