Rebuilding a rivet forge

[OddDuck]

Just what I needed, another project. Went to the saturday session at my blacksmith's association this weekend at what I thought was the member's time, but they were running a class. If anyone is curious, here's the blogspot for it, http://fieldspondblacksmithing.blogspot.com/ . I got talking to the director and they had an old rivet forge that is in the museum's collection that they wanted to fix up, and, me being a new member and trying to be Mr. Helpful, I volunteered to try and fix it. I figured where my main hobby is foundry work, I was in the best position to reproduce some of the broken parts. It was made by Boston Forge, at least that's what the blower says. Everything is free on it, all the parts turn, but it has some serious issues that make it unuseable.
Here's a few pics of the blower:


You can see the damage to the blower shell in the second one. I am going to clean off the welds, and use the repaired old one to cast a new shell (or two) to use. That's not the big problem, though.
This is the first time I have seen one of these close up, and I'm not sure what the complete mechanism looks like on a working one. The other main problem with it is this:


The arm got broken off at some point and the ratchet pawl was modified somehow, it still engages and turns the wheel, but the ratcheting action doesn't work. Is there a spring that holds the pawl against the wheel, or is the arm in the wrong position? I am planning to re-cast the arm as well and would like to know what the broken part originally looked like. Any help would be greatly appreciated.