Rear Hub
 

What would the front and rear hub spacing be on a kona paddywagon? Also could someone direct me or inform me of the different parts on a hub and what they look like. I've looked at sheldon brown's site but can't seem to figure out how the lockrings and spacers work into equation.

100/120 respectively.

Spacers work on to the hub if you have a standard sized frame and need a smaller wheel to fit. You add them to the axle and it 'lengthens' the axle. A fixed-gear hub is threaded the same way the older 5/6/7 freewheel (or any freewheel) hubs are. You screw a single cog (sprocket) on, and then a lockring on after.

The lockring has additional threading (before the freewheel threading, working from the outside of the hub in). Lockrings are reverse-threaded, which means to tighten you screw the opposite way of normal (it appears that you're loosening). Lockrings prevent the cog from unscrewing itself if you try to slow down, stop, or anything that puts back-pressure on the cog.

Freewheel side of a hub:

http://www.makergo.com/shutup/images...2008/spare.jpg
A freewheel cog simply spins on there. If your chainline needs adjusting, you can spin a spacer on there first. I used a bottom bracket lockring on one of my bikes to get a straight chainline.

Fixed side of a hub:

http://www.makergo.com/shutup/images...008/fixing.jpg

The cog goes on the inside, larger diameter threads while the lockring goes on the smaller threads. When you apply back pressure, the cog will try to unscrew only to be stopped by Mr. Lockring, which is most definitely a good thing. On some hubs, there's enough threading on the fixed side to spin the wider freewheel cog on there. I've done this on Formula/Harris hubs. For this reason, a lot of people recommend you get a fixed/fixed hub as it gives you the most options.

Sheldon also talks about using spacers on an old cassette hub to make a singlespeed. In that case, you buy kits of spacers and slide them onto the old hub to get your cog in the right spot.