Ooopsie, that went out before I was done! This'll fix it.
Some time today I'll get the scanner set up and scan in some measured drawings. Meanwhile I'll mention dimensions as we go along...
Now that the wheels and axles are covered, we need to look at the rest of the wagon parts. They are:
-- The rear bolster/axletree
-- The front bolster
-- The fifth wheel
-- The front axletree
-- The center pole
-- The tongue
-- The bed
Since it's the simplest, he first part we'll look at is the rear bolster/axletree. When done it will be about 10.5" wide by 28" long. The dado for the axle will be covered and a notch dadoed out in the top.
The rear axletree is combined with the rear bolster in this wagon. Making them separate is not necessary in this small a wagon. We want the top pf the bolster to sit a little below the level of the top of the wheels. We'll rip down a wider board so the distance from the top of the bolster to the top of the dado for the axle is 8 and 9/16ths inches (the bolster height is nine inches). This is an odd way to say the board is ripped nine inches wide but relates to the way I mount my axles. In this case the axle is 7/16" in diameter.
I prefer to cut a dado that the axle will fit into flush. And then then glue the cut off over the dado to create the same effect as drilling a hole all the way through the 28" long board.
As an aside: there is no such state of being as having too many clamps.
The way to do this on the table saw. Set the blade height equal to the axle height, and set the rip fence so the blade is centered. Rip a groove, then reverse the board and rip again. In small increments move the fence away from the blade and continue to rip and reverse and rip again. This will center the dado and will eventually result in a dado just wide and deep enough to receive the axle.
There are other ways to attach the axle, and while I prefer the dado as being strong and attractive, it's really only convenient if you have a table saw or router table. Here are some alternatives. You can bend over nails like we used to do when we were kids making 'soap -box' racers, you can use metal strap, pipe clamps, or heavy fence staples. Don't use small electric cable clamps (the white thing) I just stuck that on to remind me to mention fence staples. If you use these methods, you might want to use a plastic bearing, as the metal on metal will start squeaking sooner or later.
The dado on the bolster top is for friction mounting in an "egg-crate" joint with the center rail. It is centered in the bolster and is 1.75" deep by 1.5" wide. Here you can see it with the center rail in place. Note the clevis pin with spare washers, hitch pins, and nut. If you leave this off I guarantee you'll lose one at the event right after you've promised some brass hat you'll haul their stuff someplace.
The parts of the "egg-crate" joint. We're going to use this in several places in the wagon. Make sure it' snug. It will loosen over time and can be shimmed with tape, paper, brass sheet, etc.
It's also called a "lapped 'T' joint, half lapped center joint, and crossing lap joint.
Nibbling out the dadoes is one of the reasons I love my Ryobi BT3000K table saw (BT3K to the cognoscenti ;-) the sliding miter table is a joy, it has beaucoup attachments including a router table and affordable rail extensions. It also has a very good website chock full of suggestions for tweaking by enthusiastic owners. If you're planning to get a "contractor's saw" this one is my suggestion. There are only two flaws, one is with bearing shims (the web site will tell you how to deal with that, in 8 years I've never had a problem) the other is the saw doesn't have motor breaker. I plug mine into a "power strip" with one and have never burned out the motor, though I've occasionally bogged it down in thick hardwood.