Have you made plans for to the axle yet? Do you have enough wood there to inlet a metal rod?
When I built this carriage, I cut a groove in the 1½" x 1½" square oak stock to accept a ½" stainless steel threaded rod for the axle, then capped the groove with a piece ¼" x 1½" thick.
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I built the trail using the same laminating process you used, except I used a combination of ¾" and ¼" thick pieces of oak to get the thickness I needed. The trail ended up being five pieces (¾-¼-¾-¼-¾).
your carrage is diffent than mine,
im building the "pack carrage"
as you can see i sanded the "round" into the carrage at the required tapers, this was a bitc? i used 80grit and a sawranwrap tube,
then down to 220, i still missed getting the curve all the way to the sides without going too deep,,frustrating, but wont be seen, cept by me, and now everybody on the group here,,grin,
your sides are seperate where mine taper all the way to the tail.
and yes ive left room for my steel axel,
it will be inbedded into the bottom of the wood axel,
ill probably use drill rod, in a brass tube,
then drill out the ends of the drill rod to put in the "keepers"
for the wheel hubs,
johnp