A few items come to mind when you build your own carriages:
There needs to be a longitudinal flat piece (Stool Bed) set on top of the rear axle for the use of rectangular and a wedge shape set of bolsters (quoins) that bring the muzzle down for the firing range needed. That bed is usually supported by a rod extending through both carriage sides.
Wheels are quite small: The larger is just forward of the cap square holding down the trunions. Smaller one is about in the middle of the stool bed.
Sides are splayed out according to the taper of the barrel but usually close to 2 degrees with a transom vertically set inside at the muzzle end.
Some carriages had an extension at the front/muzzle end which is radiused side to side so that the gun could be moved by crows to fire at side angles out of the port with that piece tight against the bulwark for stabilizing the gun as well. Sometimes chocks were used but they would go flying during the firing and have to be replaced. None were used behind wheels as restraint was the function of the recoil hawser and secondarily/much less the outhaul tackle which was not meant for that purpose and would go flying around creating a hazard as the bitter end was loose. Jean B. shows the French 74 gun Frigate with holes through the middle of the carriage under the barrel for the recoil hawser. Carriages varied a lot depending upon the barrel caster and separately the carriage maker across the years, ships, and armament desired.
I have recommended Building 18th Centry Naval Artillery by Dmaian Sieknoic, before and still do as a supplement to Jean B. Just a thought. Rich (PT-2) You will be much more rewarded by making your own than buying.
