Believe or not, I actually had a little over an hour today to do some work between a dentist appointment (hooray...not cavities again) and a work related meeting. I finished the top works frame for the swing-gate and reinforced all the joints with double Simpson splice plates. Then I put the whole thing into position and leveled it. I added a temporary leg in the front and made measurements for the middle support that's going to have the casters. I cut the OSB plank that's going to hold the wheels and support the legs.
To get the correct radius to mount the fixed casters I used the Rotape with the center point being close to the hinge line and extending it out so it intersected the OSB base somewhere in the middle. The Rotape has a drafting pencil lead in the other end and I scribed the arc darkly on the OSB. I will use nuts and bolts to mount the wheels. The holes are 5/16".
This is sort of how they'll look mounted, but I just realized something looking at this picture. I best make sure that I mount the wheels from underneath since the arc is not symetrical with the board since it is struck from a offset center point. If I were to screw them on in this orientation, and then turned the board over to mount the legs, the wheels would no longer be correctly aligned with the center of rotation. Believe it or not, this is actually a benefit to me in blogging this build in such detail. As I write, I'm thinking about what's been done and what needs to be done.
I'm also going to reset the radius to move the wheels a bit more to the right giving me more clearance for the caster fasteners. I'm going to frame the top side with either 1 X 3 or 1 X 4 as a mounting point for the legs. I will screw these parts on from the underside of the OSB into the regular grain of the dimensional lumber. I don't trust OSB with screws into the side. I can't twist the board since the legs must mount square to main rail. The legs will be fastened with carriage bolts and nuts. Then I'll add sufficient diagonal bracing to stiffen up the whole deal.
