With the CNC cart completed, I could get back to working on the flip cart.  I had purposely delayed work on it because I was struggling with part of its design, which was the idea of having to outboard the casters - mounting them on the outside of the main box.  The TLDR reason I thought that would be necessary was ultimately to provide sufficient lateral stability.  With the tallest tool at 21" max height, a desired bed height for both tools at 34", the back bracing (the primary lateral support) would end up being too narrow (in height) for my comfort if the casters were mounted on the bottom of the box as is usual. 

Hence, I would build the box to sit close to the ground (1/2") and mount the casters externally on some platforms at the corners.  I had worked out how to do it, but I just didn't like the idea of making the footprint of an already largish cart (25-1/2" x 28-1/2") even larger by adding external casters.

I decided that it would be prudent to test the stability of the cart with the planned design before deciding to change anything.    So I started getting the pieces cut out.

For the hub cradles in the sides, I made a quick router jig.

I cut the bulk out with the jigsaw.

Flush trimmed on the router table.

The platform is two pieces of 3/4" plywood glued together.  I had intended to leave the long edges bare plywood, but since one face had a damaged edge, I trimmed it down and glued-on some of the same salvaged ash that I'll use for stops on the short edges later.

Flush trimming the edging was a bit cumbersome.  I didn't want to take the time to setup a tall fence, so I just used some right angle clamping fixtures to help keep the platform perfectly vertical on the router table.  It probably would have been a bit easier to do this with a hand router.  But it worked.

I then trimmed-off the excess on the short edges and will add the stops at a later time.

Each hub attaches to the platform with a pair of 8mm dominos.

I used only pocket hole screws to temporarily assemble the cart.  Once I get a sense of its stability with a tool on it, I'll disassemble it all to make some design tweaks before reassembling with glue and screws.  (The shelf and bottom panels are too long anyway.)

With some temporary stops to keep the platform from rotating, I set the planer on top and got it into position for mounting, and marked the bolt hole locations.   Here I'm checking to make sure the dust collection fitting will clear.

With small pilot holes through the top, I could remove the platform and drill the counterbore and bolt holes from the underside.

With the bolt installed backwards in the T-nut, I could tap on the bolt to seat it.

With all 4 T-nuts installed, I could temporarily mount the planer to see how the platform rotates.

Without the drum sander to counterbalance, it takes some care to flip the planer, but the rotation is smooth and even with just the pocket hole screws, the cart feels pretty stable.   After noodling on it for a while, I'm going to scrap the external caster plan and go with inset casters.  More on that in an upcoming post.