Like some others out there, I've started learning how to use Onshape. I'm still coming up-to-speed, but I really like its parametric modeling - being able to change a dimension and have it propagate to all related components automatically. I'm using this flip-top cart project as an opportunity to get more proficient with it.
Here are a few screenshots of the design so far - this is mainly to show how I'm planning to lock the platform in place. As with the rotating hub, this was another chance to differentiate my design. The expected benefits of this locking approach are:
The edge-mounted stationary stop prevents the platform from rotating past 180 degrees. This is necessary to keep the cords from getting twisted and stressed.
The edge-mounted stops should provide solid locking with a minimum of play.
It's dead simple. The pair of sliding stops will ride along either a square or dovetail bar (haven't decided), each having a quick-release cam clamp (not modeled) to lock it in place.
The cart design is not finalized, but here's how the platform should function