Erm, time for a slight (complete) redesign of the main standard.
I haven't been happy with the rise/fall mechanism all along, as the scissor lift added too much bulk and would never be fully stable which defeats the object of setting exact angles for the standard. I've spent the last couple of days going over loads of different ideas and came to the conclusion that one of my first ideas would probably be the best!
I've now drawn a new standard that incorporates rise/fall, tilt and swing in one unit which is only 45mm deep front to back and 115mm tall. It allows for 60mm of rise/fall (+40, -20), as much tilt as the lens will allow and around 45 degrees of swing in each direction. The shift is currently set using a traditional locking bolt rather than incorporating an additional motorised element to keep the overall height down as low as possible for easy use.
Rise and fall is controlled using a threaded bar
linear actuator. The stepper mounted to the top of the upright rotates the threaded rod which makes the plate attached to it with a captive nut move up and down. There are two 3mm steel rods inside the upright to keep the plate level. Tilt is controlled by another stepper that's attached direct to the lens board frame using a bracket to spread the weight. Swing is controlled by a third stepper mounted in the base of the upright pointing downwards.
At the moment I'm using a traditional locking bolt to fix the base of the standard to the focusing rail. Loosening the bolt will allow the base to shift up to 30mm in each direction. I haven't drawn it yet but there will be an overhang on each side of the focusing rail to stop the standard swinging when the bolt is released. I could have built in a fourth motorised axis for shift using another linear actuator but as it would add up to 70mm to the height I've decided to keep it more flush with the bed of the camera.
All of the new parts for the main standard will be lasercut from 4mm Acrylic. As well as being light, Acrylic won't flex which will keep everything aligned. This standard is completely interchangeable with the more traditional manual standard I've designed for the Acrylic 4x5 so I can test both out alongside each other.