We set out to redesign the walker. My dad had some Harken travelers from a sailboat to use as the track and linear bearings. I found a power window motor and ordered some XL timing belts, pulleys and bearings from McMaster Carr. We built the walker with one motor driving both pulleys and belts to lift the handlebars. But the timing belts kept slipping. Also, the quarter inch driveshaft was too flimsy. We changed the design and switched out the timing belts for a chain drive and larger drive shaft. Then finally it worked!
But this design has a fatal flaw: If the chain breaks, the whole thing will collapse. I needed something better.